Date of Award

Spring 1984

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Ocean/Earth/Atmos Sciences

Program/Concentration

Oceanography

Committee Director

Phillip R. Mundy

Committee Member

John R. McConaugha

Committee Member

Chester Grosch

Committee Member

Michael J. Doviak

Abstract

A model to estimate determinants for migratory timing of catch and escapement in a terminal salmon fishery is presented. A method was developed to estimate average seasonal migration rates of salmon through a harvest area from catch and escapement data. The time series for the total population of Copper River sockeye salmon (Oncorhynchus nerka) was reconstructed in the reference frame of the commercial harvest area from catch and escapement data.

The catchability coefficients (q), derived from the reconstructed populations were found to vary within season and between seasons. The relation between q and effort was attributed to a highly competitive fishery.

The difference found between the descriptive statistics for the time densities of catch and catch per unit of effort (CPUE) are attributed to varying q. In a highly competitive terminal fishery the time density of catch was found to be a better representation of the time density of total abundance than that of CPUE. The comparison of the time series of daily proportions of catch and CPUE was found to be a valuable diagnostic tool for determining whether q was variable over a season.

It was inferred from the reconstructed time series of total abundance that escapement from the commercial harvest area was underestimated by the sonar counter. The under estimation of escapement from the commercial harvest area may be attributed to two sources; (1) the delta stocks are higher than point estimates found by stock separation studies; (2) the enumeration of escapement to the upper Copper River spawning areas are being underestimated by the sonar counter.

The simulation model was a useful tool for investigating the behavior of migratory time densities and for evaluating the success of alternative management strategies in terms of distributing an escapement goal proportionately over time.

DOI

10.25777/nmts-qc18

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