Length and Age at Maturity for Pacific Ocean Perch (Sebastes alutus) off Oregon

Identification Information

Citation

Originator: Hannah, Robert W. and Steven J. Parker

Publish Date: 2005

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: The age and length at maturity for female fish is a critical parameter in many stock assessment models. For example, Clark (1991) and Lunsford (1999) have shown that changes in the age at 50% maturity can have a strong influence on estimated target fishing rates. For a variety of U. S. west coast rockfish species, particularly those found on the upper continental slope, age and length at maturity are not well established (Love et al. 2002). For Pacific ocean perch (Sebastes alutus), the best maturity data available have been from samples collected during the National Marine Fisheries Service (NMFS) summer abundance surveys (Hamel et al. 2003). These data cover a broad geographic range and also include a wide size range of fish, unlike some commercial fishery samples which can lack adequate numbers of small, immature fish. However, survey data are based on a simple visual assessment of maturity, so they suffer from a different but serious problem. In summer, maturity status of ovaries from winter spawning species like Pacific ocean perch can be very difficult to determine; ovaries of mature, "resting" fish are macroscopically identical to ovaries of immature fish (Gunderson et al. 1980, Nichol and Pikitch 1994). Uncertainty in summer data is best addressed by collecting samples from a wide size range of fish during seasonal periods when visual maturity determinations are more accurate. However, even with an optimal sampling period, the possibility remains that visual assessment of female rockfish maturity could be an inaccurate assessment of "functional maturity"; the successful production of larvae. Nichol and Pikitch (1994) evaluated maturity of darkblotched rockfish (S. crameri) microscopically and found that some ovaries with evidence of vitellogenesis also showed mass atresia and resorption of oocytes during development. Their findings underscore the importance of using histological evidence of maturity over visual assessment, as the difference between a functionally immature and a functionally mature female can depend on attributes visible only microscopically, even during the active reproductive season. The primary objective of this study was to collect samples of Pacific ocean perch ovaries from a wide size range of fish, during the active reproductive season and use microscopic evaluation of stained thin-sections to develop functional age and length at maturity curves for use in stock assessment for the U.S. west coast.

Purpose:

Time Period of Content:

Geographic Extent: Oregon

Status: Final

Use Constraints:

Format: PDF

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Is a physical copy maintained for reference at Headquarters? Unknown