of large areas of natural wetlands. The escape of genetically modified species and the release of medical drugs into the environment raise the concern that wild populations of fish might be endangered by fish farming. The loss of wild fish would mean the loss of potentially valuable genes as well as reduction of biodiversity.

Changes in wild species can now be closely monitored using the tools developed for analyzing and identifying genes. This allows scientists to define species, stocks, and populations that may appear similar to the eye but have important differences in their gene pools. Improving techniques for breeding captive animals, and technologies for preserving frozen eggs, sperm, and embryos, can also help conservationists restock depleted areas and maintain threatened species.

Since North Atlantic fish stocks fell so dramatically in the 1990s, many fishing communities scattered along Canada's eastern shoreline turned to aquaculture of salmon and other fish. But the more northerly communities face the challenge of protecting their captive fish stocks (especially young ones) from the cold. During the Canadian winters, much of the east coast has sub-zero seawater temperatures. These conditions would freeze halibut and Atlantic salmon raised on fish farms, making the use of sea cages in these areas all but impossible—unless stocks of freeze-resistant fish can be developed. And that is exactly what researchers at the Memorial University of Newfoundland are aiming to do, with good results so far.