On the. Management of Brown Crab Fisheries

Transcription

1 Shellfish Association of Great Britain On the Management of Brown Crab Fisheries By Dr R C A Bannister Chair of SAGB Crustacean Committee Photo credit Ken Lynham, Portland

2 On the Management of Brown Crab Fisheries by Dr R C A Bannister Chair of SAGB Crustacean Committee Fishmongers Hall, London Bridge, London, EC4R 9EL & 33 Gunton Drive, Lowestoft, NR324QA Abstract Landings of brown crab have increased markedly in many fisheries. In the last five years landings in individual fisheries have tended to peak, then decrease, partly because there are few new crabbing grounds to explore, partly because the market has become oversupplied. It is widely acknowledged within the industry that potting effort has increased due to the modernisation of traditional inshore fleets; advent of large mobile vivier crabbers; extension of the fisheries to offshore grounds and the increase in number of pots being fished. A major problem in shellfish science is the lack of available data. Nevertheless, the results of recent assessments described in this report show that a precautionary approach to crab management can be justified on the basis of existing data. The main assessment results show that in England & Wales most stocks are growth overfished; in Scotland most stocks are either fully exploited or tending towards growth overfishing; in all these areas egg production per recruit is just below a candidate limit reference level (indicating overfishing); in Ireland effort has risen substantially and LPUE has declined in proportion, but egg production per recruit is just above a candidate limit reference level. There are as yet no signs of recruitment overfishing in any of the fisheries (i.e. no decrease in the number or proportion of small crab in samples of the landings), but scientific studies of brown crab recruitment dynamics are virtually non-existent. The science shows that in most fisheries further increases in effort will not increase yield in the long term; will further reduce potential egg production and will increase the probability of causing recruitment overfishing Accordingly, this report recommends the setting of a management objective to prevent any further increase in fishing mortality in the crab fisheries, and to implement management measures to achieve this. Part C of this report discusses some options for doing this and proposes the use of input control (limited entry licensing and pot limitation). Limited entry licensing is already in being for shellfish vessels, but there is latent capacity which needs eliminating. The advantages and disadvantages of the several pot limitation options are also described. 1

3 Executive Summary Introduction Since 2 the Shellfish Association of Great Britain has been promoting the development of a policy to cap fishing effort on the stocks of brown crab (Cancer pagurus, L) round Great Britain because of concerns that increased potting effort will overfish the resource, and that the economic viability of the fishery is threatened by oversupply and reduced prices. The three parts of this report summarise A) key meetings and discussions on brown crab management over the last decade, B) current information on the distribution, stock structure, fisheries trends, assessment and status of brown crab stocks in England & Wales, Scotland and Ireland, in order to support the case for limiting fishing effort, and C) the data that need to be examined in order to develop possible pot limitation options. The report is based on existing publications and presentations, coupled with new data and assessments kindly made available by fisheries research agencies in England and Scotland, some of which will shortly be published in their own right, plus views and data from some Sea Fisheries Committees. The sources of information are fully acknowledged throughout the report. The interpretation of the information is the sole responsibility of the author, a former CEFAS scientist acting in his capacity as Chair of the SAGB Crustacean Committee, and advisor to the Director of SAGB, and does not represent any binding statements by the Departments, agencies or Committees that have contributed the material. Part A. Policy Background Part A places in the public domain key discussions that have taken place on brown crab management since 2. It highlights a) the fishery, science, and management issues discussed at an international brown crab workshop held at SAGB London in 25; b) an informal consultation by Defra in 26 to seek views on a range of crab management options; c) the results of an expert workshop held at Defra in September 28; and d) the current perceived positions of the SAGB and NFFO on brown crab management. Based on these discussions the concerns are that there is a limit to the scope for expansion onto new grounds; potting effort appears to be rising in many areas especially as the parlour pot allows fishers to set more pots but haul them less frequently; the grounds are increasingly overcrowded; but the market is seriously depressed due to oversupply. Further increases in effort will not produce more crab in the long term, but will increase the risks of recruitment overfishing. The SAGB therefore contends that it is necessary to cap effort now in order to protect the resource in the future, and to facilitate future sustainability accreditation. During the 26 Defra consultation the industry was opposed to a parlour pot ban, TACs, a licence sunset clause, and inshore vessel size limits, but favoured a higher crab MLS, a ban on landing crab claws, and improved quality control (but not by legislation). The SAGB proposes a cap on fishing effort by vessel licensing, pot limitation, and removal of latent capacity; a ban on landing crab claws and the use of brown crab for bait in the whelk fishery. SAGB also proposes an increase in lobster MLS to 9mm carapace length, and a ban on landing berried lobsters. The NFFO Shellfish Committee has opposed pot limitation, a licence sunset clause, a berried lobster ban, and any change in the crab claw rules, but favours an increase in crab MLS by 1mm carapace width, and a stepwise increase in the lobster MLS to 9mm. SAGB contends that a higher crab MLS does not meet the objective of preventing future effort increases that will eventually nullify the benefits of the higher size, and it considers that there are also risks in reopening the discussion of the crab MLS issue in Brussels, especially for the Cromer fishery for 2

4 small crabs. Comments were also available from the Sea Fisheries Committees, some of whom support pot limitation (e.g. Eastern SFJC, and Northumberland SFC, which has just introduced a byelaw limiting pots to 8 per vessel) and others may not (e.g. North Eastern SFC, which administers a pot tagging scheme among hobby fishermen). Part B Fisheries and Science This part of the report provides an up-to-date summary of the distribution of the fisheries, the main trends in landings and landings per unit effort, and the results of recent scientific studies and stock assessments in England & Wales, Scotland and Ireland. Distribution of the Brown Crab Fisheries Section 3 shows that there is an approximate three way split between recent landings recorded from England, Wales and Northern Ireland (ca 11 t), Scotland (ca 1 6 t) and Ireland (ca 13 t), and illustrates the recent distribution of brown crab fishing using statistical rectangle data for NW Ireland, Scotland, and England & Wales. For England & Wales, VMS data from the Defra data base show a widespread distribution of crab fishing by large vessels over 15m fishing in the North Sea and the Western Channel, in contrast to the localised activities of small day boats. Section 3 also describes Defra data showing the relative distribution of vessel number, pot hauls, and brown crab landings between vessels smaller and larger than 1m, and among the 6 CEFAS assessment areas. Most potting vessels in England & Wales are <1 m, but most crab landings originate from > 1 m vessels. The main fisheries are in the western Channel and Western Approaches, followed by the English east and north east coast. The remaining landings originate in the eastern Channel, South Wales, and the Irish Sea. CEFAS estimates that a higher proportion of lobster landings originate inside the 6 mile limit, whereas in the key fishing areas for brown crab a higher proportion of crab landings originates outside 6 miles, so that brown crab stocks cannot be managed by SFC byelaws alone. Stock Structure Section 4 describes brown crab stock structure using CEFAS data from larvae surveys, tagging, and the results of a comprehensive Defra-funded study of genetic structure, newly completed. Larval distributions and tagging suggest that stock structure in brown crab is regional rather than local. This is supported by recent genetic studies, which show a genetic distinction between the North Sea and the Channel, but not between the Channel, Celtic Sea and southern Ireland. The relatively high degree of genetic diversity in the recent data implies that the stocks are healthy, and the low genetic differences within regions means that scientists and managers can define management areas based on administrative or geographical convenience, similarity of métiers, or regional biological differences that affect assessment outcomes, without violating the genetic structure. Fishery Trends in England & Wales Section 5 shows the trends in crab landings from the Channel, East Anglia and Yorkshire, and the west coast. Crab fisheries have expanded onto new grounds offshore, starting in the Channel in the 197s and 198s and in the Yorkshire and East Anglia fisheries in the 199s. Since the 198s, landings in the western Channel have fluctuated without trend, but on the east coast landings increased from the 199s to reach a peak in 23, but have since declined steeply. Data on potting effort recorded in the Defra data base unfortunately present problems owing to inconsistent coverage and quality. Trends in stock abundance, in the form of brown crab landings 3

5 per unit effort (LPUE) were therefore examined using data for individual vessels from the CEFAS log book scheme, although the number of records available is limited. Log books for the east coast fisheries show considerable variation in LPUE, but overall there is either no trend, or a slight downward trend until 23, when LPUE declines more steeply in several of the records. In the western Channel, brown crab LPUE in 4 out of 5 log book records fluctuates without trend between 1994 and 24, but then declines. Elsewhere, log book records are either absent or difficult to interpret. LPUE data were examined from several SFCs, where available. North Eastern SFC data for 2-25 show that the number of pots and pot days has increased significantly, but that landings and LPUE have fluctuated without trend. In Cornwall SFC, brown crab LPUE has increased gradually since In South Wales SFC the LPUE index increased from 196 to 1987, then fluctuated without trend up to 1999, before declining steeply to 26, reaching a level similar to that last observed in 1985/6. The SFC data show records that are not necessarily the same as those derived from the CEFAS Log Book scheme, possibly because of differences in the spatial pattern of abundance. In general it remains the case that the most reliable long term data for brown crab are for landings, and that despite some improvements since the advent of shellfish licensing in 26, data on potting effort and landings per unit effort for England & Wales remain unreliable and difficult to interpret. Assessment and stock status in England & Wales Section 6 summarises the methods and results of assessments carried out by CEFAS in 29 on brown crab in 6 assessment areas round England & Wales (CEFAS, 29). The method ( length cohort analysis ) uses the average size distribution of landings sampled at ports in each assessment area for the last three years; growth data derived from historical tagging results; and maturity and egg number at size obtained from regional sampling programmes. To calculate the fishing rate (F), the model uses the growth data to convert size to age, and makes an adjustment for non-fishing mortality, which is assumed to be either 1% or 2%. The text describes the assumptions and approximations that this entails. The main output is the current fishing mortality at size, plus curves that compare how the expected yield and egg production from the stock will change if this mortality is either increased or decreased, assuming that the number of young crab entering the fishable stock does not change with each case (a per-recruit model). The egg production per recruit at each F is scaled as a proportion of the egg production per recruit at zero fishing ( %virgin EPR ). Stock status is evaluated by comparing these outputs to fishing mortality and egg production reference points. The fishing mortality reference point is Fmax, where the yield per recruit curve is at a maximum. The egg production reference points are a candidate lower limit, which is 1% of virgin egg production ( 1% virgin EPR ), which we should aim to be above, and a candidate upper target or precautionary threshold that is 25% of virgin egg production ( 25% virgin EPR ) which it would be precautionary to reach. Although these reference points are candidate values, in that they are not formally agreed, they are analogous to those used routinely in ICES finfish stock assessments, and they represent proposed benchmarks for evaluating stock status objectively. In the report the CEFAS assessment results are presented as graphs and a table for two example assessment areas (Central North Sea, and Western Channel), and in a table for all 6 CEFAS assessment areas. 4

6 The results show that except for cock crab in the Channel, where the observed maximum F at size is moderate (.2-.3), the observed F on the fully exploited size groups in most English fisheries is high (.6-1.5), especially on females. In terms of yield per recruit, brown crab in the CEFAS stock assessment areas are therefore either fully exploited i.e. at Fmax (cock crab in the western Channel), or are overexploited i.e. beyond Fmax (hen crab in the Channel, and all other fisheries and sexes). In terms of reproductive potential the stocks are overexploited, since % virgin EPR is well below the candidate precautionary level in all areas, and is just below the limit level in all areas. If the candidate reference points were formally adopted, the fisheries would be described as overfished from the egg production viewpoint, and all but cock crab in the Channel would be suffering from growth overfishing relative to Fmax. There is currently no evidence from size composition data of any prolonged decrease in the number of young crab entering the fishable stock in these fisheries, so there is as yet no evidence of recruitment overfishing, but since we cannot determine when this is likely to occur it is clear from the assessment that a precautionary approach to limiting effort is advisable. This is a minimum requirement, since in order to reach the reference points F would need to be reduced. To reach the reference levels requires substantial reductions in F depending on the area (46-76% for Fmax, 12-56% for 1% virgin EPR, and 69-84% for 25% virgin EPR), subject to the caveats described in the text about the underlying assumptions. For example, these results are based on the standard assumption that natural mortality is 1%, but if it is higher, say 2%, some results would be less pessimistic, and some overfished stocks would be re-designated fully exploited. In either case, an increase in F above the present level will not produce long term gains in yield, and it will either risk the onset of overfishing (M=2%) or intensify overfishing (M=1%), so that the minimum advice would be the same: do not increase the fishing rate above the present level. Fishery trends and assessments for Scotland Section 7 summarise the fisheries trends and the assessment of stock status for Scotland, based on results for the Scottish creel fishery assessment areas described in Mill et al., 29. Scottish landings of brown crab have increased progressively since 1975 to reach an all time high of 16 t by 26. The main increases originate from the South Minch, Hebrides, Sule, Papa and Orkney creel fishery assessment areas. As in England and Ireland, the Scottish inshore fleet has been modernised, and joined by larger vessels, including vivier vessels, fishing new offshore grounds off the north coast and west coast. Trends in effort and landings per unit effort are not available for Scotland. Scottish stock assessments use methods, assumptions and input data (e.g. average port-based size distributions) similar to those described earlier for England & Wales, although there are differences of detail, especially in the growth equations, that change the precise shape of the resulting yield curves. Outputs are curves of yield per recruit and biomass per recruit against fishing mortality, scaled as proportions of the current value. The report illustrates the size data, and the resulting yield and biomass per recruit curves, for 6 of the 12 assessment areas (East, Hebrides, Orkney, Papa, Shetland and Sule). The Shetland area is unique in being managed by Regulating Order, and data for the assessment were provided by the local managers and the North Atlantic Fisheries College. They include much a higher value of natural mortality, as described in the text. 5

