Defining the Northumberland Lobster Fishery

Transcription

1 2009 Defining the Northumberland Lobster Fishery Report to the Marine and Fisheries Agency Rachel A. Turner1, Michael H. Hardy2, Jon Green2, Nicholas V.C. Polunin1 1) School of Marine Science and Technology, Newcastle University, Newcastle upon Tyne, NE1 7RU 2) Northumberland Sea Fisheries Committee, Committee Unit 60B South Nelson Road, Cramlington, NE23 1WF

2 Report to be cited as: Turner R.A., Hardy M.H., Green J., and Polunin N.V.C. (2009) Defining the Northumberland Lobster Fishery. Report to the Marine and Fisheries Agency, London

3 Contents Summary Introduction Aims and Objectives Study Area Methods Distribution of potting activity Collection of vessel sightings Adjusting for patrol effort Distribution of fishing activity and pot density Seasonal change Habitat use Lobster landings Data sources Data reliability Data analysis Catch composition Data collection Size composition Management measures Results Distribution of potting activity Distribution of activity and pot density Seasonal change Habitat use Lobster Landings Fishing effort Lobster landings Landings per unit effort (LPUE) Spatial differences Catch Composition Overall size composition Comparison by depth zone Management measures ii

4 4. Discussion Distribution of potting activity Lobster landings Catch composition Conclusions & Recommendations Acknowledgements References iii

5 Summary This report is the first attempt to describe the lobster pot fishery in the Northumberland Sea Fisheries Committee (NSFC) district. It aimed to map potting distribution and density, analyse recent lobster landings, and collect data on size composition of catches. Inshore fisheries, particularly shellfisheries, are an increasingly important component of UK fisheries. Despite this there are relatively few regulations in place to manage shellfisheries, and a lack of information on their activity. With the value of landings in 2008 estimated at 2.9 million (Marine and Fisheries Agency data), lobster is an economically important species in the NSFC district, and it is important to assess current activity as a basis for future management. The distribution of observed fishing effort (NSFC patrol vessel sightings) was mapped using kernel density estimation and percent volume contours in GIS, estimating the home range of each landing port. Data on fishing effort from monthly returns to NSFC and the Marine and Fisheries Agency (MFA) were integrated with mapped sightings to estimate pot densities by port and on a seasonal basis. Estimated port home ranges varied from 26 km 2 to 260 km 2, with a variable degree of overlap between ports. Seasonal patterns and substrate preferences were consistent with knowledge of the local fishery, lending support to the value of these data in representing overall fishing patterns in the district. Fishers monthly returns to NSFC and MFA from were checked for reliability and used to investigate fishing effort, landings and landings per unit effort (LPUE). Overall fishing effort appears to be stable, although the median number of pots worked increased from 250 in 2001 to 300 in Reporting rates appear to be lower in following a change in data collection schemes. Landings and LPUE also appear stable, with median landings and LPUE highest in the last 3 years, consistent with fishers views that the fishery has been particularly productive during this time. Seasonal patterns in landings are similar to those in fishing effort, and spatial variation among landing ports is indicated. Median LPUE ranged from a minimum of 0.5 kg 100 pots -1 day -1 to a maximum of 1.3 kg 100 pots -1 day -1, the highest found in Cullercoats, a small port where fishing is highly targeted with a small number of pots. From July 2008 to July 2009 ten vessels participated in a logbook scheme organised by NSFC, recording summaries of catch composition on a daily basis and measuring a sample of lobsters caught on a monthly basis. Size composition of catch over the year and in different depth zones was assessed, and investigated for an initial indication of the potential implications of future management measures, specifically an increase in minimum landing size (MLS) from 87 mm to 90 mm carapace length (CL) or a ban on landing ovigerous females (berried hens). Data showed 75% of lobsters caught to be below MLS, with a modal length of 85 mm for both males and females. Differences in composition were found by season and depth zone, with a greater percentage of lobsters close to MLS caught between July and December, and a greater proportion of larger lobsters caught further offshore. Of the landed catch, 40% was between mm CL, and the percentage of landed catch comprising ovigerous females ranged from 9-28% throughout the year. Overall, the study provides valuable baseline data for future management of the Northumberland lobster fishery by NSFC, and highlights key data gaps and areas for future research. These include a need to maintain a complete picture of activity within the district (including <10 m, >10 m and Scottish vessels), and research to assess the extent to which fisheries-related data reflects the abundance and size composition of the target population. Cooperation of local fishers will be key to gaining a more complete picture of potting activity beyond six nautical miles and the relative importance of different grounds for target species. 1

