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International Council for the Exploration of the Sea Conseil International pour l’Exploration de la Mer

Advisory Committee on Fisheries Management ICES CM 2001/ACFM:02

REPORT OF THE

ARCTIC FISHERIES WORKING GROUP

ICES Headquarters 22–31 August 2000

This report is not to be quoted without prior consultation with the General Secretary. The document is a report of an expert group under the auspices of the International Council for the Exploration of the Sea and does not necessarily represent the views of the Council.

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O:\ACFM\WGREPS\AFWG\REPORTS\2001\AFWG01.doc 1

TABLE OF CONTENTS

Section Page

1 INTRODUCTION ...1

1.1 Participants ...1

1.2 Introduction ...1

1.3 General Comments ...2

1.4 Review of the estimated MBAL for Northeast Arctic cod ...2

1.5 Stock structure of cod in the NorthEast Arctic Region...3

1.6 ICES Quality Policy ...3

1.7 Reliability of Catch Statistics ...3

1.8 Scientific Presentations ...3

1.9 Nomination for New Chair ...6

1.10 Time and Venue of Next Meeting ...6

2 NORWEGIAN COASTAL COD IN SUB-AREAS I AND II ... 7

2.1 Status of the Fisheries...7

2.1.1 Historical development of the fisheries ...7

2.1.2 Landings prior to 1999 (Table 2.1)...7

2.1.3 Expected landings in 2000 ...7

2.2 Status of Research ...7

2.2.1 Fishing effort and CPUE ...7

2.2.2 Survey results (Tables 2.2, 2.3, 2.4, 2.5, 2.8) ...7

2.2.3 Age reading and stock separation...8

2.2.4 Weight at age (Table 2.6) ...8

2.2.5 Maturity at age (Table 2.7)...8

2.3 Data Used in the Assessment...8

2.3.1 Catch-at-age (Table 2.10)...8

2.3.2 Weight-at-age (Table 2.11, 2.12) ...8

2.3.3 Natural mortality ...9

2.3.4 Maturity-at-age (Table 2.13) ...9

2.3.5 Tuning data (Table 2.8) ...9

2.3.6 Recruitment indices (Table 2.8) ...9

2.4 Methods Used in the Assessment ...9

2.4.1 VPA and tuning (Table 2.09) ...9

2.4.2 Recruitment ...9

2.5 Results of the Assessment ...9

2.5.1 Fishing mortality and VPA (Tables 2.14–2.20) ...9

2.5.2 Recruitment (Table 2.8, 2.16) ...10

2.6 Comments to the Assessment ...10

2.6.1 General comments...10

2.6.2 A comparison of the assessment results and the survey results (Figures 2.1–2.3) ...10

Tables 2.1 - 2.20...11

Figures 2.1 - 2.3 ...22

3 NORTH-EAST ARCTIC COD (SUB-AREAS I AND II) ...25

3.1.1 Historical development of the fisheries (Table 3.1) ...25

3.1.2 Landings prior to 2000 (Tables 3.1–3.3, Figure 3.1A) ...25

3.2.1 Fishing effort and CPUE (Table A1)...25

3.2.2 Survey results (Tables A2-A5, A10-A11, A14-A15) ...25

3.2.3 Age-reading ...26

3.2.4 Length and weight-at-age (Tables A6-A9, A12-A13)...26

3.2.6 Condition (Figure 3.2)...27

3.2.7 Fecundity at length of pre-spawning females...27

3.2.8 Total egg production by the stock (Figure 3.3) ...27

3.3.1 Catch-at-age (Tables 3.7 and 3.8)...27

3.3.2 Weight-at-age (Tables 3.4 and 3.9–3.10) ...28

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Section Page

3.3.4 Maturity-at-age (Tables 3.5 and 3.11) ...28

3.3.7 Predation and cannibalism...29

3.3.8 Prediction data (Table 3.22, Figure 3.4)...30

3.4.1 VPA and tuning ...31

3.4.2 Recruitment (Table 3.6) ...32

3.4.3 Including cannibalism in the VPA (Tables 3.13–3.16) ...32

3.5.1 Fishing mortalities and VPA (Tables 3.17–3.21, Figures 3.1A-B, and 3.7–3.9)...33

3.6 Reference Points and Safe Biological Limits ...33

3.6.1 Biomass reference points (Figure 3.5)...33

3.6.2 Fishing mortality reference points...34

3.7 Catch Options (Table 3.23) ...34

3.8 Medium-Term Forecasts and Management Scenarios...34

3.8.1 Input data (Table 3.22) ...34

3.8.2 Methods...34

3.8.3 Results ...35

3.8.4 Management considerations ...35

3.9 Comments to the Assessment (Figures 3.6–3.9) ...35

3.10 Alternative Assessment Methods (Fleksibest)...36

3.10.1 Background ...36

3.10.2 Model description...36

3.10.3 Stock assessment using Fleksibest ...37

3.10.3.1 Time period ...37

3.10.3.2 Model stock, length and age structure ...37

3.10.3.3 Data used ...37

3.10.3.4 Model assumptions...38

3.10.4 Results from the key run ...38

3.10.5 Use of Fleksibest for predictions ...39

3.10.6 Data preparation ...39

3.10.7 Future work ...39

3.10.8 Practical considerations ...39

Tables 3.1 - 3.27...40

Figures 3.1 a-d -3.12d ...98

Tables A1 - A17 ...111

4 NORTH-EAST ARCTIC HADDOCK (SUB-AREAS I AND II) ...122

4.1.2 Landings prior to 2000 (Tables 4.1–4.3, Figure 4.1A) ...122

4.2.1 Fishing effort and CPUE ...122

4.2.2 Survey results (Tables B1-B6) ...122

4.2.3 Weight at age (Table B6) ...123

4.3.1 Catch at age (Table 4.7) ...123

4.3.2 Weight at age (Tables 4.8–4.9) ...124

4.3.3 Natural mortality (Table 4.10)...124

4.3.4 Maturity at age (Table 4.4 and 4.11) ...124

4.3.5 Data for tuning (Table 4.12)...124

4.3.7 Prediction data (Table 4.19) ...124

4.4.2 Recruitment (Tables 4.6, 4.15) ...126

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Section Page

4.5.1 Fishing mortality and VPA (Tables 4.13–4.18 and Figures 4.1A and 4.1B)...126

4.5.2 Recruitment (Tables 4.5–4.6, 4.15, 4.19) ...126

4.5.3 Yield per Recruit (Table 4.20, Figure 4.1C)...126

4.5.4 Catch options for 2000 (Table 4.21)...126

4.6 Biological Reference Points ...126

4.6.1 Biomass reference points (Figure 4.4)...126

4.6.2 Fishing mortality reference points...127

4.7 Medium-Term Forecasts and Management Scenarios...127

4.7.1 Input data (Table 4.19) ...127

4.7.2 Methods...127

4.7.3 Results (Tables 4.22–4.23 and Figures 4.1D and 4.5)...127

4.8 Comments to the Assessment and Forecasts ...127

