Authors
Henry Yuen Rishi Sharma
Report Reference
#North
American Journal of Fisheries Management 25:446–
463, 2005
Publication Date
17 Mar
2005
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Using
Simulation Techniques to Estimate Management Parameters on Snake River
Steelhead: Declines in Productivity Make Rebuilding Difficult
Abstract |
| We collected
adult and juvenile spawner recruit data on wild summer steelhead Oncorhynchus
mykiss for the Snake River and estimated parameters for €sheries
management by partitioning the data into predam and postdam periods
and €tting the Ricker and Beverton–Holt models to those time
series. The results showed a decline in productivity irrespective
of the model chosen and the way in which the pre- and postdam periods
were de€ned. However, the data were noisy and the con€dence bounds
on parameter estimates were fairly large. To reconcile the different
management goals derived from the different data sources (adult or
juvenile data) or model choice (Ricker or Beverton–Holt), we
used simulation techniques and Bayesian algorithms. The combined approach
suggests a recover y management goal (i. e. , spawning stock associated
with the maximum sustainable yield) of 60, 000 steelhead above Lower
Granite Dam. At current smolt-to-adult survival rates, the data indicate
optimal escapement of between 20, 000 and 27, 000 adults. We note
that Snake River steelhead stocks cannot be managed for recover y
escapement levels given current estimates of smolt-to-adult sur vival
rates, and we discuss alter natives for present-day management and
rebuilding over time. |
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