6 1. Introduction With <10 m vessels comprising over 75% of the UK fishing fleet, inshore fisheries are of considerable value to the UK economy and society (Defra 2006). Legislative developments such as the Marine and Coastal Access Bill, EU Water Framework Directive and EU Common Fisheries Policy review, are expected to have implications for the management of inshore fisheries, but in many cases information available on current activity is limited. This is particularly true for shellfisheries, which for the most part are managed by comparatively few regulations (Bannister 2006, Lake & Utting 2007). Shellfisheries are of increasing economic importance in the UK following declines in demersal and pelagic fish landings; in 2007 shellfish contributed 43% of the value of UK landings, an increase from 27% in 1997 (MFA 2007). There is a lack of information on the spatial distribution of this fishing activity, in particular for <10 m vessels (Woolmer 2009). In the light of increased emphasis on marine spatial planning, it is important that this knowledge gap is addressed. With 148 permit holders and landings of 145 tonnes of lobsters in 2007, lobster fishing in the Northumberland Sea Fisheries Committee (NSFC) district is nationally important and of increasing value to the local industry. The value of landings at ports within the district was estimated at 2.9 million in 2008 (MFA data). The NSFC is working to improve the basis for managing local lobster stocks and has recently introduced a pot limitation byelaw, which restricts pots worked by each permit holder to 800 within the district. However, information on the spatial distribution of inshore fishing effort is lacking and there remains a need to understand how pot numbers are distributed by the fleet. It is also desirable to have a basis for assessing changes in catch as a result of any future management measures such as an increase in the minimum landing size (MLS) or a ban on landing ovigerous females (berried hens). 1.1 AIMS AND OBJECTIVES Given the lack of assessment of the lobster fishery in the NSFC district to date, this project aims to start the NSFC on the path towards lobster fishery sustainability, the immediate purpose being to provide a foundation for future assessments and improve the basis for future management. Specifically, this project aims to achieve the following objectives: Describe the spatial distribution of potting activity and estimate pot deployment densities in the NSFC district, including variation by landing port, substrate type and season. Examine landings data for temporal changes in catch volume and variation in catch volume and effort between ports. Examine the current catch size composition and possible effects on catches of an increase in MLS. 1.2 STUDY AREA The NSFC district comprises the area from the River Tyne to the northern boundary of Northumberland, and out to 6 nautical miles (nm) from the coast (Fig. 1). Several fisheries are targeted in the district by a variety of gears (NSFC 2008). The pot fishery targets four main species: European lobster (Homarus gammarus), brown crab (Cancer pagurus), velvet swimming crab (Necora puber) and prawns (Nephrops norvegicus), with a number of vessels also using other gears at certain times of year. A variety of pots (or creels) are deployed in the district with variable entry design, dimensions and mesh sizes, and many fishers use more than one type of pot (Garside et al. 2003). Soak times are variable, depending on returns from 2

7 fishing and prevailing weather conditions. Fishers typically haul gear every 1-2 days at the height of the lobster season, but pots may be left for several days or more if poor weather prevents fishing or catches are low. The majority of pots worked are multi-purpose, and are deployed on different ground types at different times of year to target particular species. Some pots types exclude certain species (e.g. some hard-eyed pots do not allow entry of mature crabs, and prawn creels preclude entry of large lobsters), but most can be used to catch lobster if deployed in appropriate locations. While landings of lobster are lower in volume that those of brown crab, lobster is the most economically important target species in the NSFC potting fishery (Bannister 2006) and is therefore the focus of this study. Fig. 1. NSFC district and local ports Potting vessels in the district are between 4-12m in length, ranging from traditional cobles to keels, fast workers and catamarans. Individual vessels work up to 1200 pots, although the recent byelaw means that pots in excess of 800 must be deployed outside the NSFC district. Since this byelaw has come into operation (June 2009), the majority of permit holders continue to deploy fewer than 600 pots (NSFC pers. comm.).the majority of vessels work within the 12 nm limit, although a small number of faster, more modern vessels work beyond this. Crab and lobster potting is to some extent geographically restricted by the available habitat for target species and potential conflict with other gear types such as trawlers. A number of potting vessels operate pots seasonally or part time, with some skippers also using other gear or employed in other occupations. All vessels fishing commercially for shellfish within the district must hold a permit from the NSFC, and a national shellfish entitlement on a fishing licence is a prerequisite for a permit application. Vessels and hobby fishers without a permit are restricted to fishing 5 pots, with a maximum landing of 1 lobster and 5 crabs per day. There is insufficient data at the time of writing to assess the level of this recreational activity, 3

8 but recent indications from the issuing of pot tags to recreational fishers suggest that just under 200 recreational fishers are working up to 5 pots each within the district (NSFC pers. comm.). Other regulations applying to NSFC permit holders include an EU-set minimum landing size (MLS) of 87 mm carapace length (CL), a ban on landing soft or V-notched lobsters, and a pot limitation (Table 1). Table 1. Regulations applying to the Northumberland lobster fishery Management measure Legislation Minimum landing size (87 mm CL) SI 2000 NO (The Undersized Lobster Order 2000) Protection of "V" notched lobsters NSFC Byelaw 6 Protection of soft-shelled lobster NSFC Byelaw 7 Prohibition on landing parts of shellfish NSFC Byelaw 8 Redepositing of prohibited shellfish NSFC Byelaw 10 Permit to fish for and sell lobsters and other shellfish NSFC Byelaw 13 Pot limitation (800 pots for permit holders, 5 for non permit holders) NSFC Byelaw 15 While lobster fishing has traditionally been a seasonal activity, increases in efficiency of both vessels and gear (e.g. steel pots rather than wooden) have enabled fishers to work further offshore and in less favourable weather conditions. There is anecdotal evidence that quantities of gear worked by potting vessels have increased with the availability of improved hauling technology and increasing use of larger, faster vessels. Recent years have seen a decline in local trawl fleets and anecdotal evidence also suggests that former trawlers are increasingly turning to potting, which is less stringently regulated than trawling and perceived to offer a more stable livelihood. In recent years several skippers in the district have decommissioned trawling vessels and bought specialised potting vessels (NSFC, pers. comm.). With limited regulation on commercial potting at present, it is essential to take stock of current activity as a basis for future management of the fishery. 4

