Bycatch of rockfish in spot prawn traps and estimated magnitude of trap loss in Washington waters of the Salish Sea

Derelict fishing gear is a known stressor to rockfish populations in the Washington waters of the Salish Sea, including two species currently federally protected under the Endangered Species Act. In Washington and British Columbia, rockfish bycatch in actively fished (non-derelict) prawn traps has been documented in spot prawn test fisheries conducted by state and provincial government, and both live and dead rockfish have been found in derelict prawn traps encountered during derelict fishing gear removal operations in Washington. This study calculates rockfish bycatch rates in actively fishing prawn traps and provides preliminary trap loss rates for both commercial and recreational fisheries. Rockfish bycatch rates were determined through analysis of Washington Department of Fish and Wildlife (WDFW) Spot Prawn Test Fishery Data collected from 2004 to 2013. Data from WDFW creel surveys were used to update preliminary prawn trap loss rates. Interviews with WDFW marine enforcement officers were conducted to estimate the number of lost traps that are recovered before becoming derelict. The overall rockfish catch rates in Washington waters of the Salish Sea were 0.023 rockfish per trap drop, with considerable spatial and temporal variability. The lowest catch rates were consistently seen in Marine Area 7 (San Juan Islands and North Puget Sound); while the highest catch rates were seen in Marine Area 11 (south-central Puget Sound). The trap loss rate estimated for the recreational fishery is 2.33% of all traps fished. We estimate that over the years 2012 and 2013 an average of 653 recreational prawn traps became derelict each year. The accumulation of derelict prawn traps has a mostly unknown effect on benthic habitats of Puget Sound, which warrants additional research. While rockfish bycatch and prawn trap loss rates reported here are low, our findings support evaluating methods to reduce rockfish encounters with prawn traps.

Concentrations of Inorganic Elements and Fatty Acids in Geographic Populations of the Spot Prawn Pandalus platyceros

Inorganic elements and fatty acids were quantified in body segments of different size classes of the spot prawn Pandalus platyceros collected from various locations in British Columbia. Substantial differences in concentration of elements occurred in different body segments of the spot prawn, with the exoskeleton accumulating the highest number of quantifiable elements. Comparison of elements in abdomen carapace and tissue from immature males, mature males, and females indicated no correlation between element concentration and size, age, or sex of the spot prawn. Fatty acid profiles were similar for all body parts, except the hepatopancreas, and of the major fatty acids, only the content of 18:1n9 increased significantly with age of the spot prawn. Fatty acids and elements in the abdomen tissue of spot prawns from different locations were not significantly different and indicated similarity of diet irrespective of location. The concentrations of elements absorbed into the carapace of female spot prawns from separate geographic locations were substantially different, suggesting incorporation from elements in the ambient seawater, rather than uptake from diet, or any genetic variability associated with element metabolism in the spot prawn. The levels obtained for metallic elements in the spot prawn provide a measure against which future environmental impact could be assessed.