A study by University of British Columbia scientists shows
that ocean warming has had a global impact on the mix of species caught by
fishermen, replacing some of those traditionally caught in many fisheries
worldwide at least since 1970.
Previous studies indicated some species are shifting
location in response to temperature increases, with fish gradually moving away
from the equator into cooler waters.
UBC’s William Cheung and his co-authors used the temperature
preferences of fish caught around the world to determine the relationship
between fisheries catch and ocean warming. They first assembled data on the distribution
of 990 marine fish and invertebrates, when assigned each species a temperature
preference based on the average sea surface temperature in areas where that
species was predicted to have occurred between 1970 and 2000.
Then to measure changes in the composition of marine
fisheries, the researchers compiled data on the tonnage of each species caught
in the 52 marine ecosystems that account for most of the world’s fisheries.
Next, for each ecosystem and each year from 1970 through 2006, they calculated
the average temperature preference of the species, weighted by the amount
caught. Finally, the researchers determined the connection between ocean
warming and changes in fisheries catch by using a statistical model that
separates out other factors, such as fishing effort and oceanographic
variability.
A summary provided through the PEW Charitable Trusts said
the authors found that, except in the tropics, catch composition in most
ecosystems slowly changed to include more warm-water species and fewer cool-water
species.
Earlier research led by Cheung predicted continuing changes
in fish distribution and catch as oceans warm. These shifts could have several
negative effects, which may be felt most in the tropics, where water
temperatures could exceed the preferences of many tropical species, resulting
in a large reduction in catch.
Additional impacts could include loss of traditional
fisheries, decreases in profits and jobs, conflicts over new fisheries that
emerge cause of distribution shifts, and food security concerns, particularly
in developing countries. The research was published in May in the periodical Nature.
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