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

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

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

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

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

6 Q & AQ & AQ & AQ & 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 1970s1980s1990s1993- %immatures 65.0%60.0 % 87.0 % 90.6%

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

10 Probability of stock recovery 1990s is Japan’s “lost 10 years”. ) Kawai et al. (2002: Fish. Sci.68: )

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 1.Do not catch decreased fishes; 2.Do not catch immature fishes; 3.Catch temporally dominant fishes; 4.Improve selective fishing; 5.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 Stock & yield Fishing effort Y P The effort that achieves MSY can be close to the effort at which the stock collapses. Standard relationship between effort and yield Non-Standard relationship between effort and yield Non-Standard relationship between effort and yield Stock may increase in population size with increasing fishing effort

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

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