7 The results show that for most Scottish areas brown crab yield per recruit curves are relatively flat topped, and that in general, stocks are either fully exploited (F is either at or close to Fmax), or tending to growth overfishing (F is beyond Fmax, e.g. cock crab in East, Hebrides and Orkney). In all cases, the biomass per recruit curves are strongly concave, so that biomass per recruit at current F is substantially lower than it would be at lower F values. Direct comparisons between the results for England & Wales and Scotland cannot be made because the Scottish report shows proportional F, but not absolute F, and it does not compare the outputs to reference point values. Nevertheless, the results for yield and biomass per recruit indicate that the status of the fisheries in Scotland and England & Wales is broadly similar. Higher effort will not produce any long term gain, and will increase the risk of growth overfishing in some fisheries, and recruitment overfishing in others. Fishery trends and assessments for Ireland Section 8 summarises the trends and assessment results for the brown crab fishery in the principal fishing area off the coasts of Mayo and Donegal in NW Ireland, based on the report published by Tully et al, 26 (the Irish Report ). The NW fishery began in the 197s, and expanded rapidly in the 198s and 199s when the inshore fleet modernised and was joined by an offshore vivier fleet. By 24 landings and total pot hauls had reached 7+ t, and 1.3 million respectively. During this period the fleet was rationalised, the number of pots increasing from 32 in 1997 to 55 in 25, but the number of vessels falling from 153 to 63 (Tully, 28). From 199 to 24, LPUE in the offshore fishery decreased by 5%, in direct proportion to the increase in pot number. The Irish Report proposes that this was due to gear competition rather than a decline in stock abundance, because inshore, where there is less gear, LPUE declined at a lower rate. The assessment for the NW fishery used length cohort analysis to calculate egg production as a percentage of virgin egg production, as described for England & Wales, assuming that M=.1.The size composition, maturity and egg number data are described in the Irish Report. Percent virgin egg production per recruit (EPR) was calculated for both the legal minimum size of 13mm carapace width (CW) and a market threshold of 14mm CW. Curves of %virgin EPR were compared to two reference points, a limit of 2%virgin EPR, and a target of 35%virgin EPR (these are both more precautionary than the 1% limit EPR and 25% target EPR used in the CEFAS assessment). At the observed F, EPR was below the 35% target level but above the 2% limit reference level. This suggests that the stock in NW Ireland is less heavily exploited than those in England & Wales or Scotland, but direct comparison is not possible because the Irish results are presented as proportional but not absolute values. The economics of the NW fishery were examined by Tully 28. Earnings increased in proportion to pot number, with an average of 119 Euros per pot per year. Costs also increase in proportion to pot number, with an average of 87 Euros per pot per year, a net of 35 Euros per pot per year. Although the profit margin is 27%, it is modest in absolute terms. Brown crab landings along the other coasts of Ireland are described very briefly, but none of these stocks is assessed in the Irish Report. There is an interaction between the brown crab fishery and the large Irish whelk fishery off SE Ireland, where crab are used as bait. 6

8 Part C. Effort Limitation Section 9 summarises the stock status and management position for brown crab in England & Wales, Scotland and Ireland. The main findings are: In England & Wales most stocks are growth overfished (i.e. F > Fmax, except for cock crab in the Western Channel, where F=Fmax). In all areas % virgin egg production per recruit is just below a candidate limit reference level (1% virgin EPR). In Scotland most stocks are either fully exploited (at or close to Fmax), or tending towards growth overfishing (F > Fmax), and equilibrium biomass per recruit is reduced significantly by the current level of fishing. In Ireland effort has risen substantially (a four to five-fold increase in pot hauls on the north western offshore grounds) and LPUE has declined in proportion, but EPR is still above a candidate limit reference level (in this case, 2% virgin EPR, which is more precautionary than the 1% level used in the CEFAS assessments). There are some differences in the output from the assessment models between the three countries, possibly due to differences in input data, especially for growth, and some differences in the level of exploitation, but the overall conclusions for management are broadly similar in the three countries. The size of crab in the landings is generally above the mean size of first maturity. Anecdotally, there are as yet no signs of recruitment overfishing in any of the fisheries but the caveat is that scientific studies of brown crab recruitment dynamics are virtually non-existent. This is another reason for being precautionary about the level of effort. Based on the present input data and the resulting estimates of absolute or relative F the science shows that in most fisheries further increases in effort will not increases yield in the long term, will further reduce potential egg production, will increase the probability of causing recruitment overfishing Section 9 ends with the conclusion that because scientists are unable to advise what increase in F will cause recruitment failure in brown crab, and because crabbers continue to be concerned about the effect of oversupply on price and profitability, it makes sense to set a management objective to prevent any further increase in fishing mortality, and to implement measures to achieve this. For England & Wales, where %virgin EPR is below the 1% limit, there is actually a good case to reduce F significantly, but given the size of reduction required, uncertainties in the assessment method and data, and the more optimistic stock status in Ireland and parts of Scotland, it is proposed that the most acceptable overall action is to limit fishing mortality at its present level. Section 1 discusses some options for doing this, and explores fishing effort data for England & Wales that illustrate some of the underlying issues. The two methods of limiting fishing mortality are control of output (TACs and quotas) and control of input (limited entry licensing, and pot limitation). For the brown crab fishery, SAGB proposes the use of input control, since output 7

9 control raises concerns about the accuracy of calculating and allocating a TAC from existing data, and the scope for misreporting of landings. Limited entry licensing is already in being for shellfish vessels, but there is latent capacity in the form of shellfish entitlements that are not yet taken up. This is an issue, since it is difficult to envisage potters accepting a pot limitation scheme unless latent capacity is also eliminated, although the latter may be difficult to achieve for policy or financial reasons. The advantages and disadvantages of the following pot limitation options are described:- 1. Freezing the existing pot number for each vessel (no reduction in pots required), 2. Setting a single maximum for all vessels, possibly with a reduction to be reached after a grace period, 3. Setting a maximum number, but with different maxima for different regions, or inshore and offshore vessels, or for specific metiers (under 1 m vessels, large vivier vessels, inside or outside SFC limits or the 12 mile limit). 4. Setting individual vessel pot numbers by bands based on, for example, vessel length. The retention properties of the parlour pot have greatly favoured the expansion of pot numbers in both coastal and offshore waters, but this gear has becomes so widespread in England & Wales that SAGB considers a parlour pot ban would be too controversial, unless phased in over a very long sunset period. Pot number relationships were analysed using data from Defra, CEFAS log books, and SFCs, to illustrate some of the issues associated with choosing a pot limitation option. 1)The relationship between crab landings and pot hauls was examined using Defra data for 2-28 for all areas combined. There is a positive relationship, showing why scientists are concerned about increased effort, and why they favour pot limitation. Comparable data for CEFAS log books in 1995, and from Cornwall SFC from are also described. 2) LPUE versus pot hauls was examined using Defra data for 2-28 for all areas combined, and for South Wales SFC. Scatter in the Defra LPUE data makes it difficult to see if LPUE declines as effort increases, but in South Wales, LPUE, though very variable, is independent of effort at the higher levels of effort. The strong decline of LPUE at high effort levels found in Ireland is not found in these data. 3) The proportion of the fleet fishing different pot numbers was examined using Defra data for 2-28, for pot groupings from 1-5 pots up to 1+ pots. In each year the proportion of vessels fishing more than 1 pots is low. In principle these data could be used to identify a maximum pot number that contains most of the effort, but it would be preferable to use data for pots set rather than pots hauled. 4) Potting effort versus vessel length in metres was examined using Defra data for 2-28 (pot hauls), CEFAS Log Book data from 1995 to 27 (pots set), Devon SFC (pots owned), and the States of Jersey (pots owned). Despite scatter in the pot number data the relationship between pot number and vessel length is good and consistent over time, and fairly similar between data sets, suggesting this is a useful way of illustrating the features of different potting fleets. In setting a limit there is an issue whether to use the average pot number at each vessel length, or the most extreme upper limit at that length, since this clearly affects how many potters would need to reduce below any chosen limit. 8

10 5) Data for pots set versus pots hauled were examined using CEFAS log books for the English east coast, and data from the South Wales SFC permit scheme. The number of pots set is invariably higher than the number of pots hauled, and is therefore the statistic most useful in setting a pot limit (although pots hauled usually feature most in the Defra data base because that is what is reported on the day of landing). The administration of a pot limitation scheme requires the authorities to issue fishers with a permitted number of tags for identifying their pots, and to make arrangements for replacing these in the event of legitimate losses due to weather or the activity of mobile gears. As there is a cost to these tags, a decision is required how these tags should be administered and paid for. To illustrate the likely scale of the problem, the report concludes with an incomplete and anecdotal list of pot numbers for some SFCs for which this information was most readily available. Caveats The priority in this report is the capping of fishing effort in the brown crab fisheries. It is appreciated that many potters also catch lobster and velvet crab at the same time, and target these species at other seasons, but there has been insufficient time to describe the assessment results for these species, or to explore the mixed fishery aspect. It has also not been possible to undertake new research or assessments, such as those required to illustrate the implications of changes in minimum landing size. 9

11 Introduction Since 2, the Shellfish Association of Great Britain has been promoting the development of a policy to cap fishing effort on the stocks of brown crab (Cancer pagurus, L.) around Great Britain. The initiative originated from discussions at the SAGB Crustacean Committee, where members regularly voice concerns that increased potting effort will overfish the resource, and that the economic viability of the crab fishery is being threatened by oversupply and reduced prices. The SAGB goal is to ensure that brown crab stocks are fished sustainably and profitably under a management framework that will enable crab fisheries to achieve sustainability accreditation in the future. Brown crab management has been discussed on several occasions over the last few years, and in 26-7 Defra held an informal consultation on a range of possible measures. Defra is now planning a new consultation later in 29. This report, which has been compiled with the knowledge of Defra and the support of the European Fisheries Fund (EFF), aims to provide a resource that summarises the principal discussions and policy positions to date, reviews current knowledge on the fisheries and the science, and prepares the ground for the discussion of a pot limitation scheme. The report has been written almost exclusively from the brown crab viewpoint, although it is fully understood that many potting vessels fishing for brown crab also fish for lobster, velvet crab, and in some areas spider crab, at different times of the year. The Report is in four main parts: Part A: Policy Background Part B: Fisheries and Science Part C: Effort Limitation Annex 1: Figures, Charts & Diagrams Authorship and caveats The author is a former fisheries scientist and senior advisor on the management of shellfisheries and finfisheries at CEFAS Lowestoft. The report is written in his capacity as a scientific advisor to the Director of SAGB, and as the current chair of the SAGB Crustacean Committee. The report summarises what can be assembled from existing sources without starting major new research. It uses existing publications and presentations; material from meetings attended by SAGB; and draft data and reports kindly made available by agencies and individuals, whose help is gratefully acknowledged. The interpretation of this material is the sole responsibility of the author, and does not represent any binding statements or commitments on behalf of Departments, Agencies, Associations or individuals. Readers wishing to refer to this material are therefore kindly requested to clear lines with the author, either in writing or by (rcabannister@yahoo.co.uk). N.B. The Report is written as a text section, and a separate Annex containing Figures 1 to 42. A number of printed copies of the Text and Figures have been made available to key bodies and individuals, but.pdf versions have also been made so that they can be circulated more widely in electronic form. Please contact Dr Tom Pickerell, Director of SAGB, Fishmonger s Hall, London Bridge, London EC4R 9EL. 1

12 Acronyms and Symbols BIM Bord Iascaigh Mhara (Irish Sea Fisheries Board) B lim, B pa Limit biomass, precautionary biomass CEFAS Centre for Environment, Fisheries and Aquaculture Science CL, CW Carapace length, carapace width Defra Department of Environment, Food and Rural Affairs EPR Egg production per recruit F Fishing mortality rate Fmax F at the maximum on the yield per recruit curve ICES International Council for the Exploration of the Sea K Growth equation coefficient L inf Maximum length in the growth curve LPUE Landings per unit fishing effort (nominally proportional to stock abundance) M Natural mortality rate MLS Minimum landing size NFFO National Federation of Fishermen s Organisations nm Nautical mile SAGB Shellfish Association of Great Britain SFC Sea Fisheries Committee YPR Yield per recruit 11

13 Contents ABSTRACT 1 EXECUTIVE SUMMARY 2 INTRODUCTION 1 ACRONYMS AND SYMBOLS 11 CONTENTS 12 PART A: POLICY BACKGROUND 14 Section 1 Previous Meetings and Viewpoints Chronology Defra shellfish licensing meeting in International Brown Crab Workshop, Fishmonger s Hall, London, June Defra Discussion Paper on Limiting Brown Crab Exploitation, November NFFO Policy Paper on Crab and Lobster Management, February Defra Expert Workshop on Pot Fishery Management, September The current SAGB Position, Selected comments for some Sea Fisheries Committee areas 19 PART B: FISHERIES AND SCIENCE 21 Section 2 Current Sources on Brown Crab Citations of existing publications and presentations New Sources Section 3 Brown Crab Fisheries Location and scale Landings by ICES Statistical Rectangle Sample VMS data for large potters (England & Wales Vessel sizes and fishing areas (England & Wales) The proportion of potting within SFC limits 25 Section 4 Stock structure Distribution of brown crab larvae Tagging Genetic studies Conclusions on stock structure References 29 Section 5 Fishery Trends for England & Wales Defra data for regional and district landings Landings per unit effort (LPUE) from CEFAS Log Books LPUE from Sea Fisheries Committee data Summary 33 12

14 Section 6 Stock assessments for England & Wales Methodology Size distribution inputs Maturity and egg production Assessment results for Central N Sea and Western Channel Assessment results for all areas The effect of assumptions Lobster assessments References 38 Section 7 Fishery Trends and Assessments for Scotland Total and regional landings Stock abundance Stock assessment Conclusions 41 Section 8 Fishery Trends and Assessments in Ireland Trends in landings and effort Stock abundance Size distribution and maturity Stock assessment Other coastal fisheries in Ireland Economics 43 PART C: EFFORT LIMITATION 45 Section 9 Stock status and management Landings Fishing effort Stock structure and genetics Stock assessment Conclusions for management 46 Section 1 Capping effort Managing inputs Number of vessels Pot limitation options Pot type Analysing pot number data for England & Wales Conclusions Pots hauled, or pots set Pot tags, and their replacement Mixed fisheries 54 Acknowledgements 55 ANNEX 1: FIGURES, CHARTS & DIAGRAMS 56 13

