Comparison of the performance of two bottom-sampling trawls

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The performance of two bottom-sampling trawls was evaluated under various rigging configurations and operating conditions. The trawls examined were a semiballoon shrimp trawl usually towed from a single warp and a high-rise trawl towed from two warps. The geometric performance (i.e., configuration of the trawl while in operation) of the full-scale nets was measured hydroacoustically in the field, and scale models were tested in a tow tank. For the shrimp trawl, wingspread increased significantly with increased bridle length but was not significantly affected by increased speed or current direction. Headrope opening decreased with increased towing speed and bridle length. For the high-rise trawl net, wingspread and headrope opening both decreased with increased speed. In contrast to the clear differences in geometric performance related to net design, rig, and operation, the analyses of catch data from Narragansett Bay, Rhode Island, were not definitive. The high-rise trawl captured significantly more total demersal fishes and winter flounder Pseudopleuronectes americanus by weight than the shrimp trawl, but the two nets caught similar sizes of winter flounder. Catches of winter flounder in the shrimp trawl were significantly affected by towing speed and current direction; however, bridle length of the shrimp trawl did not affect these catches demonstrably. Towing speed and current direction did not significantly affect total catch, demersal fish catch, or pelagic fish catch. © By the American Fisheries Society 1989.

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Transactions of the American Fisheries Society