The Yangtze River is one of the world's busiest waterways (3), and is subject to a great range of human pressures that have had a devastating effect on the baiji. The main threat causing the decline of this species in recent years is illegal fishing using electricity, which has accounted for 40 percent of known deaths. The dolphins have also become caught in fishing gear, and engineering explosions used to keep navigation channels open are another source of mortality. Vessels carrying pesticides occasionally overturn, causing poisoning of the ecosystem, resulting in further deaths (6). An additional source of pollution comes from the 15.6 billion cubic meters of wastewater discharged into the Yangtze every year, 80 percent of which is not treated. A huge volume of boat traffic uses the river; noise levels are high and boat strikes a possibility. Furthermore, the banks of the Yangtze have been greatly modified in order to prevent flooding of adjacent land; such projects have great impacts on the ecosystem, both during construction and from the resulting habitat changes. Dam construction has been shown to reduce the availability of fish, which is exacerbated by over-fishing and pollution. The recent construction of the infamous Three Gorges Dam, the largest dam in the world, is likely to affect fish stocks and natural flooding patterns (2). For many years the baiji population is thought to have been very small, which in itself may have caused serious problems; small populations often suffer low genetic fitness and are often less able to adapt to environmental changes (2).
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