jo king: the implications of warming climate for the management of north sea demersal fisheries r.m....
TRANSCRIPT
Jo King:Jo King:
The Implications of Warming Climate for the Management of North Sea Demersal Fisheries
R.M. Cook and M.R. HeathFRS 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
)/( bSSBcTaSSBeR
R = recruitsSSB = spawning stock biomassT = temperature index
a=proportionality constantb=density dependence coefficientc=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
-3.00
-2.00
-1.00
0.00
1.00
2.00
3.00
1957
1960
1963
1966
1969
1972
1975
1978
1981
1984
1987
1990
1993
1996
1999
Te
mp
era
ture
Ind
ex
1957-1987 - cool - mean index= -0.371988-2002 - warm- mean index= +0.7
Temperature Coefficient
-0.8
-0.4
0
0.4
0.8
Par
amet
er v
alu
e
Cod
Saithe
Plaice Sole
Haddock
Herring
Whiting
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
0.00
0.50
1.00
1.50
2.00
Cod Saithe Plaice Sole
Ra
tio
Fmsy
MSY
B(Fpa)(h)/Bpa
Recent catch vs MSY in warm regime
0
50
100
150
200
250
300
350
Cod Saithe Plaice Sole
[000
t]
MSY(h)
mean catch
Bmsy(h)
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