A decade in the doldrums: depressed size-structure in the Celtic Sea fish community

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A decade in the doldrumsdepressed
size-structure in the Celtic Sea fish community
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Effects of fishing on community size-structure

• Fishing is selective and directly removes large
  individuals/species
• Removal of large piscivores leads to predation
  release which indirectly enhances small fish
  biomass

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Shift from large to small fish dominated community
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Size-based indicators

• Direct and indirect effects of fishing can be
  integrated by metrics like the Large Fish
  Indicator (LFI)
• Proportion by weight of large fish
• Where large is derived from the data

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• LFI responds to F (lag). Sustained F in the
  Celtic Sea until 2002
• Peak LFI in 1990 - low levels throughout the 2000s

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Fishing ( discarding) of recruits prevents
recovery (Monkfish, Hake, Cod, Haddock)
R
R
R
M G
R
M G
G F
G F
G F
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Models suggest a multi-decadal recovery period,
asymptote depends on F history
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• Perturbed system with LFI well below 1990
• No recovery during 2000s due to sustained F
• Some good recruitments but low survival
• Recovery depends on F history
• Decadal process - full recovery not guaranteed