Publication Date

5-2000

Series Number

121

Publisher

Fisheries Western Australia

City

Perth

ISBN

0 7309 8438 9

ISSN

1035 - 4549

Abstract

This report summarises the existing studies which have provided information on the biology, population characteristics and exploitation of the blue swimmer crab, Portunus pelagicus, in Western Australia. Gaps in the existing knowledge are also highlighted to assist in targeting new research initiatives. Portunus pelagicus matures at about one year and in temperate regions females mate only once a year. This is because mature crabs moult only once a year. It appears from studies to date that Western Australian crabs are one genetic population. This is being further investigated. Migration of the blue swimmer crab occurs between estuaries and the ocean in south-western Western Australia. In general, female crabs (which have settled into estuaries/nurseries during the late summer/autumn period the year before) move from estuaries to oceanic waters to spawn in summer. First-stage zoeae feed on the surface in the morning and this behaviour facilitates offshore movement with prevailing easterly winds in the mornings. Later zoeal stages feed on the surface in the afternoon and evening. This allows them to be transported back inshore with south-westerly sea breezes. The females move back into the estuaries for a time after spawning and may again move out during the winter due to reduced salinities in the estuaries. Male crabs which have settled (from summer spawning in the ocean) in estuaries feed and grow during late summer and autumn and move out of the estuaries when salinities decline. Males do not appear to return to the estuary.

The biological knowledge to date has been generally limited to small regions of the coastline, particularly estuaries, and may not be representative of all regions now exploited or under consideration for future exploitation. Additional information is required on a broader spatial scale incorporating seasonal variation in size, distribution, abundance and sex ratios.

In Western Australia, 150 licence holders participate in fishing for the blue swimmer crab. The commercial catches of blue swimmer crabs have risen from around 200 tonnes in 1987/88 to 740 tonnes, valued at around $2.2 million, in 1997/98. The recreational sector contributes to a significant level of catch of crabs in some regions of Western Australia including the Leschenault and Peel-Harvey estuaries and Cockburn Sound.

Research programs on crab biology, habitat requirements, movement and growth, stock structure, fishery dynamics and recreational catch and effort are under way in order to address the paucity of biological knowledge and detailed fisheries information (commercial and recreational) on the species in Western Australia.

Number of Pages

22

Keywords

Department of Primary Industries and Regional Development, Portunus pelagicus Linnaeus, stock assessment, fisheries management

Disciplines

Aquaculture and Fisheries | Biology | Marine Biology | Natural Resources Management and Policy

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