9 2. Methods 2.1 DISTRIBUTION OF POTTING ACTIVITY Distribution of fishing activity and potting density were estimated using a sample of fishing vessel positions. The data used comprised geographically referenced sightings of fishing vessels observed at sea by NSFC Collection of vessel sightings NSFC collect data on fishing vessel sightings during routine enforcement patrols. Since 2004 these records have included the name, registration and home port of fishing vessels, their geographic position and observed fishing activity. Sightings from were verified by cross-referencing with Marine and Fisheries Agency (MFA) Fishing Vessel Lists (MFA ), the NSFC permit database and communication with NSFC Fishery Officers to identify inconsistencies in vessel details, home ports or fishing activities. Sightings of crab and lobster potting (recorded as one activity; prawn potting is recorded separately) were extracted (n = 3475, 67% of all vessel sightings) and mapped using ESRI ArcView GIS 9.2 (Fig. 2a). Points outside NSFC boundaries were removed Adjusting for patrol effort A bias in patrol effort was evident towards the south of the district due to the location of the NSFC patrol vessel mooring in the Tyne (Fig. 2b). Patrol routes were obtained from the NSFC vessel and geo-referenced in ArcGIS. Information was available for 54% of patrol routes during the study period, accounting for 55% of the sightings. It is possible that some sightings were recorded by RIB patrols, the routes of which are not recorded. RIB patrols are carried out throughout the district, but may account for a greater proportion of sightings in the north of the district where patrol vessel coverage is limited. Information available differed between years (Table 2), but no change in pattern over time was apparent from visual inspection of the patrol routes. The information was therefore considered to be representative of patrol effort distribution during the study period, and patrol effort data from all years were pooled. Table 2. Sightings data and patrol route information Year Vessel Sightings Unique Potting Vessels Seen NSFC Shellfish Permits Issued NSFC Patrols Patrol routes available (%) (87) (47) (0) (58) (75) Total (54) A 3 nm 2 grid was superimposed on the NSFC district (Clark 2008), assuming that visibility would be sufficient for any fishing vessel within the same grid square to be seen by the patrol vessel. Patrol routes falling within each grid square were counted and a measure of patrol effort (PE 1) was calculated: Where: n = number of patrols passing through a grid square N = total number of patrols. 5

10 Vessel sightings in grid squares containing no patrol routes implied a degree of patrol effort in these areas unaccounted for by PE 1 (i.e. due to greater visibility than assumed or missing patrol route information). A second measure of patrol effort (PE 2) was calculated based on the assumption that patrol effort decreases with distance from patrol routes. The distance of each grid square to the nearest mapped patrol route was calculated and PE 2 calculated for each grid square to indicate the probability of a vessel being seen: Where: D max = maximum distance to patrol route D g = grid square distance from patrol route D min = minimum distance to patrol route The combined measure of patrol effort (PE) was used to weight sightings in each grid square, negatively weighting those in areas of high patrol effort and positively weighting those in areas of low patrol effort: 1 1 Fig. 2. a) NSFC sightings of potting vessels , b) patrol routes by year Distribution of fishing activity and pot density The probability distribution of fishing activity was assessed from the sample of weighted vessel locations using a fixed kernel density estimation (KDE) tool in Hawth s Tools (Beyer 2004). The smoothing factor for the KDE is important as it determines the area around a given location within which data points contribute to the probability estimate for that point (Bailey & Gatrell 1995). A range of smoothing factors was tested 6

