Transcript F32

Adaptive Management and
Community Interaction in
Fisheries
• Hiroyuki MATSUDA, (Ocean
Research Institute, University of
Tokyo, Japan)
1
Requiem to MSY
• Ecosystem is uncertain, nonequilibrium and complex
• MSY ignores all the three.
Recovery probability of mackerel
資源回復確率
70-80年代の漁獲圧なら
90 年代の未成魚乱獲
を続けると
Species replacement
AM makes chaos.
捕
食
者
密
度
被食者密度
2
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
3
Catch in Japan (1000 mt)
The pelagic fishes fluctuate
greatly even without fisheries,
Anchovy
Horse mackerels
Pacific saury
Chub mackerel
Sardine
4
Cyclic Advantage Hypothesis
The next dominant to
sardine is anchovy –
sardine
mackrel
Yes! As I predicted
The second next is chub
mackerel
Many experts agree now
Anchovy, Pacific
saury, jack mackerel
Matsuda et al. (1992) Res. Pop.
Ecol. 34:309-319
5
Q&A
Q: Will western Pacific chub
mackerel really recover?
A: It depends on the fishing
pressure.
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Large fluctuation of recruitment
Strong year classes
appeared twice
7
Immatures were caught before matured
1970s
%immatures
1980s
65.0% 60.0
%
1990s
1993-
87.0 90.6%
%
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Fishers missed chance of recovery
Kawai et al. (2002: Fish. Sci.68:961-969)
Actual
F during 1970-89
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Probability of stock recovery
Kawai et al. (2002: Fish. Sci.68:961-969)
百
万
ト
ン
資
源
回
復
確
率
1990s is Japan’s “lost 10 years”.
10
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)
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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.
12
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
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Five Principles
1.
2.
3.
4.
5.
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.
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Management in prey-predator
cycles and adaptive evolutions
(Matsuda & Abrams in review)
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Stock & yield
Effects of predator-prey
interactions on sustainable yield
dN  r(1 N ) N  fN P
dt
K
1 hN


dP  d  bfN  qE  P

1 hN
dt 

Prey abundance
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Non-Standard
relationship
Stock may increase
in population size
between
effort
and
yield
with increasing
Stock & yield
fishing effort
P
Y
The effort that
achieves MSY
can be close to
the effort at
which the stock
collapses.
Fishing effort
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If the prey is exploited,
(Matsuda & Abrams unpubl.)
dP/dt=0
dN/dt=0
dN  r(1 N ) N  fN P  qEN
dt
K
1 hN


dP  d  bfN  P
1 hN 
dt 
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If the prey is exploited,
Increasing fishing
effort decreases the
predator density
more than the prey
density.
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Cycle increases average yield.
Stock
Yield
Prey
Predator
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If fishing effort is regulated by
stock abundance,...
dN  r(1 N ) N  fN P  qEN
dt
K
1 hN


dP  d  gP  bfN  P
1 hN 
dt 
dE/dt = u(NNT)
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Feedback control by a (d)(e)
target
stock
(f)
makes irregular fluctuations.
Prey
Fishing effort
Predator
• Feedback control
may result in
extinction of either
fishery or predator.
(a)
(b)
(c)
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