Salmon

Because of their migratory habits and abundance, salmon have a long history of being a valuable source of food for people. In fact, before water pollution became a major problem, these fish were cheap and easy to get. However, with the onset of the industrial revolution, many rivers became polluted or were blocked by dams, and salmon populations declined or disappeared. Furthermore, decreases in salmon populations were intensified by increased fishing in salmon feeding habitat at sea. Fishery biologists are attempting to stem the salmon declines by enhancing wild stocks, for example, by releasing large numbers of captive-reared, young fish. This so-called "stock enhancement" can help, but it is also necessary to stop or repair the damage to aquatic habitat, and control the rate of fishing.

As a result of their decline, salmon became a high priced luxury item. Subsequently, the industry of fish farming arose, introducing the practice of rearing salmon in cages in embayments or at sea, or in ponds on land. The most popular species of salmon being farmed are Atlantic salmon, rainbow trout, Coho salmon, pink salmon, and American brook trout. Fish farming has helped to offset some of the decreases in salmon populations. However, other important problems have developed, because of chemicals used to prevent diseases in captive salmon and the build-up of organic sludge beneath fish-cages. Until measures are taken to control water pollution and to stop overfishing, salmon populations will not be able to return to their once abundant numbers.