15 PART A: POLICY BACKROUND Section 1 Previous Meetings and Viewpoints 1.1 Chronology The following principal meetings or discussions were held on brown crab during the last decade: 2 Defra shellfish conservation meeting: discussed possible pot limit 25 International Crab Workshop at SAGB. Major review of crab management 26 Defra Discussion Paper on Limiting Brown Crab Exploitation 27 NFFO Shellfish Committee paper on crab and lobster management 28 SAGB Crustacean Committee discussions on effort limitation 28 Defra expert workshop on crab & lobster measures & priorities 28/9 Transnational stakeholder meetings (Edinburgh, York, Dublin) 29 SAGB meeting (January) with Defra officials 29 Defra meeting (May) with SAGB & NFFO: Consultation preview The main outcomes are summarised below. 1.2 Defra shellfish conservation meeting in 2 A Defra conservation meeting on shellfish discussed the need to limit entry to the pot fisheries by licensing and setting a pot limit. Discussions on the latter included a possible upper limit of 125 pots per vessel, but this was not taken any further. 1.3 International Brown Crab Workshop at Fishmonger s Hall, London, June 25 The workshop was chaired by the author, and attended by representatives from England, Wales, Scotland, Northern Ireland, Ireland, France, and Channel Islands. It included catchers, processors, scientists, association representatives, national officials, and an observer from the EU (DGXIV). Points raised by the industry: Pot numbers and costs were rising in many crab fisheries There was increased competition for space on the grounds The crab market was limited, and threatened by other products Periodic oversupply was reducing prices and hence profitability Conversion of latent capacity to new effort was seen as a threat Potters resented the landings of crab and crab-claws by netters and mobile gear Prices were affected by variable quality, and the landing of soft-shelled crab 14

16 Points raised by scientists: For the new offshore pot fishery in NW Ireland, Dr Tully (BIM) showed that the index of stock (LPUE, landings per unit effort) was declining rapidly as pot number increased, but that potential egg production did not appear to be threatened. For England & Wales there were data difficulties, but despite these, CEFAS assessments showed that stocks appeared to be fully exploited, and that recruitment appeared to be stable. Existing management measures on brown crab: EU regional minimum landing sizes, and a maximum permitted weight of crab claws EU Western Waters effort regulation UK shellfish licensing, and by-catch limits Various SFC byelaws (including bans on the use of crab for bait in three SFC districts) Regional pot limit in northern France, plus a parlour pot ban in Brittany Pot limitation was then under discussion in Jersey Key conclusions were: Higher effort will not produce long term benefits It is desirable to cap effort to prevent overexploitation in the future There was no consensus on how to achieve this, despite prolonged discussion Joint stocks (e.g. between UK & France in the Channel, and between NW Ireland and W Scotland) need joint action Officials from UK and Ireland expressed willingness to develop appropriate actions. 1.4 Defra Discussion Paper on Limiting Brown Crab Exploitation, November 26 Following an article in the Defra magazine FISHING FOCUS, Defra circulated a Discussion Paper describing trends in the brown crab fisheries in England & Wales, and seeking industry views on the following range of crab measures: 1. Maximum vessel size of 7m within 3 miles 2. Limit number of pots fished: single absolute limit, or set at individual current level? 3. Pot limits for different licence types or vessel sizes e.g. 3 pots per crew member 4. Initial pot limit of, say 25, decreasing to, say, 125 over a grace period 5. Introduce sunset clause to remove unused shellfish licences 6. Increase EU regional MLS s by 1 mm in steps 7. Ban parlour pots or pot locks (replacements fundable under EFF) 8. Legislate to improve quality control 9. Ban the landing of cripple crabs 1. Reduce or ban the landing of crab claws 11. Introduce TACs and quotas based on a reference period 12. More or larger closed areas for potting 13. Closed seasons to protect spawning or soft-shelled crab 14. Legislate to reduce ghost fishing 15

17 There were 81 responses as described in the following table, based on information provided at an informal meeting between Defra and SAGB in June 27. Option Yes No Interpretation 1, vessel size inshore 13 4 Strongly disagree 2,3,4 pot limit Slight majority 5, licence sunset clause 9 14 Disagree 6, increase MLS 31 5 Strongly agree 7, ban parlour pot 5 35 Strongly disagree 8, improve quality control 15 2 Agree, but not by legislation 9, ban landing cripples 9 8 Slight majority 1, ban landing claws 22 3 Strongly agree 11, TACs and quotas 9 15 Disagree 12, closed areas 9 7 Slight majority 13, closed seasons 4 8 Disagree 14, address ghost fishing 5 3 Slight majority 61 respondents declared their operating areas as: S West (3), Wales (1), North East (7), E Channel (5), Channel Islands (3), I of Man (2), Eire (1), Northern Ireland (1), Scotland (1), so the replies were regionally biased. Summarising, there was Strong support for an increase in MLS, a ban on landing crab claws, and improving quality control (but not by legislation) Slight majority for pot limits (but concerns about what limit, what basis, and enforcement issues), closed areas, anti-ghost fishing measures, and banning cripples Opposition to TACs, licence sunset clause, and closed seasons Strong opposition to a parlour pot ban, and an inshore vessel size limit 1.5 NFFO Policy Paper on Crab and Lobster Management, February 27 NFFO Shellfish Committee took the following position on the management of brown crab and lobster: Strongly opposed to national pot limitation, on enforcement grounds Support for higher regional MLS on crab, but the status quo on crab claws Opposed to licence sunset clause, TACs, and legislation on quality control Support for incremental increase in lobster MLS to 9mm Berried lobster ban to be parked until after lobster MLS has been increased 1.6 Defra Expert Workshop on Pot Fishery Management, September 28 Defra and MFA met invited experts from SAGB, NFFO, CEFAS, Eastern SFC, and Natural England. 16

18 After discussion it was agreed that: it is desirable to improve the management of brown crab and lobster fisheries, this requires national and EU legislation, subject to CEFAS producing supporting data on the distribution of the fisheries relative to the 6 mile limit. Brainstorming sessions on a wide range of measures agreed the following priorities: For brown crab For lobster Cap effort by pot limitation (but there are serious questions about enforcement and the limit to be chosen ) Remove latent capacity (but there are issues of legality, fairness, and cost) A higher MLS can probably be implemented most quickly, but this does not prevent effort from increasing. Regional differentials should be respected, but there was concern about re-visiting the low MLS for the small-crab fishery in E Anglia ( Cromer crabs ). Increase MLS to 9mm Carapace Length (CL) in steps, possibly with a maximum size A berried lobster ban was supported by SAGB and the Eastern SFC (The SFC has a berried lobster byelaw, and had used an enforcement tool successfully in a recent prosecution). NFFO asserted that it will be harder to enforce a berried ban than an MLS, and that because current lobster recruitment is good two measures are not needed. Other measures considered but rejected Maximum landing size for crab (could be undermined by landing crab claws) Quality restrictions (should be implemented by the market, not by legislation Parlour pot ban (parlour pots are essential for retaining lobster, and for leaving pots out in bad weather, or for protecting grounds from mobile gear) Spatial closures (have potential, but there is insufficient knowledge at present, and the benefits of closed areas are usually hard to measure). 1.7 The current SAGB Position, 29 A detailed account of the SAGB position on the pot fisheries was sent to Defra in January 29. The following is an updated overview of this position: General Considerations SAGB reiterates all the concerns listed at the 25 Workshop about the effects of increasing pot number on future sustainability of the brown crab resource, the effect of oversupply on the market and price, and the combined effect of these factors on economic viability of the potting industry. Higher effort may generate a short term gain for a few, but threatens the future viability of all. The priority is to prevent overfishing now, rather than wait for crisis management later, i.e. accept a cap on effort now, to avoid harsh cuts later. This approach is compatible with the Defra 227 Vision of sustainable use of resources. 17

19 In the future, major buyers will favour shellfisheries that obtain sustainability accreditation. SAGB therefore seeks management measures that will facilitate obtaining successful sustainability accreditation in the future. Brown Crab measures: TACs Assessment methods and allocation issues are at present too uncertain to support a TAC and quota approach, which could also cause high grading and under-reporting of landings. MLS Raising MLS, although relatively easy to enforce, does not limit effort, so the benefits could be neutralized if effort goes on rising. There are concerns about the risk of provoking a one size fits all response in Brussels, and about re-visiting the low MLS for the small-crab fishery in East Anglia, which could provoke the loss of this hard-won provision. Capping Effort SAGB seeks a status-quo management regime that limits the number of vessels and the pots that they fish to the current level or to some appropriate equivalent. It is desirable to eliminate latent capacity. Enforcement of pot limits is an issue, yet other administrations cope with this (Canada, France, Jersey, and recently Northumberland SFC). Parlour Pots The growth in potting has been facilitated by the parlour pot, which accumulates the catch by reducing the escape rate (especially of lobster), so that fishers can use longer soak times. They can therefore avoid hauling in bad weather; can work more gear that is hauled less frequently; and can hold ground otherwise fished by mobile gear. SAGB recognises that some fishers are seeking a parlour pot ban, but it is also clear that this gear is now so widespread round the coast, at least in England and Wales, that a ban would be very controversial, unless it could be done using a long-term sunset clause. Crab Claws SAGB supports a significant reduction in the landing of crab claws, especially when this results from the indiscriminate capture of crabs by netters, trawlers and scallopers. Whelk bait The growing use of crabs of all sizes for bait in the whelk fisheries threatens to undermine the management of the crab resource. The SAGB Crustacean Committee has proposed that, in the first instance, a byelaw banning the use of brown crab for bait should be implemented by SFCs that are currently without such a byelaw, but longer term, national action is desirable. Lobster measures: SAGB supports an increase in MLS to 9 mm CL, in steps if necessary, and a berried lobster ban, which has been a major part of lobster management in the very large fisheries for lobster in North America. SAGB accepts that these measures could cause initial losses in catch, but since lobster recruitment is currently good, now is the best time to 18

20 Jurisdiction: implement these measures, rather than waiting for a downturn, when the impact of losses would be greater. Effective management of crab and lobster in British waters requires national and EU measures. SAGB considers that throughout the UK 12 mile territorial sea the same rules should apply to all Member States equally. 1.8 Selected comments for some Sea Fisheries Committee areas Northumberland SFC Landings are fluctuating, and crab prices have been stable for the last 15 years, but fell last year due to poor demand. Northumberland SFC favours limiting the number of pots, and has recently introduced a pot limit of 8, with a pot tagging scheme (Byelaw 15). Fishers with more than 8 pots will have to reduce their number, or fish untagged pots outside 6 miles. North Eastern SFC Fishery officers have practical reservations about implementing a pot limitation scheme because of enforcement issues. The pots used by 15 hobby fishermen in this district must be tagged. This has proved to be onerous to administer and enforce, as the tags alone coast 4-5 pa. North Eastern officers support an increase in MLS. Eastern SFJC Potting effort is high inshore (summer fishery) and offshore (year round fishery). Vessels are changing from traditional cobles inshore and mono-hulls offshore to catamarans, especially offshore. Parlour pots have replaced traditional creels. Beach boats work about 2 pots. The larger <1m boats work on average 1 pots, but two under 1m vessels from Wells are now using 3 pots. Soak time has generally increased from 24 hours to at least 48 hours. Fishery officers favour capping potting effort, and would consider other possible measures e.g. : Use of a Regulating Order to control the number and size of vessels, and the number of pots Introduce VMS for all vessels Implement a licence or permit condition to fish either inside or outside 6 miles on any one voyage, but not both, (to avoid undermining SFC byelaws) Address the use of store pots (which can undermine byelaws) Berried lobster ban Slot sizes for male and female lobsters 19

21 Devon SFC The fishery appears stable, but close to saturation point in terms of the available space for the number of pots deployed. The fishery is also limited by other fishing activity such as trawling. Cornwall SFC There have been relatively few changes to the potting fleet, but catamarans with large working decks are more prevalent, and fish from 3 to 3 n miles off. 9% of pots used are parlour pots with soft eyes, and the remainder are inkwell pots. Soak times have increased from 3 or 4 days to 7-1 days. The state of the crab stock is not yet causing concern, but there is concern over the effect of over supply by vivier potters, especially from the North Sea, and competition from crabs brought in from Ireland and Scotland. 2

22 PART B: Fisheries and Science Section 2 Current Sources on Brown Crab The rest of this report has been compiled from the publications and presentations listed in Section 2.1, and new sources listed in Section 2.2, which were kindly made available following written requests from the author. The help of the agencies, SFCs, and individuals listed at the end of the report is gratefully acknowledged. 2.1 Citations of existing publications and presentations Addison, 24: Buckland Lecture at the SAGB Conference, London.: Science and the Management of United Kingdom Crab Fisheries by Dr J T Addison, CEFAS Lowestoft (see Addison, 29: SAGB Conference Talk Achieving Sustainability and Accreditation for Crab and Lobster Fisheries by Dr J T Addison, CEFAS Lowestoft (See Bossy, 28: SAGB Conference Talk Management of Jersey Shellfisheries, by Dr S Bossy, Fisheries and Marine Resources, States of Jersey. (see Tully et al., 26: The Brown Crab (Cancer pagurus L.) Fishery: Analysis of the resource in Tully O et al., BIM Fisheries Resource Series, No 4, 26. Tully, 28: SAGB Conference Talk Management of the Brown Crab (Cancer pagurus) Fishery in Ireland by Dr Oliver Tully, Bord Iascaigh Mhara. (See New Sources Material supplied via CEFAS Lowestoft CEFAS, 28. Draft Informal Paper: Distribution of crab and lobster pot fisheries in England and Wales, December 28, CEFAS Lowestoft. Defra, 28. Science Directorate Final Report on Research Project MF23, Spatial and temporal genetic structuring of Edible Crab populations. Defra, 29. Selected landings and pot data for the brown crab fisheries of England & Wales, compiled by CEFAS from the Defra Fishing Activity Database. CEFAS, 29. Draft Report: Edible crab stock and fishery status reports 29. In preparation, CEFAS Lowestoft. 21