Tables 4.1 - 4.23...129

Figures 4.1 a-d - 4.6 a-d ...174

Tables B1 - B6 ...183

5 NORTHEAST ARCTIC SAITHE (SUB-AREAS I AND II)...189

5.1 Status of the Fishery ...189

5.1.1 Historical development of the fisheries (Tables 5.1–5.2)...189

5.1.2 Landings prior to 2000 (Table 5.1, Figure 5.1A, 5.2A)...189

5.2.1 Fishing effort and catch-per-unit-effort (Tables C1–C3) ...190

5.2.2 Survey results (Tables C4-C5) ...190

5.3.1 Catch numbers-at-age (Table 5.3) ...191

5.3.2 Weight-at-age (Table 5.4) ...191

5.3.6 Recruitment indices...191

5.3.7 Prediction data (Table 5.14) ...192

5.4.1 VPA and tuning (Tables 5.6, Figures 5.2A–C) ...192

5.4.2 Recruitment (Tables 5.12–5.13, Figures 5.3 B–C)...192

5.5.1 Fishing mortalities and VPA (Tables 5.7–5.11, Figures 5.1A-B, 5.3A-C)...192

5.5.2 Recruitment (Tables 5.11–5.13) ...192

5.6 Reference Points...193

5.6.1 Biomass reference points...193

5.6.2 Fishing mortality reference points (Table 5.15, Figures 5.1C, 5.4)...193

5.7 Catch Options for 2001 (Short-Term Predictions) (Tables 5.16) ...193

5.8 Medium-Term Forecasts and Management Scenarios (Table 5.17, Figure 5.1D)...193

5.8.1 Input data and methods...193

5.8.2 Results ...193

5.9 Comments on the Assessment and the Forecast ...194

Tables 5.1 - 5.17...195

Figures 5.1 a-d - 5.6 a-c ...217

Tables C1 a-b - C5 ...228

6 SEBASTES MENTELLA (DEEP-SEA REDFISH) IN SUB-AREAS I AND II...229

6.1.1 Historical development of the fishery ...229

6.1.2 Landings prior to 2000 (Tables 6.1–6.5, D1–D2) ...229

6.2.1 Fishing effort and catch-per-unit-effort (Table D3, Figure 6.7) ...230

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Section Page

6.2.3 Weight-at-age (Table 6.6) ...230

6.2.4 Maturity-at-age (Tables 6.7 and D8) ...230

6.2.5 Survey results (Tables A14, D4–D7, Figures 6.1–6.6)...231

6.5 Management Advice...232

Tables 6.1 - 6.7...233

Figures 6.1 - 6.7 ...243

Tables D1 - D8...252

7 SEBASTES MARINUS (GOLDEN REDFISH) IN SUB-AREAS I AND II ...259

7.1.1 Historical development of the fishery ...259

7.1.2 Landings prior to 2000 (Tables 7.1–7.5, D1 and D2)...259

7.2.1 Fishing effort and catch-per-unit-effort (Tables D9–D10, Figure 7.1a,b) ...259

7.2.3 Weight-at-Age (Table 7.9) ...260

7.2.4 Maturity-at-age...260

7.2.5 Survey results (Tables 7.6 and 7.7, D11a,b–D12a,b, Figures 7.2–7.3) ...260

7.5 Management Advice...261

Tables 7.1 - 7.9...262

Figures 7.1ab - 7.3b...269

Tables D9 - D12b ...274

8 GREENLAND HALIBUT IN SUB-AREAS I AND II...279

8.1.2 Landings prior to 2000 (Tables 8.1 – 8.5, E8)...279

8.2.1 Survey results (Tables A14, E1–E6, Figures 8.1–8.5) ...280

8.2.2 Fishing effort and catch-per-unit-effort (Table 8.6 and E7) ...281

8.2.3 Age-readings ...282

8.3.1 Catch at age (Tables 8.7 – 8.8) ...282

8.3.2 Weight at age (Table 8.7, 8.9) ...282

8.3.4 Maturity-at-age (Tables 8.7, 8.10)...282

8.3.5 Tuning data...282

8.3.6 Recruitment indices (Tables A14, E1–E6) ...283

8.5.1 Results of the illustrative VPA (Tables 8.11–8.16)...283

8.5.2 Biological reference points...284

8.5.3 Catch options for 2001 ...284

8.6 Comments to the Assessment ...284

Tables 8.1 - 8.16...285

Figures 8.1 - 8.7 ...306

Tables E1 - E8...312

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Section Page

9 SHRIMP (PANDALUS BOREALIS) (SUB-AREAS I AND II) ...317

9.1.1 Historical development of the fisheries (Table 9.1, Figure 9.1–9.2) ...317

9.1.2 Regulation ...317

9.1.3 Landings (Table 9.1, Figure 9.1) ...317

9.2.1 Surveys ...317

9.2.2 Fishing effort and CPUE (Table 9.2, Figure 9.3) ...317

9.2.3 Survey results (Tables 9.3–9.4, Figure 9.3–9.4)...318

9.2.4 Population structure...318

9.2.5 Age-reading ...318

9.2.6 Maturity-at-age...318

9.2.8 Natural mortality and predation...319

9.3 Evaluation of the Stock ...319

9.3.1 Assessment methods under progress (Table 9.5) ...319

9.3.2 Single species VPA ...320

9.3.3 Multispecies model MSVPA...320

9.4 Status of the Stock (Table 9.2–9.4, Figure 9.3–9.5) ...320

9.5 Further Cooperation ...321

Tables 9.1 - 9.5...322

Figures 9.1 - 9.5 ...329

10 WORKING DOCUMENTS ...334

11 REFERENCES ...336

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1 INTRODUCTION 1.1 Participants

Asgeir Aglen Norway

Ole Thomas Albert Norway

Morten Åsnes Norway

Michaela Aschan Norway

Erik Berg Norway

Boris Berenboim Russia

Bjarte Bogstad Norway

Vladimir Borisov Russia

Tatiana Bulgakova Russia

Ray Bowering (Chair) Canada

Santiago Cerviño Spain

Konstantin V. Drevetnyak Russia

Jens-Eric Eliassen (part-time) Norway

Åge Fotland Norway

Kristin Guldbrandsen Frøysa Norway

Åge Høines Norway

Victor Korsev Russia

Yuri Kovalev Russia

Yu. M. Lepesevich Russia

C. Tara Marshall Norway

Sigbjørn Mehl Norway

Lorenzo Motos Spain

Kjell H. Nedreaas Norway

David Orr Canada

Xabier Paz Spain

Victor Tretyak Russia

1.2 Introduction

At its November 1999 meeting ACFM decided the following:

“The Arctic Fisheries Working Group [AFWG] (Chair: Dr R. Bowering, Canada) will meet at ICES Headquarters from 22 August to 31 August 2000 to:

a) assess the status of and provide catch options for the year 2001 for the stocks of cod, haddock, saithe, Greenland halibut, and redfish in Sub-areas I and II, taking into account interactions with other species and attempting alternative assessment methods where applicable;

b) evaluate the agreed management strategy for cod, fixing F at a level that maintains SSB above 500,000 t (Bpa) and reducing the fishing mortality to F = 0.42;

c) identify major deficiencies in the assessments.