11 and resulting maps discussed with local fishers and NSFC Fishery Officers. A smoothing factor of 0.5 nm was perceived to give the most accurate representation of fishing activity. Sightings data were classified by home port and separate KDEs produced for each port within the district. The ports of Seaton Sluice, Cresswell and Whitley Bay were excluded from the analysis (19, 4 and 1 vessel sighting respectively) as they were not reported as landing ports by any vessels; typically the small number of vessels operating from these ports land at larger ports nearby. Percent volume contours (PVCs) were used to estimate the home range of each port. PVCs delineate contours containing a specific proportion of the probability density distribution. For example, the 50 PVC contains the area in which there is 50% chance of finding vessels from the port based on the sample data. For each port 50, 60, 70, 80, 90, 95 and 100 PVCs were calculated using Hawth s Tools (Beyer 2004). The 95 PVC was used as an estimate of the home range of each port. All polygons produced were clipped to the extent of the NSFC district. Information on fishing effort was obtained from the NSFC permit returns database, which contains monthly returns from potting vessels stating the maximum number of pots worked during the month, number of landings, and weight landed (see for details). Returns stating no pots were fished were excluded and fishing effort calculated as pot months per year. Pot months were calculated as the sum of pots worked in all monthly records (i.e. three monthly returns from a vessel working 200 pots = 600 pot months). This measure accounts for the estimated number of pots set and months worked by each vessel, but does not account for the number of times pots are hauled each month. An alternative would be to calculate pot hauls for each record (number of pots multiplied by number of times pots landed); however, many vessels do not haul all pots on each trip, therefore pot hauls calculated in this way may overestimate fishing effort. The mean annual number of pot months was calculated based on data, which were the only complete records corresponding to the period of sightings data collection 1. For each port the areas within PVCs were calculated and pot months allocated to polygons in proportion to the probability of fishing activity in them. For example, 50% of pot months were allocated to the area within the 50 PVC. It was assumed that vessels from Burnmouth expend 50% of their fishing effort within the NSFC district, as the port of Burnmouth is outside the NSFC district and vessels operating from here are likely to have a greater range than estimated by NSFC data. Potting densities in each polygon were estimated as pot months km -2 year -1. Where port home ranges overlapped, the highest measure of fishing effort of the overlapping polygons was allocated to the area of overlap Seasonal change Seasonal estimates of distribution of potting activity and potting density were based on data from all ports combined as there were insufficient data points to estimate seasonal KDEs for each port. The resulting maps therefore portray overall seasonal variation in the district but do not account for variation in pot months among different ports. Sightings of potting vessels were divided into four seasons (January-March, April-June, July-September and October-December) and 50, 60, 70, 80, 90, 95 and 100 PVCs were calculated from seasonal KDEs. Pot months per season were calculated as the sum of pots worked for 1 It is assumed that these figures are representative of the period , as no difference was found between annual total pot months per port from (Friedman χ 2 (4) = 1.65, p = 0.83). 7

12 monthly records within each season per year, and mean annual totals ( ) allocated to the PVCs in proportion to the probability of fishing activity, as described above. Data on pot months were incomplete beyond 2005, but are not expected to be significantly different from previous years Habitat use Habitat requirements of target species in the fishery differ, with lobster and velvet crab found on rocky ground in shallow and intertidal zones (with lobster found to depths of 60 m or more (Cobb & Castro 2006)), while brown crab is also found on coarse sediment and offshore muddy sand (Neal & Wilson 2008, Wilson 2008a, b). Data on marine habitat were available from ground-truthing video collected during marine habitat surveys from (Foster-Smith 1998). Substrate types were grouped into categories (Table 3), with areas not covered by the data categorised as unknown. Vessel sightings were analysed with information on marine habitat to assess the preference of potting vessels for habitat types. Table 3. Substrate types and categories (after Foster-Smith 1998) Substrate Classification Description Level bedrock & boulder Hard Terraced rocky area - extensive horizontal platform with 'scarps' generally <1m Rugged bedrock Hard Bedrock with vertical faces and gullies Silty bedrock Hard Bedrock with significant silt influence restricting encrusting fauna Boulder Hard Dominated by boulders >256 mm, lesser amounts of smaller sediment Boulder & cobble Hard Mixture of boulders >256 mm and cobble <256 mm Bedrock, boulder & sand Patchy Sediment overlying bedrock Boulder & sand Patchy Heterogeneous, patchy areas of boulder and sand Boulder, cobble & sand Patchy A complete mixture of sediment grades. Heterogeneous at a fine scale Cobble & silty sand Patchy Large rocks infrequent and sand component elevated Coarse sand Smooth Generally clean and poorly sorted Medium fine sand Smooth Medium fine sand Silty coarse sand Smooth Silty sand - silt stirred up by towed video Offshore silty gravel Smooth Not well sampled, but offshore seems mostly silty gravel Unknown Unknown Areas of NSFC district not covered by data The intersection of each home range with habitat data was calculated in ArcGIS, and the areal coverage of each substrate measured within the district and in each home range. The frequency of sightings occurring on each substrate was counted to indicate the level of use by potting vessels. A Chi Square goodness of fit test was used to assess the relationship between observed and expected use of each substrate within the district, assuming the expected use to be proportional to availability. Relationships between landing port and habitat use, and season and habitat use were investigated using Chi Square tests of independence. Where relationships were found, Ivlev s electivity index was used to assess preference for each substrate. Ivlev s electivity index is calculated as follows (Waddington et al. 2008): E r i-p i / r i p i Where r i = proportion of habitat available, and p i = proportional use. 2 The difference between seasonal totals from was marginally statistically significant (Friedman χ 2 (4)= 8.6o, p = 0.07), but this was strongly influenced by one Scottish vessel fishing >2000 pots in After removal of this vessel no difference was found (Friedman χ 2 (4) = 5.0, p = 0.29). 8

