フィードバック管理 と資源評価

1. フィードバック管理と資源評価 松石隆先生、菅野泰治先生、西村欣也先生はじめ北大の皆様に感謝

2. Feedback Management • Uncertainty in stock assessment • Accountability • Dynamic change in abundance • Adaptability (tuning catch effort) • Successive Monitoring!!!

3. Revised Management Procedure (RMP) in IWC • Moratorium of commercial whaling since 1982 (until RMP?) • RMP was adopted in 1994, but has not yet enforced.

4. Feedback Management for Sika deer in Hokkaido, Japan 試される大地 http://www.marimo.or.jp/Kushiro_shichou/ezosika/

5. Density-dependent hunting pressure (adaptability) %P>50%: Emergent Decrease (<4 years) 25% < %P : Gradual Decrease 5% < %P : Gradual Increase %P <5% or after the severe winter: Ban-on-Hunting Hokkaido, tested land

6. Stage-Structured Model sika deer has little densityeffect and I ignored Nc, Nf, Nm: No. of calves(0.5), females & males(≧1.5) Lfc(t)= Lmc(t)= exp[-Q(t)Hc(t)]exp[-Mc(t)]exp[-Rc(t+1)], Lff(t) = exp[-Q(t)Hf(t)]exp[-Mf(t)]exp[-Rf(t+1)] , Lmm(t) = exp[-Q(t)Hm(t)]exp[-Mm(t)]exp[-Rm(t+1)] , Hokkaido, tested land

7. Risk Management We set the upper and lower limit (%P- & %P+) of population size P such that, within the next 1 century, Prob{P<1000 individuals} < 1% Prob{%P<%P- or %P> %P+} < 5%. Therefore, %P- 5%, %P+ 50% Hokkaido, tested land 2

8. Population Indices • Catch & Watch per hunter day • Spotlight census • Helicopter census • Train accidents • Damage of agriculture & forestry • Uncertainty of absolute size Hokkaido, tested land 3

9. Population index by spotlight census for eastern Hokkaido Population estimationhas large uncertainty Hokkaido, tested land

10. Fallacy of 120 000 deer hypothesis • >30000 deer were killed every year since 1995 • Male deer is still abundant • Natural growth rate is 15-20% • Population began to decrease? • 160-240 thousand deer in 1993 Hokkaido, tested land

11. RMP for south Pacific minke whale • Pt+1-Pt = r[1-(Pt /K)z]Pt-Ct • think uncertainty in r, K, Pt /K and Pt (relative and absolute P) • no age structure • ignore uncertainty in z (density-effect)

12. IWC/SC concensus • 2000 minke whale is commercially exploitable. • Catch Limit is determined by Lt=2.12r (Pt /K-0.54)Pt • Scientific whaling catches now 400!

13. South Pacific minke whale may be decreasing! (Butterworth et al. 1999)

14. Recent IWC (SOWER) census data suggests • Minke whale population is 30%-70% as was in ca1990. • Anti-whaling NGO may think “Whaling is over”. • Japan Gov’t may think “this census is uncertain…”

15. Why do minke whale decrease? • Artifact in monitoring • Ecosystem change • Short resource (krill) • Competition with other whales • Super-Compensation

16. “Artifact Hypothesis” • RMP is realizable only under effective monitoring; • Scientific whaling does not satisfy RMP. • Precautionary approach. Commercial whaling isCritically Endangered

17. Competition hypothesis • Competition decreases • Recruitment or fecundity? • Adult mortality? • Why did the minke whale increase in the 1980s?

18. Super-Compensation • Demographic Momentumdue to drastic change in catch effort from the 1970 to 1990, • Age structure changed greatly. • Same phenomenon as southern bluefin tuna

19. Age structure is changing

20. Demographic Momentum by a Leslie type Model • Age at maturity = 11years • Moratorium in t=0 • RMP begin in t=30 • Tune recruitment,>Tune total stock. • Monitor age structure!!! • Scientific Whaling is useful

21. Conclusion • Feedback management should investigate stock size and age structure. • Temporal decrease of minke whale may be explained by demographic momentum.