Impact of Climate on Distribution and Migration of North Atlantic Fishes

1
Impact of Climate on Distribution and Migration
of North Atlantic Fishes

• George Rose, Memorial University, NL Canada

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Table of Contents

• A few platitudes
• Brief history of the North Atlantic
• Where are the fish?
• Grouping analysis of species
• Event analysis the 1920-1940 warming
• Species analysis capelin
• Ripple effects food webs

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Fish distributions and migrations
On the cod highway

• NOT random
• the result of evolution of the physiology of the
  species
• tuned to the particular biotic and abiotic
  environment of the stock
• variable at several time scales
• early indicator of ecosystem change

1992
2000
4
Environmental unit
spawning
Abiotic depth temp salinity currents oxygen
juvenile
Migration links
Biotic fishing prey predators density- dependence
feeding
5
History of North Atlantic
6
Long-term climate change
7
Most North Atlantic species have Pacific origins
(Ekman, 1953)

• The gadoids are likely the only major fish group
  whose evolutionary center is the North Atlantic

8
Where are the fish?
9
of species with latitude in N. Atlantic (data
from Briggs, 1974 Cech, 2000)
10
Sea temperatures in mid-Atlantic (data from
Ekman, 1953)
11
Depth
Depth Number of species in the North
Atlantic (data from Challenger cruise, 1800s)
12
Number of species at depth in North Atlantic
(from 150 species documented in this study)
13
Lower and upper temperature limits cumulative
of species
14
Spawning temperature limits
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Spawning salinity limits
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Grouping analysis
All North Atlantic Species - catalogued 146
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Can species be grouped into response categories?

• Feeding period requirements (temperature, depth)
• Spawning requirements (temperature, salinity,
  depth, timing)

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Shallower
Warmer
Principle Components 1 Min and Max depth 2 Min
and Max temperature
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Salinity
Deeper
Spawning Components 1 salinity 2 depth 3
temp, timing
20
General limits F1 with popn doubling time
21
Spawning limits PCs and popn doubling time
(depth,temp,timing)
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Event analysis
23
An old problem

• there have been certain periods of years in
  northern seas with higher temperatures and
  simultaneously increasing occurrence of southern
  species, for instance in the years of about
  1820-30, 1840-50, 1870-80, and 1920-
• Rollefsen and Taning, 1948

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A warm water event in the north Atlantic

• 1920-1940 (or thereabouts)

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According to Taning, 1948

• Simultaneous with this scarcity of ice in the
  waters around Iceland the winters have been
  exceedingly mild, especially during February and
  March, when the mean temperature was some 4 to 7
  oC above the normal
• This increase of the surface temperature has
  amounted to about 0.5-4.0o above the normal

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Annual air temperature
St. Johns, NL
Godthab, Greenland
Akureyi, Iceland
Bodo, Norway
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The warm 1930s mid- N. Atl.
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Species distribution changes(data from
Saemundsson, 1932 Taning, 1948 Fridriksson,
1948 Rollefsen, 1948 others)
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Norwegian skrei fishery landings, Lofoten (N) and
More (S)(data from Nakken, 1994)
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1920s
Warming fish change
No warming No fish change
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Species analysis
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A keystone species Capelin
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The dispersal of capelin from their north Pacific
origin (from Vilhjalmsson, 1994)
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Present distribution of capelin (from
Vilhjalmsson, 1994)
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Documented capelin shifts
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warm
cold
Extension of capelin spawning grounds from cold
period (1900-1920) to warm period (1920-1940)
from Vilhjalmsson 1997
37
Capelin distance moved and temperature change
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Capelin distance moved and persistence
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Ripple effects
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North Atlantic food web
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Capelin is key to

• Many fishes (e.g., cod, greenland halibut,
  salmon, charr, winter flounder)
• Seabirds
• Marine Mammals

42
Templeman, 1948, on Newfoundland caplin

• not only does it provide the nourishment on
  which the great bulk of inshore running codfish
  recover condition in June and July after
  spawning, but it is very likely in the main
  responsible for the attraction of the huge shoals
  of cod to the coast

43
warm
cold
Extension of capelin spawning grounds from cold
period (1900-1920) to warm period (1920-1940)
from Vilhjalmsson 1997
44
warm
cold
Extension of cod spawning grounds from cold
period (1900-1920) to warm period (1920-1940)
from Vilhjalmsson 1997
45
Hamilton Bank
Flemish Cap
Grand Banks
Capelin movements late 1980s
Northern cod movements early 1990s
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Cod and capelin on Newfoundland shelf in early
1990s (from ODriscoll Rose, 2001)
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Effects of lack of capeln weight of cod in
winter Iceland data from Vilhjalmsson, 2002
48
Northern cod liver index and capelin availability
(from Rose ODriscoll, 2002)
49
Cod stock historical range and biomass (from
Robichaud Rose, in press)
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Conclusions

• Distribution changes important - early indicator
  of ecosystem change
• Response differences (pelagics faster demersals
  slower, some maybe not at all)
• Capelin fast - canary in the mine
• Ripple effects capelin changes affect many
  species