Evaluation of a Large-Mesh Panel to Reduce the Flatfish Bycatch in the Small-Mesh Bottom Trawls Used in the New England Silver Hake Fishery

Abstract

Fishermen must use small-mesh bottom trawls to capture certain species of fish that cannot be retained by standard groundfish mesh sizes. These fisheries are subject to bycatch limits when such trawls are used in areas where regulated species reside. Bycatch of regulated flatfish in the small-mesh bottom trawl fishery for silver hake Merluccius bilinearis in the northwestern Atlantic is a concern of management because silver hakes are captured in areas where juvenile regulated flatfish are common. An evaluation of flatfish and silver hake behaviors using low-light underwater cameras suggested that the two species could be separated within the mouth of a bottom trawl. Using the alternate tow method, four different large-mesh panels positioned in the lower belly of the trawl were separately evaluated. One of them proved to be effective in reducing flatfish bycatch while not reducing the catch of silver hakes; a large-mesh panel constructed of 40.6-cm (16-in) stretched mesh that was diamond shaped using orange-colored nylon twine 1.6 mm (0.06 in) in diameter in the lower belly resulted in a 73% reduction in flatfish catch with no effect on the catch of silver hakes.