PRODUCTION OF FRASER-RIVER SOCKEYE-SALMON (ONCORHYNCHUS-NERKA) IN RELATION TO DECADAL-SCALE CHANGES IN THE CLIMATE AND THE OCEAN

The abundance of Fraser River sockeye salmon (Oncorhynchus nerka) stoc ks was low in the 1960s, increased to high levels in the 1980s, and po ssibly entered a period of low abundance in recent years. The abundanc e changes of the combined stocks can be separated into productivity re gimes that correspond to changes in climate trends. The most distinct change occurred when there was a major change in the climate over the Pacific Ocean in the winter of 1976-1977. The existence of natural shi fts in abundance trends means that the high returns that occur during periods of high productivity would not be expected to occur during the low-productivity periods. The response of Fraser River sockeye to cli mate changes may be a specific example of a more general response by a number of species of fishes in the Pacific and perhaps in other ocean s. Because the shift from one regime to the other occurred quickly in the 1970s, future shifts could also occur quickly. It is necessary to detect natural shifts in productivity when attempting to manage fishin g impacts to ensure that economic expectations are sound and that over fishing does not occur.