4.9.5 Norwegian spring-spawning herring

Transcription

1 4.9.5 Norwegian springspawning herring State of the stock Spawning biomass in relation to precautionary limits Acceptable Fishing mortality in relation to precautionary limits Acceptable Fishing mortality in relation to highest yield Comment Based on the most recent estimates of SSB and fishing mortality, ICES classifies the stock as having full reproduction capacity and harvested sustainably. The recruitment of the very strong 1992 year class led to an increase in SSB in 1997 to approximately 8 million t. Thereafter, SSB declined to just below 5 million t in 21 and increased again to 7 million t in 24. The year classes 1998 and 1999 are estimated to be relatively strong. Management objectives EU, Faroe Islands, Iceland, Norway, and Russia agreed to implement a longterm management plan. This plan consists of the following elements: 1. Every effort shall be made to maintain a level of Spawning Stock Biomass (SSB) greater than the critical level (B lim ) of 2 5 t. 2. For the year 21 and subsequent years, the Parties agreed to restrict their fishing on the basis of a TAC consistent with a fishing mortality rate of less than.125 for appropriate age groups as defined by ICES, unless future scientific advice requires modification of this fishing mortality rate. 3. Should the SSB fall below a reference point of 5 t (B pa ), the fishing mortality rate referred to under paragraph 2, shall be adapted in the light of scientific estimates of the conditions to ensure a safe and rapid recovery of the SSB to a level in excess of 5 t. The basis for such an adaptation should be at least a linear reduction in the fishing mortality rate from.125 at B pa (5 t) to.5 at B lim (2 5 t). 4. The Parties shall, as appropriate, review and revise these management measures and strategies on the basis of any new advice provided by ICES. ICES considers that this agreement are consistent with the precautionary approach.reference points Precautionary Approach reference points ICES considers that: ICES proposed that: B lim is 2.5 million t B pa be set at 5. million t F lim is not considered relevant for this stock F pa be set at F =.15 Target Reference Points Management has defined F y at.125 Technical basis: B lim : MBAL B pa : =B lim * exp(.4*1.645) (ICES Study Group 1998) F lim : F pa : ICES Study Group 1998 Single stock exploitation boundaries Exploitation boundaries in relation to existing management plans The management plan implies catches of 89 t in 25 which is expected to lead to spawning stock of 6.3 million tonnes in

2 Exploitation boundaries in relation to high long term yield, low risk of depletion of production potential and considering ecosystem effects The target defined in the management plan is consistent with high term yield and have a low risk of depletion production potential. Exploitation boundaries in relation to precautionary limits The current longterm management plan is considered to be precautionary. Short term implications Outlook for 25: Basis: Landings (24) = 825 1) ; F w (24) 2) =F sq =.17; SSB(24)=6966; The fishing mortality applied according to the agreed management plan (F(management plan)) is.125 Rationale TAC Basis F(25) SSB(25) SSB(26) (25) 3) Zero catch F= Status quo 117 Fsq Agreed 159 F(management plan)* management 23 F(management plan)* plan 46 F(management plan)* F(management plan)* F(management plan)* F(management plan) F(management plan)* F(management plan)* Shaded scenarios not consistent with the precautionary approach. 1) There was no agreement on the TAC in 24, but the sum of autonomous allocations from most of the individual Parties amount to 825 t. 2) F w = Fishing mortality weighted by population numbers 3) It is assumed that TAC will be implemented and that the landings in 25 therefore correspond to the TAC. Management considerations This stock has shown large dependency on the occasional very strong year class. In recent years the stock has tended to produce strong year classes more regularly. However, if the recruitment in the future should get low again, the stock is expected to decline. Ecosystem considerations Juveniles and adults of this stock form an important part of the ecosystems in the Barents Sea, the Norwegian Sea and the Norwegian coast. The herring has an important role as transformer of the plankton production to higher trophic levels (cod, seabirds, and marine mammals). Factors affecting the fisheries and the stock Regulations and their effects In the rebuilding phase of the stock, as long as the SSB was estimated to be below the MBAL level of 2.5 million t, it was an objective to keep the fishing mortality below.5 in order to rebuild the stock. With very few years of exceptions, this regulation objective was followed. A minimum landing size regulation of 25 cm has been in place since This has avoided exploitation of young and immature herring, and has led to an effective rebuilding of the stock. 359

