The rise of North Sea hake:
ecological impact and implications
for fisheries management
Alan Baudron1, Doug Speirs2, Mike
Heath2, Chris McCaig2, Paul Fernandes1
1
University of Aberdeen
2 Strathclyde University
European hake
Spawning areas
 Merluccius merluccius
 Widely distributed:
Mauritania to Norway
 Spawning from February
to July (ICES, 2012)
 Little knowledge in
northern areas
Distribution
Northern hake stock
 Northeast Atlantic: 2 large
stock units
 Northern hake stock from
Spain to Norway
 Assessment estimates for
stock unit
 5 surveys:
 North Sea (NS-IBTS): 19652012
 West of Scotland (SWC-IBTS):
1985-2011
 Ireland (IGFS): 2003-2008
 Porcupine bank (SP-PORC):
2001-2011
 Bay of Biscay (EVHOE): 19972010
Mean density estimates
 Large increase in
density (x 4) in recent
years, x 5 in North
Sea
 Huge difference
between Q1 and Q3
in the North Sea
Density (kg/km2)
Estimates for North Sea hake
 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
North Sea hake stock assessment
 Biomass: increase by a
factor 4 in quarter 1, a factor
8 in quarter 3
 Slight increase in
recruitment
North Sea hake landings
 Large landings of North Sea hake in the 1950s
 Sudden increase previously occurred in North Sea
North Sea hake
length frequencies
 Difference between
quarter 1 and quarter 3
 More large individuals
at quarter 3
 Observation
consistent through time
Quarter 1
Quarter 3
UK hake catches (kg)
2005-2011
Increase in North Sea hake: the consequences
North Sea quota share (tons)
TAC North Sea hake
 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
1935
Belgium
28
Denmark
1119
Germany
128
France
248
Netherlands
64
UK
348
Conclusions
 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?
T°C
 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
Future work
 Ecosystem
model: FishSUMS
(Speirs et al.,
2010)
 Assess
consequences of
hake increase on
NS ecosystem
 Model North
Sea fishery under
different “hake
scenarios”
Ta!
Funding: