Factors affecting hydrodynamic performance of the Nordmøre Grate System: a bycatch reduction device used in the Gulf of Maine shrimp fishery
Document Type
Article
Date of Original Version
1-1-1995
Abstract
Trawl nets used in traditional shrimp fisheries are highly non-selective. While capturing shrimp, trawl nets also retain most other animals, including juveniles of commercially important species, thus depleting stocks. To maximize the efficiency of separation of shrimp from other species in trawl net catches, hydrodynamic experiments were conducted on the Nordmøre Grate System, a shrimp bycatch reduction device. The system consisted of two elements, a funnel and a grate; and experimental variables included towing speed, webbing solidity and exit to entrance area ratios for the funnel, and angle of attack, bar diameter, and shape of the grate. Filtration efficiency was inferred from flow disturbance induced by each element, as it was towed in a still water basin. Flow measurements were taken with an electromagnetic current meter at the entrance and at the exit of each funnel and each frame supporting the grates. Water was rejected in the entrance of all funnels with non-porous webbing. Water was ejected from the exit of funnels of intermediate webbing solidity and intermediate exit to entrance area ratio. Water was entrained behind all grates except the 0.32 cm bar diameter grate. Ejection of water at the funnel exit with no rejection at the funnel mouth was attained with 0.08 entrance to exit area ratio covered with 0.4 solidity ratio webbing. Optimum filtration efficiency was observed in the grate with 0.32 cm diameter, round bars placed at a 30 ° angle of attack. © 1995.
Publication Title, e.g., Journal
Fisheries Research
Volume
24
Issue
3
Citation/Publisher Attribution
Riedel, R., and J. DeAlteris. "Factors affecting hydrodynamic performance of the Nordmøre Grate System: a bycatch reduction device used in the Gulf of Maine shrimp fishery." Fisheries Research 24, 3 (1995). doi: 10.1016/0165-7836(95)00375-K.