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Determination of the biological parameters for managing the fisheries for Mulloway and Silver Trevally in Western Australia

Farmer, B.M., French, D.J.W., Potter, I.C., Hesp, S.A. and Hall, N.G. (2005) Determination of the biological parameters for managing the fisheries for Mulloway and Silver Trevally in Western Australia. Fisheries Research and Development Corporation

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The biological data required by fisheries managers to develop plans for conserving fish stocks have been obtained for Mulloway and Silver Trevally in Western Australian waters. The first species is commercially and recreationally important and the second is caught in large numbers by recreational fishers. We have produced, for managers in the Department of Fisheries Western Australia, data on crucial aspects of the biology of Mulloway and Silver Trevally. These include data on habitats, spawning periods, size and age compositions, growth and reproductive biology in the northern and southern parts of the distribution of these two species on the west coast of Australia. Although all of the results are relevant to developing management plans for conserving the stocks of these two important species, the following are of particular relevance. The females and males of Mulloway typically reach first maturity at lengths of about 930 and 880 mm, respectively. These lengths, which are usually attained at 5 - 6 years in age, are far greater than the minimum legal length (MLL) of 500 mm for the retention of this species. In the case of Silver Trevally, the average length of females at first maturity is 60 mm greater than the current MLL of 250 mm and thus the females are exposed to one year of fishing mortality before they are able to spawn. Thus, managers will need to assess whether the current MLLs for the above two species, and particularly for Mulloway, are appropriate for ensuring that the stocks of these heavily-fished species are conserved. Management policies will also need to take into account the schooling behaviour of Mulloway at spawning as this results in this species becoming an easy target for fishers at a crucial stage in its life cycle.

Item Type: Report
Murdoch Affiliation(s): School of Biological Sciences and Biotechnology
Series Name: FRDC Project 2002/004
Publisher: Fisheries Research and Development Corporation
Notes: December 2005
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