23 2.2.2 Material from Marine Scotland: Science Mill et al., 29. Crab and Lobster Fisheries in Scotland: An Overview and Results of Stock Assessment. Marine Scotland: Fisheries Research Services, Aberdeen Material from the Sea Fisheries Committees of England and Wales Data and comments from North Eastern, Eastern, Devon, Cornwall, S Wales, SFCs Northern Ireland It is regretted that it has not been possible to include fishery data or assessments for Northern Ireland Scientific Literature Citations for scientific literature used in the text are appended at the end of each section. 22

24 Section 3 Brown Crab Fisheries 3.1 Location and scale Figure 1 (source: Addison, 24) is a schematic representation of crab fishing areas round Great Britain. Table 1 shows the approximate landings from some of these areas. Although incomplete it illustrates the scale of production in the period The total in the Table is t. Table 1. Selected data on brown crab landings Origin Year Tonnes Source England & Wales 27 ca 15 Defra data via CEFAS Scotland 25 ca 1 Mill et al, 29 Northern Ireland 24 Ca 164 Tully et al 26 NW Ireland 24 ca 8 Tully et al 26 Midwest Ireland 24 ca 6 Tully et al 26 S W Ireland 24 ca 1 Tully et al 26 S E Ireland 24 ca 35 Tully et al Landings by ICES Statistical Rectangle NW Ireland, Northern Ireland and West Scotland. Figure 2a (source: Figure 4, Tully et al 26) shows landings in tonnes for 24 from ICES rectangles off NW Ireland, Northern Ireland and West Scotland. Brown crab fishing has developed rapidly off the northwest coasts of Mayo and Donegal, but also occurs in the North Channel and off the West and North coasts of Scotland. In Ireland, fishing also occurs along the south east coast near Waterford and Wexford, and along the south and south west coasts from Kinsale to Valentia (Figure 61 in Tully et al, 26). Scotland Figure 2b (source: Figure 4, Mill et al., 29, ), shows the boundaries of Scottish Creel Fishery Assessment Areas, and the distribution of landings for 26 recorded by the Scottish Fishery Management data base for ICES rectangles round Scotland. Filled circles are landings into Scotland whilst open circles are landings made elsewhere. The main landings are from the South Minch, Hebrides, Sule, Orkney, Papa and Shetland areas. England & Wales Figure 3a (source: CEFAS 28, Figure 1) shows landings in tonnes recorded in 27 by Defra for ICES rectangles round England & Wales. 23

25 The Defra data base combines records for >1m vessels from EU log books, and <1m vessels from shellfish activity records collected under the restrictive shellfish licensing scheme. The main fisheries are in the Channel, along the east coast from Northumberland to East Anglia, especially off the Humber, and off South Wales, North Wales and Cumbria. 3.3 Sample VMS data for large potters (England & Wales) Large potters are nomadic, catching crabs on a range of grounds through the year, so their activities differ greatly from smaller vessels that fish daily from a home port on a seasonal basis. Figure 3b (source: CEFAS 28, Figure 3) shows where potting vessels > 15 m fished in 26, based on Defra VMS records. The main locations are: Western Channel Fishing occurs off Start Point, across a broad swathe of the mid-channel area, and from north Cornwall to the Scilly Isles. North Sea Fishing occurs off the Humber to the Dogger Bank; off Denmark; and east from Beachy Head. Large potters also fish off the west and north coasts of Scotland, but there is no information for these areas in the CEFAS document. 3.4 Vessel sizes and fishing areas (England & Wales) Figure 4a (source: Addison, 28) identifies the CEFAS assessment areas. Figures 4b, 5a and 5b (source: CEFAS 28, Figures 4-6) show, respectively, vessel number, pot hauls, and landings in 27, broken down by assessment area and vessel size (<1m in red, >1m in green). In Figure 4b the highest number of potting vessels is deployed in the Western Channel, followed in order by the Central North Sea, Celtic Sea, Southern North Sea, Irish Sea and Eastern Channel. Vessels <1m in length are in the majority in all areas. In Figure 5a the number of pots hauled is highest in the Central North Sea and the Western Channel, followed by the Southern North Sea and Celtic Sea, then the Irish Sea and the Eastern Channel. The majority of pots are hauled by <1m vessels. In Figure 5b the highest landings of brown crab are from the Western Channel, followed by the Central North Sea and Southern North Sea, and then the Celtic Sea. Landings from the Irish Sea and Eastern Channel are small. A high proportion of the landings originates from >1m vessels (except in the Irish Sea); effort is therefore dominated by the <1m sector, but crab landings by the >1m sector. 24

26 3.5 The proportion of potting within SFC limits Defra data are allocated to belt (-3nm, 3-6nm, 6-12nm, 12+nm) in the paper records, but not after electronic processing. CEFAS has therefore used vessel size information to estimate the amount of potting within the 6 mile boundary of Sea Fisheries Committees (future IFCAs), since the smaller vessels fish predominantly within 6 miles on a daily basis, and the larger vessels mainly fish beyond 6 miles (CEFAS 28). In Figures 4 & 5 the red and green data therefore imply that total potting effort is higher inside six miles, but that crab landings are generally higher outside 6 miles. When the landings of lobster (Figure 6a, source: CEFAS 28) and brown crab (Figure 6b), are compared on the same basis, the higher effort inside 6 miles generally corresponds to fishing for lobster rather than crab. The estimated proportions of lobster and crab caught within 6 miles in each SFC district are shown in Table 2 (source: CEFAS 28), which is based on the allocation described above, and consultation with SFCs. Table 2. Estimated % of lobster & brown crab landings inside 6 nautical miles (source: CEFAS 28) SFC area % caught inside 6 nm % caught inside 6 nm lobster crab Northumberland 9 8 North Eastern Eastern 8 85 Kent & Essex 5 5 Sussex 9 5 Southern Devon 6 4 Cornwall 55 7 Isles of Scilly 1 1 South Wales 1 95 N W/N. Wales 9 9 Cumbria 1 1 This shows that the most important brown crab fisheries in England & Wales cannot be managed effectively using SFC byelaws alone. 25

27 Section 4 Stock structure Separate management areas can be defined when the fisheries are based on individual populations that are well separated geographically, or show area-specific differences in biology (e.g. growth rate or maturity), or are based on genuinely separate stocks that are genetically different. Elucidating stock structure requires long term data on where adults spawn and release larvae, backed by migration data from tagging, and comprehensive data on genetic differences. The crab data are incomplete but strongly suggest that stock structure is regional rather than local. 4.1 Distribution of brown crab larvae CEFAS data are available for the English east coast and the western Channel, and Irish data for Mayo and Donegal. There are relatively few surveys, but the size and location of patches found so far by CEFAS are similar from year to year, and are at the regional rather than the local scale. English east coast (Figure 7, source: Addison, 24) CEFAS found large patches of brown crab larvae centred off the Humber in July 1976, 1993, and 1999 (only the 199s data are shown here) in the same area as the current fishery for mature hen crab. It is unclear how these larvae relate to the crab caught further north off Yorkshire and Northumberland, or to the south off Norfolk (where crabs are much smaller than elsewhere, Slide 52 in Addison, 24). North of Flamborough the water is stratified, and below 8 o C, at which temperature embryonic development may cease (Lindley 1987, in Nichols et al, 1982). Crab larvae are therefore found further south in warmer mixed water that is suitable for larval development but from where a rapid easterly circulation may carry them far offshore (Slides in Addison, 24). The Channel (Figure 8b, constructed from Addison, 24) CEFAS found brown crab larvae at similar locations in 1989, 22 and 23. In the eastern Channel there were small but dense patches on the French side of the Dover Straits in 1989 & 23. In the western Channel and the Celtic Sea the locations of large patches found in 22 & 23 (Figure 8b) were similar. Few larvae were found mid-way along the Channel, between o W and 2 o W. The western Channel patches occurred south west of Start Point, and further west towards the Hurd Deep. The Celtic Sea patches spread from Lands End north towards South Wales and north eastward towards Trevose. The fisheries that overlap these spawning areas (recall the VMS patches in Figure 3) generally catch both cock and hen crab, but at different times of the year. The best catches are of mature hens caught in late summer and autumn with eggs developing internally but before they have been extruded under the abdomen. 26

28 Ireland Brown crab larvae sampled off the north west coast in 21 were widely distributed from coastal to offshore waters off Mayo and Donegal (Figure 5 in Tully et al, 26), within the purple area shown in Figure 8a (taken from Tully, 28). 4.2 Tagging Most of the usable information on the direction and distance of brown crab migrations originates from tagging experiments carried out in the 197s and 198s (Bennett & Brown, 1983, Edwards, 1979) although some new work is currently being carried out in the Channel using T-bar and data storage tags (Slide 32, Addison 24, Slide 22, Addison, 29). Migration between regions Although no doubt biased by the distribution of fishing effort, the 198s data did not reveal any migratory exchange between the North Sea and the Channel, or between the Channel and the Celtic Sea, thus pointing to regional separation. Migration within regions Tagged crabs showed local and distance migrations. Males and immature females were nomadic over relatively short distances of 2 or so nautical miles, but recaptures of adult females usually indicated substantial directional movement e.g. northward along the east coast from Norfolk to Yorkshire and Northumberland, and from Yorkshire to Northumberland and Scotland (Figure 9, source: Addison, 24). westward from the eastern Channel towards Dorset, and from Dorset to Devon and Cornwall (Figure 1, source: Addison, 24). This is confirmed by the results of new tagging by CEFAS (Slide 22 in Addison, 29). southward from Cornwall and from northern Brittany (also in Figure 1) Contrasting directions of female migration in different regions have led to the interpretation that female migration is contranatant, i.e. an upstream return towards a likely place of birth. It is not clear how well this hypothesis fits with the new information that east coast crab larvae are likely to be carried offshore from the Flamborough front (and therefore at right angles to the historical direction of female migration) or that the Channel is often affected by short-term wind-driven events which cause complex changes in the direction of surface waters that could disrupt larval transport. 4.3 Genetic studies A recent Defra-funded study (Defra 28) analysed the genetic structure of brown crab samples from 32 locations around the North Sea, Channel, and Ireland (Figure 11, sourced from Defra 28). Some sites were repeated a few years apart, whilst larvae from 3 sources, and the progeny of 18 females, were also tested. The genetic markers were microsatellite DNA and mitochondrial DNA (mtdna, which is maternally inherited). Results support the conclusion that stock structure is regional, and they raise inferences about local mating and recruitment patterns in the Channel. 27

29 The main findings are: Genetic diversity is high, suggesting that it has not been affected by fishing. Genetic differences between samples were low, but were sufficient to show that there is a genetic distinction between crab in the Channel, the UK coast of the North Sea, and the Swedish part of the North Sea. There was no genetic distinction between the Channel, Celtic Sea, southern Irish Sea and SW Ireland, but crabs in these areas are distinct from crabs off the north coast of Ireland and in the North Sea. Within regions, samples showed genetic patchiness that was not constant geographically or over time. This reduces the chance of finding local stocks, or of using the genetic signature of larvae to identify their origin. The most distinct samples came from localized bays (e.g. Gulmarsfjord, Sweden; Newlyn and Brittany in the Channel) where local circulation presumably favours a degree of isolation. Genetic patchiness within regions was most marked in the Channel, where the mtdna data showed short-term fine scale patterns that could originate from local variations in reproductive success, or localised recruitment, or male-biased gene flow. In the latter process, male genes are mixed by random mating, but female genes are less mixed, which could occur if females return to their birth site, as tagging results suggest. If biological processes depend on local females, their depletion should be avoided for genetic reasons. The progeny from 18 females showed that each brood was sired by only one male, rather than by multiple males, perhaps because brown crab store sperm for successive fertilizations. Single paternity potentially restricts the number of males than can produce offspring so if this is the norm it is again important to avoid depletion of the female stock. 4.4 Conclusions on stock structure The main conclusions are: Brown crab stocks round Great Britain show high levels of genetic diversity Larval data suggest that stock structure occurs at the regional scale Genetic data show that stocks in the North Sea and the Channel are genetically distinct. There is no genetic difference between crab in the Channel, Celtic Sea, south Irish Sea and SW Ireland, but crab in these areas are distinct from crab off the north coast of Ireland and in the North Sea. There is genetic patchiness within some regions, especially the Channel, but it does not persist over time, and there is no genetic reason for sub-areas to be managed separately. Even so, this patchiness is attributable to local processes linked to hen crabs, which adds 28

30 a genetic reason to recommendations that in order to protect egg production females stocks should not be overexploited. The genetic structure revealed by this study is on a wider scale than the assessment areas that have been adopted in England & Wales and Scotland for other than genetic reasons, e.g. for data collection reasons, or because fishing métiers are associated with groups of fishing grounds or landing places, or because there are local differences in growth rate or size of maturity that may affect the results of assessments, but are not significant genetically. 4.5 References Bennett, D. & C. Brown (1983). Crab (Cancer pagurus) migrations in the English Channel. Journal of the Marine Biology Association of the UK, 63, Edwards, E. (1979). The Edible Crab and its fishery in British Waters. Fishing News Book Ltd, Farnham Surrey, England. Lindley, J.A., Continuous plankton records: the geographical distribution and seasonal cycles of decapod crustacean larvae and pelagic post-larvae in the north- eastern Atlantic Ocean and the North Sea, J. mar. biol. Ass. U.K. 67: Nichols, J.H.,Thompson, B.M. & Cryer, M.,1982. Production, drift and mortality of the planktonic larvae of the edible crab (Cancer pagurus), off the north-east coast of England. Neth. J. Sea Res. 16:

