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フィードバック管理フィードバック管理と資源評価と資源評価

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

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Feedback ManagementFeedback Management

• Uncertainty in stock assessment–Accountability

• Dynamic change in abundance–Adaptability (tuning catch effort)

• Successive Monitoring!!!

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Revised Management Revised Management Procedure (RMP) in IWCProcedure (RMP) in IWC

• Moratorium of commercial whaling since 1982 (until RMP?)

• RMP was adopted in 1994, but has not yet enforced.

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Feedback Management for SFeedback Management for Sika deer in Hokkaidoika deer in Hokkaido, Japan, Japan

http://www.marimo.or.jp/Kushiro_shichou/ezosika/

試される大地試される大地

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Density-dependent hunting Density-dependent hunting pressure pressure (adaptability)(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 landHokkaido, tested land

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Stage-Structured ModelStage-Structured ModelNc ( t 1)

N f (t 1)

Nm (t 1)

0 2r(t)L ff (t) 0

L fc ( t) / 2 L ff (t) 0

Lmc ( t) / 2 0 Lmm (t)

N c (t)

N f (t)

Nm (t)

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)] ,

sika deer has little density

sika deer has little density

effect and I ignored

effect and I ignored

Hokkaido, tested landHokkaido, tested land

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Risk ManagementRisk ManagementWe 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 landHokkaido, tested land

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Population IndicesPopulation Indices• Catch & Watch per hunter day• Spotlight census• Helicopter census• Train accidents• Damage of agriculture & forestry

–Uncertainty of absolute sizeHokkaido, tested landHokkaido, tested land

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Population index by spotlight Population index by spotlight census for eastern Hokkaidocensus for eastern Hokkaido

Population estimation

Population estimation

has large uncertainty

has large uncertaintyHokkaido, tested landHokkaido, tested land

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Fallacy of 120 000 deer Fallacy of 120 000 deer hypothesishypothesis

• >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 landHokkaido, tested land

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RMP forRMP for south Pacific minke whale 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)

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IWC/SC concensusIWC/SC concensus

• 2000 minke whale is commercially exploitable.

• Catch Limit is determined byLt=2.12r (Pt /K-0.54)Pt

• Scientific whaling catches now 400!

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South Pacific minke whale mSouth Pacific minke whale may be decreasing!ay be decreasing!

(Butterworth et al. 1999)

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Recent IWC (SOWER) Recent IWC (SOWER) census data suggestscensus 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…”

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Why do minke whale decrease?Why do minke whale decrease?

• Artifact in monitoring

• Ecosystem change –Short resource (krill)

–Competition with other whales

• Super-Compensation

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““Artifact Hypothesis”Artifact Hypothesis”

• RMP is realizable only under effective monitoring;

• Scientific whaling does not satisfy RMP.

• Precautionary approach.

Commercial whaling is

Commercial whaling is

Critically Endangered

Critically Endangered

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Competition hypothesis Competition hypothesis

• Competition decreases –Recruitment or fecundity?

–Adult mortality?

• Why did the minke whale increase in the 1980s?

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Super-CompensationSuper-Compensation

• Demographic Momentumdue to drastic change in catch effort from the 1970 to 1990,

• Age structure changed greatly.• Same phenomenon as southern

bluefin tuna

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Age structure is changingAge structure is changing

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Demographic Momentum Demographic Momentum by a Leslie type Modelby 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

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ConclusionConclusion

• Feedback management should investigate stock size and age structure.

• Temporal decrease of minke whale may be explained by demographic momentum.