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Changes in catch rates and length and age at maturity, but not growth, of an estuarine plotosid (cnidoglanis macrocephalus) after heavy fishing

Chuwen, Benjamin M., Potter, Ian C., Hall, Norman G., Hoeksema, Steeg D. and Laurenson, Laurie J. B. 2011, Changes in catch rates and length and age at maturity, but not growth, of an estuarine plotosid (cnidoglanis macrocephalus) after heavy fishing, Fishery bulletin, vol. 109, no. 3, pp. 247-260.

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Title Changes in catch rates and length and age at maturity, but not growth, of an estuarine plotosid (cnidoglanis macrocephalus) after heavy fishing
Author(s) Chuwen, Benjamin M.
Potter, Ian C.
Hall, Norman G.
Hoeksema, Steeg D.
Laurenson, Laurie J. B.
Journal name Fishery bulletin
Volume number 109
Issue number 3
Start page 247
End page 260
Total pages 14
Publisher National Marine Fisheries Service
Place of publication Seattle, Wash.
Publication date 2011
ISSN 0090-0656
1937-4518
Summary The hypothesis that heavy fishing pressure has led to changes in the biological characteristics of the estuary cobbler (Cnidoglanis macrocephalus) was tested in a large seasonally open estuary in southwestern Australia, where this species completes its life cycle and is the most valuable commercial fish species. Comparisons were made between seasonal data collected for this plotosid (eeltail catfish) in Wilson Inlet during 2005-08 and those recorded with the same fishery-independent sampling regime during 1987-89. These comparisons show that the proportions of larger and older individuals and the catch rates in the more recent period were far lower, i.e., they constituted reductions of 40% for fish ≥430 mm total length, 62% for fish ≥4 years of age, and 80% for catch rate. In addition, total mortality and fishing-induced mortality estimates increased by factors of ~2 and 2.5, respectively. The indications that the abundance and proportion of older C. macrocephalus declined between the two periods are consistent with the perception of long-term commercial fishermen and their shift toward using a smaller maximum gill net mesh to target this species. The sustained heavy fishing pressure on C. macrocephalus between 1987-89 and 2005-08 was accompanied by a marked reduction in length and age at maturity of this species. The shift in probabilistic maturation reaction norms toward smaller fish in 2005-08 and the lack of a conspicuous change in growth between the two periods indicate that the maturity changes were related to fishery-induced evolution rather than to compensatory responses to reduced fish densities.
Language eng
Field of Research 070499 Fisheries Sciences not elsewhere classified
Socio Economic Objective 830199 Fisheries - Aquaculture not elsewhere classified
HERDC Research category C1 Refereed article in a scholarly journal
Copyright notice ©2011, National Marine Fisheries Service
Persistent URL http://hdl.handle.net/10536/DRO/DU:30040430

Document type: Journal Article
Collections: School of Life and Environmental Sciences
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Every reasonable effort has been made to ensure that permission has been obtained for items included in DRO. If you believe that your rights have been infringed by this repository, please contact drosupport@deakin.edu.au.