13 Available habitat was considered here to be the proportional areal coverage of each substrate within the district, and habitat use indicated by the proportion of vessel sightings occurring on each substrate. Values of E range from -1 to 1, with negative values suggesting selection against or inaccessibility of the habitat, and positive values suggesting selection for the habitat. Values near zero indicate that use is proportional to availability (Strauss 1979, Waddington et al. 2008). 2.2 LOBSTER LANDINGS Data sources From NSFC byelaws required shellfish permit holders to submit monthly returns detailing landings (kg) 3, fishing gear worked (pot numbers, days pots at sea, and hauls per month) and landing port. In 2006, NSFC data collection was superseded by the MFA data collection scheme. The MFA collect data under separate schemes for >10 m vessels (daily logbooks) and <10 m vessels (monthly catch returns). Copies of records are added to the NSFC database, but the NSFC do not receive data on returns from >10 m vessels, or from vessels whose main fishing area is outside the NSFC district. The latter applies to vessels from Scotland and from ports south of the NSFC district. Vessels from south of the Tyne rarely fish in the NSFC district and represent <1% of the mean annual lobster landings in the district from These records have been included in yearly totals but excluded from analyses of individual ports. Conversely, Scottish vessels have a significant fishing presence in the north of the district, with 10% of mean annual gear worked and 11% of mean annual landings from Note however that these vessels also fish in Scottish waters, therefore only a proportion of this effort is likely to be in the NSFC district. Scottish vessels fishing within the district are predominantly from Burnmouth; a small number of records from other Scottish ports have been grouped with Burnmouth vessels for analysis. Since 2006 the NSFC database is therefore missing two key components: >10 m vessels and Scottish vessels, which together comprised on average 16% of NSFC shellfish permit holders from Supplementary data on these vessels was available from Marine Scotland (total monthly landings by Scottish vessels in the NSFC district , obtained August 2008) and the MFA (total annual landings per vessel for >10 m vessels with an NSFC shellfish permit , obtained August 2008). There was a three month period of overlap between the two data collection schemes (Jan-Mar 2006). Duplicate records for this period were removed before the two data sets were merged, and duplicate monthly returns (returns submitted under same vessel registration number for the same return month) for all years were checked against paper records and removed where necessary. In total, 7830 monthly returns from were available for analysis (data from 2008 was incomplete at the time of analysis) Data reliability The NSFC carry out spot checks at landing sites to estimate numbers of lobsters landed by individual vessels. Records from 290 spot checks during 2007 were cross-referenced with database entries to identify any consistent errors in reporting or potential misreporting, and to verify reliability of data from individual 3 Landings are combined for nets and pots, but targeted netting for shellfish represents <1% of total fishing effort (Garside et al. 2003) 9

14 vessels. A weight range was estimated using length-weight data compiled through monitoring of lobster landings throughout the district, which gave a minimum weight of 0.3 kg and a maximum of 1.8 kg per lobster (data from Biological Sampling Database, Centre for Environment Fisheries and Aquaculture Science, obtained April 2009). In most cases data on lobster landings in NSFC database entries were within the estimated weight range based on Fishery Officer estimates of numbers landed (Table 4). While in a small number of cases the database entry was above or below the estimated weight range, a greater problem was the number of cases in which a database entry was not available. In some cases this could be due to grouping the landings of more than one day s catch when recording data on forms (common where small quantities are landed or catches are not weighed by wholesalers each day), but may also indicate nonreporting by some vessels. As such there was no rationale for excluding any particular vessel from the analysis; instead it should be noted that the information contained in the database potentially underestimates actual fishing activity. Table 4. Cross-referencing of NSFC spot checks with monthly returns from fishers Database entry Frequency (%) Within estimated range 174 (60%) Below estimated range 16 (6%) Above estimated range 24 (8%) Not available 76 (26%) Total Data analysis Monthly records from the NSFC database were analysed to investigate fishing effort, lobster landings, and landings per unit effort. Fishing effort was measured using the number of vessels actively fishing per year (considered to be the number of unique vessels submitting returns to the NSFC/MFA), the total number of pots worked (the sum of the maximum number of pots worked by each vessel during each year), the median number of pots worked (calculated using all monthly returns, reflecting pots actually in use over the course of each year 4 ), and the number of pot months (as described above 2.1.3). Annual landings were calculated for the district as a whole (sum of monthly landings for all vessels) and for each individual port (sum of monthly landings by vessels at each landing port). Median monthly landings per vessels were also calculated each year for the district and for each landing port. A measure of landings per unit effort (LPUE) was calculated as kg 100 pots -1 day -1. This measure standardises lobster landings according to the number of pots worked by a vessel, although it potentially masks variability in effort as the number of times pots are hauled is likely to vary between vessels and from month to month. An alternative measure of LPUE is to incorporate the number of landings per month to calculate landings per pot trip (i.e. pot trips = pots worked x number of landings). However, this measure also has shortcomings as it is common for some vessels to haul only a proportion of their pots on each trip, while others may haul all pots on each trip. The former measure was used as information on pot landings per month was incomplete, but where both measures could be calculated they were found to be strongly correlated (Spearman s rho = 0.84, p<0.001). Outliers in LPUE data (Z>3.29, possibly resulting from mistakes in recording or data entry) were removed prior to analysis. 4 I.e. numbers of pots worked by vessels active for more months of the year receive greater weighting as these vessels submit more monthly returns. 10

