Download Top predators in the Barents Sea, dependent on capelin?

Mette Skern-Mauritzen, Per Fauchald, Edda Johannesen, Ulf Lindstrøm
SEAPOP, Tromsø, April 2011
NORWEGIAN INSTITUTE FOR NATURE RESEARCH
August – september , 2003 – 2010
Synoptic, spatial data on:
• Zooplankton
• 0-group fish
• Pelagic fish
• Cod (also diet)
• Seabirds
• Marine mammals
The joint Russian – Norwegian Ecosystem survey
August – September, 2003 - 2010
Capelin – fluctuating key species





Repeated stock collapses
Adverse effects on top predators
Collapse in 2003 – no effects?
Capelin biomass, age 1+, acoustic survey
8
7
Million tonnes
6
Ecosystem
survey
5
4
3
2
1
0
1973 1976 1979 1982 1985 1988 1991 1994 1997 2000 2003 2006
Year


The joint Russian – Norwegian Ecosystem survey
August – September, 2003 - 2010
Capelin – fluctuating key species
Key questions:
•
How was the spatial structure of the pelagic community
during the capelin poor years 2003-2007
•
What are the implications for trophic interactions
•
How do top predators respond to the return of the capelin?
Average distributions, the capelin poor years 2003 – 2007
Lower and mid trophic levels
Blue whiting
Herring
Capelin
Polar cod
Pelagic fish:
Geographically
segregated
0-Cod
0-Herring
Southern prey community
Fish
Northern prey community
Zooplankton and fish
0-Capelin
0-Polar cod
Amphipods
Krill
O-group fish:
Geographically
segregated
Zooplankton: depleted in
south and central BS predation
Top predators
Cod age2
Cod imm
Cod maturing
Cod mature
Cod: Polar front and
northwards
Whiteb. dolphin
Fin whale
Minke whale
Humpback whale
Atl. puffin
Com. guillemot
Brün. guillemot
Little auk
Kittiwake
Baleen whales: Limited
and overlapping
distributions
Diving seabirds:
Geographically
segregated
N. fulmar
Surface feeding seabirds:
Extensive distributions,
overlapping
Average distributions, the capelin poor years 2003 – 2007
TOP PREDATORS
South
North
0.5
1.0
Top predators vest
L. auk
Minke wh.
0.0
Fin wh.
C. Guillem.
T50
Kittiwake
-0.5
Puffin
Humpb. wh.
Fulmar
Cod50.75
Br. guillem.
White-b. dolph.
-1.0
c(0, 0)
Depth
Cod75
Cod20.50
Cod20
-1.0
-0.5
0.0
c(0, 0)
0.5
1.0
Principal component analyses
of averaged distributions
Top predators – a wide variety of
spatial niches
Average distributions, the capelin poor years 2003 – 2007
0.0
-0.5
SEABIRDS vs PREY
South
North
Polar cod
L. auk
Blue whit.
C.
Guillem.
Herring
Amphipods
0-Polar cod
Krill
Fulmar
Kittiwake
0-Haddock
0-Herring
Puffin
0-Cod
Br. guillem.
Capelin
0-Capelin
-1.0
-0.5
0.0
c(0, 0)
0.5
Principal component analyses
of averaged distributions
Top predators – a wide variety of
spatial niches
Northern top predators, associated
with krill, amphipods, polar cod,
many north of the capelin
Southern top predators, associated
with herring, 0-group fish
-1.0
c(0, 0)
0.5
1.0
Bird prey vest
1.0
Average distributions, the capelin poor years 2003 – 2007
0.5
1.0
Whale prey vest
SEABIRDS
WHALES
vs PREY
South
North
Polar cod
Blue whit.
0.0
-0.5
Herring
Amphipods
0-Polar
cod
Humpb. wh.
Krill
0-Haddock
0-Herring
0-Cod
White-b. dolph.
Capelin
0-Capelin
-1.0
-0.5
0.0
c(0, 0)
0.5
Top predators – a wide variety of
spatial niches
Northern top predators, associated
with krill, amphipods, polar cod,
many north of the capelin
Southern top predators, associated
