Fishes: The Animal Answer Guide

10. Human Problems (from a fish’s viewpoint)

117 Chapter 10 Human Problems (from a fish’s viewpoint) Give a man a fish and he’ll eat for a day. Teach a man to fish and he’ll deplete the oceans. The Book of Bob, Ironies 24:7 Are any fishes endangered? Many fish species have gone extinct recently, and many more are in danger of extinction. The official, global list of threatened and endangered species is kept by the International Union for the Conservation of Nature (IUCN). IUCN publishes a Red List of endangered plants and animals that it updates regularly. The most recent list identified 93 fish species that had gone extinct and 1,170 species worldwide that were threatened with extinction. We know this list is incomplete because the best records are from industrial and developed countries whereas most fish species live in tropical, developing countries where record keeping is not as good. It is likely that between 20 and 35% of the world’s 11,000 species of freshwater fishes and perhaps 5% of 17,000 marine species are in serious decline or already extinct. North America has about 1,200 freshwater fish species, of which about 500 to 550 (40 to 45%) need protection. Of the 900 freshwater fishes that occur in the United States, 124 are protected under the Endangered Species Act. Such legal action seldom occurs until a species is close to extinction , which means that many more than 124 are threatened. At both global and national levels, most endangered fishes live in fresh water, and all known extinctions involved freshwater fishes. These statis- 118 Fishes: The Animal Answer Guide tics reflect the degree to which we have altered, degraded, and destroyed freshwater habitats and their inhabitants. And although ocean fishes on the whole are not as threatened as freshwater fishes, many marine fishes have declined greatly in numbers. The main causes of decline and extinction are habitat alteration (disturbance of river and stream bottoms and shoreline vegetation, dam building , water withdrawal, turning natural rivers and streams into channels and ditches), introduced species, chemical and sediment pollution, hybridization , and overfishing. Often, several causes work together to cause declines. Main causes differ in different locales, with habitat disturbance being the chief culprit in fresh water and overexploitation from fishing (and habitat disruption from destructive fishing practices) causing the most declines among ocean fishes. Behind all these problems are human overpopulation and overconsumption. Which are the most endangered fishes in the world and in the United States? Experts disagree (of course), but there is an official list of species that cannot be traded between countries because of low and declining numbers. Trade is restricted by the Convention on International Trade in Endangered Species (CITES). The list includes nine fishes: African and Indonesian coelacanths (Latimeria), Shortnose and Baltic sturgeons (Acipenser brevirostris and A. sturio, Acipenseridae), Golden Dragonfish (Scleropages formosus, Osteoglossidae), Julien’s Golden Carp (Probarbus jullieni, Cyprinidae), Cui-ui Sucker (Chasmistes cujus, Catostomidae), Mekong Giant Catfish (Pangasianodon gigas, Pangasiidae), and Totoaba (Totoaba macdonaldi , Sciaenidae). The coelacanths and Totoaba are the only marine species currently on the list but there have been recent efforts to add the Atlantic Bluefin Tuna (Thunnus thynnus, Scombridae) to CITES. Of the 124 endangered and threatened species protected in the United States, it is hard to say which are in greatest danger of extinction because many are on the brink. Fishes that live in springs and spring runs, especially in desert regions, and in caves are very sensitive to water pollution, water withdrawal, and introduced species. This group includes several minnows, pupfishes, cavefishes, darters, and topminnows. Other families with several endangered species are suckers and sturgeons. In the Pacific Northwest region, many distinct genetic races of salmon have gone extinct or are in need of protection. Will fishes be affected by global warming? Global warming is just one aspect of global climate change, and climate change will influence most of the environmental factors that determine where fishes live. These factors include temperature extremes, oxy- gen availability, floods, droughts, major storms, and habitat loss. All these aspects of climate change can potentially affect the genetics of populations, the interactions between fishes and plants and other animals, as well as the roles that fishes play within ecosystems. Global warming will likely lead to alterations in wind direction and strength, which in turn will alter ocean currents. Ocean currents determine the timing and locales of spawning of ocean fishes, the dispersal...