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Size‐Dependent Selection at the Footgear of a Groundfish Survey Trawl
Author(s) -
Walsh Stephen J.
Publication year - 1992
Publication title -
north american journal of fisheries management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.587
H-Index - 72
eISSN - 1548-8675
pISSN - 0275-5947
DOI - 10.1577/1548-8675(1992)012<0625:sdsatf>2.3.co;2
Subject(s) - groundfish , fishery , pleuronectes , gadus , skate , escapement , electrofishing , bycatch , limanda , atlantic cod , rockfish , fishing , whiting , environmental science , oceanography , abundance (ecology) , fish <actinopterygii> , biology , flatfish , fisheries management , geology
Three trawl bags were attached underneath the footgear of a multispecies groundfish survey trawl to estimate escapement of Atlantic cod Gadus morhua , American plaice Hippoglossoides platessoides , yellowtail flounder Pleuronectes ferrugineus , and thorny skate Raja radiata . Data from 26 fishing hauls on the Grand Bank, off the coast of Newfoundland, were used in the study. Net efficiency of the survey trawl reached 50% for the two flounder species greater than 24 cm and for Atlantic cod exceeding 35 cm, but efficiency never exceeded 42% for any size of thorny skate, Catchability coefficients ranged from 0.24 to 0.44. Trawl vulnerability was size‐dependent for Atlantic cod, American plaice, and yellowtail flounder but not for thorny skate, Escapement of small fish underneath the footgear was affected by the towing speed and type of footgear. The highly variable abundance indices of prerecruit Atlantic cod, American plaice, and yellowtail flounder on the Grand Bank seen in bottom‐trawl surveys from year to year could be explained by size‐dependent selection at the footgear of the survey trawl.