Research Document - 2005/096

A review of rougheye rockfish Sebastes aleutianus along the Pacific coast of Canada: biology, distribution, and abundance trends

By Haigh, R., N. Olsen, and P. Starr

Abstract

This paper reviews the current data on the biology, distribution, and abundance trends for rougheye rockfish Sebastes aleutianus. The information contained herein is primarily for use in a COSEWIC status report on this species. It is not meant to be a comprehensive stock assessment. This species has a mean weight of 1.585 kg/fish. Allometric growth shows no difference between the sexes; and males are generally no bigger than females of equal age. With an estimated age-of-50%-maturity at 20.3 years, and an assumed natural mortality rate of 0.035, generation time is roughly 48 years. Posterior model estimates of total mortality rate Z for the survey year 1997 range from 0.034 to 0.063, with a mean of 0.048. Commercial age proportions in 1996 yield essentially the same estimate of Z, ranging from 0.028 to 0.061 with a mean of 0.045. In 2003, older age classes appear truncated and younger fish predominate. The posterior distribution of Z ranges from 0.060 to 0.113 with a mean of 0.091. According to commercial trawl records, rougheye rockfish prefer depths between 171 m and 658 m. Using this preference, a bathymetric analysis estimates the potential extent of occurrence at 37,145 km² and the area of occupancy at 18,530 km². However, based on trawl and logline observations, the area of occupancy could easily equal 35,100 km². Within its habitat, the two dominant concurrent species are arrowtooth flounder Atheresthes stomias and Pacific ocean perch Sebastes alutus. Total removal of rougheye rockfish from BC coastal waters by the commercial fleet from 1971 to 2005 equals approximately 16 million fish. Survey indices of abundance are currently not useful for assessing rougheye rockfish population trends. The Hecate Strait assemblage, WCVI shrimp trawl, and NMFS triennial surveys are too shallow. The QCS shrimp survey, while showing an increasing abundance trend, is too limited in areal extent. The QCS synoptic survey, which will become the most reliable, currently has too few data points. The commercial trawl CPUE indices show a slightly increasing trend in 3CD and essentially flat trends in 5AB and 5E.

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