15 Spatial variability in effort, landings and LPUE was based on analysis of data by landing port. Analysis was restricted to data from , which contained complete information for the potting fleets (i.e. including data on Scottish and >10 m vessels). While data were obtained on landings for >10 m and Scottish vessels in , comparable information on effort was not readily available. The spatial distribution of landings was mapped by home port and by season (kg km -2 ), allocating seasonal or port landings to PVCs (as described in 2.1.3). Maps were based on mean annual totals (by port/season) from , corresponding to the sightings data used to estimate distribution of fishing activity, and include data on landings of >10 m and Scottish vessels in In the case of >10 m vessels information on seasonal distribution of landings was not readily available and total annual landings were therefore allocated proportionally to seasonal PVCs based on seasonal distribution of 2005 landings. 2.3 CATCH COMPOSITION Data collection In June 2008, 10 fishing vessels from 7 ports in the district were asked to participate in a logbook scheme for 12 months. Vessels taking part worked between 270 and 800 pots, which varied in size and design. Skippers were asked to sample two fleets of pots 5 each day they were at sea to record basic information on catch composition and fishing effort, and one fleet per month in which more detailed information on size composition was recorded (Table 5). As random sampling of pots was not feasible, each skipper was asked to choose fleets representative of their fishing effort and location (Starr & Vignaux 1997). Fishers were not asked to sample the same fleets on each trip as different sets of gear may be hauled on alternate trips. Table 5. Data collection variables for daily and monthly logbook Variable Daily (summary) Monthly (size composition) Fishing activity Catch composition Total number of pots Soak time Sample fleet location Sample fleet depth Pot type Weather and sea conditions Other species caught Total weight & number of lobsters landed Number of lobsters caught in sample fleets: Above MLS Below MLS Ovigerous V-notched Number of pots in sample fleet Soak time Sample fleet location Sample fleet depth Pot type Weather and sea conditions Other species caught Size (carapace length, mm) of each lobster caught: Male Female Ovigerous V-notched A pilot survey was carried out in June 2008, and data entry forms were amended where necessary on the basis of feedback from fishers. Background information on gear use and fishing practices was also collected from each skipper taking part. Data collection ran from July 2008 to July 2009, with a total of 3585 daily fleets sampled for summary data and 135 monthly fleets sampled for size composition, measuring 4852 individual lobsters (Table 6). 5 One fleet typically comprises between 20 and 40 pots. 11

16 Table 6. Data collected in logbook scheme Vessel Days at sea Daily fleet samples Monthly samples Lobsters measured Total Size composition Monthly lobster measurements were standardised to frequency per 100 pots, and used to plot the length frequency distribution of the sampled catch. 6 Analysis was restricted to lobsters between mm, however only 1 lobster was recorded >130 mm (137mm), and 87 recorded <60 mm (67 male, 20 female). The data therefore includes over 98% of the catch from the pots sampled. Standardised length frequencies from the monthly survey data were used to assess the composition of the catch in terms of male, female and ovigerous lobsters. The proportion of the catch <MLS and >MLS was also assessed using both daily and monthly sample data, and the two datasets compared using a Mann-Whitney U test. The proportion of the catch above and below MLS throughout the year was assessed using daily sample data. Further analysis was carried out using monthly sample data to test the relationship between size of lobsters caught and season using a Chi Square test of independence. For this purpose length frequency data were categorised into size classes of 5 mm intervals up to 100 mm CL, and 10 mm intervals from mm. Monthly sample data included the geographic position of each fleet sampled and the water depth at that location. Depth measurements were categorised as 0-10 m, m, m and >30 m. The length frequency distribution was plotted for each depth zone and a Chi Square test of independence used to assess the relationship between depth and frequency of lobsters in each size class Management measures Monthly survey data was used to determine the proportion of landed catch that is currently between mm CL throughout the year (and would therefore be affected by a potential increase in MLS from 87 mm to 90 mm). The proportion of landed catch that was ovigerous throughout the year was also calculated to assess the possible impact of a ban on landing ovigerous females. 6 All records submitted for July (2008 and 2009) were combined on the basis that no difference in size was found between the two years (U = 35363, Z = -0.35, p = 0.72). 12

17 3. Results 3.1 DISTRIBUTION OF POTTING ACTIVITY Distribution of activity and pot density Vessel sightings throughout the district indicated the distribution of observed fishing activity, highlighting hotspots for lobster and crab potting (Fig. 3a). Home ranges of ports within the district (Fig. 3b) range from 26 km 2 to 260 km 2 (Table 7). Observation-area curves suggest there may be insufficient data to adequately estimate home range for some ports however, so estimates for Cullercoats, Berwick and Burnmouth, where there were low numbers of vessel sightings, should be treated with caution. When estimates of port home ranges are overlaid it is apparent that while some ports appear to have exclusive use of large areas, in other areas there is considerable overlap between port home ranges (Fig. 3c). Table 7. Port home range (HR) estimates Port Vessel sightings (total ) HR (95 PVC) (km 2 ) % HR overlapping with other port HR Amble Beadnell Berwick Blyth Boulmer Burnmouth Craster Cullercoats Holy Island Newbiggin North Shields Seahouses Incorporation of data on pot months (Fig. 3d) gives a further indication of the distribution of fishing effort throughout the district. Allocation of mean annual pot months to the home range contours of each port resulted in a minimum of 4 pot months km -2 year -1 within the 100 PVC contour, and a maximum of almost 700 pot months km -2 year -1 within the 50 PVC. The overall picture is similar to that of the KDE (Fig. 3a), but suggests a higher degree of fishing effort in the far north of the district and lower fishing effort in the central area than indicated by the KDE, adjacent to the port of Craster in particular Seasonal change Seasonal home ranges for the district s vessels were at a minimum of 605 km 2 during July to September, and a maximum of 800 km 2 October to November, from a total possible area of 1404 km 2 (NSFC district). Pot month data (Fig. 4. a-d) shows a distinct seasonal pattern, with the level of fishing activity highest in summer months and concentrated close inshore. The median number of pot landings (days per month that pots are hauled) is highest during Jul-Sep (median = 16, compared to median = 7 Jan-Mar, and median = 10 both Apr-Jun and Oct-Dec, K-W χ 2 (3) = 928, p<0.001) therefore the maps presented here potentially underestimate the disparity in fishing effort between seasons. 13

