Transcript Document 7816071

Fisheries
Fish as Food
Commercial Fisheries
Trends in World Fisheries
Solutions?
Commercial Fisheries
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•
•
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•
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Traps
Trawls
Purse seines
Gillnets
Longlines
etc…
Purse seining
Trawling
Fish size-selective grid
Cod Fishery - Norway
Gillnetting
Longlining
Technological Improvement in Fisheries
Tuna catches under floating
objects
World Fishing Fleet Capacity
40
30
Non corrected
20
10
2000
1990
1980
1970
0
1960
Gross Registered Tonnage (106 tons)
Corrected
Production of Marine Fisheries
100
Capture
Million tonnes
80
60
40
20
mariculture
0
1950
1960
1970
1980
1990
2000
EEZs Claims
Production ( million tonnes)
Global Trend in Landings
100
50
1800
1840
1880
Year
1920
1960
2000
Catches per 100 hooks (Japanese fleet)
1952
1964
1958
1980
Myers & Worm, 2003
Development Phases of World Fisheries
Phase IV Senescent
90%
80%
70%
Phase III Mature
60%
50%
40%
Phase II Developing
30%
20%
Phase I Undeveloped
10%
1993
1991
1989
1987
1985
1983
1981
1979
1977
1975
1973
1971
1969
1967
1965
1963
1961
1959
1957
1955
1953
0%
1951
Percentage of resources
100%
State of Fish Stocks 1999
Recovering
Depleted
Overexploited
Fully exploited
Moderately exploited
Undeveloped
0%
10%
20%
30%
40%
50%
Trends in States of Fish Stocks
60%
Fully Fished
50%
40%
Moderately fished: U+M
30%
20%
Overfished: O+D+R
10%
0%
1970
1975
1980
1985
1990
1995
2000
2005
Ratio between Present & Historical Landings
1. Antarctic
2. Atlantic, Southeast
3. Pacific, Southeast
4. Atlantic, Northwest
5. Atlantic, Western Central
6. Pacific, Eastern Central
7. Medit . & Black Sea
8. Pacific, Northeast
9. Atlantic Southwest
10. Atlantic Eastern Central
11. Atlantic Northeast
12. Indian Western
13. Pacific Central Western
14. Pacific Southwest
15. Pacific Northwest
16. Indian Eastern
0.14
ANT
0.39
ASE
0.43
PSE
0.44
ANW
0.71
ACW
0.73
PEC
0.81
MBS
0.83
PNE
ASW
0.86
AEC
0.87
ANE
0.92
0.94
IW
PCW
1.00
PSW
1.00
PNW
1.00
IE
1.00
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Population Size (N)
Maximum Sustainable Yield
= Growth
= Maximum Sustainable Yield
Time (t)
Growth / Yield
Maximum Sustainable Yield
Fishing effort
Simple Abundance Model
Single Species Models
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Assessment models are biased because they do not incorporate the
predation by other species.
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Assessment models are limited because of their emphasis on equilibrium
solutions, such as MSY.
•
Assessment models do not usually account for environmental changes,
whether interannual or interdecadal.
•
A correct assessment approach requires that a multi-species framework
be used.
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Harvest recommendations from single-species assessment do not
consider the needs of other species.
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Harvest recommendations from single-species assessment involve the
deliberate fishing down of a population and therefore adversely change
the ecosystem.
•
The single-species approach is invalidated, because overfishing has
occurred for at least a majority of the world’s fisheries.
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Single-species approaches do not account for the indirect effects of
fishing (e.g. bottom fishing on habitat quality).
Fishing at MSY level: is it good or bad?
0%
50%
100
PSE
50%
PEC
“BAD”
AEC
ANT
ANT
PCW
ANE
PNW
ASW
IE
PNE
ANW
PNW
ASW
ACW
MBS
PEC
ANE
“GOOD”
ASE
ANW
AEC
PCW
PSE
IW
IW
PSW
ACW
A: if fishing at MSY is “good”
“GOOD”
PSW
MBS
IE
100 %
“BAD”
B: if fishing at MSY is “bad”
Neoclassical Sustainability
Modern Sustainability
Fishery induced changes in world fish composition
Fishing Down the Food Web
Shark Populations NE Atlantic
Baum et al. 2003
• Fisheries have significantly contributed to
human development and can still do so
• There are problem areas and avenues for
positive change
• Change will never be at no cost; but….
Solutions?
Historical Succession of Coastal Ecosystems
1. Over-exploitation of large predators
2. Collapse “Ecosystem Engineering” species
3. Rise of Microbes
Jackson et al. 2001
Historical fishing consequences
Jackson et al. 2001
Historical fishing consequences
Jackson et al. 2001
Historical fishing consequences
Jackson et al. 2001
Jackson et al. 2001