At the request of Norway during the winter of 2000, shrimp (Pandalus borealis) in Sub-area I and II was also added to the list of stocks identified in ToR (a) above. As well, a recent request from Russia to perform a review of the estimated MBAL for NEA cod was added to the agenda of the Working Group. However, no additional time was given to address these additional items.

The above Terms of Reference are set up to provide ACFM with the information required to respond to requests for advice/information.

AFWG will report to ACFM at its October/November 2000 meeting.”

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1.3 General Comments

This year the working group made advances on several fronts. The work progressed very well and under a reasonable time schedule. The fact that nearly all the data were available at the beginning of the meeting was largely responsible for being able to do this. In addition, the meeting was well attended and for most stocks there were two or more individuals processing and analysing the data, which helped to speed up the presentation of the assessment results. It also helped that both the NEA cod and haddock had been assessed earlier in the year and set the stage for those assessments at the current meeting. Nevertheless, with the large number of recommendations for new analyses it is anticipated that next year’s meeting will have an increased workload and considerably more time may be necessary for plenary discussions.

1.4 Review of the estimated MBAL for Northeast Arctic cod

In response to a request made by the Russian representative to the Joint Russian-Norwegian Fisheries Commission (letter to ICES General Secretary from Mikhail Dementiev dated August 7, 2000) the WG reviewed the use of a biomass reference point for Northeast Arctic cod. The discussions centred on two main issues:

1. revising the historical age-specific values of maturity, weight and natural mortality;

2. developing additional reference points based on reproductive potential.

A brief summary of the discussions on both issues follows.

Revising historical growth and mortality parameters – Current values of SSB use constant values for weight and maturity at age for the years prior to 1981 and 1982, respectively. Consequently, the majority of observations in the stock/recruit relationship do not account for interannual variation in growth. Furthermore, natural mortality at age (M) is assumed to be constant and equal to 0.2. Since 1984 this value has incorporated cannibalism but this does not decrease the uncertainty in the estimation of M. Age-dependent variation in M is not accounted for in the stock dynamics (Tretyak WD 18). These shortcomings in the assessment are being addressed by several initiatives. The historical time series of SSB has been reconstructed using maturity ogives of Jørgensen (1990) and modelled values of weight and M at age (Tretyak et al. WD 40). Using data from the Norwegian catches (1900–1945), Russian sources for 1930–1955 and the ogives of Jørgensen (1990), estimates of SSB were reconstructed back to 1900 (Hylen WD 15).

Historical values of maturity at age and weight at age are also available from published Russian sources (Ozhigin et al.

1994; Ponomarenko and Yaragina 1994). Revision of historical weight and maturity at age (1946–1981) is also being undertaken at IMR using data from the Lofoten fishery and international sampling programs. Scientists at IMR will present a new time series for SSB at the next meeting of the WG. At that time, the effect of using these revised time series on estimates of SSB will be determined and, if necessary, the Bpa will be recalculated. With respect to incorporating age- and time-dependent variation in M into the assessment, it was agreed that is more complex task (consistency of incorporating cannibalism, differences between males and females in M at age). Therefore, this is a long-term goal of the assessment.

Developing reference points based on stock reproductive potential – the utility of the current B_pa for Northeast Arctic cod is questionable due to the weakness of the stock/recruit relationship (Borisov WD 41). There is a growing body of research into the reproduction of long-lived gadoid stocks which suggests that SSB may not be indicative of the reproductive potential either of individuals or of the stock (Marshall WD 29). More precise estimates of the reproductive potential of the Northeast Arctic cod stock are currently being developed through collaborations between scientists at PINRO and IMR (Marshall et al. WD 13). These estimates combine information on abundance, stock structure (age, size, and maturity composition) and reproductive status of individuals over the full time period (1946- present). This research program is also investigating the effect of fishing mortality on the reproductive potential of the stock (Marshall and Yaragina WD 14). The Russian ichthyoplankton survey database (1959–1993) is also being used to describe interannual variation in egg abundance in relation to recruitment (Mukhina 1999). On the basis of progress that is being made on this issue, reference points which are specifically designed to conserve the reproductive potential of the stock will be provided to the next WG meeting. This goal will benefit from the ongoing activities of the NAFO Working Group on Reproductive Potential (2000–2001).

Related issues – data on variation in length at age is central to research on growth and reproductive potential.

Developing a joint database describing interannual variation in mean length at age or age length keys would be useful.

Towards this goal, it was agreed that Russian scientists would investigate the possibility of assembling annual age/length keys or mean length at age which could be combined with Norwegian data from the Lofoten fishery.

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1.5 Stock structure of cod in the NorthEast Arctic Region

In spite of the fact that biological peculiarities of cod allocated in the coastal regions of the Norwegian and Barents Seas have been studied for more than 50 years, the validity of separation of the independent coastal cod stock from the NEA cod stock is still disputable.

The study of cod spawning regions, eggs and larvae drift, migration (by tagging), rates of growth and maturation, parasites composition, genetic markers (Rollefsen, 1933; Jakobsen, 1987; Fevolden and Pogson, 1995, 1996; Mork and Giaever, 1999) indicate the ecological variation of cod in the NEA Region (Borisov et al, 1999).

Nevertheless, taking into account the certain isolation of cod living in the coastal zone, the specifics of the coastal fishery, it was decided to consider the coastal cod (in the framework of ICES) as isolated from NEA cod. Scientific investigation should continue in order to further elucidate the stock structure of this important cod resource in the NEA region.

1.6 ICES Quality Policy

The Fisheries Adviser presented the adopted ICES Quality Policy to the Working Group. In particular, he noted the need for transparency in the assessment and advisory process. This requires a better defined and a more strict policy on how data should be documented. He also noted that it is the entire chain from sampling to advice that needs to be transparent but that significant parts of that chain lies with the national fisheries research institutes. ICES will discuss with the national laboratories the need for such documentation and are aware that there are initiatives both nationally and regionally to improve documentation of the basic data for fish stock assessments. Finally, the Fisheries Adviser introduced the concept of having an assessment manual and assessment handbooks as part of the documentation of the assessments.

ICES sees this as a longer term project and has started the work by improving the working procedures in ACFM. This work is done in parallel with the Bureau work on revising the advisory structures of the Council.

In the discussion that followed the presentation it was pointed out that much of the requirements for documentation are met through the working documents presented to the working groups. It was also noted that fish stock assessment is a dynamic area where the interpretation of data varies between meetings.

1.7 Reliability of Catch Statistics

Accurate catch statistics are a prerequisite for reliable catch at age analysis (like VPA) and for reliable predictions of catch and stock. Any kind of underreporting (discards, black landings, reporting under other species name) preclude the use of a converged VPA as an absolute estimate of stock size. If the proportion of underreporting vary on an annual basis, even the usage of the converged VPA as a stock index is precluded.

The accuracy of the official catch statistics available to this Working Group has never been quantified, and all the analytical assessments are based on the rather poorly supported assumption that catch figures are reasonably accurate.

There is growing evidence that both discarding and black landings could have been serious in the Barents Sea in recent years (Nakken WD8). A report from an observer on a trawler fishing cod in autumn 1998 indicated about 20% discard rate (Schöne WD4, 1999 WG). The same observer also reported considerable discards of saithe in the trawl fishery for cod.

There is still no basis for properly quantifying the underreporting of catches in the Arctic, and at present inaccurate catch statistics could represent a serious error in the assessments of the Arctic stocks. Putting more weight on survey results could improve the evaluation of current state of the stocks. The problem would still remain in the forecast: How to predict the real catches and stock development caused by a certain quota setting? As long as these problems persist, there is a strong need for additional precaution when setting quotas.

1.8 Scientific Presentations

WD 1 (presented by T. Marshall) – statistical models predicting mean Kola section temperature were developed and used to predict monthly values for 1997 and 1998 from observed values six months earlier. The prognosis indicates similar temperatures in 2001 as in the past two years.

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WD 2 (presented by T. Marshall) – a time series of ambient temperature for each age class for the time period 1978 to 2000 was presented. Ambient temperatures experienced by cod ages 1,2 and 3 were lower than those at the fixed Kola section while ambient temperatures for cod age 6 and older are higher than those at the Kola section.

WD3 (presented by A. Aglen) – logbook data from Norwegian trawlers were standardized between individual vessels and used to calculate cpue per day. For each month those values were used to calculate an area-weighted average. The annual average was calculated from the monthly averages. It was not considered for use in the present assessment, since no further comparisons with other stock indicators were presented.

WD4 (presented by A. Aglen) – Based on suggested improvements in the xsa tuning of NEA cod, the following modifications to the May assessment were examined: 1) reduce the plus group from 15 to 13; 2) leave out the Svalbard survey, because it covers a rather small part of the total cod area and it shows unusual catchability trends; 3) Leave out ages 1 and 2 in tuning, since they could be subject to variable unaccounted natural mortality, discarding, and mesh size changes in some tuning fleets; and 4) Reduce time tapering from 20 to 10 years (see WD 3 at May 2000 meeting). The four modifications combined gave a valuable improvement to the retrospective pattern in the sense that the tendency of underestimating most recent F was not evident any longer. This modified procedure was therefore considered to be better and was therefore accepted.

WD5 (presented by A. Aglen) – Growth predictions of cod based on estimated consumption and a bioenergetic model were presented. The document comments that the predictions might be too pessimistic in the present situation when fishing mortality is expected to decline considerably. Therefore the results were not used in the stock predictions.

WD 6 (presented by M. Aschan) – the shrimp stock biomass seems to respond on the landings (128,000 t) but does not show a response to high cod consumption (>300,000 t) in 94–99. Consumption of shrimp may have been overestimated because: 1) cod may be feeding in the trawl: 2) cod stomachs are pooled by age groups; 3) cod stomachs have not been consistently sampled in the spring; and 4) ambient temperatures are not used in the consumption estimates.

WD 7 (presented by B. Bogstad) – knowledge of the selection factors in use in the various fisheries (gear, area and season) together with information on size/age distributions from Norwegian surveys and reported catches (landings) and/or TACs were used to predict catch numbers at age for the years 1995–2000. Estimated catch at age was generally considerably higher than observed. In particular, the estimates of catches of 4 and 5 year olds in 1995 and 1996 were much higher than observed catch numbers.

WD 8 (presented by B. Bogstad) - a review of available reports on reliability of catch (landings) statistics for Northeast Arctic cod in recent years is given. These may have been substantial. The editor of a Norwegian fishing magazine has indicated some 300,000 tonnes of black landings of cod in Norway as a total over the period 1995–1998. This was based on crude comparisons of landings (both domestic and foreign vessels), exports, and domestic consumption. It is argued that recent year’s landings should be neglected completely in the assessment of this stock.

WD 9 (presented by B. Bogstad) – attention is drawn to the fact that the estimated fishing mortality in the assessment year tends to be a considerable underestimate (on average 25%) compared to the converged VPA values obtained some years later. This fact should be specifically mentioned in the advice.

WD 10 (presented by B. Bogstad) - the main features of the new assessment model for Northeast Arctic cod (Fleksibest) are described. The data used in the model runs are described. Further work with the model and possible applications to other stocks are briefly described.

WD 11 (presented by B. Bogstad) – an overview of recent research aimed at predicting recruitment of Northeast Arctic cod is given. The aim is to construct models, which predict the abundance and average length of a cohort at the recruitment age. Both survey data, data on predation on cod and environmental information (zooplankton, temperature etc.) should be utilised in such predictions.

WD 12 (presented by T. Marshall) – updated time series for weight-at-length, liver condition, maturity at length, fecundity at length, total egg production and proportion repeat spawners for Northeast Arctic cod were presented.

Values for 2000 suggest that the reproductive potential of individual spawners is near average values but that the reproductive potential of the stock is constrained by the low abundance of spawners.

WD 13 (presented by T. Marshall) – total lipid energy in the livers of mature females (units of kJ) was proposed as an additional measure of the reproductive potential of the Northeast Arctic cod stock. Total lipid energy (1946 to 1996)

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shows a significant, positive relationship with recruitment to age 3 and, combined with environmental data, can be used to predict recruitment.

WD14 (presented by T. Marshall) – to better resolve fishery effects on stock dynamics of Northeast Arctic cod, separate indices of the potentially harvestable biomass and reproductive potential in the stock were estimated for 1946 to 1996.

WD 15 (presented by K. Nedreaas) – shows the variation in abundance, year-class strength and fishing mortality of North-East Arctic cod during the twentieth century. A VPA for the time period 1913–1999 was run using new historic data until 1946 and the current ICES database for the later years. A relationship of CPUE vs. stock size for the years 1913–1929 was used to estimate stock size from available CPUE data for the years 1900–1912. The results were considered very useful for revising the biological reference points of this stock.

WD 17 (presented by V.Tretyak) – notes a methodological shortcoming concerning relationship between the values of F and SSB. The current procedure for estimating F_pa for NEA cod uses the relationship between SSB and F of the same year. It seems more reasonable to use the correspondence between SSB value and of fishing mortality in the previous years (for example, average F for 3 previous years), the values of fishing mortality which in fact determine the value of SSB in the year under consideration.

WD 18 (presented by V.Tretyak) – presents a mathematical model, suggesting that instantaneous coefficients of the cod natural mortality (M) change with increasing from 3 years and older. The model explicit reflects a conceptual relationship between M of cod, maturity age and theoretical maximum possible lifetime of fish, and implicit, linear and weight growth. Theoretical premises of the model are formulated, and a method of estimating its parameters is suggested. The values of M can be used for assessing the stock, setting biological reference points and TAC of the cod.

WD 19 (presented by M. Aschan) – presents the history of the fishery, regulation, catch and effort data and the status of the shrimp research in the Barents Sea and Svalbard area. The status of the stock and assessment methods being investigated are presented. Several problems were identified: age reading, lack of good biological data from commercial catches, logbook statistics do not allow separation of single and multiple trawl data, the cod consumption estimate and available vessel time.

WD 20 (presented by S. Mehl) – new trawl and purse seine CPUE series and an extended acoustic survey index series are presented and tried in exploratory XSA runs for Northeast Arctic saithe. All series seems to perform slightly better than the old ones.

WD 21 (presented by K. Nedreaas) – proposes how to build a maturity model for North-East Arctic haddock. Observed values may be so variable that a modelled ogives would be preferred. In the present procedure data from surveys are combined in order to get an improved model for the haddock population. Maturity is modelled as both proportion mature in numbers and in biomass for sexes combined and for females only.

WD 22 (presented by Å. Høines) – presents a summary of the Norwegian Greenland halibut survey along the continental slope from 68^oN to 80^oN during 1994 – 1999. The purpose of the cruise is to explore the main distribution area and to estimate the number and biomass of the fishable stock of Greenland halibut in the Norwegian Sea – Barents Sea region.

WD 23 (presented by K. Nedreaas) – presents a summary of the Norwegian juvenile Greenland halibut investigations in the Arctic north and east of Spitsbergen during 1996–1999. The main goal of these surveys are to establish a time series of recruitment indices and to investigate annual variation in distribution pattern.

WD26 (presented by T. Bulgakova) – proposed the procedure of residual mortality M1 estimation for the Barents Sea shrimp with the help of MSVPA model for 4-species community (cod, capelin, shrimp, herring). Many MSVPA program runs are carried out with different M1. Estimated shrimp biomass time series were compared to the results of annual spring surveys. Estimated shrimp stock biomass by years obtained by MSVPA are on the average 3.7 times higher than the survey estimates.

WD27 (presented by Yu. Kovalev) – presents food composition of the Barents Sea cod for 1984–1999 and consumed biomass time series for the same period in tons and in mill. sp. for main prey species (cod, shrimp, capelin, haddock).

The main features of cod feeding in 1999 were increasing predominance of shrimp (to 11% by weight as in previous year) and capelin (up to 38%) and a reduction in cannibalism (up to 6%).

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6

WD 28 (presented by B.Berenboim and V. Korzhev) – presents input data for the Barents Sea shrimp: total catches by age groups and years 1980–1999; total landings by years; tuning data for VPA in 1985–1999; catch and effort data by years and quarters for 1984–1999.

WD 40 (presented by Y.Kovalev) – presents a method of reconstructing cod stock weight-at-age data from 1949 to 1984 using variable natural mortality coefficients (WD#18), maturation ogives series for 1949–1981 established by Jorgensen (1990) and reconstructed stock weight-at-ages data for 1949–1982. It was shown that SSB values estimated with using of new data are considerably lower in period 1949–1980. The mean SSB value for 1949–1999 was 329 thousand tones against 502 thousand tones according to the current assessment made by AFWG.

WD 41 (presented by V.Borisov) – compared the values of cod SSB and abundance of year classes at age 3 over the full time period (1946–present). The relationship between cod SSB and recruitment is absent. Therefore the using of MBAL principal for NEA cod stock management is doubtful. Strong year classes appear both in the years of high SSB and low SSB and vice versa. The reason is that the abundance of cod at age 3 (by VPA) depends mainly on survival conditions, but not on SSB. On this basis, one should not follow the MBAL-criterion for cod fishery management.

1.9 Nomination for New Chair

The Working Group was pleased to unanimously endorse the nomination of Mr. Sigbjørn Mehl as the new chairman of the Arctic Fisheries Working Group.

1.10 Time and Venue of Next Meeting

The Working Group supports the ICES proposal to move the annual meeting of the AFWG to spring time. In order to allow sufficient time for both data preparation and sufficient lead time for the ensuing ACFM meeting in May, the Working Group proposes the dates of April 24–May 3, 2001 for it’s next meeting. Given that ICES headquarters will be undergoing substantial renovations during spring of 2001, Norway kindly has offered to host the next meeting of the Working Group in Bergen.

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2 NORWEGIAN COASTAL COD IN SUB-AREAS I AND II 2.1 Status of the Fisheries

2.1.1 Historical development of the fisheries

The fishery is conducted both with trawlers and with smaller coastal vessels using traditional fishing gears like gillnet, longline, jig and purse seine. In addition to quotas, the fishery is regulated by the same minimum catch size, minimum mesh size on the fishing gears as for the North-East Arctic cod (NEAC), maximum by-catch of undersized fish, closure of areas having high densities of juveniles and by seasonal and area restrictions.

2.1.2 Landings prior to 1999 (Table 2.1)

From 1996, the Norwegian Institute of Fisheries and Aquaculture Ltd (Fiskerforskning) has separated the catches into the two types based on biological sampling (Berg et al. 1998). The method is based on otolith-typing. This is the same method as is used in separating the two stocks in the surveys targeting NEAC. The catches of Norwegian Coastal cod (NCC) have been calculated back to 1984. During this period the catches have been between 25,000 and 75,000 t. The estimated landings of NCC in 1998 reported to the Working Group is 51,572 t and the provisional figure for 1999 is 40,732 t (Table 2.1).

In addition, the landings of NCC calculated using the old method (only based on time and area of capture) are given in Table 2.1.

2.1.3 Expected landings in 2000

No estimate of expected landings for 2000 is available for NCC. However, assuming that the catch of NCC is proportional to the Norwegian catch of NEAC and applying a linear regression over the nine last years (1991–1999) such that; Catch NCC=12,734 + 0.1426* Norwegian catch NEAC (R² = 0.85), the expected landings of NCC in 2000 are 40,313t. This is about the same level as in 1998. However, taking into account the declining stock of NCC this could be an overestimate.

2.2 Status of Research 2.2.1 Fishing effort and CPUE

There are no available data on fishing effort and CPUE for this stock.

2.2.2 Survey results (Tables 2.2, 2.3, 2.4, 2.5, 2.8)

A Norwegian trawl-acoustic survey was conducted along the coast from Varanger to Stadt in October-November 1999 using RV Jan Mayen. In 1999 the survey covered the same areas as the coastal surveys in 1995–1998.

The trawl-acoustic coastal survey in 1999 estimated a total survey biomass of NCC of about 64,000 t (52 million fish) for the coastal area from Varanger to Stadt at 62ô N (Tables 2.2, 2.3, 2.8). The spawning biomass accounted for 24,000 t (9 million fish) of this total (Tables 2.4, 2.5). Thus, spawners make up about 38% of the total biomass. Eighty percent of the total coastal biomass was distributed from the Russian border to 67ô N and 20% south of 67ô N (Norwegian statistical areas 06 and 07). The bulk of the biomass was comprised of age classes 3–5 (Table 2.3).

The data indicated a higher proportion of NCC in the fjords and to the South compared with the northern and outer areas. In the Norwegian statistical areas 06 and 07 (south of 67^o N) nearly all otoliths collected were of the NCC type, which is similar to the results of the 1995–1998 surveys (ICES 1996; ICES 1997; ICES 1998; ICES 1999; ICES 2000).

The numbers of NCC per age-class from all the coastal surveys is given in Table 2.8. The total numbers decreased in 1999 compared with the 1998 survey.

The Norwegian 2000 coastal survey (October-November) will be conducted in a similar way as the previous ones to further extend the time series for NCC over its distribution area.

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8

2.2.3 Age reading and stock separation

Age readings of the NCC both from the surveys and from the catches, are done the same way as for the NEAC. Co- operation between the Fiskeriforskning in Tromsø, Institute of Marine Research in Bergen and PINRO in Murmansk regarding the otolith reading is continuing.

