Semi-pelagic trawling in the U.S. West Coast groundfish bottom trawl fishery: Effects on catch efficiency and seafloor interactions

Reducing the impacts of bottom trawling on seafloor habitats is a management priority in the U.S. West Coast groundfish bottom trawl fishery as well as other trawl fisheries internationally. Modifications to conventional bottom trawls, such as semi-pelagic trawl technology, are commonly used in demersal fisheries to reduce trawl-seafloor interactions by elevating the doors and portions of the sweeps off the seafloor. This study evaluated changes in catch efficiency and trawl geometry between a conventional bottom trawl outfitted with bottom-tending doors and the same trawl modified with midwater doors to fish semi-pelagically. We observed the seafloor interactions using Dual-frequency IDentification SONar (DIDSON) and quantified the reduction in trawl-seafloor interactions by periodically placing an altimeter on the semi-pelagic trawl door to measure height off bottom. Across the tows where the altimeter was used, results showed that the midwater doors fished off bottom >96% of all tow durations at a minimum height of 0.6 m. The midwater doors also spread 43 m wider on average than the conventional doors, which was significant (p 96% of all tow durations.•DIDSON imaging sonar was used to examine trawl-seafloor interactions.•Results show the semi-pelagic trawl can effectively harvest demersal groundfishes.•Tra