18 Fig. 3. a) KDE of vessel sightings (all ports), b) 95 PVC home range estimates, c) overlap between port home ranges, and d) distribution of fishing effort (pot months km -2 year -1 ). Further details in text. 14

19 Fig. 4. Seasonal distribution of pot months (mean annual total ): a) Jan-Mar, b) Apr-Jun, c) Jul-Sep, d) Oct-Dec Further details in text. 15

20 From October to December fishing effort is distributed more widely and fishing effort remains relatively high, while from January to June fishing effort is lower but remains concentrated further offshore Habitat use Information on marine substrate was available for 803 km 2 (57% of the NSFC district), with the remaining area comprising unknown substrate (Fig. 5). A total of 2669 (79%) vessel sightings fell within the coverage of the habitat data. Fig. 5. Distribution of substrate categories (after Foster-Smith 1998), see Table 3 for description of categories The observed distribution of vessel sightings among substrate types was different to their expected distribution according to the availability of each substrate within the district (χ 2 (3) = 1220, p < 0.001). Vessels showed the strongest preference for hard ground, and a weak preference for patchy ground, together with a weak avoidance of smooth ground, and stronger avoidance of unknown habitat types (Table 8). Table 8. Overall preference for substrate types (all ports, all seasons) Substrate Area km 2 (%) Vessel sightings (%) Hard 303 (22) 1492 (44) 0.34 Patchy 302 (21) 868 (25) 0.08 Smooth 198 (14) 309 (9) Unknown 601 (43) 737 (22) E 16

21 Differences in habitat electivity may result from actual preferences for or against substrata, or differences in the accessibility of each substrate to vessels, as low availability of a habitat type tends to make it appear selected against when using Ivlev s index of electivity (Strauss 1979). All substrata were represented to varying degrees in the home range of each port (Fig. 6). There was a relationship between home port and the frequency of vessel sightings on each substrate type (χ 2 (3) = 470, p < 0.001), although Ivlev s electivity index (Fig. 7a) shows a similar overall pattern of preferences throughout the district. Differences between ports may be due to variable accessibility of different substrate types from each home port. For example, the electivity index suggests patchy substrate is avoided at Amble and Newbiggin, yet this substrate is not widespread near these ports (Fig. 5). A relationship was also found between season and substrate use (χ 2 (9) = 241, p < 0.001). Ivlev s electivity index again suggests that overall preference/avoidance patterns between substrate types are similar across all seasons, but with a greater preference for hard ground in summer, when the majority of fishing effort is focused close inshore (Fig. 7b). Area (km 2 ) Unknown Smooth Patchy Hard Landing port Fig. 6. Composition of port home range E 0.0 E Hard Patchy Smooth Unknown -1.0 Hard Patchy Smooth Unknown North Shields Cullercoats Blyth Amble Boulmer Craster Seahouses Holy Island Berwick Newbiggin Beadnell Burnmouth Jan-Mar Apr-Jun Jul-Sep Oct-Dec Fig. 7. Preference for substrate types by a) port and b) season 17

22 3.2 LOBSTER LANDINGS Fishing effort The number of NSFC shellfish permits issued and percentage of vessels submitting monthly returns remained relatively constant under NSFC data collection, which ended in March 2006 (Table 9). In each year there were a number of vessels holding shellfish permits that did not submit returns, in most cases because they were not actively targeting shellfish (Garside et al. 2003, NSFC pers. comm.). The lower percentage of vessels submitting monthly returns in coincides with the change in data collection schemes. Supplementary data from the MFA and Marine Scotland on landings by >10 m and Scottish vessels respectively accounted for 12 additional vessels in 2006 and 15 in 2007 (included in Table 9). After incorporating these vessels, data still suggest a drop in return rates following the end of data collection by NSFC, with the percentage of permit holders submitting returns to the relevant authorities around 20% lower than in Total pot numbers in the district appear to have remained relatively constant over time when missing data for Scottish and >10 m vessels are factored in to estimates, though data suggest an increase in the median number of pots worked per vessel (Table 9). No trend is apparent in the median number of pot landings per month. Table 9. Fishing effort, lobster landings and LPUE Year Permits issued Active vessels (% total) Monthly returns b Total pots worked b Median pots per vessel b Median pot landings per month b Total landings (t yr -1 ) Median landings (kg vessel -1 month -1 ) b (70%) (74%) (76%) (71%) (76%) (56%) a (30713) (57%) (29670) Median LPUE (kg 100 pots -1 day -1 ) b a Submission rates for 2006 based on April onwards, following change in data collection schemes b No information available for >10 m and Scottish vessels after March Figures in parentheses under total pots worked include estimates for >10 m and Scottish vessels (assumed to be the same as mean annual totals for these groups) Lobster landings A seasonal pattern in total lobster landings is evident, with highest landings occurring in late summer (Fig. 8). A seasonal pattern is also evident in median landings per vessel (Fig. 9), with peaks occurring in summer months. Peak landings appear to be higher in than in previous years; this may be related to increased quantities of gear being worked per vessel as there is a significant correlation between number of pots worked and monthly lobster landings (Spearman s rho = 0.50, p < 0.001). No trend is evident in lobster landings over the years for which data are available. When data for >10 m and Scottish vessels are taken into account, landings in are comparable to previous years (Fig. 8). Given the apparent decline in reporting rates during the available data may still underestimate lobster landings during these years. 18