A total of 2734 cod otoliths were sampled during the 1999 survey. These were separated into NCC type (2021) and NEAC (713). As in previous years, NCC were found throughout the survey area. The 1999 survey data shows the same pattern as the 1995 and 1996 surveys. The proportion of the NCC increases going from north to south along the Norwegian coast. The NCC type otoliths dominate south of 67^o N (Norwegian statistical areas 06 and 07). Although the proportion is lower, there is significant biomass of NCC north of 67^o N. It must be emphasised that the Norwegian coastal surveys have been conducted in August-November, and therefore there may be more NEAC in this southern area at other times of the year, especially during the spawning season in the winter time.

2.2.4 Weight at age (Table 2.6)

The weight-at-age (weighted average) from the trawl-acoustic survey in 1999 was at the same level as in 1998 for ages younger than 7 years. Weight at age for ages older than 7 years are uncertain due to the limited number of age samples.

A running average for the 5 most recent years for cod 7 years and older was therefore used in the assessment. Weight at age for NCC is well above the present level for NEAC. There is a general tendency for cod to be heavier when caught further south along the coast (Table 2.6). The same tendency was found for the surveys in 1995–1998 (ICES 1996;

ICES 1997; ICES 1998; ICES 1999; ICES 2000).

2.2.5 Maturity at age (Table 2.7)

The maturity at age is estimated from the data collected at the Norwegian coastal survey. This is not an optimal way to do it because the survey is conducted in the early autumn when the stage at the maturity scale is hard to define. Further improvement of maturity ogives is recommended. The age at 50% maturity (M₅₀) for the NCC was estimated to be slightly above 5 years old on average for the surveyed area in 1999 (Table 2.7). There are some variations between the different areas. The 1999 data show that the average M₅₀ is at about the same level to that found in the 1998 survey (ICES 1999). The average M₅₀for the NEAC in 1997 is close to 7 years old (ICES 1999).

2.3 Data Used in the Assessment 2.3.1 Catch-at-age (Table 2.10)

A detailed breakdown of the catches of NCC for the period 1984 to 1999 has been done to form the basis of a VPA.

This was carried out by analysing Norwegian landings of cod by vessel size, area caught, landed as given by the Norwegian Directorate for Fisheries, and cod samplings from commercial catches done by the Institute of Marine Research, Bergen to separate NCC and NEAC by otolith type.

The separation of the Norwegian catches into NEAC and NCC is based on:

- No catches outside the 12 n.mile zone have been allocated to the NCC catches.

- The catches inside 12 n.mile zone are separated into quarter, fishing gear and Norwegian statistical areas.

- From the otolith structure, catches inside the 12 n.mile zone have been allocated into NCC and NEAC. The Institute of Marine Research in Bergen has been taking samples of commercial catches along the coast for a long period.

This new method of splitting the catches between NCC and NEAC is described in a working document submitted to AFWG in 1998 (Berg et al. 1998).

The catch-at-ge for the period 1984–1999 is given in Table 2.10.

2.3.2 Weight-at-age (Table 2.11, 2.12)

The weight-at-age in the stock, used in the assessment, is obtained from the Norwegian coastal survey. However, few cod older than 7 years were caught, and a five years running average is therefore used from 1995 and onwards. From

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1984–1994 the weight-at-age in the stock is the same as weight-at-age in the catch because no survey data from this period are available.

2.3.3 Natural mortality

A fixed natural mortality of 0.2 was used.

2.3.4 Maturity-at-age (Table 2.13)

The maturity-at-age data from 1995–1999 are obtained from the Norwegian coastal survey. From 1984–1994 the maturityat-age data are obtained from the commercial catch data because no survey data from this period are available.

The proportion mature at age is given in Table 2.13.

2.3.5 Tuning data (Table 2.8)

The acoustic indices (age 2–10+) from the Norwegian coastal survey conducted late autumn (1995–1999) have been used in the tuning (Table 2.8).

2.3.6 Recruitment indices (Table 2.8)

The only recruitment indices (ages 0 and 1) available for this stock is the acoustic index from the Norwegian coastal survey (Table 2.8).

2.4 Methods Used in the Assessment 2.4.1 VPA and tuning (Table 2.09)

Tuning of the VPA was carried out using Extended Survival Analysis (XSA), using the default settings for the XSA with the following exceptions: (1) catchability was set to be stock size dependent for ages younger than 3, and age dependent for ages 7 and older; (2) The survivors estimate was shrunk towards the mean F of the final 2 years or the 4 oldest ages (Table 2.9).

2.4.2 Recruitment

The only recruitment indices (<2 year) available for this stock is the acoustic estimate from the Norwegian coastal survey. However, the abundance of cod less than 25 cm is difficult to estimate from a trawl acoustic survey because this length group tends to inhabit shallow water close to the shore where trawling is impossible. Therefore the estimates are rather uncertain.

2.5 Results of the Assessment

Considering the shortness of the time series of the tuning data the WG was concerned that small changes in the XSA settings would produce highly variable results with respect to absolute values of fishing mortality and population estimates. Nevertheless, it was felt that the assessment did illustrate true trends in the fishing mortality and population size.

2.5.1 Fishing mortality and VPA (Tables 2.14–2.20)

The average age 4–7 fishing mortalities in 1999 were estimated to be 0.45 (Table 2.14). The highest fishing mortalities for these age groups was estimated from 1984–1988 (0.49–0.62). In 1990 and 1991 the lowest F-values was estimated (0.18 and 0.17). However, the fishing mortality has increased steadily from 1991 onwards. At present the F_(4–7) =0.45.

The total biomass of the stock in the period from 1984–1999 has been between 150,000 t and 310,000 t (Tables 2.18, 2.20). At the end of 1999 the biomass was estimated to be the lowest observed and only about half the biomass estimated five years ago in 1995. The spawning stock biomass has been between 86,000 t and 226,000 t (Tables 2.19, 2.20). As for the total stock biomass, the lowest observed SSB was estimated in 1999. The SSB has declined steadily from 1994 to present. The SSB at the end of 1999 was only about half the average in the period 1984–1999.

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10

A summary of landings, fishing mortality, stock biomass, spawning stock biomass and recruitment since 1984 is given in Table 2.20.

Although no reference points regarding F-values and SSB have been calculated for NCC the status of this stock has to be considered far from optimal because both the total biomass and SSB at present are at the lowest observed level. In addition, the recruitment (age 2) has steadily decreased since the early nineties, and was in 1999 (1997 year class) at the lowest observed level in the time series. Results from the 1999 Norwegian coastal survey also indicate year classes below average for 1998–1999. The low recruitment level will further decrease both the total biomass and the SSB for at least 3–4 years unless the fishing mortality is considerably decreased for the next years.

2.5.2 Recruitment (Table 2.8, 2.16)

Both the survey in 1999 (age 0–3, Table 2.8) and the XSA-estimate (age 2 and 3, Table 2.16) indicate lower than average year classes from 1996–1999.

2.6 Comments to the Assessment 2.6.1 General comments

There is no explicit management of this stock. In accordance with the precautionary approach, management objectives should be defined. Considering the status of this stock, biological reference points consistent with these objectives should be identified and implemented as a basis for advice.

