Research Document - 1999/208

Optimal Production of Chinook Salmon from the Stikine River.

By D.R. Bernard, S.A. McPherson, K.A. Pahlke, and P. Etherton

Abstract

Optimal production of adult chinook salmon Oncorhynchus tshawytscha from the Stikine River was investigated with information from a stock assessment program (1975-1997) and catch sampling programs on the Canadian inriver commercial and aboriginal gillnet fisheries and on the U.S. marine commercial gillnet and recreational fisheries. Stock assessment was based on aerial surveys, mark-recapture experiments to estimate abundance of large (mostly age 1.3 and older) salmon over the spawning grounds, a weir over the Little Tahltan River, and a radiotelemetry study to determine distribution of spawning salmon. Counts at the weir on the Little Tahltan River represented on average an estimated 19% of all large spawners in the Stikine River watershed; depending on water clarity, an estimated 48% or 36% of large fish above the weir were counted on average in aerial surveys. Estimates of relative age composition from carcass surveys (1981 - 1988) on the Little Tahltan River were similar to estimates from samples taken at the weir (1985 - 1988). Few age 1.2 salmon were present over the spawning grounds in any year; salmon age 1.4 usually dominated. Measurement error in estimated spawning abundance was an estimated 9% of all variance. Residuals from a fit of a linearized, log-transformed version of Ricker's exponential stock-recruit model to the data showed no autocorrelation in process error. Spawning abundance that would on average produce maximum sustained yield (10,983) was estimated at 17,368 large chinook salmon with simulated 90% confidence intervals of 11,838 and 39,907. Some statistical bias (~18% ) was indicated in the estimate. Considering that estimated spawning abundance has been above 17,368 large chinook salmon since 1986 (excluding 1995), we concluded that this population has probably recovered from overfishing incurred in the 1970's. We recommend annual aerial surveys be suspended, reinstatement of a coded-wire tag program to estimate marine harvests and smolt abundance, and continuation of the current stock assessment program based on catch sampling, escapement sampling, the mark-recapture experiment, and the weir on the Little Tahltan River.

Key words: Chinook salmon, Oncorhynchus tshawytscha, Stikine River, spawning abundance, mark-recapture; age composition, escapement goal, stock-recruit analysis, maximum-sustained yield.

Complete document (PDF, 524 KB)

Accessibility Notice

This document is available in PDF format. If the document is not accessible to you, please contact the Secretariat to obtain another appropriate format, such as regular print, large print, Braille or audio version.