23 Jan-01 May-01 Sep-01 Jan-02 May-02 Sep-02 Jan-03 May-03 Sep-03 Jan-04 May-04 Sep-04 Jan-05 May-05 Sep-05 Jan-06 May-06 Sep-06 Jan-07 May-07 Sep-07 Total lobster landings (t) NSFC data MFA data Fig. 8. Total lobster landings by NSFC shellfish permit holders (t) (MFA data: solid line includes supplementary data on >10 m and Scottish vessels, dotted line extrapolates to mean return rate of previous years) Median landings (t vessel-1 month-1) NSFC data MFA data Jan-01 May-01 Sep-01 Jan-02 May-02 Sep-02 Jan-03 May-03 Sep-03 Jan-04 May-04 Sep-04 Jan-05 May-05 Sep-05 Jan-06 May-06 Sep-06 Jan-07 May-07 Sep-07 Fig. 9. Median lobster landings Landings per unit effort (LPUE) LPUE appears to be stable over the years for which data are available. Seasonal patterns are similar to those of median monthly lobster landings but with a tendency to higher peaks (Fig. 10). 7 6 Median LPUE (kg 100 pots -1 day -1 ) NSFC data MFA data Jan-01 May-01 Sep-01 Jan-02 May-02 Sep-02 Jan-03 May-03 Sep-03 Jan-04 May-04 Sep-04 Jan-05 May-05 Sep-05 Jan-06 May-06 Sep-06 Jan-07 May-07 Sep-07 Fig. 10. Median monthly LPUE 19

24 3.2.4 Spatial differences Over 40% of mean annual landings were from vessels in Amble and Seahouses, home to the largest active potting fleets, together working 40% of potting gear operated within the district. Blyth, North Shields and Scottish vessels together worked a further 30% of the fishing gear within the district (although Scottish vessels operate their gear in both the NSFC district and Scottish waters, with approximately 50% of effort estimated to be within the district (NSFC fishery officers, pers. comm.)). All other ports were home to small fleets, operating 5% or less of total pots worked (Table 10). In most cases the percentage of total landings from each port is within 1-2% of the percentage of total gear worked, the main exception being Holy Island, where a small fleet landed 10% of the mean annual total lobster landings. Table 10. Fishing effort, lobster landings and LPUE by port, (totals based on mean annual totals, medians based on pooled data) Landing Port Active vessels* (% total) Total pots worked (% total) Median pots vessel -1 Median pot landings Total landings, t yr -1 (% total) Median landing, kg vessel -1 month -1 Median LPUE, kg 100 pots -1 day -1 Amble 25 (24) 5834 (19) (18) Beadnell 7 (7) 1481 (5) (3) Berwick 5 (5) 1451 (5) (6) Blyth 13 (13) 3328 (11) (9) Boulmer 3 (3) 1344 (4) (4) Scotland 5 (5) 2825 (9) (11) Craster 3 (3) 1549 (5) (4) Cullercoats 2 (2) 221 (1) (1) Holy Island 5 (5) 2149 (7) (10) N Shields 14 (13) 2947 (10) (7) Newbiggin 7 (7) 1508 (5) (5) Seahouses 15 (14) 5969 (20) (23) There are differences between ports in the median number of pots worked per vessel, ranging from 40 in Cullercoats to 500 by Scottish vessels. Ports with a higher median pot number coincided with higher median pot landings per month, although it is perhaps more likely that vessels operating a large number of pots haul only a proportion of their gear on each fishing trip. The highest landings per vessel per month also corresponded to ports with the highest median number of pots worked per vessel, although these were not necessarily the ports with the highest LPUE (Table 10). Median LPUE ranged from 0.5 to 1.3 kg 100 pots -1 day -1, with the highest LPUE found in Cullercoats. Landings per unit area ranged from a minimum of 2 kg km -2 yr -1, to a maximum of 484 kg km -2 yr -1 (Fig. 11). The highest estimates of landings per unit area were at Holy Island, with maximum values at all other ports below 300 kg km -2 yr

25 Fig. 11. Estimated distribution of lobster landings by port (mean annual totals ) Seasonal estimates of the distribution of landings again highlight the importance of summer months (July- September) in the lobster fishery, with mean annual landings per unit area reaching 313 kg km -1 season -1 (Fig. 12). Landings per unit area were much lower for the rest of the year, reaching a maximum of 86 kg km -1 season -1 in some areas during Oct-Dec, and a maximum of 42 kg km -1 season -1 from Jan-Jun. 21

26 Fig. 12. Estimated distribution of lobster landings by season (mean annual totals ): a) Jan-Mar, b) Apr-Jun, c) Jul- Sep, d) Oct-Dec 22