2.6.2 A comparison of the assessment results and the survey results (Figures 2.1–2.3)

Both the assessment and the surveys from 1995–1999 show a declining stock. The estimated number of cod 2 year and older in the surveys is approximately 60 percent of the estimated number from the XSA in four of the five years (Figure 2.1). It therefore seems like the survey and the XSA assessment reflect the changes in the stock number quite well. For ages 2–4 year the survey indexes and the XSA estimates are very well correlated. For ages 5–7 the correlation is good except in 1997 for 5 and 6 years old cod. The proportion of cod estimated in the survey was at a higher level this year.

The correlation for ages older than 8 year is somewhat worse mainly due to few individuals caught in the surveys. There is a general trend towards decreasing catchability with increasing age, except for cod older than 7–8 years (Figure 2.1–

2.3).

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Table 2.1 Landings of Norwegian Coastal cod in Sub-areas I and II.

Year Landings in '000 t.

As calculated from samples and reported to

AFWG

By area and time of capture

1960 - 43

1961 - 32

1962 - 30

1963 - 40

1964 - 46

1965 - 24

1966 - 29

1967 - 33

1968 - 47

1969 - 52

1970 - 49

1971 - *)

1972 - *)

1973 - *)

1974 - *)

1975 - *)

1976 - *)

1977 - *)

1978 - *)

1979 - *)

1980 - 40

1981 - 49

1982 - 42

1983 - 38

1984 74 33

1985 75 28

1986 69 26

1987 61 31

1988 59 22

1989 40 17

1990 28 24

1991 25 25

1992 42 35

1993 53 44

1994 55 48

1995 57 39

1996 62 32

1997 63 36

1998 52 29

1999 41 23**)

Average 54 35

*) No data

**) Provisional data

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O:\ACFM\WGREPS\AFWG\REPORTS\2001\AFWG01.Doc 12

Table 2.2 Estimated survey number (x1000) of Norwegian Coastal cod at age from the Norwegian coastal survey during the autumn 1999.

Age

Area 0 1 2 3 4 5 6 7 8 9 10+ Total

03 East Finnmark 20 1044 2006 2174 2389 1263 465 88 25 25 25 9524

04 West Finnmark/Tromsø 14 4829 5295 3842 3368 3324 1229 313 68 24 29 22335

05 Lofoten/Vesterålen 476 1449 2323 2038 1229 585 182 86 8368

00 Vestfjord 173 1098 1750 1078 454 212 4765

06 Nordland 220 580 1052 629 766 549 94 63 63 4016

07 Møre 108 881 1030 621 161 12 173 2986

Total 34 6850 11309 12171 10123 7197 3052 850 242 112 54 51994

Table 2.3 Estimated survey biomass (tonnes) of Norwegian Coastal cod at age from the Norwegian coastal survey during the autumn 1999.

Age

Area 0 1 2 3 4 5 6 7 8 9 10+ Total

03 East Finnmark 0 63 484 1640 3421 2401 1209 299 81 201 230 10029

04 West Finnmark/Troms 0 320 1568 3169 5238 7081 3465 1379 527 146 337 23230

05 Lofoten/Vesterålen 32 426 1951 3405 2812 1693 1016 875 12210

00 Vestfjord 13 401 1327 2319 1312 934 6306

06 Nordland 26 159 717 747 1481 1334 397 614 873 6348

07 Møre 23 612 1429 1830 687 85 1632 6298

Total 0 477 3650 10233 16960 15774 8720 4723 2097 1220 567 64421

Table 2.4 Estimated survey spawning stock number (x1000) of Norwegian Coastal cod at age from the Norwegian coastal survey during the autumn 1999.

Age

Area 0 1 2 3 4 5 6 7 8 9 10+ Total

03 East Finnmark 0 0 40 152 549 632 307 88 25 25 25 1843

05 Lofoten/Vesterålen 0 0 0 0 346 430 380 182 86 0 0 1424

00 Vestfjord 0 0 66 53 248 195 123 0 0 0 0 685

06 Nordland 0 0 0 32 57 123 209 54 63 63 0 601

07 Møre 0 0 0 31 56 26 5 99 0 0 0 217

Total 0 0 159 383 2165 3134 1995 651 242 112 54 8895

Table 2.5 Estimated survey spawning stock biomass (tonnes) of Norwegian Coastal cod at age from the Norwegian coastal survey during the autumn 1999.

Age

Area 0 1 2 3 4 5 6 7 8 9 10+ Total

03 East Finnmark 0 0 10 115 787 1201 798 299 81 201 230 3722

05 Lofoten/Vesterålen 0 0 0 0 579 984 1100 1016 875 0 0 4554

00 Vestfjord 0 0 24 40 533 564 542 0 0 0 0 1703

06 Nordland 0 0 0 22 67 237 507 226 614 873 0 2546

07 Møre 0 0 6 43 164 110 32 930 0 0 0 1285

Total 0 0 56 315 3544 6778 5716 3478 2097 1220 567 23771

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Table 2.6 Weight (gram) at age (year) for Norwegian Coastal cod from the Norwegian coastal survey during the autumn 1999.

Age

Area 0 1 2 3 4 5 6 7 8 9 10+

03 East Finnmark 12 60 241 754 1432 1901 2600 3398 3240 8040 9200

04 West Finnmark/Troms 8 66 296 825 1555 2130 2819 4406 7750 6083 12036

05 Lofoten/Vesterålen 67 294 840 1671 2288 2894 5582 10174 0 0

00 Vestfjord 75 365 758 2151 2890 4406 0 0 0 0

06–07 Nordland/Møre 149 528 1031 2062 2339 2529 7599 9746 13857 0

Weighted average 10 70 323 841 1675 2192 2857 5556 8665 10893 10500

Table 2.7 Percent mature at age for Norwegian Coastal cod at age from the Norwegian coastal survey during the autumn 1999.

Age

Area 0 1 2 3 4 5 6 7 8 9 10+

03 East Finnmark 0 0 2 7 23 50 66 100 100 100 100

04 West Finnmark/Troms 0 0 1 3 27 52 79 73 100 100 100

05 Lofoten/Vesterålen 0 0 0 0 17 35 65 100 100 100 100

00 Vestfjord 0 0 6 3 23 43 58 75 100 100 100

06–07 Nordland/Møre 0 0 0 3 9 16 38 57 100 100 100

Weighted average 0 0 1 3 21 44 65 77 100 100 100

Table 2.8 Estimated survey numbers at age (x1000) of Norwegian Coastal cod from the coastal surveys from 1995–1999.

Age

YEAR 0 1 2 3 4 5 6 7 8 9 10+ TOTAL

1995 2157 28707 20191 13633 15636 16219 9550 3174 1158 781 579 111785

1996 - 1756 17378 22815 12382 12514 6817 3180 754 242 5 77843

1997 5632 30694 18827 28913 17334 12379 10612 3928 1515 26 663 130523

1998 35098 14455 13659 15003 13239 7415 3137 1578 315 169 128 104197

1999 34 6850 11309 12171 10123 7197 3052 850 242 112 54 51994

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Table 2.9

Lowestoft VPA Version 3.1 25/08/2000 15:07 Extended Survivors Analysis Coastal cod (run: XSANCC10/X10) CPUE data from file fleet

Catch data for 16 years. 1984 to 1999. Ages 2 to 10.

