Accounting for Uncertainty in Estimates of Escapement Goals for Fraser River Sockeye Salmon Based on Productivity of Nursery Lakes in British Columbia, Canada

摘要

For certain populations of sockeye salmon Oncorhynchus nerka, spawner and recruit data are either absent or too limited to estimate escapement goals (target abundance of spawners). In some cases, scientists instead use data on productivity of nurserylakes; however, many such analyses have not accounted for uncertainties. We therefore extended a previously developed lake productivity method for estimating escapement goals (the photosynthetic rate [PR] model) by using a Bayesian statistical approach that takes several sources of uncertainty into account. Utilizing data for Fraser River, British Columbia, sockeye salmon stocks, we compared this Bayesian PR method with stock-recruitment analysis. In six of seven cases, probability distributions of spawner abundance goals from the Bayesian PR method were 27% narrower on average than those from the stock-recruitment method. In four of seven cases, the Bayesian PR method produced higher median estimates of target spawner abundance than did stock-recruitment analysis; the other three pairs of estimates were within 7% of one another. We suggest that the Bayesian PR method is a potential alternative to using stock-recruitment data to estimate escapement goals for sockeye salmon populations.