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The characteristics of the fish and crab assemblages of the Leschenault Estuary. Inter-period comparisons and their management implications. South West Development Commission Report, December 2010

Veale, L., Coulson, P., Hoeksema, S., Tweedley, J., Hall, N. and Potter, I. (2010) The characteristics of the fish and crab assemblages of the Leschenault Estuary. Inter-period comparisons and their management implications. South West Development Commission Report, December 2010. Centre for Fish and Fisheries Research, Murdoch University

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Abstract

A total of 14,200 fishes was caught in the lower and middle regions of the Leschenault Estuary using a 21.5m seine net in each season between winter 2008 and autumn 2010. This total was only 3% less than the 14,601 fishes caught using the same seine net at the same sites twice seasonally in 1994, i.e. with the same amount of fishing effort. The numbers of species recorded in 2008-10 (36) and 1994 (33) were also similar. The above absence of a marked difference in the abundance of fish is consistent with the similarity in the mean densities of fishes per sample in the two periods. However, the mean number of species per sample and measures of diversity were greater in the current than earlier period.

The eight most abundant species in 2008-10 ranked among the 11 most abundant species in 1994. Furthermore, the five most abundant species in 1994, which collectively accounted for ~ 90% of the total number of fish caught in that period, ranked amongst the top six species in 2008-10, recognising, however, that they contributed less, i.e. ~ 69%, to the total number of fish in that later period. These five species were the Elongate Hardyhead Atherinosoma elongata, the Sandy Sprat Hyperlophus vittatus, the Yelloweye Mullet Aldrichetta forsteri, the Silverfish Leptatherina presbyteroides and the Southern Longfin Goby Favonigobius lateralis.

The far greater contributions of the most abundant species in 1994 than 2008-10 reflects the extreme dominance of the Southern Longfin Goby and Sandy Sprat in the earlier period. These two species thus contributed nearly 70% to the total number of fishes caught in the earlier period, compared with only 35% by the two most abundant species, i.e. Elongate Hardyhead and Sandy Sprat, in the later period. This helps account for the diversity of the fish fauna being less in the earlier period.

Publication Type: Report
Murdoch Affiliation: Centre for Fish and Fisheries Research
Publisher: Centre for Fish and Fisheries Research, Murdoch University
URI: http://researchrepository.murdoch.edu.au/id/eprint/9387
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