ENVIRONMENTAL-EFFECTS ON THE DISTRIBUTIONS OF GROUNDFISH IN HECATE STRAIT, BRITISH-COLUMBIA

Hecate Strait, British Columbia, is an area of variable topography wit h a variety of bottom habitats, which supports an important mixed-spec ies groundfish fishery. A previous analysis identified three character istic assemblages of groundfish species. In the present study, we iden tify relationships between the dominant species of these assemblages a nd environmental conditions in early summer 1989 and 1991: bottom type and depth (invariant conditions) and temperature (a variable conditio n). Three categories of species were identified: (i) those consistentl y associated with particular depths and temperatures between years, (i i) those with variable depth and temperature associations, and (iii) t hose with no apparent relationships to depth, temperature, or sediment type. Category (i) was dominated by flatfishes and could be further s eparated into groups associated with deep and cool, shallow and warm, and intermediate depth and temperature conditions. Category (ii) inclu ded roundfishes plus Pacific halibut (Hippoglossus stenolepis) and wer e widely distributed. At least one species (Pacific cod (Gadus macroce phalus)) tended to maintain a particular temperature range while chang ing its depth range between years. Identification of significant assoc iations between fish species and habitat conditions is the first step towards incorporating environmental information into survey abundance indices and reducing by-catch problems.