31 Section 5 Fishery Trends in England & Wales This section describes fishery trends in England & Wales. The England & Wales assessments are described in Section 6. Trends for Scottish and Irish fisheries are described in Sections 7 and 8. Section 5.1.describes regional and district landings from Defra sources (Defra, 29). Sections 5.2 and 5.3 describe regional stock abundance from CEFAS and SFC sources. 5.1 Defra data for regional and district landings Annual Defra data (Defra, 29, extracted by CEFAS) were summed for <1m and >1m vessels for regions and districts. Recent data may be boosted by improved collection of <1m data since 26 under the shellfish licensing scheme. Landings into other countries are not included. There has been no quality checking of the data at source. Regional Landings Figure 12 shows trends in annual landings of brown crab, lobster and velvet crab. The graphs are stacked for North Sea, Channel, and West coast ports. In Figure 12a, brown crab landings increased from the 197s up to 2, before starting to decline. The trend is dominated by the Channel fishery, which first expanded in the 197s, followed by an increase in the small West coast fishery since the 198s, and a strong increase in the North Sea since the late 199s. In Figure 12b, lobster landings increased progressively, especially from the North Sea in the late 199s, due to increased recruitment in recent years, and better data for <1m landings. In Figure 12c, velvet crab landings increased on the North Sea coast since 2. District Landings (Figure 13) In the North Sea (Figure 13a) landings increased in Yorkshire, but mainly in Lincolnshire and East Anglia due to the offshore fishery, but have declined since 23. In the Channel (Figure 13b) landings mainly originate in South Devon, but declined slightly in favour of an increase east of Devon and in south Cornwall. On the West coast (Figure 13c) a fluctuating upward trend since 198 originates mainly from North Cornwall and Wales. Crab landings have therefore increased in most areas, but have declined recently on the east coast. 3

32 5.2 Landings per unit effort (LPUE) from CEFAS Log Books The scientific index of stock abundance is the LPUE, landings per unit of fishing effort e.g. kilos per 1 pot hauls, provided that the data collected are fully representative of the fleet, and are not biased by spatial, seasonal or catchability issues. An index based on total landings and total effort from the Defra data base for English pot fishing areas proves to be problematic because of inconsistent recording (especially of the effort data) and because landings are biased towards the larger vessels but effort is biased towards the smaller vessels (CEFAS pers comm.).the alternative is to use data from the CEFAS log book scheme. This provides more consistent records of landings and pots hauled by individual vessels, but covers only a small part of the active fleet, and not necessarily all of the crab fishing grounds. Log book records are shown in Figures 14 and 15 (sourced from CEFA 29). North Sea Figure 14a (Central North Sea) shows LPUE trends for vessels fishing north (solid lines) and south (dashed lines) of the Tyne. Figure 14b (Southern North Sea) compares the LPUE for three vessels in south Yorkshire (solid lines), and three in North Norfolk (dashed lines). LPUE fluctuates without trend north of the Tyne LPUE fluctuates and declines south of the Tyne, in North Norfolk, and in one of 3 records in Yorkshire Eastern Channel: There are no CEFAS log-book records for this area. Western Channel and Western Approaches Figure 15a shows the trends for 5 western area crabbers LPUE is stable in 4 records from 1992 to 24, then declines One record is parabolic, and difficult to interpret Celtic Sea: there are no records for this area. Irish Sea Figure 15b shows 3 records of very different duration and trend that do not provide any coherent picture 5.3 LPUE from Sea Fisheries Committee data Northumberland SFC There were pot hauls in 25 (last year of permit data), landing kg of brown crab (= 1.55.kg per pot haul), and pot hauls in 28 (Defra data) landing kg of brown crab (= 1.44 kg per pot haul). A stable LPUE in this period is consistent with Figure 14a. 31

33 North Eastern SFC LPUE data kindly made available by the SFC for 2-25 are shown in Tables 3 and 4 for inshore and offshore components of the fishery (inside and outside 6 nm). Table 3 Inshore Year Pots Pot days Tonnes LPUE (millions) Kg/pot day Inshore, the total numbers of pots has risen from 54 to 735, and total pot days have increased from 11.9 to 14.9 million pot days. Recent crab landings increased up to 24, then fell in 25. LPUE (Kg /pot day) increased up to 23 but then decreased. Table 4 Offshore Year Pots Pot days Tonnes LPUE (millions) Kg/pot day Offshore, the number of pots has fluctuated between 12 and 22. Total pot days, landings and LPUE have all varied but without trend. These records are more stable than those in Figure 14b. Brown crab LPUE is higher offshore than inshore, probably because inshore effort may target lobster more effectively whereas offshore effort targets brown crab more effectively. Cornwall SFC Figure 16 shows the trends in crab landings and LPUE from and Landings peaked in 22-4 and then declined, but LPUE (kg per 1 pot hauls) shows an upward trend that is not consistent with Figure 15a presumably because of spatial differences. South Wales SFC Figure 17 shows the long term trend in pot-hauls, landings, and LPUE (kilos per 1 pots hauled) for the South Wales Sea Fisheries Committee district, calculated from permit scheme data. In an expansion phase of this fishery from 198 to 199, effort, landings, and LPUE followed a similar trend, increasing several fold, before stabilizing from 199 to Since then, effort has 32

34 fluctuated widely but without trend, whereas landings halved from 1997 to 2, then fluctuated at the lower level. Since 1996 the combination of high effort and lower landings has sharply reduced LPUE to a level last seen in the 198s. It is not clear if this decline is due to a change in the brown crab stock, or in targeting, or whether the catchability of brown crab has been reduced by an increase in the catch rate of spider crab in recent years (P.Coates, pers comm.). 5.4 Summary Defra data show that in England & Wales, brown crab landings originate mainly from the western Channel, East Anglia, and Yorkshire. Fisheries have expanded onto new grounds offshore, starting in the Channel in the 197s and 198s, and in the Yorkshire and East Anglia fisheries in the 199s. Since the 198s, landings in the western Channel have fluctuated without trend, but on the east coast landings increased from the 199s to reach a peak in 23, but have since declined steeply. CEFAS experience shows that potting effort recorded in the Defra data base presents problems owing to incomplete coverage, and inconsistent recording and processing. Trends in stock abundance in the form of brown crab LPUE are therefore best examined using data for individual vessels from the CEFAS Log Book scheme, although the number of records available is very limited. Log books for the east coast fisheries show considerable variation in LPUE, but overall there is either no trend, or a slight downward trend, until after 23, when LPUE declines more steeply in several of the records. In the western Channel, brown crab LPUE in 4 out of 5 log book records fluctuates without trend between 1994 and 24, but then declines. LPUE data were also examined from several SFCs, where available. Data for North Eastern SFC for 2-25 shows that the number of pots and pot days has increased, but that landings and LPUE have fluctuated without trend. In Cornwall SFC, brown crab LPUE has increased gradually since In South Wales SFC, LPUE increased from 196 to 1987, then fluctuated without trend up to 1999, before declining steeply to 26, reaching a level similar to that last observed in 1985/6. 33

35 Section 6 Stock assessments for England & Wales CEFAS has recently assessed the brown crab stocks in the assessment areas defined in Figure 4a. This section is based on a pre-publication draft report on these assessments (CEFAS 29, hereafter called the CEFAS Report ) use of which is gratefully acknowledged. 6.1 Methodology The jargon name for the model used in the CEFAS (and the Scottish and Irish assessments) is length cohort analysis, whose inputs and outputs are described below. Size data inputs Because crustacea cannot be aged routinely, the assessment starts with the size distribution of crabs in the landings, derived from sampling at the ports by the Marine Fisheries Agency and CEFAS. Sample size data were compiled for each assessment area, raised to total annual landings for the area, and averaged for the last three years to reduce variability. The sexes were assessed separately. Fishing mortality, F. The model calculates the rate of depletion on each size class due to fishing (harvest rate, or fishing mortality, F, in the scientific jargon). Output from the model is a graph showing F on each size class ( F-at-size array ). Growth and natural mortality The model uses growth data to convert the decline in numbers at size to the decline in numbers over time, with an adjustment for the underlying natural death rate. The natural mortality rate is not known but is assumed to be 1% (M=.1 in the scientific jargon). CEFAS also used an alternative 2% assumption, which has been omitted here for simplicity. (Assumptions in this process are unavoidable. They are akin to those made when navigating by dead reckoning : they are not perfect, but are the best available when information is unknown). The growth parameters are shown in Table 5, together with those used in the Scottish assessments described in Section 7. Other inputs to the length cohort analysis are fully tabulated in CEFAS 29. Table 5: Growth parameters and natural mortality used for brown crab assessments. Growth parameters Length-Weight relationship Mortality Source K L (mm) a b M England & Wales CEFAS 29 Male ,.2 Female ,.2 Scotland Mill et al, 29 Males Females Shetland Tallack Males Females

36 Yield per recruit and egg production per recruit The model uses the current F-at-size array to predict how the size distribution, catch ( yield ) and potential female egg production will change if the F array increases or decreases. Output is a yield per recruit curve (YPR), which shows how yield changes as F changes, and an egg production per recruit (EPR) curve, which shows how EPR changes as F changes. The outputs are plotted as absolute values, or as proportions of the values at current F, but EPR is usually expressed as a ratio of the EPR at zero fishing ( %virgin EPP ) to show the proportion of virgin egg production lost due to fishing. The term per recruit means that the model uses the same number of young crab entering the smallest size class, even at the highest F, since we do not yet know what high value of F will affect crab recruitment. Reference points The aim of an assessment is to show whether or not the current fishing rate is sustainable. In this report this is assessed by comparing the YPR and % virgin EPR at the current F, to the following reference values used in the CEFAS Report, based on suggestions in the literature (see below): Fmax = the fishing mortality at the maximum on the YPR curve 25% of virgin EPR = candidate target or precautionary reference level 1% of virgin EPR = candidate limit reference level The word candidate is used because reference points have not been agreed formally for crab and lobster fisheries in Europe, although Fmax is a universal standard in fisheries science, and the EPR reference points have the same aim as the biomass reference points (B pa and B lim ) used for finfish stocks in the EU. To be precautionary using these candidate reference points, stocks should be maintained above 25% virgin EPR, and definitely NOT BELOW the 1% virgin EPR level (In the USA, a fishery where EPR is below 1% of virgin EPR is called overfished by definition). The basis for EPR reference points was examined by Goodyear (1989), Clark (1991), and Mace & Sissenwine (1993). A comparable approach is adopted for brown crab in Ireland by Tully et al (26), as described in Section Size distribution inputs (Figure 18) Figure 18 (source: the CEFAS Report) shows the size data in two contrasting crab areas. Central North Sea, 23-28, Figure 18a Hen and cock crab are caught in similar numbers. The overall range is 13mm - 21mm CW, but the most frequent (modal) size is 13-14mm for cocks and 13-16mm for hens. Size frequency is fairly constant over time. Western Channel, 23-28, Figure 18b The catch is mainly hen crab. The overall range is 14mm 25mm CW, and the modal sizes in both sexes are 16mm-19mm. Size frequency is similar over time. Size plots for all of the assessment areas can be found in the CEFAS Report. 35

37 6.3 Maturity and egg production (Figures 19, 2) Figure 19 (source: Addison, 29) compares the size of crab landed from the Western Channel and Southern North Sea to the curve of crab maturity versus size. Most crab landed from the Western Channel, and many from the Southern North Sea, should be mature and could have spawned before capture. Figure 2 (source: CEFAS 29) shows how the number of eggs produced by hen crabs ( fecundity ) varies with size (from.5 million at small sizes up to 3.5 million at 2mm CW). Hens larger than 2mm CW will produce even higher numbers. This is much higher than the number of eggs produced per female lobster for example (thousands), and should give brown crab populations some resilience to the effects of exploitation, although because brown crab eggs are smaller than lobster eggs they probably have a lower survival rate. 6.4 Assessment results for Central N Sea and Western Channel These results are discussed separately in order to explain the nature of the output. Results for all assessment areas are tabulated later in Section 6.5. Central North Sea (Figure 21) Figure 21a shows how fishing rate, F, varies by size class for each sex. Female F increases up to in the largest sizes. Male F increases up to.8 at 16mm CW, but then fluctuates in the range.4 to 1.2 for the larger sizes. The variability in the larger sizes probably stems from sampling variability in the input data. Mathematically, the F values shown are written as instantaneous rates, the highest of which represent depletion rates of 6-7% per annum (similar to that on North Sea cod a few years ago). Figure 21b shows curves for YPR (convex) and % virgin EPR per recruit, (concave) plotted against F (scaled as the proportion below and above the present F). Present F is well beyond Fmax (that giving maximum YPR). To achieve Fmax would require a large (7%) reduction in F. At the present F, EPR (the dotted concave curve) is below the lower horizontal line depicting 1% virgin EPR. In the USA this would be defined as overfishing. (N.B. CEFAS assessments also calculate the number of male and female spawners per recruit (SPR), again as a percentage of the virgin population. This produces two other concave curves shown as solid lines in Figure 21b, which are compared to another reference point (35% of virgin spawner per recruit). These results are discussed in CEFAS 29, but, for simplicity, not here. On this evidence, crab in the Central North Sea could be called overfished: F is very high on both cock and hen crabs, which are exploited beyond maximum sustainable yield per recruit, and % virgin egg production per recruit is below the limit reference point. 36

38 Western Channel and Western Approaches (Figure 22) Figure 22 shows results for F against size, and for YPR and % virgin EPR against F. In Figure 22a, female F increases up to.7 at 18mm CW and then stabilises. Male F increases to.3 at 17mm CW, then declines slightly. Male F is equivalent to a moderate 25% harvest rate, but female F is equivalent to a 5% harvest rate (less than the North Sea, but still high) In Figure 22b, male F is close to Fmax, but female F is well beyond Fmax. As in the North Sea, % virgin EPR (dotted line) at the present F is below the 1% reference point. On this evidence, this fishery is fully exploiting cock crabs but overfishing hen crabs. Sample results in tabular form Figure 23 shows the previous results in numerical form, to pave the way for Figure 24, which tabulates the results for all assessment areas. These are the author s interpretation of results cited in the CEFAS Report. Left hand column: The highest F on each sex (from the graph of F against size class) Central columns: these show whether current F is above or below F max, and the % change in F required to attain F max. Right hand columns: for females only, these show the % virgin EPR at the present F compared to the 25% and 1% EPR reference values, and the cut in F required to reach the reference values. 6.5 Assessment results for all areas (Figure 24) Figure 24 tabulates the CEFAS assessment results for all areas, in the same style as Figure 23. The main conclusions are: Current F is above Fmax in all cases except cock crab in the western Channel. The cut in F needed to attain Fmax is %, depending on the area In all fisheries, current EPR is below the 1%virgin EPR limit reference level, and well below the precautionary (target) 25% virgin EPR reference level. The cut in F to attain the 1% limit level ranges from 12-56%. The cut in F to attain the 25% target level ranges from 69-84% Therefore, subject to the caveats mentioned below, it is concluded that: Brown crab stocks in the CEFAS assessment areas are either exploited at Fmax (cock crab in the western Channel) or beyond Fmax (growth overfishing: hen crab in the western Channel, and all other fisheries and sexes), 37

