Symposium Abstract: Habitat Associations of Upper Slope Rockfishes (Sebastes spp.) and Co-Occurring Demersal Fishes in Ascension Canyon, California
J. J. Bizarro, J. M. Field, H. G. Greene, R. N. Lea, and J. deMarignac
Due to their typical life history patterns (slow growth, late age at maturity, extreme longevity) deepwater rockfishes (Sebastes spp.) are especially susceptible to overfishing, as evidenced by recent declines in most commercially targeted stocks. To establish effective Marine Protected Areas (MPAs), the interaction between fishes and their available habitats must be determined. Our objectives were to describe habitat associations for upper slope rockfishes and co-occurring fish species within the headward part of Ascension Canyon at both large (1 to 10s of kilometers) and small (10s to 100s of meters) scales. Geologic structure and lithology were investigated using high-resolution multibeam bathymetric and backscatter data. These data were interpreted to produce habitat maps of the study area. Seafloor features and fish assemblages were then surveyed using the Delta submersible at 50-meter intervals between 200 and 350 m. Thirty-two ten minute transects were completed between two distinct, largescale habitat types. At 200 and 250 m, stripetail (Sebastes saxicola} and greenstriped (S. elongatus) rockfishes were the dominant fish species. At 300 and 350 meters, splitnose (S. diploproa) and shortspine thornyhead (Sebastolobus alascanus) were the most abundant rockfishes. Large and smallscale habitat associations of these and several other commercially important demersal fishes were also determined.