A study of changes in groundfish trawl catching efficiency due to differences in operating width, and measures to reduce width variation

The influence of trawl width on the ability of a survey trawl to capture groundfish was tested by comparing catch rates between paired tows with and without a constraint line that reduced the operating width of the trawl. The vertical distribution of fish near and above the seafloor was recorded wit...

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Bibliographic Details
Published in:Fisheries research 1998-06, Vol.36 (2), p.139-147
Main Authors: Rose, Craig S, Nunnallee, Edmund P
Format: Article
Language:English
Subjects:
ANCHURA
Animal, plant and microbial ecology
Applied ecology
ATHERESTHES
Atheresthes stomias
Biological and medical sciences
CATCH COMPOSITION
Catchability
CHALUTAGE
COMPOSICION DE LA CAPTURA
COMPOSITION DE LA CAPTURE
Constraint
Exploitation and management of natural biological resources (hunting, fishing and exploited populations survey, etc.)
Fundamental and applied biological sciences. Psychology
HIPPOGLOSSOIDES
Hippoglossoides elassodon
LARGEUR
Marine
PESCA A LA RASTRA
Survey
THERAGRA CHALCOGRAMMA
Trawl
TRAWLING
WIDTH
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Summary:The influence of trawl width on the ability of a survey trawl to capture groundfish was tested by comparing catch rates between paired tows with and without a constraint line that reduced the operating width of the trawl. The vertical distribution of fish near and above the seafloor was recorded with an echo sounder to test for the incidence of fish diving into the path of the trawl during the tows. Arrowtooth flounder ( Atheresthes stomias), flathead sole ( Hippoglossoides elassodon) and walleye pollock ( Theragra chalcogramma) were captured at higher rates (fish per area swept) by a survey trawl fished in the restricted (narrow) configuration. The greatest difference occurred for pollock. The difference in catch rates was consistent across size groups within each species. Correlations detected between catch rates of pollock and echo-integration values for targets well above the trawl height indicated that some of these fish may have been diving from midwater into the path of the trawl. Differences between the correlation patterns with and without constraint lines indicate that the diving behavior may be affected by the presence of the line.
ISSN:0165-7836
1872-6763
DOI:10.1016/S0165-7836(98)00099-X