Fleet, First, Last, First, Last, Alpha, Beta , year, year, age , age

FLT04: Norw. Coast. , 1995, 1999, 2, 9, .750, .850

Time series weights :

Tapered time weighting applied Power = 3 over 20 years Catchability analysis :

Catchability dependent on stock size for ages < 3 Regression type = C

Minimum of 5 points used for regression

Survivor estimates shrunk to the population mean for ages < 3 Catchability independent of age for ages >= 7

Terminal population estimation :

Survivor estimates shrunk towards the mean F of the final 2 years or the 4 oldest ages.

S.E. of the mean to which the estimates are shrunk = .500 Minimum standard error for population

estimates derived from each fleet = .300 Prior weighting not applied

Tuning had not converged after 100 iterations

Total absolute residual between iterations 99 and 100 = .00088

Final year F values

Age , 2, 3, 4, 5, 6, 7, 8, 9

Iteration 99, .0179, .1090, .1961, .4474, .4998, .6695, .5776, .5882 Iteration **, .0179, .1090, .1960, .4473, .4996, .6694, .5775, .5879

Regression weights

, .976, .990, .997, 1.000, 1.000

Fishing mortalities

Age, 1995, 1996, 1997, 1998, 1999 2, .026, .036, .056, .035, .018 3, .049, .100, .137, .161, .109 4, .134, .186, .186, .286, .196 5, .244, .459, .258, .383, .447 6, .333, .361, .445, .449, .500 7, .453, .450, .596, .554, .669 8, .417, .590, .804, .620, .577 9, .364, .495, .602, .587, .588

XSA population numbers (Thousands) AGE

YEAR , 2, 3, 4, 5, 6, 7, 8, 9,

1995 , 3.47E+04, 2.07E+04, 2.07E+04, 2.65E+04, 2.16E+04, 9.92E+03, 4.71E+03, 2.02E+03, 1996 , 3.77E+04, 2.77E+04, 1.61E+04, 1.48E+04, 1.70E+04, 1.27E+04, 5.16E+03, 2.54E+03, 1997 , 2.70E+04, 2.98E+04, 2.05E+04, 1.10E+04, 7.66E+03, 9.68E+03, 6.62E+03, 2.34E+03, 1998 , 1.79E+04, 2.09E+04, 2.12E+04, 1.40E+04, 6.94E+03, 4.02E+03, 4.37E+03, 2.43E+03, 1999 , 1.57E+04, 1.42E+04, 1.46E+04, 1.31E+04, 7.79E+03, 3.63E+03, 1.89E+03, 1.92E+03, Estimated population abundance at 1st Jan 2000

, 0.00E+00, 1.26E+04, 1.04E+04, 9.80E+03, 6.84E+03, 3.87E+03, 1.52E+03, 8.70E+02, Taper weighted geometric mean of the VPA populations:

, 3.37E+04, 2.99E+04, 2.52E+04, 1.92E+04, 1.25E+04, 7.42E+03, 3.59E+03, 1.64E+03, Standard error of the weighted Log(VPA populations) :

, .4336, .3977, .3628, .3581, .3701, .3931, .4840, .6414,

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Table 2.9 (continued)

Log catchability residuals.

Fleet : FLT04: Norw. Coast.

Age , 1995, 1996, 1997, 1998, 1999 2 , .09, -.25, .26, .07, -.16 3 , -.24, .02, .22, -.07, .07 4 , -.02, .04, .13, -.09, -.05 5 , -.23, .27, .39, -.26, -.17 6 , -.26, -.33, .97, -.14, -.25 7 , -.05, -.30, .30, .23, -.19 8 , -.34, -.73, -.11, -1.41, -.87 9 , .07, -1.23, -3.29, -1.47, -1.65

Mean log catchability and standard error of ages with catchability independent of year class strength and constant w.r.t. time

Age , 3, 4, 5, 6, 7, 8, 9

Mean Log q, .0251, .0077, .0936, -.1319, -.5662, -.5662, -.5662, S.E(Log q), .1700, .0873, .3061, .5504, .2613, .9241, 2.0826,

Regression statistics :

Ages with q dependent on year class strength

Age, Slope , t-value , Intercept, RSquare, No Pts, Reg s.e, Mean Log q

2, 1.78, -2.579, -7.42, .79, 5, .24, -.27,

Ages with q independent of year class strength and constant w.r.t. time.

Age, Slope , t-value , Intercept, RSquare, No Pts, Reg s.e, Mean Q

3, .86, .505, 1.37, .82, 5, .16, .03,

4, .94, .206, .55, .82, 5, .09, .01,

5, 1.93, -1.050, -9.08, .30, 5, .58, .09,

6, 1.89, -.863, -7.99, .24, 5, 1.07, -.13,

7, 1.08, -.296, -.13, .81, 5, .32, -.57,

8, .69, .825, 3.48, .70, 5, .36, -1.26,

9, -.47, -.570, 10.37, .05, 5, .62, -2.09,

Terminal year survivor and F summaries :

Age 2 Catchability dependent on age and year class strength Year class = 1997

Fleet, Estimated, Int, Ext, Var, N, Scaled, Estimated

, Survivors, s.e, s.e, Ratio, , Weights, F

FLT04: Norw. Coast. , 10735., .308, .000, .00, 1, .501, .021

P shrinkage mean , 29875., .40,,,, .306, .008

F shrinkage mean , 4907., .50,,,, .193, .045

Weighted prediction :

Survivors, Int, Ext, N, Var, F

at end of year, s.e, s.e, , Ratio, 12617., .22, .47, 3, 2.140, .018

Age 3 Catchability constant w.r.t. time and dependent on age Year class = 1996

FLT04: Norw. Coast. , 11132., .212, .002, .01, 2, .830, .102

F shrinkage mean , 7413., .50,,,, .170, .150

at end of year, s.e, s.e, , Ratio,

10390., .20, .12, 3, .605, .109

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Table 2.9 (continued)

FLT04: Norw. Coast. , 10152., .174, .103, .59, 3, .858, .190

F shrinkage mean , 7930., .50,,,, .142, .237

9803., .17, .09, 4, .572, .196

FLT04: Norw. Coast. , 6326., .157, .098, .62, 4, .834, .476

F shrinkage mean , 10134., .50,,,, .166, .323

6841., .15, .12, 5, .797, .447

FLT04: Norw. Coast. , 3748., .153, .082, .53, 5, .798, .512

F shrinkage mean , 4412., .50,,,, .202, .450

3873., .16, .07, 6, .461, .500

FLT04: Norw. Coast. , 1435., .163, .111, .68, 5, .769, .698

F shrinkage mean , 1845., .50,,,, .231, .580

1521., .17, .10, 6, .601, .669

Age 8 Catchability constant w.r.t. time and age (fixed at the value for age) 7 Year class = 1991

FLT04: Norw. Coast. , 1029., .193, .190, .98, 5, .639, .507

F shrinkage mean , 646., .50,,,, .361, .719

870., .22, .18, 6, .846, .577