1. WP4: Models to predict & test recovery strategies Cefas: Laurence Kell & John Pinnegar Univ. Aberdeen: Tara Marshall & Bruce McAdam

2. Objectives Evaluate alternative recovery strategies and identify the relative value of –Information –Control Synthesise available models and data on key processes that may affect stock recovery in a common framework Use framework to evaluate alternative management strategies that are robust to uncertainty Quantify and compare the impacts of alternative management strategies in order to produce a suite of strategies to achieve stock rebuilding

3. 1) Preparation of input data 2) Choice of performance criteria and management objectives 3) Specify base-case scenario 4) Perform evaluations Tasks

4. Starting state of system Performance Statistics used to evaluate performance of management procedures against objectives Operating Model represents the “true” dynamics of “ the biological system against which performance will be measured Observation Error Model generation of data on fishery and stock(s) Management Procedure Assess status of stock and set management options depending upon perceived status of fishery stock(s) Simulation through time Figure 1. Conceptual framework From WP 5 Alternative management strategies Current Stock Status Future Stock Status From WP 1,2,3 Process models or alternative hypotheses e.g. alternative assumptions about Natural mortality Maturity Recruitment Discards Weights at age Model of data collection/sampling Feeds into WG Stock Assessment Recovery? Yield of target/non-target stocks

5. Framework for the Evaluation of Management Strategies FEMS proposed and prototyped a generic framework known as FLR through a variety of contrasting case studies Why? Despite constant efforts made to regulate fisheries fishing capacity remains above that necessary to sustainable exploit marine resources. However, while the need to develop alternative management strategies is widely recognised it is almost impossible to develop these by conducting large-scale experiments on fish stocks. There has therefore been a trend towards the use of computer simulation to develop management strategies that meet multiple, but often conflicting management objectives, and are robust to uncertainty FLR is available from http://www.flr-project.org http://www.flr-project.org

6. Process error: natural variability (in both time and space) in dynamic processes of the populations (e.g. recruitment, predation, growth and migration) and of the fisheries Model error: related to the ability of model structure to capture the core of the system dynamics, many models are assumption rich but data poor Observation error: related to collecting in-situ observations, such as total catch, catch composition (e.g. length, age, sex), research survey indices, effort Estimation error: related to estimating parameters of various models used in the assessment procedure, such as growth models, stock-recruitment models, virtual population analyses, statistical models Implementation error: because management actions are never implemented perfectly and may result in realised total catch, catch composition and effort that differ from those intended, e.g. misreporting. Uncertainty

7. Software Catalogue Software Catalogue Model Error? Relates to the ability of any one model structure to capture the core of the system dynamics, many models are assumption rich but data poor. FEMS was tasked by the European Commission with specifying

8. Cod and Climate Hypotheses were that climate change acts through Growth, optimum temperature for growth Growth, optimum temperature for growth Juvenile survival Juvenile survivalor Carrying capacity Carrying capacity Therefore impacts on Recovery Long-term yields Sustainable levels

9. Management strategies Strategies investigated were either those adopted by or under consideration by the European Commission Short-term –Recovery plans (30% increase in SSB) Long-term –Harvest control rules (ensure F B PA )

10. Recovery Plans –This was because recovery in the short term depended upon conserving fish that have already recruited Short-term –Despite contrasting climate change hypothesises, magnitude of the change in temperature and the mechanism through which it acts (i.e. juvenile survival or carrying capacity), the predicted recovery time was little affected

11. Recovery Plans –This was because recovery in the short term depended upon conserving fish that have already recruited Short-term –Despite contrasting climate change hypothesises, magnitude of the change in temperature and the mechanism through which it acts (i.e. juvenile survival or carrying capacity), the predicted recovery time was little effected –Recovery would be delayed however if bycatch of cod in non-target fisheries was not controlled

12. Long-term Scientific advice on safe biological limits to exploitation depends upon the correct hypothesis Reduced survival of recruits? Reduced survival of recruits? Reduction in range? Reduction in range? Since consequences are ↓ F lim if recruit survival reduced ↓ F lim if recruit survival reduced ↓ B lim if range reduced ↓ B lim if range reduced However, the correct mechanism can only be detected through biological studies rather than through stock assessment

13. North Sea Flatfish 100mm > 55° 80mm < 55° 80mm < 55° Plaice in the North Sole in the South However, the distribution of plaice and sole varies wrt 55°

14. North Sea Flatfish 100mm > 55° 80mm < 55° 80mm < 55° Plaice in the North Sole in the South However, the distribution of plaice or sole may change wrt 55° The productivity of plaice and sole has also changed over time

15. Cod and Climate Hypotheses were that climate change acts through Growth, optimum temperature for growth Growth, optimum temperature for growth Juvenile survival Juvenile survivalor Carrying capacity Carrying capacity Therefore impacts on Recovery Long-term yields Sustainable levels

16. Management strategies Strategies investigated were either those adopted by or under consideration by the European Commission Short-term –Recovery plans (30% increase in SSB) Long-term –Harvest control rules (ensure F B PA )

17. Recovery Plans –This was because recovery in the short term depended upon conserving fish that have already recruited Short-term –Despite contrasting climate change hypothesises, magnitude of the change in temperature and the mechanism through which it acts (i.e. juvenile survival or carrying capacity), the predicted recovery time was little affected

18. Recovery Plans –This was because recovery in the short term depended upon conserving fish that have already recruited Short-term –Despite contrasting climate change hypothesises, magnitude of the change in temperature and the mechanism through which it acts (i.e. juvenile survival or carrying capacity), the predicted recovery time was little effected –Recovery would be delayed however if bycatch of cod in non-target fisheries was not controlled

19. Long-term Scientific advice on safe biological limits to exploitation depends upon the correct hypothesis Reduced survival of recruits? Reduced survival of recruits? Reduction in range? Reduction in range? Since consequences are ↓ F lim if recruit survival reduced ↓ F lim if recruit survival reduced ↓ B lim if range reduced ↓ B lim if range reduced However, the correct mechanism can only be detected through biological studies rather than through stock assessment

20. North Sea Flatfish 100mm > 55° 80mm < 55° 80mm < 55° Plaice in the North Sole in the South However, the distribution of plaice and sole varies wrt 55°

21. North Sea Flatfish 100mm > 55° 80mm < 55° 80mm < 55° Plaice in the North Sole in the South However, the distribution of plaice or sole may change wrt 55° The productivity of plaice and sole has also changed over time