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The rise of North Sea hake: ecological impact and implications for fisheries
managementAlan Baudron1, Doug Speirs2, Mike
Heath2, Chris McCaig2, Paul Fernandes1
1 University of Aberdeen2 Strathclyde University
European hake
Merluccius merluccius
Widely distributed: Mauritania to Norway
Spawning from February to July (ICES, 2012)
Little knowledge in northern areas
Distribution
Spawning areas
Northeast Atlantic: 2 large stock units Northern hake stock from Spain to Norway Assessment estimates for stock unit 5 surveys:
North Sea (NS-IBTS): 1965-2012 West of Scotland (SWC-IBTS):
1985-2011 Ireland (IGFS): 2003-2008 Porcupine bank (SP-PORC):
2001-2011 Bay of Biscay (EVHOE): 1997-
2010
Northern hake stock
Large increase in density (x 4) in recent years, x 5 in North Sea Huge difference between Q1 and Q3 in the North Sea
Mean density estimates
Northern hake survey biomass = mean density * area
qsurvey = Northern hake survey biomass / Northern hake assessment biomass
North Sea TSB = North Sea hake survey biomass * (1/qsurvey)
Length at 50% maturity (L50)
North Sea SSB = North Sea TSB > L50
North Sea recruitment = number of age 1 individuals
Estimates for North Sea hake
Biomass: increase by a factor 4 in quarter 1, a factor 8 in quarter 3
Slight increase in recruitment
North Sea hake stock assessment
Large landings of North Sea hake in the 1950s
Sudden increase previously occurred in North Sea
North Sea hake landings
Difference between quarter 1 and quarter 3
More large individuals at quarter 3
Observation consistent through time
Quarter 1 Quarter 3North Sea hake length frequencies
Increase in North Sea hake: the consequences
CFP: relative stability
2010: 2941 tons of hake landed by Scottish vessels in the North Sea
CFP reform: discard ban
Hake “choke” species for North Sea demersal fisheries
TAC North Sea hake 1935
Belgium 28
Denmark 1119
Germany 128
France 248
Netherlands 64
UK 348
North Sea quota share (tons)
Increase in North Sea hake: WHY? Fishing? Northern hake recovery plan since 2004 Environment? Hake recruitment variability impacted by environmental
conditions (Sánchez & Gil, 2000) Something else?
Conclusions
Are hake here to stay? Situation different from the 1950s North Sea temperature increase Low cod biomass
Hake migrations Temperature? Inflow? Prey? Little knowledge about hake in North
Sea (spawning/feeding areas?)
Implications for fisheries management Relative stability Quotas do not reflect the regional stock abundance
T°C
Ecosystem model: FishSUMS (Speirs et al., 2010)
Assess consequences of hake increase on NS ecosystem
Model North Sea fishery under different “hake scenarios”
Future work