Two trawl nets, the \"Ribas net\" and a Faroe Island design prototype, were constructed and tested at sea on a commercial vessel, against a conventional two-seam groundfish net, which served as a control. The two experimental nets both modify the top half of a trawl net; the Ribas by using large square mesh and the Faroese by removing much of the twine at the top of the net. The project goal was to reduce cod as bycatch up to 75-90% (and perhaps dogfish (Squalus acanthias) bycatch as well). This net was designed to target the following species: yellow tail flounder (Pleuronectes ferruginea), winter flounder (Pleuronectes americanus), American plaice (Hippoglossoides platessoides), windowpane flounder (Glyptocephalus cynoglossus), and skate (Rajidea).
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Seventy pairs of alternate tows with the control net resulted in reductions of cod bycatch of >76% for both nets. Catch rates of sublegal yellowtail flounder were also >74% lower for both nets compared to the control. There were, however, reductions in the legal catch of yellowtail and winter flounders. Underwater video showed cod exiting the nets through the top mesh or gap made by removal of the twine. The results of this project have been presented to the New England Fishery Management Council Multispecies Plan Development Team, which encouraged participants to demonstrate the performance of the Ribas net in off-shore areas. The participants have continued the research with Saltonstall-Kennedy funding. However, modified versions of both nets were included as options in Amendment 13 to the Groundfish Fishery Management Plan. (from final report)
\"Groundfish Trawl nets Designed to Reduce the Bycatch of Cod\": Fishing log of experimental tows included in analysis.
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Project Leader:Michael Pol Massachusetts Division of Marine Fisheries
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final report
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Two experimental trawl net designs substantially reduced catch rates of Atlantic cod Gadus morhua while allowing the targeting of flatfish Pleuronectidae, as compared to a standard net design. The \"Ribas\" and \"topless\" nets both modify the top half of a trawl net; the Ribas net by using large square mesh; the topless net by removing much of the netting in the top square of the net. Seventy pairs of alternate tows showed reductions of cod catch rates (kg/hr) that exceeded 76% for both nets. Catch rates of yellowtail flounder Limanda ferruginea below MLS (~33 cm TL) were more than 74% lower for both nets, compared to a standard flatfish trawl. Reductions of catch rates for winter flounder Pseudopleuronectes americanus below MLS (~33 cm TL) exceeded 61%. Significant reductions occurred in catch above MLS for yellowtail (>32%) and winter flounders (>44%) with some evidence that this reduction was lower for the topless trawl. Underwater video showed cod exiting the nets through the top mesh and through the gap made by the removal of twine. These results demonstrate that separation of Atlantic cod from flatfish is possible and practical. (from final report abstract)
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associated datasets:
\nCod by-catch reducing gear: fishing log