The Davis Strait - DCE - Nationalt Center for Miljø og Energi

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2007). Ecosystem changes associated with the warm period during the 1920s
and 1930s included the expansion northwards ofboreal species, such as cod,
haddock and herring, while colder water species such as capelin retreated
northwards. Higher recruitment and growth led to increased biomass of important
commercial species (i.e. cod and herring). During a period (1960-
1970) of reduced air and ocean temperatures, cod abundance (including cod
larvae) declined again in this region (Horsted 2000, Drinkwater 2006). Coinciding
with the decrease in cod was an increase in northern shrimp (Pandalus
borealis) and Greenland halibut (R. hippoglossoides). Meanwhile, the shrimp
fishery replaced cod as a dominant industry in West Greenland (Hamilton et
al. 2003).
A similar response by cod as that observed during the previous warm period
could be expected in the present warming period. For the West Greenland
offshore cod stock, their abundance, recruitment, and individual
growth rates have increased during the recent warming, but continue to remain
at levels much reduced compared with those observed during the early
20th century warming (Drinkwater 2009). It is not yet possible to indicate
how far north Atlantic cod would be distributed if temperatures increase
further.
For shrimp (Pandalus borealis), duration of egg development and hatching
are determined by local bottom temperature and are correlated to the spring
phytoplankton bloom (Koeller et al. 2009). Shrimp appears to have adapted
to present local temperatures and occurrence of spring bloom in matching
hatching to food availability. Changes in water temperatures and food base
composition may influence the distribution and abundance of northern
shrimp.
Current knowledge on the distribution and abundance of capelin (Mallotus
villosus) in Greenland (including the assessment area) and elsewhere suggests
that expected climate changes in the region would have a large impact
on this important species. Minor temperature increases will most likely increase
capelin productivity, provided sufficient prey resources are available
(Hedeholm et al. 2010). A more pronounced increase in water temperature
will probably result in a northward shift in distribution (Hansen & Hermann
1953). Moreover, a stable capelin spawning population in the southernmost
part of Greenland could disappear from this area (Huse & Ellingsen 2008).
Changes in physical conditions in high latitude ecosystems will probably also
affect fisheries. Positive effects of warming have already been documented
for the distributions and abundance of Arcto-Norwegian cod (MacNeil et
al. 2010). This population shows stronger year classes in warm years and
poor year classes in cold years, and warming has led to a northern range expansion
in Norway (Drinkwater 2006, Drinkwater 2009). As a result of
warming, yields are predicted to increase by approximately 20% for the
most important cod and herring stocks in Iceland, and approximately 200%
in Greenland over the next 50 years (Arnason 2007). Climate-driven fish invasions
into Arctic marine ecosystems, including the assessment area, are
expected to exceed those of any other Large Marine Ecosystem (Cheung et
al. 2010). Despite possible positive effects of climate warming predicted for
fisheries, it is still not clear how invading species interact with native species
and how this affects food web interactions, including those in the assessment
area.