Depth distributions and time-varying bottom trawl selectivities for Dover sole (Microstomus pacificus), sablefish (Anoplopoma fimbria), and thornyheads Sebastolobus alascanus, and S. altivelis) in a commercial fishery

• Published in: Fishery bulletin (Washington, D.C.) Vol. 99; no. 2; pp. 309 - 327
• Main Authors: Jacobson, L D, Brodziak, J, Rogers, J
• Format: Journal Article
• Language: English
• Published: 01-04-2001
• Subjects: Anoplopoma fimbria; Marine; Microstomus pacificus; Sebastolobus alascanus; Sebastolobus altivelis; INE, USA
• ISSN: 0090-0656

We estimated size-specific depth distributions and commercial bottom trawl fishery selectivities for Dover sole (Microstomus pacificus), shortspine thornyhead (Sebastolobus alascanus), longspine thornyhead (S. altivelis), and sablefish (Anoplopoma fimbria) along the U.S. west coast. Depth distributions are size-specific because fish migrate ontogenetically to deep water. With ontogenetic migration, fishery selectivities of commercial bottom trawls depend on depth of fishing because large fish are most common in deep water. Depth distributions were similar for northern and southern areas and for males and females. Results show ontogenetic migration in sablefish, suggest a possible weak ontogenetic migration in longspine thornyhead, and confirm ontogenetic migration patterns already reported for Dover sole and shortspine thornyhead. Fishery selectivities varied among species, between areas, and changed dramatically over time for most species as fishing effort moved into deep water. Our approach used biological data collected during research bottom trawl surveys but was generally not affected by size selectivity of bottom trawl survey gear. Uncertainty in our commercial bottom trawl selectivity estimates was mostly from length-specific capture probabilities (or vulnerabilities) for fish in the path of commercial bottom trawls. Our estimates complement selectivity estimates from stock assessment models. The approach may be useful whenever the geographic distribution of fish depends on size or age, fishing effort is not randomly distributed geographically, and survey estimates of fish density, bathymetric data, and commercial fishing effort information are available.