Testing of Two Selective Flatfish Sorting-Grid Bycatch Reduction Devices in the U.S. West Coast Groundfish Bottom Trawl Fishery

Abstract

In the U.S. West Coast limited-entry (LE) groundfish bottom trawl fishery, catches of stocks with restrictive harvest limits (e.g., Darkblotched Rockfish Sebastes crameri, Sablefish Anoplopoma fimbria, and Pacific Halibut Hippoglossus stenolepis) continue to hinder many fishermen’s ability to fully utilize their quota shares of more abundant flatfish stocks (e.g., Dover Sole Microstomus pacificus and Petrale Sole Eopsetta jordani). We used a recapture net to examine the size-selection characteristics of two selective flatfish sorting-grid bycatch reduction devices (BRDs), which were designed to reduce catches of Pacific Halibut and non-flatfish species while retaining target flatfishes. The two devices were identical in materials and design except that the sorting-grid dimensions differed (BRD-1: 6.4- × 25.4-cm grid size; BRD-2: 6.4- × 30.5-cm grid size). The size selectivity for rockfishes, other roundfishes, Pacific Halibut, English Sole Parophrys vetulus, and Rex Sole Glyptocephalus zachirus did not differ significantly between the two designs. However, for 53–58-cm TL Arrowtooth Flounder Atheresthes stomias, 39–53-cm TL Dover Sole, and 36–49-cm TL Petrale Sole, BRD-1 retained significantly higher proportions of these length-classes than did BRD-2. Combined, the mean flatfish retention by weight (not including Pacific Halibut) was 89.3% (95% confidence interval [CI] = 87.1–91.5%) for BRD-1 and 81.7% (95% CI = 80.0–83.4%) for BRD-2. Compared to previous flatfish sorting-grid selectivity work conducted in the LE bottom trawl fishery, BRD-1 showed the ability to improve the overall retention of flatfishes while reducing catches of nontarget and constraining species.

Received August 16, 2017; accepted October 3, 2017

ACKNOWLEDGMENTS

We thank the captain and crew of the F/V Miss Sue for providing at-sea assistance with this research. Funding for this study was provided by the Saltonstall–Kennedy Competitive Research Program of the National Oceanic and Atmospheric Administration, National Marine Fisheries Service.