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

Density (kg/km2)

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

UK hake catches (kg) 2005-2011

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 1935Belgium 28Denmark 1119Germany 128France 248Netherlands 64UK 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

Ta!

Funding: