Improving pelagic fish retention in sampling trawls with a fish funnel
I.K. Workman, C.W. Taylor and J.W. Watson

The first step in managing a resource is to develop an effective sampling technique to assess and monitor that resource. Pelagic fish species pose a particularly difficult sampling problem since many of them are able to out-swim and escape standard sampling trawls. This was the problem the National Marine Fisheries Service encountered in the 1980s when they set out to assess the potential of underutilized fish resources in the Gulf of Mexico. Standard sampling trawls were too small to effectively sample the resources, so larger, high-opening, bottom trawls were adopted. The larger trawls were more effective, but most of the faster swimming pelagic species were able to escape these nets especially during haul back. To reduce fish escape, webbing panels, attached inside the trawls ahead of the cod ends, were tested. Initial tests were conducted with two single panel designs: a fish flap and a “floppa”. Neither design reduced fish escapement. A multi-panel conical fish funnel design was tested and found to increase fish retention by trapping fish after they passed through it. When used in combination with a technique known as pulsing the trawl, the fish funnel substantially increased trawl catch rates with no indication of fish escape.

Keywords: Fish trawl, fish flap, fish funnel.
Contents of this volume Sci. Mar. 59(3-4) : 581-585 Back PDF
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