Tasty Fish Grow Smaller in Warming Ocean

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Fish sandwiches may be skimpier in the future as the planet’s oceans continue to warm.

Biologists measured progressively smaller average lengths of edible fish in the northern Atlantic Ocean between 1970 and 2008. Six economically-important fish species — haddock, herring, Norway pout and plaice — declined in length by an average of 23 percent.

The fish lived in different environments from bottom-dwelling plaice to surface-skimming herring. The range of habitats suggested that some common factor was altering the entire ocean community in the North Sea, a section of the Atlantic rimmed by Scandinavia, Great Britain and Germany.

ANALYSIS: Climate Change Could Shrink Animals

During those same 38 years, the average seafloor water temperature increased by 0.2–0.6 degrees Celsius per decade, for a total of one to two degrees C, in the North Sea. Besides the increasing water temperature, no other factor, such as commercial fishing, affected the fish universally, noted the authors of the study published in Global Change Biology. The biologists concluded that climate change may be shrinking economically important fish species.

“We would anticipate that synchronous reductions in length across species could be occurring in other regional seas experiencing a strong degree of warming,” study leader Alan Baudron of the University of Aberdeen, told the Guardian.

However, not every fish measured by the study declined. Sole and cod both approximately maintained their sizes. Haddock and whiting, on the other hand, decreased in length by approximately 29 percent in parts of their ranges.

ANALYSIS: Animals, Plants Shrinking as Climate Warms

North Sea fisherman’s commercial success may decrease along with the shrinking fish. The weights of individual fish caught declined by between three and 48 percent between 1978 and 1993, noted the biologists. Plaice and haddock suffered most serious declines in weight.

As the ocean warms, less oxygen dissolves into the water. Fish depend on that dissolved oxygen to breathe. Smaller fish in the North Atlantic may survive better in oxygen poor waters, wrote the study’s authors, since the animals need to intake less of the dissolved gas.