Bull kelp, Nereocystis luetkeana, abundance in Van Damme Bay, Mendocino County, California

Size and density data were collected for Nereocystis luetkeana sporophytes from kelp beds in Van Damme Bay, Mendocino County during May, June and July 1990. Length and weight measurements were made on individual plants from representative size groups collected from depths of 6.1 m and 12.2 m. Mean sporophyte weight was 268 g (SD 393 g), while mean stipe length was 214 cm (SD 275 cm). Densities were determined separately for those plants which had reached the surface and for all plants within the water column. Sixty-five 12.7 m2 surface quadrats yielded mean surface densities of 2.2 (SD 1.5) and 2.7 plants/m2 (SD 1.3) in June and July, respectively. Individual plants were counted within 42 1x5 m plots along benthic transect lines yielding average densities of 2.7 (SD 4.5) and 5.2 plants/m2 (SD 3.0) in May and July, respectively. Combined density and size data from July 1990 and kelp bed area estimates from fall 1988 for Van Damme Bay yielded a biomass estimate of 640 metric tons distributed over 45.7 hectares. (15pp.

Relationships among temperature, depth, and abundance of commercially important fish captured by trawl vessels in the Kodiak area of the Gulf of Alaska, USA

Thesis (M.S.) University of Alaska Fairbanks, 2004Increased understanding of the factors influencing fish distributions and abundance may improve fisheries management and stock assessment models and may provide the fishing industry with a means to reduce bycatch. I investigated the associations of ambient seawater depth and temperature with catches of commercially important species in the Gulf of Alaska. Time-depth recorders were attached to trawl nets to collect depth and temperature data during commercial bottom trawl fishing operations. The data collected from these recorders were combined with species composition data collected by onboard observers to determine associations between these physical variables and catch of fishes. Parameters for depths and temperatures where target species were abundant were identified. Pacific cod were captured in abundance in depths shallower than 130 m while withstanding water temperatures ranging from 2.8 to 8.5°C. Rockfishes were abundant in depth ranging from 52 m to 353 m and temperatures ranging from 4.9 to 8.3°C. Shallow-water flatfishes were captured in abundance in depths shallower than 97 and temperatures from 2.6 to 10.7°C. Deep-water flatfishes were abundant in depths greater than 115 m and water temperatures ranging from 3.8 to 6.5°C. Arrowtooth flounder, Pacific halibut, and walleye pollock were found in all temperatures and depths analyzed