Warmer ocean temperatures and an ever-escalating global climate will cause fish to shrink dramatically over the next 40 years, according to research published Sunday in the scientific journal Nature Climate Change.

Using "high emissions" scenarios developed by the United Nations' Intergovernmental Panel on Climate Change (IPCC), scientists with the University of British Columbia created a model to predict how oxygen levels and water temperature affects the growth of more than 600 species of fish.

What they found was shocking: "Marine fish are generally known to respond to climate change through changing distribution and seasonality," William Cheung, the study's lead author, said in prepared text. "But the unexpectedly big effect that climate change could have on body size suggests that we may be missing a big piece of the puzzle of understanding climate change effects in the ocean."

Because fish tend to have a higher metabolism in warmer water, and because warmer water offers fish less oxygen, the research predicts fish will not only move to cooler areas but their actual development into adulthood would be affected because their bodies cannot fully mature.

"We show that assemblage-averaged maximum body weight is expected to shrink by 14–24% globally from 2000 to 2050 under a high-emission scenario," researchers explained. "About half of this shrinkage is due to change in distribution and abundance, the remainder to changes in physiology."

The UN's Food and Agriculture Organization said in 2010 that about 53 percent of the world's fish stocks are fully exploited, while about 32 percent are already overexploited and in decline. That's thanks to human populations over-fishing at a rate nearly three times what the ocean can replenish, which supplies at least 15 percent of the annual protein intake for more than 3 billion people.

"A warmer and less-oxygenated ocean, as predicted under climate change, would make it more difficult for bigger fish to get enough oxygen, which means they will stop growing sooner," study co-author Daniel Pauly added.

Without drastic action to curb emissions that cause climate change, not only will fish size be disrupted, but changes to the ocean ecosystems may also disrupt the human food chain and cause mass migrations away from coastal areas as people search for food and jobs elsewhere.

The U.N. Security Council warned in 2011 that climate-driven resource scarcity may soon become a primary source of human conflicts, but an effective international response could prevent worst-case scenarios.


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