3 These regulations have contributed to a rebuilding of the stock to levels well above precautionary limits. When the fishery expanded in the mid 199s, a long term management plan was agreed; this plan is cited above. At the meeting on Fisheries Consultation on the management of Norwegian springspawning herring (Atlanto Scandian) herring stock in Reykjavik, Iceland in October 23, the coastal states (European Union, Faroe Islands, Iceland, Norway, and Russia) did not reach any agreement regarding the allocation of the quota. At a following NEAFC meeting on the management of Norwegian springspawning herring stock in Copenhagen, the parties were unable to reach any agreement on quota allocations. However, there seemed to be an unwritten understanding between the parties to accept the TAC proposed by ACFM to limit the total catches to 825 t in 24. Changes in fishing technology and fishing patterns The main catches from the fishery in 23 were taken by Norway (438 t), Russia (123 t), Iceland (13 t), and Faroe Islands (23 t). Lesser catches were taken by a number of EU fleets (42 t). The fisheries in general follow the migration of the stock closely as it moves from the wintering and spawning grounds along the Norwegian coast to the summer feeding grounds in the Jan Mayen, Svalbard, and international areas. The Norwegian fishery exploits the stock as it migrates to and remains at the wintering areas and during the spawning period. The Icelandic fishery takes place mainly in May and June, and most catches are taken in international waters and in the Jan Mayen EEZ. The main Russian catches are taken along the shelf region of the Norwegian EEZ in spring as the stock moves from the spawning grounds, and also in August and September in the eastern part of the international area and in the Norwegian zone. The Faroese catches, taken mainly in spring and early summer, are from the Norwegian zone and from the Jan Mayen area. Most of the EU catches are taken in the international area and in the Norwegian zone. In 22 the nonnorwegian fleets fished more young herring than Norway. This was due to the emigration from the Barents Sea of the 1998 and 1999 year classes. These year classes did not appear to any great extent in the area where the main Norwegian fishery took place (fjord areas in northern Norway). A large increase in fishing effort, new technology, and environmental changes contributed to the collapse of this stock around 197. Recruitment failed in second half of 196s when the SSB was reduced below 2.5 million t. Starting in 1989 a succession of aboveaverage to very strong year classes were produced, promoting full recovery of the SSB and allowing expansion of fisheries. Up to 1994, the fishery was almost entirely confined to Norwegian coastal waters. Since 1992 the coastal fishery has increased sharply. During the summer of 1994 there were also catches in the offshore areas of the Norwegian Sea for the first time in 26 years. The geographical extent of this fishery increased in 1995, with nine nations participating and a total catch exceeding 9 t. The fishery expanded further in 1996 and the annual level of the fishery was in the order of million t in the period The environment The Norwegian spring spawning herring carries out extensive migrations in the NE Atlantic. Feeding has mainly taken place along the polar front from the island of Jan Mayen and NEwards towards Bear Island. Over the last 25 years the southern and western Norwegian Sea has become colder and fresher while the eastern Norwegian Sea is warmed. In 23 the westerly distribution of the Atlantic Water increased and a relative large westerly distribution is also expected in 24. In 23 the herring migration was more southerly and westerly than in the years before. There are indications that environmental factors might be used in predicting fish recruitment. Scientific basis Data and methods The advice is based on an analytical assessment, which takes into consideration catch data, acoustic surveys of adults and juveniles, larval survey, and tagging data. Different model formulations have been applied to assess this stock. When using almost the same data the models SeaStar and ISVPA performed similarly (showed the same overall trend and status of the stock). However, it is at present impossible to compare the methods in terms of statistical fit to the data because they do not give comparable statistical output. The choice of data series and the way of their handling makes differences in the results of the models. The SeaStar model has been chosen for final assessment as in previous years. This model allows for using more data sources than the other considered model. However, the retrospective analysis indicates significant uncertainty in the estimates, Figure

