HATCHERY AND WILD PRODUCTION OF PACIFIC SALMON IN RELATION TO LARGE-SCALE, NATURAL SHIFTS IN THE PRODUCTIVITY OF THE MARINE-ENVIRONMENT

Pacific salmon have been fished extensively for at least a century and artificial production of Pacific salmon has been a management strateg y to improve production for almost as long. Hatchery production is con sidered important because it is commonly believed that the carrying ca pacity for salmon in the ocean has remained more or less constant and is underutilized as a consequence of limited production of smelts in f resh water. Since the mid-1960s, there has been an increase in hatcher y production, partly as a response to a desire to increase catch and p artly because of improved hatchery techniques. Since the late 1970s th ere has been a dramatic increase in the total Pacific salmon catch. Th e increases in catch are now known to result from a large-scale shift in the productivity of the sub-arctic Pacific and management and enhan cement actions. Environmental indices changed about 1989-1990 and may indicate that the productive regime of the 1980s has ended. This would imply that under natural conditions Pacific salmon abundance would de cline. There are no clear indications of what to expect in the new reg ime, but it is apparent that the massive production of artificially re ared Pacific salmon would not be necessary in a less productive regime . OF concern is the impact that the large numbers of artificially rear ed salmon will have on wild salmon stock levels. (C) 1997 Internationa l Council for the Exploration of the Sea.