A Size-Selective, Near-Zero Mortality Trawl for....
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GRANT NUMBER:  NA66FD0011           NMFS NUMBER:  95-NER-009

REPORT TITLE: A Size-Selective, Near-Zero Mortality Trawl for Silver Hake

AUTHOR: Amaru, William Hugo

PUBLISH DATE:  December 1996

AVAILABLE FROM:  National Marine Fisheries Service, Northeast Region, One Blackburn Drive, Gloucester, MA 01930-2298.  PHONE: (978) 281-9267


Any mesh used in New England to capture regulated species in the regulated mesh area of the federal EEZ less than the present 6" regulated minimum, must result in the capture of regulated species not in excess of 5% of the total when measured by weight.   This requirement has rendered the use of small mesh bottom trawls historically used to capture silver hake (Merluccius bilinearis) illegal in all but a small part of the regulated mesh zone.  To allow a fishery for silver hake to continue under the new regulations, a stipulation permitting a modified small mesh net was introduced, based on the proven success and acceptance of the Nordmore grate in the Northern U.S. shrimp fishery.  It called for the use of the grate with 40mm. spacing between the bars and the limited use of ground gear between the net and doors this combination held out some hope that a silver hake fishery could continue, little use of the new configuration is taking place. The difficulties encountered in correctly installing and using the grate are problematic.  It is more difficult to use for a strong swimming fin fish like silver hake, which actively seeks to escape from the net.  Also, the largest silver hake cannot be taken because the narrow (40mm. or about 1 5/8") openings in the grate exclude not only regulated species but larger silver hake from capture in the codend.   Goals of this project were to develop a net and grate separation system which together allow larger silver hake to be retained while maintaining a <5% by-catch level, and to encourage pre-spawning and less valuable small whiting minimal stress when escaping the net.  A 45mm grate opening was used and 15 fathoms of ground gear were added to the 15 fathom leg system.  Square mesh was placed in varying configurations in the body of the net and the codend to encourage easy escapement for juvenile fish.   Research results were presented to various audiences.  Videographic details of fish behavior were recorded.

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