The rise of North Sea hake: ecological impact and implications for fisheries management Alan Baudron 1, Doug Speirs 2, Mike Heath 2, Chris McCaig 2, Paul Fernandes 1 1 University of Aberdeen 2 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):  West of Scotland (SWC-IBTS):  Ireland (IGFS):  Porcupine bank (SP-PORC):  Bay of Biscay (EVHOE): 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

Density (kg/km 2 )

 Northern hake survey biomass = mean density * area  q survey = Northern hake survey biomass / Northern hake assessment biomass  North Sea TSB = North Sea hake survey biomass * (1/q survey )  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 3 North Sea hake length frequencies

UK hake catches (kg)

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 hake1935 Belgium28 Denmark1119 Germany128 France248 Netherlands64 UK348 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

Ta! Funding: