Global warming could have many impacts on fish and other aquatic species. Some bodies of water may become too warm for the fish that currently inhabit those areas; but warmer temperatures may also enable fish in cold ocean waters to grow more rapidly. Global warming may also change the chemical composition of the water that fish inhabit: the amount of oxygen in the water may decline, while pollution and salinity levels may increase. Loss of wetlands could diminish habitat and alter the availability of food for some fish species. Scientists have examined the implications for three types of fisheries: (1) inland freshwater fisheries found in non-tidal rivers, lakes, and streams; (2) coastal fisheries, which extend from tidal freshwater rivers, to estuaries, to coastal ocean fisheries; and (3) deep ocean fisheries.
Inland Fisheries
Higher water temperatures may have the most important implications for inland fisheries. Like plants and birds, most species of fish tolerate — and many require — winter cooling and summer warming by tens of degrees.
Coastal Fisheries
Wetland loss, salinity changes, and higher temperatures are all likely to affect finfish and shellfish in the coastal zone. The most vulnerable species are those that either reproduce in coastal wetlands, spend their entire lifetimes in an estuary, or both.
Ocean Fisheries
Scientists generally expect fish on the high seas to be less affected by global warming than coastal and inland fisheries.