By-catch: problems and solutions

By-catch is one of the most significant issues affecting fisheries management today. Incidental mortality of species which are long-lived and have low reproductive rates is a conservation problem affecting marine mammals, sea birds, sea turtles, sharks and other groups. By-catches can affect biodiversity through impacts on top predators, the removal of individuals from many species, or by elimination of prey. The by-catch issue is also one of waste; the millions of tons of protein dumped in the ocean, and the waste of animal lives is often condemned on moral grounds. For the economist, it generates additional costs without affecting the revenues, and may hinder profitability. For the fishers, it causes conflicts among fisheries, it gives fishers a bad public image, generates regulations and limitations on the use of resources, and frequently has negative effects on the resources harvested through the mortality of juvenile and undersized individuals of the target species before they reach their optimal size from the point of view of future yield.

Several examples of major by-catch issues are described, focusing also on the solutions to the problems which have been developed by scientists, fisheries managers and members of the fishing industry itself. By-catch is an extremely complex set of scientific issues, not only an economic, political, or moral one. Although only a few fisheries include by-catches of the target species in their stock assessment (e.g. Pacific halibut), it is clear that by- catch management will be an integral part of most future ecosystem management schemes. These considerations, together with the introduction of environmental variability and a better handling of scientific uncertainty, should lead to more intelligent ways to harvest our resources.