Harvest of Ovigerous Pink Shrimp in the Oregon and California Trawl Fisheries

Identification Information

Citation

Originator: Hannah, Robert W.

Publish Date: 1992

Online Link: None

BPA Project #:

Contact Information

Agency: Oregon Department of Fish and Wildlife

Name: Cedric Cooney

Job Position: Natural Resources Data and Systems Manager

Telephone: 503-947-6094

E-Mail Address: cedric.x.cooney@odfw.oregon.gov

Description

Abstract: Recently, ODFW research efforts on pink shrimp have focused on identifying environmental and parent-stock effects on recruitment. These efforts have demonstrated a strong influence of ocean environmental factors on recruitment, but failed to show a dependence of recruitment on parent stock (Hannah 1991a ODFW, draft). In evaluating the influence of parent stock, we have utilized September-October mean catch-per-unit-effort (CPUE) as an index of spawning stock biomass, which is assumed to measure reproductive output. The absence of parent-stock effects on recruitment is not surprising; documented stock-recruitment relationships are rare for shrimp. However, the pink shrimp fishery provides a long data series,: with large fluctuations in parent stock, precisely the conditions required to detect a stock-recruitment relationship. Recent data (Hannah 1991b ODFW, draft) suggest that age-specific, and length-specific average fecundity in pink shrimp may show considerable interannual fluctuations. This finding is based upon very limited sampling, and needs further study to define the magnitude and frequency of variations in fecundity. However, the finding is significant, in that it may partly explain the lack of success to date in defining a stock-recruitment function for pink shrimp. Simply put, if length-specific fecundity is quite variable, then the standard measures of parent stock; numbers of parents, parent biomass, and estimates of larval release based on static average fecundity values, may be poor measures of shrimp reproductive output. To further investigate the influence that fishing exerts on recruitment, we need to focus on improving how we measure reproductive output. Another potential source of error in using spawning stock biomass to index reproductive output is the harvest of egg-bearing females. The fishery catches egg-bearing shrimp near the end of the season in October, and also the following April, sometimes in large numbers. This catch, especially in the spring just prior to larval release, may be depressing the reproductive output of the stock below the levels implied by CPUE at the end of the previous season. The purpose of this study is to analyze the sample data from the trawl fishery to determine the potential impact of catching egg-bearing shrimp. A secondary objective is to determine how a change in the fishing season for shrimp might reduce this impact.

Purpose:

Time Period of Content:

Geographic Extent: Oregon and California

Status: Final

Use Constraints:

Format: PDF

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