Climate change and fisheries Keith Brander ICESGLOBEC Coordinator

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Climate change and fisheriesKeith
BranderICES/GLOBEC Coordinator
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Whats this talk about?
Blowed if I know
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• Climate affects fisheries
• Climate affects biodiversity
• Fisheries affect biodiversity
• Fishing has a bigger effect on biodiversity than
  does climate change
• Our time series of changes in fish populations
  mainly come from fisheries

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Characteristics of marine fish populations
compared with terrestrial populations and
freshwater fish

• Large population sizes
• Fewer boundaries to migration
• High fecundity
• Often have dispersive planktonic stage
• Undergo large population fluctuations
• Humans dont live in the sea

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Effects of climate on fish and fisheries
How do you distinguish between climate and
fisheries effects?

• Look at periods prior to fishing
• Look for effects (e.g. stock increase) which are
  unlikely to be due to fishing

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Cod landings at Greenland
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Spread of Cod at West Greenland

• 1900 Cape Farewell Fiskenes Bank
• 1917-18 Frederikshaab
• 1919 Godhaab
• 1922 Sukkertoppen
• 1927-30 Christianshaab and first direct evidence
  of spawning DANA 1925
• 1931-36 Umanak
• Late 1930s Upernavik
• Late 1960 decline and retreat

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West Greenland during the period of warming from
1920
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from Quero, Du Buit and Vayne, 1998
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Mullus surmulletus
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Annual landings of sole in the Kattegat-Skagerrak
(ICES Division IIIA).
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Conclusions about climate and fisheries

• affects distribution (migration, growth,
  recruitment, mortality)
• change in (relative) abundance
• temperature is not the only factor

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Conclusions about climate and fisheries (from
ACIA report)

• Local extinctions at the edges of the current
  range for salmon, sturgeon, etc.
• Increased productivity of other species in
  northern seas due to temperature increase
• Current near-collapse makes fisheries very
  sensitive to climate change

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What do we mean by loss of biodiversity?
Effects of climate on biodiversity

• species extinction
• stock extinction which may or may not entail-
• loss of alleles
• loss of genotypes
• adverse change in genotype frequency
• change in (relative) abundance
• what about changes in distribution?

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Geographic differences can be used to show
probable environmental effects
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Conclusions about effects of climate on
biodiversity

• there are probably very severe effects on some
  sensitive systems e.g. coral reefs and these will
  also affect fish
• most of our information is about changes in
  distribution and relative abundance
• should biodiversity be measured in a Eulerian or
  Lagrangian way?

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Fishing causes mortality and is usually
selective.
Effects of fisheries on biodiversity
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Effect of fishing on life expectancies
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Decline in maximum fish size in the Northern
North Sea
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The common skate grows to nearly 3 m long. It
used to be common from Morocco to Northern Norway
(including the western Baltic), but is now rare
and locally extinct.
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Fishing causes mortality and is usually
selective. Therefore it may cause
Conclusions about effects of fisheries on
biodiversity

• species extinction
• stock extinction which may or may not entail-
• loss of alleles
• loss of genotypes
• adverse change in genotype frequency
• change in (relative) abundance

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North Sea cod spawning stock biomass
Present biomass is at a historic low Variability
is not only due to fishing there are climate
effects
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