Factors Limiting Juvenile Sockeye Production and Enhancement Potential for Selected BC Nursery Lakes

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In this report we present summaries of our current knowledge of freshwater factors limiting sockeye production from 60 B.C. lakes. Data were collected between 1977-2000. Quantity of data available for each lake varied, ranging from intensive multi-year ecosystem studies on some lakes to one-time limnological surveys on others. The lakes are located in five of the six DFO management areas (none are in Yukon-Transboundary). Seventeen of the lakes are in the B.C Interior, eight are in the Central Coast, four are in the Lower Fraser, the majority (25) are in the North Coast, and six are in the South Coast. They make up about two-thirds of the total sockeye nursery lakes in B.C. Their total surface area is 3,586 km2, which is approximately 90% of the total area of B.C. nursery lakes. Freshwater factors limiting sockeye production in these lakes are varied, but in the majority of lakes and years fry recruitment is insufficient to fully utilize their productive capacity. Most of the lakes are oligotrophic and strongly nutrient-limited, thus juvenile sockeye growth and/or survival could be improved by nutrient additions. We identify opportunities for enhancement and restoration of the lakes’ sockeye stocks, which in addition to lake fertilization include increasing escapements, fry outplants, spawning channels, improvements to spawning grounds, and control of competitors or predators.