Bridging Gaps in Fish Biology and Fisheries Management: Hard Lessons and Warnings from Two Large Inland Water Systems in British Columbia

摘要

Dangers of incomplete understanding in functional processes of fish ecology, physiology and behaviour, as well as fisheries management, are reviewed for two major British Columbia watersheds - the Kootenay Lake system, part of the upper Columbia River, and the Fraser River system, draining a quarter of the province and supporting one of the largest populations of salmonids in the world. The Kootenay system in the last 50 years has been subject to massive cultural eutrophication, then cultural oligotrophication, and most recently an expensive large-scale experimental but controlled "reeutrophication", all with substantial effects on its major recreational fisheries. Furthermore mid-twentieth century introduction of "freshwater shrimp" (Mysis relicta)to bridge an apparent food web gap for rainbow trout (Oncorhynchus mykiss), produced unexpected and only temporary "success" in a non-target kokanee (Oncorhynchus nerka) fishery, along with widespread problems throughout many other large lakes of western North America by its inappropriate introductions elsewhere in misguided hopes to repeat the Kootenay "success." Throughout much of the twentieth century, the Fraser system enjoyed one of the most intensive and pervasive levels of fish ecological, physiological and behavioural research coupled with strong management at the local salmonid stock level, as well as at provincial, federal and even international levels. Nevertheless there were many gaps in understanding and appropriate action ranging from major tributary impoundment in its upper reaches, problems of upstream fish passageway by blockage in its middle reaches, loss of vital estuarine rearing habitat, as well as climate change effects on near-shore and offshore marine waters where intensive commercial and recreational fisheries take place. Indeed in some ways the gaps seem to be widening to gulfs, which if not soon bridged, may result in irrevocable degradation of its world-class salmonid fisheries.