39 Percentage virgin egg production per recruit in all areas is below candidate limit and target reference levels. If the candidate reference levels had been formally adopted, the fisheries would all be classed as overfished from an egg production viewpoint, and all but cock crab in the western Channel would be growth overfished relative to Fmax. 6.6 The effect of assumptions. The estimates of fishing rate, F, and the shape and elevation of the yield per recruit and egg production per recruit curves, depend on the input data, especially the growth equations, and on the assumption about natural mortality M. For example, the draft CEFAS Report shows that if M is 2%, instead of 1%, some results will be less pessimistic, and some stocks would be judged fully exploited instead of overexploited.. Figure 24, based on M=.1, is therefore a precautionary scenario. The choice of M does not affect the conclusion that an increase in F will not produce long term benefits: increasing F will intensify overfishing in the low M scenario, and will increase the risk of overfishing in the high M scenario. The minimum advice is the same: do not increase F above the present level. 6.7 Lobster assessments The CEFAS Report contains assessments for lobster, but these have not been described here. 6.8 References Clark, W.G., Groundfish exploitation rates based on life history parameters. Can. J.Fish. Aquat. Sci., 48, Goodyear, C.P., Spawning stock biomass per recruit: the biological basis for a fisheries management tool. ICCAT Working Document, SCR/89/82, 1pp. Mace, P.M. and M. P. Sissenwine, How much spawning is enough? In: Risk evaluation and biological reference points for fisheries management. Edited by S.J.Smith, J.J. Hunt,and D. Rivard. Can. Spec. Publ. Fish. Aquat. Sci. 12, pp

40 Section 7 Fishery Trends and Assessments for Scotland Section 7.1.describes total and regional landings in Scotland Section 7.2 summarises recent draft regional stock assessment results from Mill et al, 29 (hereafter called the Scottish Report ), use of which is gratefully acknowledged. 7.1 Total and regional landings Figure 25a (source: Scottish Report) shows the trend in total landings of brown crab into Scotland, with landings of lobster and velvet crab for comparison. The data originate from sales notes, EU logbooks, and shellfish forms collected by Marine Scotland: Compliance (formerly the Scottish Fisheries Protection Authority) plus data on crabs caught in Scottish waters but landed in Northern Ireland and Ireland. Brown crab landings have increased steadily since 1975 to reach an all-time high in 26 (the most recent data available). Velvet crab landings increased from , then varied with little or no trend. Lobster landings have varied with little or no trend. Figure 25b shows brown crab landings from each assessment area (X denotes landings from outside the main assessment areas). The main increases in landings originate from South Minch, Hebrides, Sule, Papa and Orkney. Traditionally, Scottish creel fishing has been an inshore activity carried out mainly by boats <1m, but the fishery now includes mobile vivier vessels up to 18m.in length. Effort data are not available in the Scottish fisheries. The Scottish Report notes that inshore boats are working up to 5 creels in strings of 2-3, and vivier boats up to 15 pots in strings of up to 1, but it is not known how many creels, parlour pots, and inkwells are in use at the present time. A unique feature is the management of the Shetland fishery by Regulating Order. 7.2 Stock abundance Trends in stock abundance, as indicated by LPUE, are not available for the Scottish fisheries Stock assessment Methodology Scottish assessment procedures are similar to those already described in Section 6.1 for England & Wales. Annual catch at length for 5mm size classes derived from Scottish market sampling data was averaged for 22-25, then analysed by length cohort analysis using published growth data (Table 5) and an assumed natural mortality of.1. Shetland data were provided by local 39

41 managers and the North Atlantic Fisheries College. The size distributions found in Scotland are broadly similar to those observed in the English fisheries in the North Sea, and brown crab in Scotland mature at 13-15mm CW, which is similar to the upper end of the maturity size curves shown for England & Wales. The outputs in the Scottish Report are yield per recruit (YPR) against fishing mortality (F), as for England & Wales, but stock biomass per recruit against F is shown instead of egg production per recruit, and candidate reference point values have not been used. The Scottish Report also presents the results of assessments on velvet crab and lobster, but these are not described here. Inputs and results for brown crab Inputs and outputs for 6 examples of the 12 assessment areas are shown in Figure 26 (East, Hebrides and Orkney) and Figure 27 (Papa, Shetland and Sule). The Figures are sourced from the Scottish Report. East, Hebrides, Orkney (Figure 26) This shows size distributions, and curves of yield and biomass per recruit against F for each area. The axes for yield, biomass and F are standardised as proportions of the current values. On the size distribution plots, n = numbers measured, and the numbers in brackets are mean size (CW). Crabs that are sampled range in size from 13-21mm CW, with hen crab somewhat larger than cock crab. Landings are mainly cock crab in East, hen crab in Hebrides, and roughly equal proportions of both sexes in Orkney. Scottish yield per recruit curves are relatively flat-topped, and are similar in all three areas. For hen crab, current F (solid vertical marker line) appears to be fairly close to Fmax, but for cock crab F is well beyond Fmax (approximated by the dotted vertical marker line). At current F, biomass per recruit is substantially lower than at lower F values. Therefore hen crabs are at least fully exploited, and cock crabs appear to be overexploited. Papa, Shetland, Sule Figure 27 Crabs in the landings sampled from Sule and Papa have a greater mean size (and maximum, up to 22 mm) than at Shetland. Papa and Sule are mainly hen crab fisheries, but in Shetland hens and cocks are caught in equal proportions. YPR curves are flat topped, and in all three areas current F is at or close to Fmax for both sexes. At current F, biomass per recruit is substantially lower than at lower F values. It should be noted that the Shetland assessment uses a higher M (See Table 5) than the other assessments. In these areas crabs are fully exploited. Results for other assessment areas are shown in the Scottish Report 4

42 7.4 Conclusions YPR curves in the Scottish Report show that current F in the principal Scottish fisheries is either at or beyond Fmax. Some fisheries are fully exploited and in others cock crabs appear to be overexploited relative to Fmax. Higher effort will not produce long term gains in yield in any of the fisheries. The shapes of the YPR curves differ slightly from those found in the CEFAS assessments for England & Wales, most probably due to differences in the growth equations. The shape of the Scottish biomass per recruit curves implies that at current F the stocks are significantly lower than they would be at lower F values. This cannot be compared to the depletion of virgin EPR found in English stocks since the CEFAS Report does not present biomass per recruit data, and the Scottish Report does not cite virgin biomass per recruit. Nor can a direct comparison be made between the fishing mortality values, since the Scottish Report does not show the absolute F at size arrays illustrated in the CEFAS Report. 41

43 Section 8 Fishery Trends and Assessments in Ireland Tully et al 26 (hereafter called the Irish Report) give a full account of the development and status of brown crab fishing in Ireland up to 24-5, with emphasis on the north western fishery (located in Figure 8). The distribution of early stage crab larvae in July 21 suggests that the fishery is supported by a single stock, since spawning occurs widely throughout the area, particularly inshore (Figure 5 in the Irish Report). Crab migration is probably linked to this spawning area since crabs tagged on the coast in 21 dispersed to seaward in the autumn, but crabs tagged at the edge of the shelf undertook a counter migration to the east and north east Trends in landings and effort The NW fishery began on a small scale in the 197s, but expanded rapidly in the 198s and 199s when the inshore fleet was modernized and was joined by an offshore vivier fleet. Landings increased from 25t in 199 to 7t in 24, and the number of pot hauls in the offshore fishery increased from 28 in 199 to 1.3 million in 24 (The Irish Report). There was some rationalization during this period because although the number of traps in use increased from 32 to 55, the number of active vessels declined from 153 in 1997 to 65 in 25 (Tully 28). The distribution of fishing is shown in slide 19, Tully Stock abundance Since 1991 LPUE has declined at different rates in various area-season combinations of data described in the Irish Report. In the annual average offshore LPUE (kilos per pot haul) the decline is 5%, shown in Figure 28a (Figure 16 in the Irish Report). The Irish Report proposes that this decline is due to gear competition rather than a decline in stock abundance, since a plot of LPUE against effort for a set of index vessels in the offshore fishery shows that LPUE declines in direct proportion to the increase in pots hauled (Figure 28b, source: Figure 36 in the Irish Report). Such a plot does not prove cause and effect, but it is noteworthy that inshore, where there is less gear, LPUE declines at a lower rate (Figures 42 and 43 in the Irish Report). 8.3 Size distribution and maturity The size of crab in the landings (13mm - 21mm CW, p 31 in the Irish Report) is similar to that for most of the Scottish and English fisheries. Most of the crab in this size range will have had a chance to spawn before capture, since the average size of first maturity is 12mm CW, and all are mature by 14mm CW (Figure 48 in the Irish Report), a range similar to that quoted previously for Scotland. 42

44 8.4 Stock assessment As in England and Scotland, the brown crab stock in NW Ireland has been assessed by lengthcohort analysis, using local data on growth, maturity, and fecundity, and an assumed natural mortality of.1. The state of the stock is diagnosed by calculating egg production per recruit (EPR) as a % of virgin (unfished) egg production. The fecundity data are shown in Figure 28c (source: Figure 49 in the Irish Report). Curves of EPR at F relative to virgin EPR were calculated for minimum sizes of 13mm CW (the legal size limit) and 14mm CW (a market threshold). EPR at current F was compared to two reference levels, a limit level of 2% of virgin EPR (a higher, more precautionary level than the 1% limit used in the CEFAS assessment) and a target level of 35% of virgin EPR, which Tully et al (26) view as a possible proxy for maximum sustainable yield. Figure 28d (Figure 5 in the Irish Report) shows that EPR at current F is above the 2% limit for both minimum sizes, but below the 35% target level. To reach the target level (proxy MSY) requires a 4% reduction in F at the 13mm CW minimum size, and a 1% reduction in F at the 14mm CW minimum size. These results imply that the stock in NW Ireland is less heavily exploited relative to reference points than the stocks in England & Wales, and possibly in Scotland too, although direct comparisons between F in the three assessments cannot be made as the Irish data in Figure 28d are plotted using proportional not absolute values. 8.5 Other coastal fisheries in Ireland The Midwest Fishery Crab from this fishery are landed into Galway and Clare. Landings varied from 4-63 tonnes between 1994 and 24. The fishery is not assessed in the Irish Report. The Southwestern Fishery Crab from this fishery are landed into Cork and Kerry. Landings increased rapidly after 1997 to reach 35 tonnes by 24, originating mostly from within 12 miles of the coast (p 41 in the Irish Report). The Irish Report does not assess the status of the stock. The Southeastern Fishery Crab from this fishery are landed into Waterford and Wexford. Landings increased from 4 tonnes in 1997 to 1 tonnes in 24 (p 38 in the Irish Report). The number of pots increased from 5 in 1996 to 225 in 22 (Figure 59 in the Irish Report). The Irish fishery is mainly inshore, but French vivier crabbers fish offshore in ICES Division VIIg. Crab from the southeastern stock are used extensively as bait in the important whelk fishery off Wexford. The Irish Report does not assess the status of this stock. 8.6 Economics Tully (28) provides an insight into the economic status of the crab fishery in NW Ireland, where total earnings increase in proportion to the total number of pots used (Figure 29a, source: Tully, 28), with an average of 119 Euros per pot. Costs were also proportional to the number of 43

45 pots used (Figure 29b), with an average of 87 Euros per pot, leaving a net profit of 35 Euros per pot (Figure 29c). These data suggest that although the profit margin per pot was 27% of the income per pot, the absolute value is relatively modest, and in terms of gross income it seems fairly obvious why the fleet has tended towards fishing fewer vessels but more pots. 44

46 PART C: EFFORT LIMITATION Section 9 Stock status and management This section provides a stand alone summary of the previous sections, and makes a management recommendation. 9.1 Landings Landings of brown crab have increased markedly in many fisheries, whether starting in the 197s and 198s (western Channel), or the199s (English east coast, several fisheries west and north of Scotland, and the Irish fisheries). In the last five years landings in individual fisheries have tended to peak, then decrease, partly because there are few new crabbing grounds to explore, partly because the market has become oversupplied. 9.2 Fishing effort It is widely acknowledged within the industry that potting effort has increased due to modernisation of traditional inshore fleets advent of large mobile vivier crabbers extension of the fisheries to offshore grounds more pots being fished. A major problem in shellfish science is the lack of effort data of sufficient longevity and quality to validate what seems to be self evident on the ground. To remedy this requires much more research into the patchwork of existing data, and more robust quality control of data collection by the agencies, than appears to be possible with current resources. Nevertheless, the results of recent assessments described earlier in this report, and summarised below, show that a precautionary approach to crab management can be justified on the basis of existing data. 9.3 Stock structure and genetics Larval distributions and tagging suggest that stock structure in brown crab is regional rather than local. This is supported by recent genetic studies, which show a genetic distinction between the North Sea and the Channel, but not between the Channel, Celtic Sea and southern Ireland. The relatively high degree of genetic diversity implies that the stocks are healthy, and the low genetic differences within regions means that scientists and managers can define management areas based on administrative or geographical convenience, similarity of métiers, or regional biological differences that affect assessment outcomes, without violating the genetic structure. 45

