Angler For Ever

As of 2006, the IUCN Red List describes 1,173 species of fish as being threatened with extinction.^[44] Included on this list are species such as Atlantic cod,^[45] Devil's Hole pupfish,^[46] coelacanths,^[47] and great white sharks.^[48] Because fish live underwater they are much more difficult to study than terrestrial animals and plants, and information about fish populations is often lacking. However, freshwater fish seem particularly threatened because they often live in relatively small areas. For example, the Devil's Hole pupfish occupies only a single 3 m by 6 m pool.^[49]

Main article: Overfishing

In the case of edible fishes such as cod and tuna a major threat is overfishing.^[50][51] Where overfishing persists, it eventually causes the collapse of the fish population (known as stock) because the population cannot breed fast enough to replace the individuals removed by fishing. One well-studied example of the collapse of a fishery is the Pacific sardine Sadinops sagax caerulues fishery off the coast of California. From a peak in 1937 of 790,000 tonnes the amount of fish landed steadily declined to a mere 24,000 tonnes in 1968, at which point the fishery stopped as no longer economically viable. Such commercial extinction does not mean that the fish itself goes extinct, merely that it can no longer sustain a profitable fishery.^[52] The main tension between fisheries science and the fishing industry is the need to balance conservation with preserving the livelihoods of fishermen. In places such as Scotland, Newfoundland, and Alaska the fishing industry is a major employer, so governments have a vested interest in finding a balance between conserving fish stocks while maintaining an economic level of commercial fishing.^[53][54] On the other hand, scientists and conservations push for increasingly stringent protection for fish stocks, warning that many stocks could be wiped out within fifty years.^[55][56]

See also: Environmental effects of fishing

A key stress on both freshwater and marine ecosystems is habitat degradation including water pollution, the building of dams, removal of water for use by humans, and the introduction of exotic species.^[57] An example of a fish that has become endangered because of habitat change is the pallid sturgeon, a North American freshwater fish that living in rivers that have all been changed by human activity in a variety of different ways.^[58]

Introduction of exotic species has occurred in a variety of places and for many different reasons. One of the best studied (and most severe) examples was the introduction of Nile perch into Lake Victoria. Since the 1960s the Nile perch gradually exterminated the 500 species of cichlid fishes found only in this lake and nowhere else. Some species survive now only in captive breeding programmes, but others are probably extinct.^[59] Carp, snakeheads,^[60] tilapia, European perch, brown trout, rainbow trout, and sea lampreys are other examples of fish that have caused problems by being introduced into alien environments.