4 Comparison with previous assessment and advice: The model used this year is the same as used last year (SeaStar). This year s estimate of the spawning stock in 23 is 5.8 million t, which is the same value as estimated for 23 last year.the estimated stock size is rather imprecise. Historically there has been tendency to overestimate the spawning stock. The standard deviation of the spawning stock, derived from bootstrap replicates, has increased considerably from last year. The distribution is also more skewed than last year. Source of information Report of the Northern Pelagic and Blue Whiting Fisheries Working Group, 27 April 24/ACFM:24) 4 May 24 (ICES CM Year ICES Advice Predicted catch corresp. to advice Agreed 1987 TAC TAC TAC TAC No fishing from a biological point of view No fishing from a biological point of view No increase in F Gradual increase in F towards F.1 ; TAC suggested No increase in F 513 None 1 96 TAC ACFM Catch 1996 Keep SSB above 2.5 million t None Keep SSB above 2.5 million t Do not exceed the harvest control rule Do not exceed the harvest control rule Do not exceed the harvest control rule Max Do not exceed the harvest control rule Do not exceed the harvest control rule Do not exceed the harvest control rule ) Do not exceed the harvest control rule ) 25 Do not exceed the harvest control rule 89 1 Autonomous TACs totaling 9 t; 2 Autonomous TACs totaling t were set by April There was no agreement on the TAC, the number is the sum of autonomous allocations from most of the individual Parties. Weights in t. 361

5 Norwegian springspawning herring Landings 25 Landings in 1 t Fishing Mortality F weighted (ages 514) F Fpa Recruitment (age ) Recruitment in billions Spawning Stock Biomass SSB in 1 t SSB Blim Bpa 362

6 Stock Recruitment Recruitment (age ) in billions SSB in 1 t SSBRec. Blim Bpa SSB in 1 t Precautionary Approach Plot Period Fishing Mortality (ages 514) FSSB 23 Fpa Blim Bpa 363

7 364 Table Total catch of Norwegian springspawning herring (tonnes) since Data provided by Working Group members. Year Norway USSR/ Russia Denmark Faroes Iceland Ireland Netherlands Greenland UK Germany France Poland Sweden Total ,161 7,17 7,619 13,713 1,436 22,76 19,824 12,864 18,577 13,736 16,655 23,54 53, , ,256 18, ,76 88,77 74,64 73,683 91, ,771 38, , ,161 86, ,925 74,64 713,5 495,36 487, ,14 2,6 26, 18,889 2,225 15,123 11,87 11, 13,337 32,645 74,4 11, ,29 168,9 124,49 157, ,261 19,54 113, ,846 3,577 6,681 44,292 35,519 37,1 34,968 24,38 18,998 14,144 2,911 57,84 52,788 59,987 68,136 55,527 68,625 34,17 32,32 27,943 21, ,19 164,957 22, ,789 23, ,35 77, ,197 12,727 19,541 11,179 2,437 2,412 8, ,969 19,664 8,694 12,827 5,871 6,439 9,392 8,678 2, ,131 25,149 15,971 19,27 14,96 12,23 3,482 9, ,978 6,19 7,3 3,298 1,588 3,17 3,371 1,5 65 1,226 22,424 19,499 14,863 14,57 14,749 9,818 9,486 6,431 13,161 7,17 7,619 13,713 1,436 22,76 19,824 12,864 18,577 13,736 16,655 23,54 53, , , ,36 135,31 13,83 86,411 84,683 14, , ,228 95,51 1,22,283 1,426,57 1,223,131 1,235,433 1,27,21 77,66 86,86 733,494 1 Preliminary, as provided by Working Group members.

8 Table Norwegian springspawning herring Year Recruitment SSB Landings F weighted Age Ages 514 thousands tonnes tonnes Average

9 SSB mill tons 12 Retrospective Analysis Norwegian Spring Spawning Herring Year Figure Retrospective plot of Spawning Stock Biomass estimates from SeaStar for Norwegian spring spawning herring. 366