Adaptive Management and Community Interaction in Fisheries

1. Adaptive Management and Community Interaction in Fisheries • Hiroyuki MATSUDA, (Ocean Research Institute, University of Tokyo, Japan)

2. Recovery probability of mackerel 捕食者密度 70 - 80 年代の漁獲圧なら 90 年代の未成魚乱獲 被食者密度 を続けると 資源回復確率 Requiem to MSY • Ecosystem is uncertain, non-equilibrium and complex • MSY ignores all the three. Species replacement AM makes chaos.

3. What is Adaptive Management? =Adaptive Learning & Feedback Control Data Fish Stock Dynamics with Fishery Dynamics Model State Variable Decision Making of Fisheries Management Toshio Katsukawa: Doctoral dissertation 2002

4. Anchovy Horse mackerels Pacific saury Chub mackerel Sardine Catch in Japan (1000 mt) The pelagic fishes fluctuate greatly even without fisheries,

5. sardine mackrel Anchovy, Pacific saury, jack mackerel Cyclic Advantage Hypothesis The next dominant to sardine is anchovy – Yes! As I predicted The second next is chub mackerel Many experts agree now Matsuda et al. (1992) Res. Pop. Ecol. 34:309-319

6. Q& A Q: Will western Pacific chub mackerel really recover? A: It depends on the fishing pressure.

7. Large fluctuation of recruitment Strong year classes appeared twice

8. Immatures were caught before matured

9. F during 1970-89 Fishers missed chance of recovery Kawai et al. (2002: Fish. Sci.68:961-969) Actual

10. 百万トン資源回復確率 Probability of stock recovery Kawai et al. (2002: Fish. Sci.68:961-969) 1990s is Japan’s “lost 10 years”.

11. Future of Pelagic Fish Populations in the north-western Pacific: • If overfishing of immatures continues, • Chub mackerel will not recover forever; • If cyclic advantage hypothesis is true, • Sardine will not recover forever; • Do not catch immatures too much • The overfishing is an experiment for my hypothesis. (Adaptive mismanagement)

12. Conclusion #1 • Pelegic fish has fluctuated without fisheries; • Collapse of sardine is not due to overfishing; however, • The impact of fisheries on pelagic fishes when it was at low levels is too high to recover.

13. Conclusion #2 • Over-fishing may cause impact on both a target species and other species. • Monitor target and other species for fisheries controlling procedures • Future stock depends on not only impact on a target but also other species & habitats. • These are hypotheses. We need risk assessment and adaptive management

14. Five Principles • Do not catch decreased fishes; • Do not catch immature fishes; • Catch temporally dominant fishes; • Improve selective fishing; • Monitor not only a target species, but its prey, predator, competitor etc.

15. Management in prey-predator cycles and adaptive evolutions(Matsuda & Abrams in review)

16. Effects of predator-prey interactions on sustainable yield Stock & yield Prey abundance

17. Non-Standard relationship between effort and yield Non-Standard relationship between effort and yield Stock may increase in population size with increasing fishing effort The effort that achieves MSY can be close to the effort at which the stock collapses. P Stock & yield Y Fishing effort

18. If the prey is exploited,(Matsuda & Abrams unpubl.) dP/dt=0 dN/dt=0

19. If the prey is exploited, Increasing fishing effort decreases the predator density more than the prey density.

20. Cycle increases average yield. Stock Yield Prey Predator

21. If fishing effort is regulated by stock abundance,... dE/dt = u(N-NT)

22. (a) (b) (c) (d) (e) (f) Feedback control by a target stock makes irregular fluctuations. Prey • Feedback control may result in extinction of either fishery or predator. Fishing effort Predator