Impact of Fishing on the Abundance of Marine Species

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Impact of Fishing on the Abundance of Marine
Species

• Rainer Froese
• IfM Kiel
• rfroese_at_ifm.uni-kiel.de

Kathleen Kesner-Reyes MSI Quezon
City kkesner_reyes_at_hotmail.com
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Background

• Fishing down the food web gtgt
• Global catch declining gtgt
• Fish biomass in the North Atlantic gtgt

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Materials and Methods

• FAO Production data, 1950-1999, for marine areas
  only, no bivalves, seaweeds, corals
• ICES Catch data, 1973-1999
• Species items treated as fisheries
• North Sea Catch data 1903-1998 (SAUP)
• Resilience and Trophic Level from FishBase
  www.fishbase.org

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Materials and Methods (Basking shark)
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Material and Methods
Status of fishery Criteria applied to 932 species items
Undeveloped Year before maximum year and production less than 10 of maximum value.
Developing Year before maximum year and production 10-50 of maximum value.
Fully exploited Production larger than 50 of maximum value.
Overfished Year after maximum year and production 10-50 of maximum value.
Collapsed / Closed Year after maximum year and production less than 10 of maximum value.
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FAO Marine Catches 1951-1998
?
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Overfishing is Increasing
Percentage of species items in FAO production
data that were overfished within 10 years after
the fishery was first fully exploited.
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New Resources Species Composition
Preferred Habitat 1951-1960 1979 -1988
Demersal 73 (44) 195 (36)
Pelagic 34 (20) 112 (20)
Reef-associated 5 (3) 26 (5)
Deep Sea 4 (2) 27 (5)
Mixed habitats 52 (31) 190 (35)
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Resilience / Productivity of SpeciesMusick,
Fisheries 1999
Parameter High Medium Low Very low
rmax (1/yr) gt 0.5 0.16 0.50 0.05 0.15 lt 0.05
K (1/yr) gt 0.3 0.16 0.30 0.05 0.15 lt 0.05
Fecundity (1/yr) gt 10,000 100 1000 10 100 lt 10
tm (yrs) lt 1 2 4 5 10 gt 10
tmax (yrs) 1 3 4 10 11 30 gt 30
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Dynamics of OverfishingCatch by Resilience /
Productivity Group
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Recent Status of Best Perfomers

• Of 25 fisheries that had 30 or more fully
  exploited years before 1989, thereafter
• 8 were partly (1-9 years) overfished
• 2 were fully (10 years) overfished
• 1 was collapsed

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The Northeast Atlantic, ICES
?
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Overfishing in the North Sea
Sandeel
Catch composition of landings from the North Sea
from 1903 to 1998
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Fishing Down the Food Webin the North Sea
Trends in mean trophic level of annual landings
from the North Sea
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Impact of Fishing on CoML

• No extinctions of marine species due to fishing
  yet
• Near extinctions and extirpations are
  increasing
• Abundances of most organisms are drastically
  altered from virgin state
• CoML must deal with Shifting baseline effect

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Most landed fish are immature
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New Approaches
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New Approaches
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New Approaches
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New Approaches

• Restrict fishing to cohort after first and before
  second spawning
• Determine amount to be taken from ecosystem
  studies
• Involve ALL stakeholders AND the public

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Dynamics of Overfishing

• Discussion
• Thank You

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Dynamics of OverfishingFishing Down the Food Web
gtgtPauly et al., Science 1998
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Dynamics of OverfishingFishing Down Size
ltltFroese et al. 2000
Canada, Northwest Atlantic
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Dynamics of Overfishing ltltWatson Pauly, Nature
2001