New research forecasts effects of climate change on fish size

Changes in ocean and climate systems could lead to smaller fish, according to a new study led by fisheries scientists at the University of British Columbia. Climate change is expected to raise ocean temperatures and may reduce oxygen in some areas, which in turn makes it difficult for fish to grow. The study, published Sept. 30, 2012 in the journal Nature Climate Change, provides the first global projection of the potential reduction in the maximum size of fish in a warmer and less-oxygenated ocean.

The researchers used computer modeling to study more than 600 species of fish and found that the maximum body weight of an individual fish could decline by 5 to 39 percent, with a median of 10 percent in all oceans. Additionally, this and previous studies predict fish stocks are likely to shift their distribution from the tropics toward cooler seas, resulting in an increased amount of smaller-bodied fish and decreased amount of larger-bodied species in northern and southern habitats. This paper reports on the combined effect of these changes induced by climate and ocean changes (see graphic)—the average fish size in habitats around the globe will decline by 14 to 24 percent. The effect appears to be especially strong in the tropics and areas near 30 degrees latitude north and south. 

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