Huse

Interactions between fish
stocks in relation to
climate change
Geir Huse
Challenges of the changing Arctic: Continental Shelf,
Navigation, and Fisheries, 25-28 June, Bergen
Outline
•Introduction
•Interations in:
– the Barents Sea
–the Norwegian Sea:
•Concluding remarks
2014 – The Great Jubilee Year!
Johan Hjort
Johan Hjort 1914:
Fluctuations in the
great fisheries of
northern Europe
Foundation for modern fisheries science
A herring scale
4
Johan Hjort
3
2
1
6
5
7
Johan Hjort
Proportion
Age of herring
4
3
2
1
6
5
7
The prime minister opened the
Hjort Centre for Marine Ecosystem dynamics
18. February
Themes:
1. Effects of climate
change on
ecosystems
2. Potential for
increased food
production in the
sea
Key
commercial
pelagic fish
stocks in the
North
Atlantic:
• Abundant
• Widespread
• Interacting
Climate change will result in new and
possibly intensified interactions
From Trenkel & al (2014)
The Barents Sea
Cod
Capelin
Herring
Herring and capelin interaction
in the Barents Sea
Strong herring recruitment
Help!
From Gjøsæter & al (2013)
Total prey consumption by cod
(1000 tonnes)
Cod-capelin interactions in the
Barents Sea
10000
9000
Long rough dab
8000
Blue whiting
G. halibut
7000
Redfish
Haddock
6000
Cod
5000
Polar cod
Herring
4000
Capelin
3000
Shrimp
Krill
2000
Amphipods
Other
1000
0
1984
1986
1988
1990
1992
1994
1996
1998
2000
2002
2004
2006
2008
2010
2012
From Bogstad & al (2013)
Snow crab colonising the Barents Sea
“Model simulations
indicate potential
annual catches to
reach the 25.00075.000 tons range
within the next 10
years”
C.Hvingel & J. Sundet
The Norwegian Sea
•The Norwegian Sea is
ideal habitat for overwintering of Calanus
•Utilised by migratory
fish stocks:
The
Norwegian
Sea
The
Barents
Sea
•NSS herring
•Blue whiting
•Mackerel
The North
Sea
The mackerel
expansion in
the Nordic Seas
Year
2012
2010
Blue Whiting
2008
2006
2004
2002
2000
Mackerel
1998
1996
1994
1992
1990
1988
Biomass of pelagic fish (mill. tonnes)
Zooplankton index
Plankton production and fish consumption
Herring
18
16
14
12
10
8
6
4
2
0
From Huse & al. 2012
Plankton production and fish consumption
Blue Whiting
Mackerel
Herring
Zoo. index
16
14
12
10
8
6
4
2
Year
2012
2010
2008
2006
2004
2002
2000
1998
1996
1994
1992
1990
0
1988
Biomass of pelagic fish (mill. tonnes)
Zooplankton index
18
From Huse & al. 2012
Plankton production and fish consumption
”Bottom up”
Blue Whiting
Estimated C/P ratio
Herring
Modelled C/P ratio
14
0.8
12
10
0.6
8
0.4
6
4
0.2
Consumption/production ratio
1
16
2
Year
2012
2010
2008
2006
2004
2002
2000
1998
1996
1994
1992
0
1990
0
1988
Biomass of pelagic fish (mill. tonnes)
Zooplankton index
Mackerel
Zoo. index
18
”Top down”
From Huse & al. 2012
Length of herring, mackerel and blue whiting (age 6)
Strong decline in mackerel length at age
Do mackerel feed on blue whiting and
herring larvae?
(From Payne & al 2012)
The Norwegian Sea
•Food competition
within and between the
stocks
•Potentially high
predation by mackerel
on herring and blue
whiting larvae
Bluefin tuna
on the way?
The
Norwegian
Sea
The
Barents
Sea
The North
Sea
Concluding remarks
• Interactions between fish stocks can be very
important to population dynamics both
through predation and competition
• Climate variability and change affects
recruitment and distribution and interactions
• Stocks with pelegic eggs are more flexible in
relation to climate change
• Multispecies management should be
attempted, but requires a careful
examination of costs and benefits
Are multispecies management and
ecosystem processes implemented in
fisheries management?
A global review of 1265 fish stocks
(Mauritzen & al submitted)
Number of cases (2%) is low, but related
to level of science support
 26 cases where
ecosystem info
is used
Thanks for your attention!
Foto: Kjartan Mæstad

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