The implications of warming climate for the management of north sea demersal fisheries
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Jo King:. The Implications of Warming Climate for the Management of North Sea Demersal Fisheries. R.M. Cook and M.R. Heath FRS Marine Laboratory, P.O. Box 101, 375 Victoria Road, Aberdeen, AB11 9DB, UK. Very Important People.

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The Implications of Warming Climate for the Management of North Sea Demersal Fisheries

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Jo King:

The Implications of Warming Climate for the Management of North Sea Demersal Fisheries

R.M. Cook and M.R. Heath

FRS Marine Laboratory, P.O. Box 101, 375 Victoria Road, Aberdeen, AB11 9DB, UK


Very Important People

  • Net Benefits: A sustainable and profitable future for UK fishing. Cabinet Office Prime Minister’s Strategy Unit, London, UK

  • Inquiry into the future of the Scottish Fishing Industry. Royal Society of Edinburgh, Edinburgh, UK

  • Concluded fishing the main cause of decline in demersal stocks


A well informed press

Fishing News March 2004: Natural changes affect stocks- maybe more than fishing

Nature 2004. Climate findings let fishermen off the hook


Temperature Effects

  • High temperature associated with lower recruitment in cod (O’Brien et al, Planque and Frédou, Clark)

  • Temperature affects biology of plaice and sole (van der Veer and Witte, Wegner et al)

What is the relative contribution of temperature and spawning stock biomass to recruitment?


Stock-Recruit Model

R=recruits

SSB=spawning stock biomass

T=temperature index

a=proportionality constant

b=density dependence coefficient

c=temperature coefficient

Assumed gamma errors


North Sea Stocks

  • Cod

  • Haddock

  • Whiting

  • Saithe

  • Plaice

  • Sole

  • Herring (honorary demersal fish)


Spawning biology

  • Demersal fish spawn in spring (Feb-April)

  • Eggs are pelagic

  • Temperature may be proxy for environmental effects in early life stages

  • Herring spawn in autumn, benthic eggs- not obvious that SST is relevant


North Sea Temperature Index

  • IBTS data for February SST

  • 10 fixed stations

  • Performed single factor analysis

  • Factor explains about 80% of variance

  • Used factor as index of temperature


North Sea Temperature index

1957-1987 - cool - mean index= -0.37

1988-2002 - warm- mean index= +0.7


Temperature Coefficient


Performance Indictors

  • MSY- Maximum sustainable yield

  • Fmsy- Fishing mortality to produce MSY

  • Bmsy- Spawning stock biomass as MSY

  • Bpa- ICES minimum ‘safe’ spawning stock biomass (usually calculated in ‘cold’ regime)

  • Fpa- ICES maximum ‘safe’ fishing mortality (usually calculated in ‘cold’ regime)


Equilibrium Calculations

  • Age structured production model

  • Used temperature modified Ricker S-R model

  • Fixed growth, natural mortality, maturity and selection pattern

  • Calculated values for cool and warm regime

  • Assumes annual temperature anomalies are consistent with equilibrium


Warm versus Cold Regime


Recent catch vs MSY in warm regime


Conclusions

  • Detectable effect of temperature on cod, saithe, plaice and sole recruitment

  • In warm regime, cod, plaice and sole cannot reach their minimum safe biomass (Bpa) if fished at current agreed Fpa

  • Cod can sustain a larger catch even in warmer regime provided recovery is possible

  • Long term yields of flatfish expected to decline

  • Saithe appears to benefit from warmer temperatures


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