Catchability of pelagic trawls for sampling deep-living nekton in the mid-North Atlantic

Heino M, Porteiro FM, Sutton TT, Falkenhaug T, Godoe OR, & Piatkowski U (2011). Catchability of pelagic trawls for sampling deep-living nekton in the mid-North Atlantic. ICES Journal of Marine Science 68 (2): 377-389. DOI:10.1093/icesjms/fsq089.

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Abstract

Material collected in summer 2004 from the Mid-Atlantic Ridge between Iceland and the Azores with three pelagic trawls was used to estimate relative catchabilities of common fish, cephalopod, decapod, and jellyfish species. Catchability is defined as the ratio of numbers caught between two trawls, standardized for towed distance. Taxon-specific catchability coefficients were estimated for two large pelagic trawls with graded meshes, using a smaller pelagic trawl with a uniform mesh size as the reference trawl. Two of the trawls were equipped with multiple opening-closing codends that allowed sampling of different depth layers. Generalized linear and mixed models suggest that most of the taxa have catchabilities much lower than expected from the area of opening alone, indicating that only a few species are herded by the large mesh at the mouth of larger trawls. Catchability coefficients across taxa show a very large spread, indicating that the sampled volume for the larger trawls with graded meshes was highly taxon-specific. Part of this variability can be explained by body size and taxonomic group, the latter probably reflecting differences in body form and behaviour. The catchability estimates presented here form the basis for combining data for quantitative analyses of community structure.

Item Type: Article
Uncontrolled Keywords: Catchability; Gear comparison; Mid-Atlantic Ridge; Nekton; Pelagic ecosystem; Sampling
Research Programs: Evolution and Ecology (EEP)
Bibliographic Reference: ICES Journal of Marine Science; 68(2):377-389 (January 2011)
Depositing User: IIASA Import
Date Deposited: 15 Jan 2016 08:45
Last Modified: 23 Feb 2016 12:10
URI: http://pure.iiasa.ac.at/9625

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