1. Beth Scott Research Fellow University of Aberdeen What happens when you institutionalise science? Using North Sea cod as an example

2. Outline A brief look back at history of fisheries science/management The essential guide to the understanding of fisheries management Why it has all gone wrong fish as animals sexual maturity and genetics migration and mating behaviour climate change What can be done?

3. Fisheries science A European institution since 1902 (ICES - International council for the exploration of the seas) Fishing records for 1000 years and scientific investigation from the mid 1800’s Johan Hjort - 1914 Identified fundamentals of biology of cod.

4. The good and the bad Hjort’s (1914) conclusions have had a most powerful influence on fisheries research He argued that the number of juvenile fish surviving each year were not due to variations in the quantities of eggs spawned but that they were most likely due to annual fluctuations in the amount of plankton available as food for the larvae, and to dispersal patterns (where the larvae were ‘blown’ to). Good - it laid the foundations for explorations which try to identify what influence climatic effects has on the production of food and hence on survival of young fish. Bad - it assumes there is no relationship between the number of fish reproducing and the success of juvenile survival.

5. Fisheries science and the fisherman In the beginning the interaction was positive - the goal was to understand why fishing was better in some years and some areas - to help the fishing community. Fisheries science was at the forefront of ecological research, questioning animal behaviour, population dynamics and climatological interactions.

6. Technological advances horsepower, Sonar (fish finders

7. Law of the Sea 1978 (200 mile limit for management) Recognition that the sea’s resources were not inexhaustible. The need to have tools for agreeing international standards for management limits. Introduction of Mathematical modelling - the beginning of setting in stone the direction of research.

8. The essential guide to fisheries management To understand why fisheries is managed the way it is - with one number called the TAC (total allowable catch).

9. Recruitment  Number of juveniles surviving to 1 year  Number of animals big enough to be caught in the fishery

10. Spawning stock Biomass  The total sum in weight of the mass of fish that are mature and capable of spawning that year.

11. Maximal sustainable yield RECRUITS STOCK - BIOMASS OF SPAWNERS Stocks thought to be more productive at lower rather than higher levels due to 1) a low number of adults can successfully produce a high number of recruits and 2) there is ‘interference’ (density dependence) of a larger stock size with survival and growth of recruits. Level at which stock is recommend to be fished in order to keep surplus production at maximum level

12. Fisheries Management across the world is based on the assumption that there is a real relationship between the weight of the stock and subsequent recruitment.

13. Why the collapses ?

14. 100 years of catch information The fishing was reduced during the first and second world wars Technologically enhanced catches

16. Continuously high and increasing fishing pressure leads to loss of big fish

17. Fisheries Resource Conservation Council (FRCC) in 1997 “One factor in the collapse of Atlantic Canada’s groundfish fisheries was a lack of attention to the logical connection between the spawning and future recruitment of young fish.” “The reproductive capacity of the stock appears not to be properly measured by the absolute volume of spawning biomass, as generally assumed.”

18. Do 10 small cod really have the same reproductive output as one of these mother cod? Stock (SSB) / Recruitment Relationship Assumes constant number of eggs / per gram of biomass.

19. Critical Factors ignored once the methodology for assessing and predicting population size is institutionalised Fish are individual animals not biomass! At lower levels of stock sizes there is also a lack of older/larger individuals. What does heavy fishing pressure do to other aspects of a fish’s behaviour and what are the effects in the longer term?

20. Decrease in Field Work: It’s expensive. Biology is time consuming. Computer modelling is cheap and fast. Photo by John Dunn

21. IBM: From individuals to the Population Reproductive output of COD over the spawning season Comparison of 6 populations with same spawning stock biomass. Decrease in reproductive output in more heavily fished populations Differences in output due to assumptions about the relationship between mother and egg quality. Shift in peak date of 3 weeks - such that the majority of production is later Day of the year Reproductive output What happens when you only have young fish left in the spawning population?

22. First time vs second time spawners First time spawn fewer and smaller eggs than second and subsequent spawners A very low percentage of first time spawners eggs that are fertilised or hatch successfully.

