Warmer, oxygen-poor waters, combined with migration and the consequences of over-fishing will cause fish to decrease in size by as much as 24 percent by 2050, according to a recent study published in Nature Climate Change (subscription required).
Researchers used computer models to predict the effects of greenhouse gas emissions continuing at the current rate on the physiology, distribution, migration and population of 600 marine fish species. Because warmer waters increase their metabolic rate, fish will need more oxygen. But warmer water holds less oxygen and mixes less well with nutrient-rich layers of cold water, thereby reducing fish growth.
Average fish size in an assemblage will also decline as smaller tropical fish migrate to temperate or polar regions.
The results of warming compound the consequences of years of over-fishing that has prevented many fish from reaching full size.