47 9.4 Stock assessment Current stock status has been assessed for the main fisheries in England & Wales, Scotland, and N W Ireland. Fishing mortality at size, estimated from the size distribution of the landings, has been used to generate yield per recruit and egg per recruit curves for comparison with reference points (England & Wales, NW Ireland), or yield per recruit and biomass per recruit curves (Scotland). The principal conclusions are:- In England & Wales most stocks are growth overfished (i.e. F > Fmax, except for cock crab in the Western Channel, where F=Fmax). In all areas % virgin egg production per recruit is just below a candidate limit reference level (1% virgin EPR). In Scotland most stocks are either fully exploited (at or close to Fmax), or tending towards growth overfishing (F > Fmax), and equilibrium biomass per recruit is reduced significantly by the current level of fishing. In Ireland effort has risen substantially (a four to five-fold increase in pot hauls on the north western offshore grounds) and LPUE has declined in proportion, but EPR is still above a candidate limit reference level (in this case, 2% virgin EPR, which is more precautionary than the 1% level used in the CEFAS assessments). There are some differences in the output from the assessment models between the three countries, possibly due to differences in input data, especially for growth, and some differences in the level of exploitation, but the overall conclusions for management are broadly similar in the three countries. The size of crab in the landings is generally above the mean size of first maturity. Anecdotally, there are as yet no signs of recruitment overfishing in any of the fisheries (i.e. no obvious decrease in the number or proportion of small crab in samples of the landings), but the caveat is that scientific studies of brown crab recruitment dynamics are virtually non-existent. This is another reason for being precautionary about the level of effort. 9.5 Conclusions for management Based on the present input data and the resulting estimates of absolute or relative F the science shows that in most fisheries further increases in effort will not increases yield in the long term, will further reduce potential egg production, will increase the probability of causing recruitment overfishing Since crabbers continue to be concerned about the effects of oversupply on market price, and scientists are unable to advise what increase in F is likely to cause recruitment failure, it makes good sense to set a management objective to prevent any further increase in fishing mortality in the crab fisheries, and to implement management measures to achieve this. This would also be a significant step towards fulfilling the criteria for sustainability accreditation. 46

48 In fact this is a minimum requirement for fisheries in England & Wales, where F is beyond Fmax, and EPR is already below the candidate limit reference point (1% virgin EPR). For these fisheries there is a clear case for reducing F in order to lift EPR above the limit level to a precautionary or target level (25%virgin EPR in England). In England & Wales, the assessments indicate that this would require cuts in F in the following range, depending on the fishery: to attain Fmax 46-76% to attain 1%virgin EPR 12-56% to attain 25%virgin EPR 69-84%. Because these are severe reductions, and there remain some unresolved uncertainties in the science and the market, it is suggested that at present the most appropriate minimal action is to contain fishing mortality at the current level. The science appears to justify a similar conclusion for the Scottish and Irish fisheries on a precautionary basis, although their assessment results indicate that these stocks could be less heavily exploited. 47

49 Section 1 Capping effort To stabilise F, the options are to control input (i.e. cap effort) or to control output (landings). Controlling output by TACs and quotas raises concerns about the accuracy of calculating and allocating TACs using existing crab data, and fears that a TAC regime would lead to inappropriate behaviours such as misreporting of landings. Some groups of catchers have been discussing the use of voluntary limits on landings in order to hold or raise prices, but although this might produce short term benefits, it does not constitute a formal policy to limit effort long-term in order to protect the resource for the future. With this in mind SAGB still considers that the most appropriate approach is to manage inputs by capping effort, difficult though that may be. 1.1 Managing inputs The mortality generated by a potting fleet depends on such factors as the number of active vessels, the number of pots they put in the water, pot efficiency (pot type, size, and fittings) frequency of hauling (season length, fishing pattern, weather, market, soak time) The major factors that regulators could control best are the number of vessels, the number of pots, and possibly the type of pot, leaving the other factors to the operational instincts and needs of fishermen. 1.2 The number of vessels Under the National Restrictive Shellfish Licensing Scheme, potting round Britain is already limited to vessels that have qualified for a shellfish entitlement, except that there is a latent capacity problem due to vessels with shellfish entitlements that are not yet fishing for shellfish. This is a difficult issue to resolve. Active potters may resist accepting additional management measures unless latent capacity is eliminated, but clearly those who hold latent entitlements will be reluctant to lose them, whether on principle, or without financial compensation. This raises policy and financial issues for departments, unless the industry itself considers developing a selffunded buy-out scheme. 48

50 1.3 Pot limitation options Detailed consideration needs to be given to the basis on which pot numbers could be limited, and some of the issues are indicated in the options discussed below. 1) Freezing existing pot number for each vessel Freeze licensed vessels at their current number of pots, which would have to be notified and verified on the basis of records, and tagged for administrative and enforcement purposes. In principle this should not disadvantage any fisher, but it does give the edge to those who have already increased their pot number. A question arises over what limit should apply to vessels in the latent capacity category that decide to take up potting. 2) A single maximum for all vessels, possibly to be reached after a grace period A potentially simpler approach is to select or negotiate a single maximum for all vessels irrespective of size or location. To ensure agreement this would probably require: either, a high pot number at or above the top end of the current range, with the risk that vessels using less pots will go to the maximum, thus actually increasing effort. or, setting an intermediate number that is above the effort currently used by a majority of vessels, but that requires the remainder to reduce pot number, say over a grace period. Some large potters say they are already fishing 3 pots or more. Should the maximum be, say, 3 now, but 15 after, say, a 5 year grace period, or when a shellfish licence is transferred? Should these be negotiated figures, or should they be decided by analysing data on numbers, as described in Section 1.5? 3) Separate maxima A variant on the above is to set or negotiate different maxima, whether at the national or local level e.g. for different regions? inshore and offshore vessels (e.g. inside or outside 12 miles, or within an SFC*)? specific métiers e.g. nomadic vivier vessels? *Northumberland SFC has recently introduced a maximum number of 8 pots (Byelaw 15). 4) A banding approach Set individual pot numbers for different bands based on a vessel length or crew number formula. This could use the same formula for all vessels & areas, or separate formulae for different categories such as those in option 3. Readers may wish to re-visit these options after looking at the pot number data in Section

51 1.4 Pot type As noted in Section 1.7, the growth in potting has been facilitated by the parlour pot, which accumulates catch by reducing the escape rate, especially of lobsters, so that fishers can use longer soak times. Potters can therefore avoid hauling in bad weather, can expand by working more sets of gear that are hauled less frequently, and can hold ground by leaving the gear out for long periods, in some cases for the whole year, especially in areas also worked by mobile gear. From an impartial viewpoint, a ban on the parlour pot would surely promote a significant reduction in potting effort. Options include introducing a ban after a long grace period, or by staged reductions, or for replacement gear only. The reality is that this gear is now used almost exclusively in most fishing areas, at least in England & Wales, so a ban would be strongly opposed (as in the 26 discussions) especially by lobstermen, and especially if pot number is also restricted, as the efficiency of the parlour pot would then be deemed even more desirable. There is also a question whether an extra entitlement of creels would be requested to compensate for a parlour pot ban. On balance, it is almost certainly unrealistic to seek a parlour pot ban. The immediate priority is to cap total existing effort, irrespective of pot design. 1.5 Analysing pot number data for England & Wales This section analyses potting data for England & Wales in order to stimulate discussion about the basis for pot limitation. The data originate from the Defra data base and the CEFAS Log Book scheme, courtesy of CEFAS, and from some SFCs. The Defra data comprise pot-hauls for all fishing areas and ports combined, and they should be regarded as illustrations only, since they have been used as recorded, without removing the inconsistencies that they are known to contain Crab landings versus crab effort (Figures 3-32) This relationship is examined using data from Defra and from the Cornwall SFC. Figure 3 relates annual crab landings to average daily pot-hauls for all areas in England & Wales, for 2 to 28, with 28 highlighted. The more gear hauled, the higher the landings, although there is a wide scatter on the landings axis, especially in the 5-1+ pot range. This scatter is partly due to differences in catch rate between fishing areas, as indicated in Figure 31, which compares CEFAS Log Book data for different fishing areas in one sample year (1995), but is probably also due to spatial variations in catch rate and targeting. This proportional relationship, which has a similar slope across the time series, explains why fishers tend to invest in more gear, and why more gear means a higher exploitation rate. Figure 32 compares crab landings to total pot hauls using data from Cornwall SFC for and The variation in effort between periods in this data set is substantial. For hen crab, landings tend to be higher with higher effort, as in the Defra data, but this is not the case for cock crab. 5

52 It is worth considering further whether relationships of this type could be used to explore the reduction in effort that might be required to achieve a specified reduction in landings Crab LPUE versus crab effort (Figure 33 & 34) The relationship between LPUE and crab effort is examined using Defra data and data from the S Wales SFC permit scheme. Figure 33 presents Defra data in the form LPUE (kilo per 1 pot hauls) plotted against average daily pot hauls for 2 to 28, with different symbols for the different areas. The aim is to find evidence that LPUE declines with increasing pot number (as shown earlier for NW Ireland). There is a suggestion of this in some areas and years (e.g. Central North Sea, 22-4, and 26), but it is difficult to make clear cut conclusions owing to the considerable scatter in the LPUE data. This probably reflects a combination of factors such as LPUE differences between areas, differences in targeting, and spatial variations in abundance and catchability, which cannot be resolved without much more detailed analysis. Figure 34 plots LPUE (kg per 1 pot hauls) against total pot hauls for S Wales SFC permit data since 198, kindly supplied by the SFC. For a few years LPUE initially increases in proportion to pot hauls, but then levels off for a large proportion of the time series, albeit with considerable variation. In the later years therefore crab LPUE is independent of the level of effort. Owing to the scatter in LPUE, neither of these plots confirms the inverse relationship between LPUE and effort found in N W Ireland The proportion of the fleet fishing different pot numbers (Figure 35) Figure 35 shows England & Wales vessels grouped according to their average daily number of pot hauls using Defra data for 22-28, with 28 highlighted. The pot groupings range from 1-5 up to 1+, but note that the scale is not subdivided evenly. In principle these data could help to identify a maximum pot number that is likely to contain a high proportion of the effort, leaving a modest proportion to be regulated. From 2-25 most vessels hauled between 1 and 75 pots per day. Curiously, from 26, the number and proportion of vessels increased substantially in the lower half of this range (<4 pots), probably because of better collection for < 1m vessels under the licensing scheme. The majority of vessels appear to be fishing with a relatively low number of pots, which is consistent with earlier information that a majority of the potters use <1m vessels. The proportion of vessels hauling 1+ pots is therefore very low throughout the series. Setting a maximum pot limit based on this extreme of the distribution will therefore affect mainly the largest vessels, which also have most influence on the market, although there is then a risk that a large proportion of the fleet becomes free to increase effort substantially without penalty. Comparable data for NW Ireland are shown in Figure 54 of the Irish Report. Note that in practice, as discussed in Section 1.7, this plot should preferably use pots set, not pots hauled. 51

53 1.5.4 Potting effort versus vessel length (Figures 36-39) This is examined using data from Defra, CEFAS log-books, Devon SFC, and Jersey. Figure 36 relates average daily pot-hauls to vessel length using Defra data for all areas from 2 to 28, with 28 highlighted. There is considerable scatter, but on average pot-hauls are proportional to vessel length. Most vessels are in the 4 to 15m length range, with daily pot hauls less than 1-15, but there are some larger vessels in the plots, and a few records in the 1-3 pot range. The slope of the plots is fairly consistent year on year. Figure 37 shows similar plots for 1995 to 27, but based on CEFAS Log Book data for the 6 assessment areas in England & Wales. In this plot, effort is the mean number of pots set, not hauled. The sample size is small, and the vessel size range is up to 12m only, but effort falls into the same range as before, mostly below 1. Except for some high records in Yorkshire, where there is a significant offshore crab fishery, there does not appear to be a marked difference between areas. Figure 38 shows the number of pots owned per vessel against vessel length for South Devon, from the Devon SFC Potting Vessel Survey for 28. Vessel size ranges from 4 to 15m, and effort is proportional to vessel length, with a range and variation of pot number similar to that in Figure 36. Figure 39 shows pot number per vessel against vessel length for Jersey (source: Bossy, 28). Pot number is proportional to vessel length up to 11m and a maximum pot number of about 13. It is encouraging that the relationship between pot hauls or pot number and vessel length in these plots shows strong similarities between different areas and different data sources. 1.6 Conclusions The form and relative consistency of the plots described in Sections (frequency distributions of the number of vessels by pot number grouping) and (pot number versus vessel length) suggests that these are good ways of exploring the structure of potting effort in a fishery, and could reasonably be used to determine, respectively, a single upper maximum pot limit, or a set of limits for various vessel length bands. Such relationships could be explored for the entire fleet (as done here), or for different groups of potting vessels, e.g.: vessels fishing in separate regions, vessels fishing inside or outside an SFC boundary, or the territorial limit, vessels fishing nomadically in a range of different fishing areas. When comparing pot number versus vessel length, an important decision has to be made whether to use the average values of pot number at each length (which involves half the vessels having to reduce pot number), or an upper limit at each length (as shown on the Jersey plot in Figure 39), either of which may be determined by statistical modeling. 52

54 1.7 Pots hauled, or pots set The data described above mostly show the number of pots hauled, which is usually recorded because it is the information relevant to the landings on the day of reporting, so that LPUE can be calculated accurately. With the use of the parlour pot, however, which allows fishermen to work more gear than they can haul in a day, the number of pots hauled on any one day is generally less than the number of pots set in the water. A pot limit should be set on the maximum fishing capacity, however, which must be the number of pots that are set, especially as pots that are set but not hauled are still fishing. The importance of this is shown by the following examples: Figure 4 (source: slide 32 in Addison, 29) shows a time series of CEFAS log book data for average pots hauled and set per day, for the east coast north and south of the Wash. Although this is a small sample of the fleet, average pots set per day increases year-on-year much more rapidly than the number of pots hauled per day. Figure 41 compares the number of pots hauled to the number of pots set using permit scheme records for the S Wales SFC district in 27. Average daily hauls were approximately 5% of the number of pots set. 1.8 Pot tags, and their replacement Pot limitation schemes in Canada, the USA, and Jersey, are administered by issuing fishers with numbered tags or toggles of coloured plastic that must be affixed to their traps (e.g. Figure 42, for Jersey). Fishers receive the number of tags equal to their entitlement, either at the start of the scheme, or the start of each season. The scheme needs to include a protocol for replacing legitimate losses of pots (and tags) due to bad weather or mobile gear, but which also prevents fictitious losses being used to gain more tags illegally. A decision is also required as to whether or not tag allocations can be traded. In addition to field enforcement costs, the administration of such schemes carries a cost for pot tagging proportional to the total number of pots permitted in the fishery, unless this cost is passed on to fisherman. As noted in Section 1.8, the North Eastern SFC estimated that the cost of pot tags for 15 hobby fishermen was 4-5 per annum, since a new colour is issued every year. In the Northumberland SFC scheme, the permitted number of tags is issued by the Committee initially, but subsequent replacements must be applied for in writing, and purchased. Since cost implications depend on the number of pots in the fishery, the following list shows the pot number currently used in some fisheries discussed in this report (these are examples only and do not purport to be a complete list). Northumberland SFC Potters can use up to 8 pots each under Byelaw 15. At the time of writing (August 29), 86 of 122 permit holders were active, and fishing a total of 35 pots, but this number could increase in the remaining months of the summer. A further 75 pots were being worked by hobby fishermen. 53

