Climate change is dulling the survival instincts of fish

"Aquaculture may provide an 'accidental' long-term experiment that can help climate-change predictions," said marine biologist Robert Ellis.

By Brooks Hays

EXETER, England, Oct. 21 (UPI) -- The sensory systems of fish are short-circuiting, and a new study blames climate change.

As the climate warms, the ocean is soaking up more carbon dioxide. According to scientists at the University of Exeter, the influx of CO2 is disrupting fishes' sense of smell, sight and hearing.


Broadly speaking, fish are losing their wits -- and their bearings. Haywire sensory systems have some fish ignoring signals of danger and have others swimming directly toward predators instead of away.

Somehow, researchers surmise, CO2 is disrupting the way fish brains process sensory signals. How exactly isn't clear. What is clear, the problem is sure to get worse.

The oceans' CO2 levels are expect to rise by a factor of 2.5 by the end of the century. To prepare for this world, authors of the latest study -- published in the journal Global Change Biology -- recommend marine biologists turn their attention to farm-raised fish, many of which live in tanks with CO2 level 10 times higher than the ocean.

"Aquaculture may provide an 'accidental' long-term experiment that can help climate-change predictions," Robert Ellis, a marine biologist focusing on the effects of climate change, explained in a news release. "There is the enticing possibility that fish and shellfish previously grown in high CO2 aquaculture conditions over multiple generations can offer valuable insights regarding the potential for aquatic animals in the wild to adapt to the predicted further increases in CO2."


In holding tanks, farmed fish don't have predators to worry about, and their food supply is relatively constant. But research shows CO2 changes can affect them as well. Extremely high CO2 levels disrupt the digestion of cod, but small increases in CO2 accelerate growth rates -- a boon for fish farmers.

"Our research will allow fish farmers to optimize conditions, and specifically CO2 levels, to improve growth and health of their fish, profitability and the long-term sustainability of the industry," said study co-author Rod Wilson. "This is really important given that aquaculture is the only way we will increase seafood production to feed the growing human population, particularly given wild fish stocks are over-exploited."

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