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Climate change could cause some fish species to shrink by nearly 25%

Ben Anderson

A new study that modeled the impact of climate change on more than 600 fish species says that most of those species could shrink by between 14 and 24 percent by the year 2050. Additionally, as the concentration of oxygen in the Earth’s waters decreases, some species may move away from equatorial waters toward the Arctic.

The study, conducted by researchers from the University of British Columbia, Princeton University and the National Oceanic and Atmospheric Administration, has broad implications -- not only for the Earth’s ecosystems, but for the seafood industry as well as sport fishermen.

If that doesn’t get you excited, take this theoretical figure: in 2011, Alaska brought home 5.4 billion pounds of seafood worth $1.9 billion, by far the most among U.S. states. If that catch were reduced by 25 percent, it would mean a loss of 1.35 billion pounds and $475 million from state fisheries.

Fortunately -- for Alaska at least -- the study reports that the world’s oceans can expect to see different reductions, and the Pacific Ocean may dodge the brunt of the incredible-shrinking-fish projection.

“The projected decrease is largest in the Indian Ocean (24 percent), followed by the Atlantic Ocean (20 percent) and Pacific Ocean (14 percent),” the study says, which modeled distribution, abundance and body size of populations between the years 2001 and 2050.

The study, published in the journal Nature Climate Change, attributed the shrinkage to warming temperatures on the ocean floor and a reduction in the concentration of oxygen available in the Earth’s oceans. In the Pacific Ocean, for example, temperatures are expected to increase by about .1-degree Celsius by 2050, even as the levels of oxygen decline.

The exception to this rule comes in the Arctic Ocean, where the temperature increase is among the most extreme -- about .2-degrees Celsius -- but the oxygen levels are predicted to remain mostly steady.

This means that the large fishes that currently inhabit the Pacific Ocean could find their way north, taking advantage of warming Arctic waters with oxygen levels similar to their previous habitat. Such movements aren’t unprecedented, the study notes.

“Marine fishes are observed and projected to shift their distributions and abundance as temperature, primary productivity and other ocean conditions change,” the authors note. “These will mediate the effects of such changes on the metabolism and body weight of the organisms.”

In other words, fish will reduce in population and change their normal habitats in an attempt to maintain their weight, rather than allowing the reduction. Of course, with the temperature increases and oxygen reductions occurring similarly in four of the world’s five major oceans, not all fish species will be able to avoid the change.

While the study notes that the modeling “requires a number of assumptions and simplifications to represent and project long-term changes in the complex biological and earth systems,” it predicts that approximately 75 percent of the studied species can expect some reduction in size by 2050.

Alaska, as you may know, produces more seafood than any other U.S. state. And doing most of the heavy lifting to ensure that No. 1 ranking are the ports of Dutch Harbor, Akutan and Kodiak, which all sit among the top five nationwide for the amount of seafood landed, and which all sit in the southern portion of the state. Who knows, though, by the time 2050 rolls around, maybe those ports will be Nome, Wainwright and Kotzebue.

Contact Ben Anderson at ben(at)alaskadispatch.com