Konferansebidrag pdf (6.689Mb)

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Spatial distribution of fish stocks in a climate perspective

Nordic Climate Fish Conference 2011, Solstrand

Geir Odd Johansen

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Overview

• FishExChange objectives

• The FishExChange database

• Data examples

• Looking for important factors influencing the variation in geographical distribution

• Ambient temperature

• The complex interplay

• Conclusions

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FEC principal objective

• Evaluate the effect of climate change in the Barents Sea and adjacent areas on

distribution of fish stocks, in perspective of national marine areas

• Further, evaluate what effect this will have on division of national fish quotas and

economical consequences for the fisheries Spatial approach

FEC objectives

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FEC Task 2

• The fish stocks

– Based on deliverables from Task 1 (oceanography)

– Age specific spatial fields (maps) of historical fish distributions

• Mechanisms behind spatial distribution

– Links to climate indicators – Interactions between species – Cover most of the life history

– Spatial fields (maps) of most likely future fish distribution

FEC objectives

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Challenge

Data heterogeneity in space and time

The FEC database

Allowing data to meet in a common

framework and making them talk

together!

Climate data

Model output

Fish survey data

Fisheries data Horizontal, vertical, and temporal structure on different scales

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Data from fish surveys in the FEC database

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Data from fish surveys in the FEC database

• Commercial species

• Based on different sources of raw data

• Synoptic surveys for abundance estimation

• Trawl catches corrected for swept area

• Comprehensive metadata

• Protocols for planning, preparation of data and input

• Data catalogues with temporal coverage

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Data from fish surveys in the FEC database

• 0-group autumn, pelagic trawl

– Blue whiting, capelin, cod, Greenland halibut, haddock, herring, mackerel, redfish, saithe and polar cod

• Cod, bottom trawl

– Winter survey, 5 cm size groups, age 1-13+

– Summer/autumn/ecosystem surveys 5 cm size gr.

• Haddock, bottom trawl

– Winter survey, 5 cm size groups, age soon

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Data from fish surveys in the FEC database

• Capelin, acoustic surveys autumn

– Age 1-5

• Polar cod , acoustic surveys autumn

– Age 1-5

• Saithe, acoustic survey autumn planned

– Winter survey, 5 cm size groups, age soon

• + T, salinity and catch data

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Other interesting species

• Blue whiting

(Micromesistius poutassou Risso, 1827)

• Entering the BS from south-west

• High abundance in 2001-2007

• Interact with other species

Distribution area Spawning area

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Other interesting species

• Atlantic mackerel (Scomber scombrus L.)

– Observed at least as north as 74°N

– Recently caught off the Murman coast

• Several fish species related to benthic habitats (e.g. eelpouts (Zoarcidae) and sculpins (Cottidae)

– Habitat specific

– Sensitive to temperature variation

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What about the data?

Data example

• Example: Winter bottom trawl survey in the Barents Sea

• 1981-2009

• Cod ≥ 45 cm (~ catchable size)

• Density (No. Fish / nmi²)

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50° E 30° E

10° E

75° N70° N

1981

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50° E 30° E

10° E

75° N70° N

1982

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50° E 30° E

10° E

75° N70° N

1983

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50° E 30° E

10° E

75° N70° N

1984

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50° E 30° E

10° E

75° N70° N

1985

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50° E 30° E

10° E

75° N70° N

1986

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50° E 30° E

10° E

75° N70° N

1987

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50° E 30° E

10° E

75° N70° N

1988

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50° E 30° E

10° E

75° N70° N

1989

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50° E 30° E

10° E

75° N70° N

1990

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50° E 30° E

10° E

75° N70° N

1991

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50° E 30° E

10° E

75° N70° N

1992

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Expansion of survey area from

1993 and onwards!

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50° E 30° E

10° E

75° N70° N

1993

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50° E 30° E

10° E

75° N70° N

1994

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50° E 30° E

10° E

75° N70° N

1995

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50° E 30° E

10° E

75° N70° N

1996

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50° E 30° E

10° E

75° N70° N

1997 Limited survey coverage

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50° E 30° E

10° E

75° N70° N

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50° E 30° E

10° E

75° N70° N

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50° E 30° E

10° E

75° N70° N

2000

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50° E 30° E

10° E

75° N70° N

2001

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50° E 30° E

10° E

75° N70° N

2002

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50° E 30° E

10° E

75° N70° N

2003

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50° E 30° E

10° E

75° N70° N

2004

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50° E 30° E

10° E

75° N70° N

2005

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50° E 30° E

10° E

75° N70° N

2006

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50° E 30° E

10° E

75° N70° N

2007

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50° E 30° E

10° E

75° N70° N

2008

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50° E 30° E

10° E

75° N70° N

2009

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Distribution of NEA cod

Variation in geographical distribution

50° E 30° E

10° E

75° N70° N

1994

1980 1985 1990 1995 2000 2005 2010

71.5 72.0 72.5 73.0

Year

Centre of gravity, cod > 45 cm, °N

74 75 76 77 78

Ice cover - southern limit, °N

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Distribution of NEA cod

In the Barents Sea, cod appeared in large quantities on Bear Island Bank in response to the warming of the early 20^th century, resulting in the reestablishment of a cod ﬁshery there after an absence of almost 40

