Research Document - 2002/124

Meziadin Lake Biological Escapement Goal and Considerations for Increasing Yield of Sockeye Salmon (Oncorhynchus nerka)

By Bocking, R.C., Link, M.R., Baxter, B., Nass, B., Jantz, L.

Abstract

Meziadin Lake has historically produced sockeye salmon (Oncorhynchus nerka) returns ranging from 145,500 to 1.7 million, and averaged 523,000 total returns with an average escapement of 174,600. Two lake euphotic zone capability models (EV and PR), a Ricker stock-recruit function and fry recruitment analysis indicate that escapements between 155,000 and 185,000 are within the optimal range for the system. Above 200,000 spawners, the probability of returns being less than replacement increases, while at escapements below 150,000, and as low as 50,000, there have been good levels of recruitment. Nass sockeye are currently managed to a total aggregate escapement goal of 200,000.  Historically, Meziadin sockeye have comprised between 45% and 95% of this aggregate. Accordingly, this management approach will tend to result in net escapements to Meziadin of between 90,000 and 190,000 sockeye. These escapement levels are within the "safe" limits for ensuring adequate recruitment of Meziadin sockeye. There is some evidence that the yield of sockeye from Meziadin Lake could be increased by increasing fry size and hence, survivals from smolt to adult through a lake fertilization program. However, we recommend that experimental manipulations of lake productivity not be considered further until assessment and management procedures to safe-guard the weaker stocks are developed or the capability to harvest Meziadin sockeye surplus to escapement at terminal locations is developed. Without improved information on the productivity of weaker Nass sockeye stocks, there can be little justification for changing the overall Nass escapement goal of 200,000.

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