Effect of climate change on fish distribution and dynamics in the North Atlantic Keith Brander ICESG

1
Effect of climate change on fish distribution and
dynamics in the North AtlanticKeith
BranderICES/GLOBEC Coordinator
2
Jean-Claude Quero Ital.J.Zool.,65 Suppl.493-499
(1998)
3
people are interested in changes in marine
ecosystems.
4
Northward extension of cod stock from 1920 to
late 1930s. Published in 1939
5
(No Transcript)
6

• It comes up to the shore here from the great fish
  pond which is the Icelandic Sea, towards the
  winter when the great part of other fish have
  left the land. And the herring does not seek the
  shore along the whole, but at special points
  which God in his Good Grace has found fitting,
  and here in my days there have been two large and
  wonderful herring fisheries at different places
  in Norway. The first was between Stavanger and
  Bergen and much further north, and this fishery
  did begin to diminish and fall away in the year
  1560. And I do not believe there is any man to
  know how far the herring travelled. For the
  Norwegian Books of Law show that the herring
  fishery in most of the northern part of Norway
  has continued for many hundreds of years,
  although it may well be that in punishment for
  the unthankfulness of men it has moved from place
  to place, or has been taken away for a long
  period.
• Clergyman Peder Claussøn Friis (1545-1614)

7
Norwegian spring spawning herring
8
Herring migration - traditional
from Vilhjalmsson 1997
9
Herring migration 1965 - 66
from Vilhjalmsson 1997
10
Herring migration 1995
from Vilhjalmsson 1997
11
Did the decline of the NSS herring begin before
the fishing pressure increased ?Data from
Toresen 2000 and OWSM
Norwegian spring spawning herring
12
Climate change or fishing?

• Both climate and fishing affect populations
• The level of fishing is excessive on most stocks
• Populations increase when climate (and other
  conditions) are favourable
• (distribution and abundance are linked)

13
Ratio of catch of warm/cold species
14
Ratio of catch of warm/cold species
15
(No Transcript)
16
PART I A Recent Shift in North Pacific Climate
SST Anomalies
El Niño, PDO Pattern
La Niña, -PDO Pattern
17
Climate shifts perturb fisheries and have
socio-economic impacts.
Late 1960s
Late 1970s
1980s
Bottom trawl surveys, Pavlov Bay, AK (from
Botsford et al. 1997)
(from Anderson and Piatt, 1999)
18
PART I Global Teleconnections
1994-1997
1998-2001
shift in North Atlantic atmospheric forcing
shift in North Pacific atmospheric forcing
Climate acts globally, but is modulated locally
19
Digression on regional differences

• The effects of climate regime shifts on fish
  stocks are well known for the Pacific
• The science has moved on from description to
  modelling and improving detection
• The North Atlantic lags some way behind, partly
  because climate effects are less obvious.

20
Poleward range shifts in terrestrial species

• Global meta-analysis of gt1700 species showed
  average poleward shift of 6.1 km per decade.
• The analysis generates very high confidence
  that climate change is already affecting living
  systems.

Parmesan and Yohe Nature 42137-42 (2003)
21
North Sea plankton

• For nerds
• Monthly values of the first PC (33.78 of the
  total variability).
• Main variables by order of importance
• mean abundance of C. finmarchicus
• mean abundance of euphausiids
• mean size of calanoid copepod
• mean abundance of C. helgolandicus
• calanoid copepod biomass
• mean abundance of Pseudocalanus spp.

Months
Years (1958-1999)
This does not mean that changes in plankton are
the only cause of decline in cod
22
Evidence that climate effects are stronger when
fish stocks are at low levels

• NAO (North Atlantic Oscillation) has a regular
  geographic pattern of effects on SST (and wind,
  cloud cover, precipitation) and on ecosystems
• NAO affects cod recruitment on the same pattern
  European cod stocks show a common response
• Recruitment is higher when NAO is low
• Meta-analysis shows that the effect is strongest
  when spawning stock levels are low

23
Geographic pattern of effect of NAO on sea
surface temperature
24
Fitting a Ricker S/R curve with an NAO term

• R exp( RMAX/ SSBMAX) SSBexp(-SSB/SSBMAX)
  exp(cNAO)

25
Red symbols indicate strength and sign of effect
of NAO on cod recruitment
26
NAO has a strong effect on recruitment when SSB
is lowP that R is independent of NAO low SSB
lt0.001med SSB lt0.1high SSB gt0.5
27
Interaction between climate and fish stock
indicators

• Recruitment is affected by environment
• Effect of NAO on cod is consistent with its
  geography
• European cod stocks are sensitive when spawning
  stock biomass (SSB) is low
• We need to develop recruitment models which test
  for environmental effects related to SSB

Recovery of cod stocks depends a lot on
favourable environmental conditions
28
North Pole.
Last glacial maximum.
Present day.
sea ice
sea ice
Source Climap project.