1. Barents Sea capelin management technology – Some problems Sigurd Tjelmeland sigurd@imr.no Assessment meeting, Murmansk, 2011 Assessment meeting, Svanhovd, 2012

2. Apology! The work I will present and the accompanying WD should have been finished much earlier. It is difficult to digest the material in a short time I ran into difficult estimation problems that consumed lots of time I did as well as I could I am sorry

4. Where we stand (2011) Evaluated by WKSHORT –Good evaluation on method –Inadequate description (in spite of paper) One lesson: There are no serious critics but ourselves New Stock Annex –Covered the path from 2003 –Little involvement –Detailed comparison with CapTool lacking –Parsimonuous model Ambition: Transparency and sound scientific footing, unlike other assessments Building up everything anew at IMR, Sigurd and Sam

5. Where we stand (2011) The present CapTool model has worked well Reasonble recruitment Reasonable catch

6. Lack of resources – serious situation (2011) Not much ownership to methodology among the assessment group How do we overcome this constraint? More serious as we approach revision of HCRs Better Russian-Norwegian integration –On the Norwegian side 2 workers (Sigurd and Sam) –On the Russian side?

7. In focus 2011: The assessment model takes account of uncertainties both in the survey estimate and in other input data. However, consumption of prespawning capelin by mature cod is neglected in the assessment model, as the mature cod is thought to overlap with prespawning capelin to a little extent, and not feed to any appreciable extent before spawning. Biological samples have for the recent years shown that this is only partly true, and that mature cod may consume an appreciable but hitherto unquantified amount of prespawning capelin. In the present situation of an extreme large mature cod stock there is therefore an appreciable model uncertainty in the assessment. Also, There is intense feeding of capelin by cod in the extreme north of the Barents Sea in the autumn in recent years while the overall natural mortality of capelin as measured by consecutive surveys has not been high. This may invalidate the assumption in the model of evenly distributed natural mortality (except for prespawning capelin) over the year. This assumption is needed to calculate the natural mortality on mature capelin during October-December. These two shortcomings of the assessment model create an uncertainty in the assessment even if care was taken to select years for applying natural mortality during October-December that reflect the present situation as well as possible.

8. Answer to the challenges Similar model in quarter 4 as in quarter –All cod eats all capelin Model consumption by mature cod in quarter 1 Model consumption of immature capelin in quarter 1 Until 2015: –Testing harvest rules –Recruitment functions

9. Do more biology? Trawl fishing incidental mortality Collection of fishermen’s observations

10. Estimation No weighting of stomach content data Likelihood Ages 3-9 for consumption per cod, not summed Difficult estimation, parameters confounded Maturation parameters estimated using early part of timeseries, as before Part of mature cod consuming capelin in Q1 starts after this time period and increases gradually until 1995 Last year not included (not very important)

11. Tested for distribution of consumption per cod Lognormal Normal, constant CV Normal, constant standard deviation Gamma Gamma, exclude low-catch years Lognormal and gamma approximately equal, exclusion of low-catch years not evaluated (different number of likelihood terms)

13. Comparison GammaLognormal Uncertainty Q10.9181.01 Uncertainty Q40.8230.995 partImmatureCap0.2450.272 partMatureCod1.0 Likelihood cons capelin249.307267.216 Likelihood cons other368.18343.121 Last SSB0.146 Suitability for mature cod: 0.5 Distribution for capelin maturation: gamma

14. Estimation variants, gamma distribution for consumption per cod Sigmoid maturation Sigmoid consumption New suitability Exclude low- catch years Uncertainty Q1 0.9080.90750.9080.9650.851 Uncertainty Q4 0.8230.8200.820.8530.823 partImmatureCap 0.2450.2440.2520.2450.428 partMatureCod 1.0 Likelihood cons cap 249.307249.288247.566205.054147.543 Likelihood cons cod 368.180370.810372.452361.761242.664 Last SSB 0.1460.1480.1400.0570.489 Capelin abundance likelihood not shown, but prefernce for models as close to the present model as possible

16. Estimation variants, gamma distribution for consumption per cod, relaxing assumptions Increase capelin 50% Suitability mature cod 1 Consump tion 75% Cod 75% Uncertainty Q1 0.9180.8800.9170.8890.895 Uncertainty Q4 0.8230.8240.8260.8220.833 partImmatureCap 0.2450.3290.2410.2560.254 partMatureCod 1.0 Likelihood cons cap 249.307272.544251.529402.582264.637 Likelihood cons cod 368.18369.394367.664478.668368.537 Last SSB 0.1461.020.1170.3450.372

18. Historic SSB for chosen model replicates (25) SSB-distributions changed!

19. Future work Streamlining catch data Building up the new software –Sam, Ute, Anatolii Recruitment functions, HCR estimation –Sigurd (present software) –Sam, Ute, Anatoliy (new software) Summary of situation at next March meeting (to get attention in Institutes) Web page update by end of October