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World Fish Populations Will Shift With Changing Climate

Ocean fisheries will see drastic changes in response to warming oceansShifting patterns of animal migration spurred by changing climate is already clearly evident for many land-based species. Research by the Sea Around Us Project at the University of British Columbia recently published in the journal  Global Change Biology suggests the same will likely happen for ocean fisheries as well. The conclusion is that warming oceans will impact 1,066 species, from krill to shark.

As on land, disrupting global climate has some positive local effects amongst the overall environmental decline. For ocean species the hardest hit will be in the tropics, where “catch potential” could decline by as much as 40 percent. But go north and the warmer ocean will increase catch potential from 30 to 70 percent. The number of fish balance out, it is the type and distribution of marine populations that are likely to see dramatic changes.

“Overall, there will be no difference in the global catch,” said Daniel Pauly, one of the study’s authors.Where those fish will be found is what will substantially change.

“There will be winners and losers,” Pauly said. “Northern Europe, especially Norway and Iceland, and Alaska will win out. Countries that are in the tropics, for example in the Caribbean or Southeast Asia, will lose out.” Except for Hawaii and Alaska, the United States will not be on the list of winners.

Researchers have observed species migration in some regions has already begun as fish respond to changes in temperatures and oxygen content of ocean water.

Where people depend on fish

One major concern the research highlights is the effect declining fish populations in the tropics will effect people from poorer regions of the world that depend most on fish for protein. Already people living in sub-Saharan Africa and south Asia are faced with growing food shortages due to climate change. Last week the International Food Policy Research Institute released a study projecting dramatic declines in rice and wheat crops by mid-century, leading to a greater dependence on fish from the sea – fish that will no longer be there due also to climate change.

“Many tropical island residents rely heavily on the oceans for their daily meals,” lead author William Cheung of the University of East Anglia said in a statement. “These new findings suggest there’s a good chance this important food source will be greatly diminished due to climate change.”

“It is devastating,” added Pauly. “Basically you have lots of people living at the edge of the sea. They depend on fisheries, not in the way we do in northern countries. So income-wise and consumption-wise they are affected directly by the decline in catch.”

Other dangers not considered in study

As if all this weren’t enough, the report does not take into account other serious problems and how they might affect fish populations, such as ocean acidification and expanding “dead zones,” issues that Pauly said scientists plan to take up in future studies.

In February, the U.N. Food and Agriculture Organization said in a report that climate change is compounding the effects of existing threats to commercial fisheries, such as pollution and overfishing.

Sources and further reading
Guardian
ClimateWire (subscription)

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