Harvest Control Rules in a multispecies world: The Barents Sea and beyond. Daniel Howell IMR Bergen

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1 Harvest Control Rules in a multispecies world: The Barents Sea and beyond Daniel Howell IMR Bergen

2 Single species HCR

3 Multispecies HCRs Will give examples of Existing multispecies HCRs (explicitly or implicitly) Single species HCRs that need a wider perspective Only examples, this is a major topic in fisheries research around the world at the moment WGSAM ToR F: Explore the consequence of multispecies interactions and environmental factors in practical multispecies advice for fisheries management (MSY related and other biological reference points)

4 Multispecies HCR: Barents Sea Capelin Forage fish, industrial fishery, important prey Eaten by cod (among others) Start to mature in summer Survey maturing fish in early autumn Swim south to near coast the following spring Spawn and die Fished en route with an escapement HCR 95% chance for SSB>200,000 tonnes

5 Multispecies HCR: Barents Sea Capelin Recognized early in the fishery that predation was critical in stock assessment and management Cod predation is large and variable Between survey and catch Incorporated in the capelin model, which calculates cod-induced predation Allow the cod to eat their fill, catch the remaining surplus First done for assessment in 1990

6 Multispecies new cod HCRs Possible new HCRs for cod have been tested Two of these account for multispecies effects One implicitly: Increasing F at high cod biomass One explicitly: Increase F a high cod and low capelin biomass

7 Implicit multispecies: Current Barents Sea cod HCR XSA stock assessment Most cannibalism before the fish enter the fishery Not required in assessment (but affects recruitment) Straight single species assessment and HCR BUT: HCR requires three year forecasts Cannibalized fish in year 1 are definately important in the fishery by year 3

8 Existing Barents Sea cod HCR Even though the HCR is written in single species terms, cannibalism affects recruitment and projection of stock size which in turn affects the quota So the rule has a certain amount of implicit recognition of multispecies interactions

9 N.E. US herring HCR Aiming to develop a HCR for herring, considering their role in the ecosystem Important commercial catch But also important prey for a range of predators Whales (humpbacks) and other marine mammals, bluefin tuna, groundfish (cod, etc), spiny dogfish, striped bass, bluefish, Need to balance catch against importance as a food source Here in a more general way than for our capelin

10 Single species HCR in multispecies world I have shown a few multispecies examples Will become more and more common Most HCRs are single species Probably in the future most HCRs should still be single species But that doesn t mean that we should ignore multispecies effects Doing so can cause all sorts of problems

11 Single species HCR affecting ecosystem Kaplan and Leonard, 2012

12 Ecosystem affecting single species HCR Stability constraints (e.g. maximum +/-10% annual change in TAC) are thought to reduce overall yield while giving greater stability and predictability But once you start looking at multispecies effects this may not be true Example later today

13 Mixed fisheries Species do not exist in isolation HCR from one species can affect other species caught by the same fleet sector Need to consider the interactions when evaluating HCRs

14 Mixed fisheries, simplified N.Sea example BEAM INDUSTRIAL OTTER PELAGIC Sprat Norway pout Sandeel Poor cod Long rough dab Dab Herring Horse mackerel Lemon sole Sole Mackerel Whiting Witch Gurnard Plaice Starry ray Haddock Cuckoo ray Monkfish Cod Saithe

15 Discussion Species do not exist in isolation We should consider the wider ecosystem when harvesting them Honestly, did I really need to write that?? But that doesn t mean that every stock assessment or HCR should be multispecies

16 HCRs are not stock assessments HCRs say what the catch should be for any given stock level Stock assessments work out what the stock level is right now. Much more need for multispecies considerations in HCR evaluation than in stock assessment

17 Do as much as is needed Stock assessments should be as simple and robust as possible Only include multispecies if you would get the assessment very wrong otherwise Same for HCRs Often a single species HCR is perfectly appropriate But it should be evaluated in a multispecies context to make sure it still makes sense

18 Do as much as is needed Stock assessments should be as simple and robust as possible Only include multispecies if you would get the assessment very wrong otherwise Same for HCRs Often a single species HCR is perfectly appropriate But it should be evaluated in a multispecies context to make sure it still makes sense

19 Choice between species Within a trophic level, harvesting every species close to individual MSY makes sense MSY must in some sense be proportional to productivity But once you consider different trophic levels there are choices to be made Do we harvest forage fish or leave them as prey? How do manage species competing for the same prey? Can t maximize all harvests at the same time

20 HCRs in an ecosystem context General realisation that we want to evaluate HCRs in a multispecies (or ecosystem) context A lot of work going on around the world on this Multispecies HCRs in the Barents Sea Altantis studies in Australia, the California Coast Current, Gulf of Mexico Ensemble modelling studies in the North Sea

21 Ecosystem context Do we want to include absolutely everything in our models when testing a HCR? Do I even need to answer that? We need to consider the most important factors Species interactions are an obvious candidate We need ecosystem assessments to inform the choices made in designing and testing a HCR

22 Summary HCRs should be considered in an ecosystem context Evaluated to account for the main interactions WHERE NECESSARY the HCR should include explicit multispecies or ecosystem considerations But even single species HCRs should be evaluated in an multispecies context Should work alongside ecosystem assessments

23 REDUS There is a new project starting in IMR REDUS (REduced UNcertainty in Stock assessment) Aimed at incorporating information on uncertainty in data into the assessments Part of the project is to build a MSE tool that can test HCRs against a variety of different operating models Including multispecies ones