55 North Eastern SFC From 2-25, the number of pots ranged from inshore, and offshore, as described in Section 5.3. Eastern SFJC Currently, active pot numbers are 27 in Norfolk inshore, 16 in the Wash and Norfolk offshore, and 11 in Suffolk. Devon SFC In 28, 81 vessels worked pots inside the South Devon district (=275 each on average), and 17 vessels worked 8554 pots in the North Devon district (= 5 each on average). South Wales SFC At the time of writing (August 29) 88 active permit holders were fishing a total of pots (= 139 pots each on average). Jersey 2761 pots in 27, of which 2166 are parlour pots (source: States of Jersey website) North West Ireland 55 traps were in use in 25 (Tully, 28). 1.9 The Mixed Fishery The priority issue in this report is the capping of fishing effort in the brown crab fisheries. It is appreciated that, except for larger vessels, including vivier crabbers that probably fish crab for most of the year, there are many potters who only fish brown crab seasonally, and will switch to lobster and velvet crab fishing at other times. Measures to set pot limits for the brown crab fishery must therefore impact on the mixed fishery, but unfortunately there has been no time to consider this in the report. Nor has there been time to assess the details of a minimum landing size approach, which could apply to each species individually, and hence simplify the mixed fishery aspect. 54

56 Acknowledgements Thanks to the following for their help at various stages of this project Dr Peter Hunt and Dr Tom Pickerell, SAGB. SAGB Crustacean Committee, especially Chris Venmore, Ken Lynham, David Sale. NFFO, including Trevor Bartlett, Gary Hodgson, Gary Redshaw. Keri Torney, Sally Comber, Luke Warwick, Ashley Wilson of Defra, Colin Penny (ex Defra). Julian Addison, Mike Smith, Steve Lovewell, Andy Lawler, CEFAS Lowestoft. Helen Dobby, Marine Laboratory, Aberdeen. Oliver Tully, BIM, Ireland. Simon Bossy, States of Jersey. Michael Hardy, Northumberland SFC. David McCandless, North Eastern SFC. Matthew Mander, Eastern SFJC. Keith Bower, Sarah Clark, Devon SFC. Samantha Davis, Cornwall SFC. Phil Coates, Leanne Llewellyn, S Wales SFC. Stephen Atkins, Greta Hughes, Rob Eccles, North Western & N Wales SFC. Peter Winterbottom, Association of SFCs. 55

57 ANNEX 1: FIGURES, CHARTS & DIAGRAMS This Annex contains Figures 1 to 42 as referenced in the previous text sections. 56

58 Figure 1. Brown crab fishing areas in Great Britain D3 D4 D5 D6 D7D8 D9 E E1 E2 E3 E4 E5 E6 E7 E8 E9 F F1 F2 F3 F4 F5 F6 F7 F8 Rockall Bank Porcupine Bank Faeroe Bank La Chapelle Bank Schematic (from Addison, 24) Bannister, 29

59 Figure 2. Brown crab landings Ireland & Scotland by ICES rectangle Figure 2a (from Tully et al 26) Figure 2b ((from Mill et al 29, draft) Bannister, 29

60 Figure 3. Brown crab landings in England & Wales Figure 3a. Landings 27 (Defra data from CEFAS 28) Figure 3b. Defra VMS data, 26 (from CEFAS 28) Bannister, 29

61 Figure 4. Defra brown crab data by CEFAS assessment area <1 m >1 m geart ype=pot s Central N Sea W Channel Southern N Sea Celtic Sea E Ch Irish Sea C N Sea Cel t i c Sea E Channel I ri sh Sea S N Sea WChannel f mu vessel si ze <1m >=1 Fig 4a. (Addison, 29) CEFAS assessment areas Fig 4b. (Cefas 28) Vessel number by size & area Bannister, 29

62 Figure 5. Defra brown crab data by CEFAS assessment area More pot hauls by <1 m vessels More landings by >1 m vessels Pot t ers geart ype=pot s Pot Hauls 4 Landings C N Sea Cel t i c Sea E Channel I ri sh Sea S N Sea WChannel C N Sea Cel t i c Sea E Channel I ri sh Sea S N Sea WChannel SMU f mu vessel si ze <1 >1 vessel si ze <1m >=1 Fig 5a (CEFAS 28) Pot hauls by vessel size & area Fig 5b (CEFAS 28) Landings by vessel size & area Bannister, 29

63 Figure 6. Defra brown crab data by CEFAS assessment area More lobster landings inside 6 miles More crab landings outside 6 miles 5 geart ype=pot s 5 geart ype=pot s C N Sea Cel t i c Sea E Channel I ri sh Sea S N Sea WChannel vessel si ze <1m >=1 Fig 6a (CEFAS 28) Lobster landings by vessel size & area f mu C N Sea Cel t i c Sea E Channel I ri sh Sea S N Sea WChannel f mu vessel si ze <1m >=1 Fig 6b (CEFAS 28) Crab landings by vessel size & area Bannister, 29

64 Figure 7. Stock Structure in North Sea (CEFAS data, Addison 24) July 1993 Crab larvae at similar location year on year Cirolana 7a/93 Nos/m² East Coast spawning fishery July June bottom temp Blue area too cold for larval development? Nos / sqr m / day Green area OK. Cirolana 4/99 Both grids Bannister, 29

65 Figure 8. Stock Structure in Channel, Celtic Sea, & Ireland Figure 8a (Tully, 28) Figure 8b (Cefas larvae data, Addison, 24) Larvae at similar locations year on year. Stocks at regional not local scales. Bannister, 29

66 Figure 9. Historical recaptures of brown crab tagged off English east coast Northward migration of brown crab tagged in Yorkshire & Norfolk (Illustration sourced from Addison, 24) Bannister, 29

67 Figure 1 Slide from Addison 24, after Cuillandre et al 1984 Bannister, 29

68 Figure 11. Defra-funded study of brown crab genetic structure 25 8, Royal Holloway College & Cefas Project MF23 Genetic diversity high, & not affected by fishing N Sea and Channel are genetically distinct Channel, Celtic & Irish Seas NOT distinct N coast of Ireland distinct from S E Ireland Within Channel, some genetic patchiness possibly due to local recruitment or females migrating back to birth areas 32 Sample sites Sampling eggs suggest sired by only one male so need to protect spawning stock Bannister, 29

69 Figure 12. Regional landings of Brown Crab, Lobster, Velvet crab, England & Wales Tonnes North Sea Coast Channel coast West coast Fig.12a. Brown crab Official Defra data extracted by CEFAS Tonnes N.Sea coast Channel coast West coast Fig. 12b. Lobster Bannister, 29 Tonnes East Coast Channel Coast West Coast Fig. 12c Velvet crab

70 Figure 13. Brown Crab Landings by District Tonnes Northumberland Yorkshire East Anglia & Lincs. Fig.13a East of Devon South Devon South Cornwall Fig.13b Tonnes 6 3 Official Defra data extracted by CEFAS Tonnes North Cornwall Wales North west Fig. 13c 3 Bannister,

71 Figure 14. Brown Crab trends in LPUE Fig. 14a From CEFAS log books kilos/1 pots (Cefas 29 Draft Report) Fig. 14b LPUE kg/1 pots LPUE kg/1 pots solid - North of Tyne dashed - South of Tyne Central North Sea solid - Yorkshire coast dashed - North Norfolk Southern North Sea Bannister, 29

72 Figure 15. Brown Crab trends in LPUE From CEFAS log books kilos/1 pots (Cefas 29 Draft Report) Fig. 15a Fig. 15b LPUE kg/1 pots LPUE kg/1 pots Western Channel Irish Sea Bannister, 29

73 Figure 16. Brown Crab landings and LPUE, Cornwall SFC Edible Crab Landings from CSFC District (Source: CSFC Permit Returns Database) 25 Female Edible Crab 12 E d ib le C ra b L a n d ed (to n n es Male Edible Crab Combined LPUE E d ib le C ra b L P U E (K g /1 P o H a u ls) Year Bannister, 29

74 Figure 17. Brown Crab Landings, Pot hauls and LPUE (kg/1 p h) Plotted from South Wales SFC permit scheme data Pot Hauls ('s) S Wales SFC Pot Hauls & Brown Crab Landings Landings 1 Pot hauls Year Landings (tonnes) S Wales SFC Pot Hauls & Brown Crab LPUE Pot hauls ('s) Pot hauls LPUE LPUE (Kg/1 pot hauls) Year Bannister, 29

75 Figure 18. Size frequency of crab landings, England & Wales Fig. 18a Central North Sea Fig.18b Western Channel Male Female Bannister, 29 Male Female Male Female 2 1 Male Female (From CEFAS 29, draft)

76 Figure 19. Size frequency versus maturity at size, England & Wales (From Addison, 29) Proportion mature Western Channel Female Male Female LD Male LD Nos at CW (thousands) Proportion mature CW Numbers, s 1 35 Current sizes in the fishery are greater than mean size of maturity Bannister, 29 Proportion mature Southern North Sea Female Male Female LD Male LD CW Carapace width, mm Nos at CW (thousands)

77 Figure 2. Brown Crab Fecundity, England & Wales Numbers of eggs versus size (from CEFAS, 29, draft) 4 Eggs (millions) y =.187e.268x R 2 = Carapace width, mm Bannister, 29

78 Figure 21. Assessment results for Central North Sea (from Cefas, 29, draft) Fig.21a Fishing rate per size class Fig. 21b Yield per recruit curves F F female F male Y P R YPR female YPR male %VirgSPR female %VirgSPR male %VirgEPR female % virg in S P R o r E P R size class (mm) F multiplier Proportion of present fishing rate overfishing Bannister, 29 % virgin egg production per recruit Present fishing rate

79 Figure 22. Assessment results for Western Channel (from Cefas, 29, draft) Fig. 22a Fig. 22b F female F male 6 5 YPR female YPR male %VirgSPR female %VirgSPR male %VirgEPR female F Fishing rate high on females males moderate on males Y P R % v i rg in S P R o r E P R size class (mm) F multiplier SCIENTIFIC CAVEATS: values & shape of curves depend on growth & natural death rate Females are overfished Bannister, 29

80 Figure 23. Assessment results for Central North Sea and Western Approaches (from Cefas, 29, draft) Fishing Reference Point: F max Reference Points: Rate 25% & 1% Virgin Egg per Recruit Highest F Sex Status To get to Ref Pt. Observed Status Cut in current F Fmax F Central North Sea Central North Sea.6-1. F F>Fmax -68% 25% 6% < -8% M F>Fmax -71% 1% 6% < -43% Western Channel & Approaches Western Channel & Approaches.6-.8 F F>Fmax -47% 25% 9% < -69%.2-.3 M F<Fmax 8% 1% 9% < -12% V high fishing rate on females BIG cuts in effort required to optimise yield and to increase egg production above reference levels Bannister, 29

81 Figure 24. Assessment results for all areas. (from CEFAS 29, draft) Fishing Reference Point: F max Reference Points: Rate 25% & 1% Virgin Egg per Recruit Highest F Sex Status To get to Ref Pt. Observed Status Cut in current F Fmax F Central North Sea Central North Sea.6-1. F F>Fmax -68% 25% 6% < -8% M F>Fmax -71% 1% 6% < -43% Southern North Sea Southern North Sea F F>Fmax -74% 25% 5% < -82% M F>Fmax -76% 1% 5% < -53% Eastern Channel Eastern Channel.3-1. F F>Fmax -57% 25% 7% < -74% M F>Fmax -46% 1% 7% < -32% Western Channel & Approaches Western Channel & Approaches.6-.8 F F>Fmax -47% 25% 9% < -69%.2-.3 M F<Fmax 8% 1% 9% < -12% Celtic Sea Celtic Sea F F>Fmax -59% 25% 8% < -76% M F>Fmax -65% 1% 8% < -29% Irish Sea Irish Sea.5-1.5? F F> Fmax -72% 25% 6% < -84% ? M F> Fmax -63% 1% 6% < -56% Bannister, 29

82 Figure 25a Figure 25. Brown crab landings in Scotland Clyde East Hebrides Figure 25b Mallaig North Orkney Papa Shetland South east Sule Ullapool S Minch Bannister, 29 (from Mill et al, 29)

83 Figure 26. Assessment inputs and results for Scotland (1) (Mill et al 29) female male East Hebrides Fully exploited or beyond Orkney Biomass per recruit Bannister, 29 YPR < > % of F

84 Figure 27. Assessment inputs and results for Scotland (2) (Mill et al 29) Papa Shetland Fully Exploited Sule Bannister, 29 YPR BPR

85 Figure 28 Assessment inputs and results for NW Ireland (from Tully et al 26) Fig. 28a LPUE falls over time Fig.28c Fig. 28b LPUE decline is driven by increase in pot number? Fig. 28d Egg per recruit is below target but above the limit point at current F and MLS Bannister, 29

86 Figure 29 Economic data for NW Ireland Crab Fishery Fig 29b Fig. 29a Value Fig. 29c Pots Bannister, 29 (from Tully, 28)