years (Blacker, 1957). Cod also penetrated farther east to Novaya Zemlya and north of West Svalbard, during the 1920s (Beverton and Lee, 1965). Similar effects at west Greenland and Iceland.

Drinkwater 2005

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Spawning sites of NEA cod

Cold periods:

- Southwards displacement

- Decreasing spawning biomass Hot periods

- Northwards displacement - Increasing spawning biomass

Sundby and Nakken (2008) IJMS

2,5 3,0 3,5 4,0 4,5 5,0

1900 1920 1940 1960 1980 2000

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NEA cod the first year of life

1980 1985 1990 1995 2000 2005 2010

11000001400000

Survey area

spatdat$Year

spatdat$AOS

1980 1985 1990 1995 2000 2005 2010

4e+058e+05

Area of occupancy

spatdat$Year

spatdat$AOO

1980 1985 1990 1995 2000 2005 2010

25303540

Easterly centre of gra

spatdat$Year

spatdat$CenterX

1980 1985 1990 1995 2000 2005 2010

30323436

Northerly centre of g

spatdat$Year

spatdat$CenterY

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NEA cod 1 yr old, winter

1980 1985 1990 1995 2000 2005 2010

4e+056e+058e+05

Survey area

spatdat$Year

spatdat$AOS

1980 1985 1990 1995 2000 2005 2010

2e+056e+05

spatdat$Year

spatdat$AOO

1980 1985 1990 1995 2000 2005 2010

32364044

Easterly centre of gr

spatdat$Year

spatdat$CenterX

1980 1985 1990 1995 2000 2005 2010

242832

spatdat$Year

spatdat$CenterY

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NEA cod 4 yr old, winter

1980 1985 1990 1995 2000 2005 2010

4e+056e+058e+05

Survey area

spatdat$Year

spatdat$AOS

1980 1985 1990 1995 2000 2005 2010

3e+055e+057e+05

spatdat$Year

spatdat$AOO

1980 1985 1990 1995 2000 2005 2010

3032343638

Easterly centre of gra

spatdat$Year

spatdat$CenterX

1980 1985 1990 1995 2000 2005 2010

26283032

spatdat$Year

spatdat$CenterY

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NEA cod 8 yr old, winter

1980 1985 1990 1995 2000 2005 2010

4e+056e+058e+05

Survey area

spatdat$Year

spatdat$AOS

1980 1985 1990 1995 2000 2005 2010

1e+053e+05

spatdat$Year

spatdat$AOO

1980 1985 1990 1995 2000 2005 2010

263034

Easterly centre of gr

spatdat$Year

spatdat$CenterX

1980 1985 1990 1995 2000 2005 2010

252729

spatdat$Year

spatdat$CenterY

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Stock abundance

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Ambient temperature

Ambient temperature

Based on bottom temperatures in winter

1 yr old, winter 4 yr old, winter

8 yr old, winter

1980 1985 1990 1995 2000 2005

12345

Ambient temperature for cod

ambient_temp$year

ambient_temp$codT1

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Factors influencing geographical distribution

The complex interplay

Planque et al. 2010 spatial

distribution geographical

attachment

environmental conditions

density dependent habitat selection

spatial dependency

demographic structure Persistence

species interactions

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Conclusions

Conclusions

• Cod does not show signs of moving out of Norwegian exclusive economic zone - - - yet

• The period 1980-2010 is short in a global climate perspective

• Study effects of climate variation

• Abundance is important for area of occupancy of a fish stock

• Important fish stocks for at least 1000 years

• “Always” present even if climate varies?

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Future challenges

“Prediction is very difficult, especially of the future”

Niels Bohr, Danish physicist (1885 - 1962)

Temperature in the Kola hydrographic section

2,5 3,0 3,5 4,0 4,5 5,0 5,5 6,0

1900 1920 1940 1960 1980 2000 2020 2040 2060 2080

Temperatur

År

?

Year-to-year variation Long-time trend Long-term prognosis

”unknown situation”

”known situation”