Result of 2016 Harvest Control Rule evaluation for Barents Sea capelin. Bjarte Bogstad (IMR), Dmitry Prozorkevich (PINRO), Samuel Subbey (IMR)

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1 Result of 2016 Harvest Control Rule evaluation for Barents Sea capelin Bjarte Bogstad (IMR), Dmitry Prozorkevich (PINRO), Samuel Subbey (IMR)

2 Outline Present and past management strategy How has this performed historically? Stock recruitment relationship and Blim Evaluation of Harvest Control Rule The way forward

3 Capelin Biomass (1+) stock and catch of and Barents Sea catch capelin (million history tonnes) Stock Stcok 5 4 Catch Catch Year

4 Capelin management history Based on annual acoustic survey estimate in September, which is taken to be an absolute estimate 14 cm maturation length, total spawning mortality Target SSB kt (Hamre and Tjelmeland 1982) First capelin collapse in last half of 1980s fisheries closed Predation by immature cod on mature capelin in January March can be calculated based on cod stomach content data and this was included in assessment model after the capelin stock recovered in 1990 Present HCR (95% probability of SSB > 200kt) developed in late 1990s Elimination of autumn fishery since late 1990s now only fishery on mature capelin just prior to spawning (1 April)

5 Capelin prediction 95% probability for SSB > 200 kt

6 How has capelin management been in retrospect? We recalculated the spawning stock and TAC based on the present model and estimate of the cod stock, back to 1991 Would have got lower TACs than those set historically However, the fishery does not seem to have hampered recruitment significantly in this period (but the fishery in 1986 when the advice was zero probably affected the recruitment that year negatively) Management since the early 1990s has been sustainable (but not necessarily precautionary)

7 TAC advice historic and revised according to present data and models (Gjøsæter et al. 2015)

8 SSB estimates historic and revised (Gjøsæter et al. 2015)

9 What happens to the maturing capelin biomass where does it go?

10 Stock recruitment plot and influence of herring (Gjøsæter et al. 2016) Recruitment age 1 (billion) SSB (1000 tonnes)

11 Request from JNRFC The existing harvest control rule with varying probabilities for the spawning stock biomass to be above 200 thousand tonnes (i.e. 80, 85, 90 or 95 %). This gives a total of 4 different rules to be explored, one of which corresponds to the existing harvest control rule. The effect of each of the harvest control rules for cod stated above on the capelin yield should be explored.

12 ICES precautionary definition for short lived stocks The existing harvest control rule is to assure that tons SSB are left for spawning with 95% probability or equivalent that there is at most a 5% risk that the SSB goes below Blim ( = t) i.e. applying the ICES approach of using a 5% criterion that SSB drops below Blim for evaluating whether a HCR is precautionary or not. Clearly, changing the risk levels as indicated in the requests means that the resulting HCR is not precautionary in the ICES sense if the Blim of tonnes is maintained.

13 Blim Set somewhat above the 1989 SSB (ca 100 kt) which gave the highest SSB observed A bit arbitrary way of setting Blim but no argument for changing it was found during the evaluation in 2016

14 Result of evaluation (I) An examination of the stock dynamics in recent decades, when the current HCR (based on 95% criterion for SSB < B lim ) or the previous HCR (based on a similar escapement strategy) was in operation, suggests that this HCR resulted in sustainable exploitation. The overall effect of allowing a higher probability of SSB < B lim would be that the fishery would be opened at a lower survey biomass (maturing capelin), the TAC would increase and the resulting spawning biomass would be lower, potentially increasing the risk of recruitment failure. The 2015 survey estimate for capelin was low and would have led to closure of the fishery in 2016 under all suggested HCRs.

15 Result of evaluation (II) Using the 5% risk criterion in the HCR, a survey biomass (maturing capelin) result below around 1.15 million tonnes suggests that the fishery will be closed. Each doubling of the risk from 5% to 10% and from 10% to 20% adds t to the TAC and the minimum survey biomass that will allow a fishery is lowered by about t. This applies to cod biomasses which are expected under current management and current productivity of the Northeast Arctic cod stock, i.e. for an immature cod biomass around 1.8 million tonnes.

16 Result of evaluation (III) Barents Sea Capelin HCR for Different Risk levels TAC '000 t Survey estimate ('000 tons) 5% 10% 20%

17 Future improved multispecies inclusion Long term simulations of capelin stock, for given management strategies for cod and herring Such simulations have been done before, but need for improvement e. g. of modelling the effect of predation by mature cod on capelin This is more important than before because now the mature cod is a much bigger proportion of the total cod stock than in previous years with high cod F

18 Capelin maturing stock vs limit for fishery based on evaluation 4.0 Capelin maturing stock (million tonnes) Maturing stock

19 Short term outlook All the suggested HCRs for capelin would have given a zero catch advice for 2016 Low immature stock autumn 2015 indicates that a zero advice for 2017 also is very likely

20 Summary Capelin management since the early 1990s has been sustainable (but not necessarily precautionary) Effect of changing the present HCR to a less conservative one has been explored No reason to change to any of the alternative rules suggested (and those would not be precuationary according to ICES guidelines) More conservative HCRs than the present one have not been explored