Species compositions of elasmobranchs caught by three different commercial fishing methods off southwestern Australia, and biological data for four abundant bycatch species

Jones, Ashlee A. and Hall, Norman G. and Potter, Ian C. (2010) Species compositions of elasmobranchs caught by three different commercial fishing methods off southwestern Australia, and biological data for four abundant bycatch species. Fishery Bulletin, 108(4), pp. 365-381.

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Abstract

Commercial catches taken in southwestern Australian waters by trawl fisheries targeting prawns and scallops and from gillnet and longline fisheries targeting sharks were sampled at different times of the year between 2002 and 2008. This sampling yielded 33 elasmobranch species representing 17 families. Multivariate statistics elucidated the ways in which the species compositions of elasmobranchs differed among fishing methods and provided benchmark data for detecting changes in the elasmobranch fauna in the future. Virtually all elasmobranchs caught by trawling, which consisted predominantly of rays, were discarded as bycatch, as were approximately a quarter of the elasmobranchs caught by both gillnetting and longlining. The maximum lengths and the lengths at maturity of four abundant bycatch species, Heterodontus portusjacksoni, Aptychotrema vincentiana, Squatina australis, and Myliobatis australis, were greater for females than males. The L50 determined for the males of these species at maturity by using full clasper calcification as the criterion of maturity did not differ significantly from the corresponding L50 derived by using gonadal data as the criterion for maturity. The proportions of the individuals of these species with lengths less than those at which 50% reach maturity were far greater in trawl samples than in gillnet and longline samples. This result was due to differences in gear selectivity and to trawling being undertaken in shallow inshore waters that act as nursery areas for these species. Sound quantitative data on the species compositions of elasmobranchs caught by commercial fisheries and the biological characteristics of the main elasmobranch bycatch species are crucial for developing strategies for conserving these important species and thus the marine ecosystems of which they are part.

Item Type: Article
Title: Species compositions of elasmobranchs caught by three different commercial fishing methods off southwestern Australia, and biological data for four abundant bycatch species
Personal Creator/Author:
CreatorsEmail
Jones, Ashlee A.
Hall, Norman G.
Potter, Ian C.
Refereed: Yes
Journal or Publication Title: Fishery Bulletin
Volume: 108
Number: 4
Page Range: pp. 365-381
Date: 2010
ISSN: 0090-0656
Issuing Agency: United States National Marine Fisheries Service
Subjects: Biology
Ecology
Fisheries
Item ID: 8734
Depositing User: Patti M. Marraro
Date Deposited: 07 Jun 2012 14:46
Last Modified: 07 Jun 2012 14:46
URI: http://aquaticcommons.org/id/eprint/8734

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