Evaluation of a Selective Flatfish Sorting Grid Bycatch Reduction Device in the West Coast Bottom Trawl Fishery

This study evaluated a selective flatfish sorting grid bycatch reduction device (BRD) designed to reduce catches of rockfishes, sablefish, and Pacific halibut in a nearshore flatfish fishery off the U.S. west coast. A recapture net was used to quantify fish escapement and retention by weight. Generalized linear mixed modeling (GLMM) was used to compare the proportion of fish catch at length to determine if retention was length-related. The mean retention of flatfishes (five species evaluated) ranged from 68.1% to 92.3% with an overall mean retention of 85.6%. Petrale sole displayed the highest percent retention, whereas arrowtooth flounder exhibited the lowest. Catches of rockfishes, sablefish, and Pacific halibut were reduced by 74.3%, 97.0%, and 90.3%, respectively. GLMM showed retention was significantly length-related for rockfishes, sablefish, and three of the flatfish species evaluated. Flatfishes <57 cm in length were retained in the trawl in significantly greater proportions. Rockfishes >32 cm in length and sablefish >42 cm in length were retained in the trawl in significantly lower proportions. Significantly fewer Pacific halibut were retained in the trawl across all lengths. The BRD demonstrated the ability to substantially reduce catches of rockfishes, sablefish, and Pacific halibut while retaining flatfishes.