The Longspine Thornyhead Fishery along the West Coast of Vancouver Island, British Columbia, Canada: Portrait of a Developing Fishery

A fishery for thornyhead Sebastolobus spp. started in the early 1990s along the Pacific coast of Canada, primarily in response to market demand from Japan. As the fishery evolved, the deepwater longspine thornyhead S. altivelis became a desirable species because it is easily targeted and commands high prices. Its congener, shortspine thornyhead S. alascanus, largely remained a bycatch species in other mid-depth fisheries along the continental slope. This paper describes the developing longspine thornyhead fishery off the western coast of Vancouver Island, British Columbia. We illustrate how the fishery migrated from its place of origin, possibly to maintain high catch rates as the resource was depleted. Analyses of the factors that significantly influence catch rates demonstrate that a model without factor interactions does not adequately describe the data. Length analysis shows that longspine thornyheads decrease in size with depth, a trend opposite to that for shortspine thornyheads. We also investigate the diversity of fish species caught in longspine thornyhead tows using the Shannon–Wiener index and find that diversity decreases with depth and increases in a northerly direction. Finally, we highlight issues of broad interest to managers of developing fisheries.