23. Condition / Population structure - effect on SRP

24. Sexual Maturation The age or size of a fish when it becomes sexually mature is very flexible and may be density dependent via food limitations and /or genetic. Function of growth history (food and temperature) Fish that are heavier (i.e. more surplus energy) at a given length have a higher probability to be sexually mature. length Better condition Length 50% Maturity

25. Sexual Maturity: Effects of fishing? Fishing pressure may have caused shifts in sexual maturity and fecundity. Cod on Canadian East coast - maturity at smaller size and age (shift from 4 to 2 years of age) If density driven - i.e. more food per fish - why are they no larger at age and yet higher fecundity? Age Life time reproductive output/ size at age Mature early Mature later now

26. Genetic Selection? Most fish are caught before they can spawn - therefore the only ones getting to spawn are those fish that mature early. If that is a trait with a degree of heritability than fishing pressure is acting as a very large selective force to kill all fish that don’t mature early. Early maturity comes with a cost in length of life and smaller size at maturity and slower growth rates. If timing of and size at maturation are heritable - genetic models predict it will take natural section at least 250 years before we can hope to see the re- appearance of genotypes for longer lived, bigger bodied, later maturing cod.

27. Resilience because so fecund? Jeff Hutchings - points out that high fecundity does not mean high resilience (think of tree seeds?) Most fished populations do not spring back 34 7 49 Doing worse Not recoveredRecovered

28. Fish Migrate Fish - just like many other animals - migrate. They migrate for the same reasons - making use of seasonal and spatial changes in resources They have constraints for - best routes and where to have babies (for fish the need is to be ‘upsteam’ - even if attaching your eggs)

29. Do fish learn? What physical clues / constraints can there be? - currents - bottom features - watermass type How much is from watching what others do? A. Corton - Herring not coming back Before 1960’s Now

30. Cod Highways George Ross constraints for cod migration - water can’t be too cool (> 2 0 C) Found 80% of the stock in one gully - following large scouts

31. Migrating cod scouts out in advance

32. Cod spawning behaviour along the migration route Pairs rise above concentrated group

33. The interaction of spawning location, timing and size/age of fish has also been largely ignored. Spawning locations, timing and size groups Big Fish Medium Small Fish Does it matter where and when you kill fish during spawning?

34. Eggs to Larvae Location of where the larvae end up are heavily dependant on the effects of weather and on where eggs were released. Will they be transported farther or kept near area of spawning?

35. Mortality during spawning Fish are more concentrated Male and females are more likely to be in different locations at different times Do some locations contain - ‘better’ spawners than others?

36. Lots of big fish fewer big fish very few big fish Different quality of spawning areas

37. Climate = Food but it is the factor we can’t really control or manage Condition of adults -which leads to the number and quality of eggs Feeding opportunities for larvae - which leads to the survival changes for juveniles North Atlantic Oscillation Spawning liver condition Recruitment

38. Look at stratified vs mixed regions in the North Sea Spatial and seasonal pattern of water mass characteristics in the North Sea

39. A day in the life of a fish We must understand fish as animals. Ask questions about population structure, genetic selection, condition, spawning behaviour and climate effects before we can begin to imagine that we understand a species well enough to manage it. To describe their habitat one must use physical characteristics in 3 dimensions and time.

40. New relationships? Including age/size specific fecundity and viability should decrease uncertainty in stock-recruitment relationships. A new index for stock characteristics should produce a clearer relationship between survival and the spawning stock

41. North Sea cod Reproductive Output 1963-1999 (using mean length at age) Picture of years vs # eggs vs mean egg size

43. What to do? Decrease Fishing pressure If you want reliable, sustainable fisheries you must accept that they can only be fished at low levels of fishing effort to keep around a needed number of older, wiser, bigger, better breeding fish. North Sea cod - that is 4-5 times lower than the current level. The longer lived the species - the lower the level of fishing allowed.

44. Wait for the news of the next one Monk fish!