Oceans Get Hotter, Fish Shrink
It could soon be much, much harder to find Nemo according to a new study in Nature about how fish size is affected by changes in temperature, lower oxygen content and other ocean biogeochemical properties (including rising acidification). Specifically, fish could shrink in size by as much as 14 to 20 percent from now until 2050 due to the warming of the ocean.
Indeed, a 2011 study already showed that the size of haddock in the North Sea is declining.
The Ocean’s Fish Are Getting Smaller and Smaller
Researchers from the University of British Columbia used computer modeling to study the effects of changes in the ocean and climate systems on 600 species of fish. The study’s lead author, William Cheung, emphasized that he and his colleagues were “surprised to see such a large decrease in fish size.” Fish in the tropics, who are smaller-bodied, are especially affected by warmer ocean temperatures and will migrate to regions that are now temperate or even to polar ones.
Cheung’s co-author, Daniel Pauly, explained why warmer ocean temperatures can lead to smaller fish:
It’s a constant challenge for fish to get enough oxygen from water to grow, and the situation gets worse as fish get bigger. 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.
In warmer waters, the metabolic rate of fish increases so they need more oxygen. But, because warm water holds less oxygen, the fishes’ growth will be limited.
A University of York professor, Callum Roberts, who was not a participant in the study, said that Cheung’s and Pauly’s findings were the “most comprehensive to date.” He also suggested that fish size could shrink even more, with deep ramifications not only for marine ecosystems but also for global food supplies as currently “one billion people rely on fish for primary animal protein and that is going to increase, especially in developing countries” and as overfishing is already reducing the amount of fish.
Climate change is already proving detrimental to marine life, it goes without saying. Roberts also points out that, with overall ocean temperature higher, the warmer waters at the surface mix less with the colder ones below. The result is fewer nutrients for fish as the colder waters contain most of the nutrients. “We are already seeing some evidence of this, as oceanic ‘deserts’ are getting larger,” he tells the Guardian.
Sea Levels To Keep Rising Due to Global Warming
If shrinking fish are not reason enough to cut greenhouse gas emissions, another just-published study offers more evidence to do so. According to this study, an ”irreversible warming” of earth has been “triggered” by greenhouse gases and will lead to sea levels rising for thousands of years.
European scientists used computer modeling to predict changes in sea levels over millennia as the result of reductions in land ice in Greenland and Antarctica and the warming of the oceans. One researcher, Professor Philippe Huybrechts, made the dire statement that, should climate change be “severe and long-lasting,” it is not only that the oceans will heat up and fish will shrink but “all ice will eventually melt.”
Get ready for a hotter future world with tinier and tinier fish, unless we do even more to cut down on greenhouse gases.
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Photo by Marko D Photography