with herring, 0-group fish
-1.0
c(0, 0)
Minke wh.
Fin wh.
Principal component analyses
of averaged distributions
1.0
• Northern community of generalist top predators:
• Brünnichs guillemots, cod, baleen whales
• Associated with zooplankton and pelagic fish:
• Krill, amphipods and polar cod important alternative prey in capelin poor
years
• Southern community of piscivorous top predators:
• Common guillemots, puffins, white-beaked dolphins
• Associated with herring and 0-group fish
• Cod: Dietary responses and energy consumed
• Seabirds and baleen whales: Spatial responses
Capelin biomass, age 1+, acoustic survey
8
Million tonnes
7
6
5
Ecosystem
survey
4
3
2
1
0
1973 1976 1979 1982 1985 1988 1991 1994 1997 2000 2003 2006
Year
2004
2005
2006
Prey
groups
capelin
polar cod
herring
krill
amfipods
shrimp
2007
2008
2009
other fish
other inv
2007
2009
Individual consumption (wieght) for cod 50-75 cm average values for 35 x35 nm grid cell.
Edda Johannesen et al. In prep.
2004
2005
2006
Prey
groups
capelin
polar cod
herring
krill
amfipods
shrip
2007
2008
2009
other fish
other inv
More capelin in the diet with
more capelin in the system
2009
2007
Individual consumption (wieght) for cod 50-75 cm average values for 35 x35 nm grid cell.
Edda Johannesen et al. In prep.
Eneregy consumption
Does the annual, averaged energy consumption by the cod stock
increase with increasing capelin abundance in the system?
Log (Capelin abundance)
Edda Johannesen et al. In prep.
Thick-billed murre
Yeart
Yeart+1
- Year-to-year changes
in distribution
- 50 km grid cells
Thick-billed murre
Regression model:
Δbirdx,y
~ Δfishx,y+ ΔFISH
change in
distribution
change in
abundance
Per Fauchald et al. In prep.
Fulmarus glacialis
Larus hyperboreus
Rissa tridactyla
+
-
+
-
+
+
+
-
+
+
-
YEAR
Ice melting
SPAT
YEAR
SPAT
YEAR
SST
Herring
-
-
SPAT
Capelin
YEAR
+
SPAT
Alle alle
Uria lomvia
Fratercula arctica
Uria aalge
YEAR
SPAT
Polar cod
Regression models:
How is year-to-year changes related to changes in the spatial distribution
(SPAT) and yearly average (YEAR) of pelagic fish and oceanography?
+
+
+
+
+
Per Fauchald et al. In prep.
Do the whales respond to the return of the capelin?
Sightings 2010
N
Finnhval
Fin wh.
Whale observations 2010
Capelin distribution 2010
1
2-3
4-5
6 - 10
11 - 102
Knølhval
Humpb.
1
2-3
4-5
6 - 10
11 - 102
Vågehval
Minke
1
2-3
Green bacground shades:
Mean distribution 2003 - 2007
4-5
6 - 10
11 - 102
- Stable late summer / autumn distributions
- independent of changing capelin abundance
- Increasing overlap with capelin due to northern capelin distribution shift
Mette Skern-Mauritzen et al (2011)
- Few positive, few negative, mostly no strong responses to
changing capelin abundance
- Northern top predators are generalists
- availability of alternative prey species compensated for
low capelin densities in 2003 - 2007
-Preliminary results: interactions with capelin much stronger
in winter
- limited extent of pelagic habitat due to sea ice
- limited availability of alternative prey species



Excellent platform for
 studies of large scaled ecosystem processes
 cross sector and institutional cooperation
Required, in an ecosystem based approach to
management
Seabirds – high priority
Nils Øien
Takk for oppmerksomheten