Abstract

Euastacus bispinosus Clark is the basis of a recreational fishery in south-western Victoria. It is most commonly reported from stream reaches with well vegetated catchments. Two populations in south-west Victoria were each studied for two years to provide information for management of the species. Crayfish were most active in winter, and large, egg-bearing females were numerically dominant in catches during the winter brooding season (May to October-November). During the summer nonbrooding season, catch rates were low, and juvenile males dominated catches. Population density at one site, estimated using a cumulative marking technique, was one crayfish (>85 mm occipital carapace length) for every 2-5 metres of bank. Most animals moved less than 75 m during the study period. Based upon these catch characteristics, and life history data published elsewhere, E. bispinosus does not appear to be suitable for exploitation, unlike many European and North American crayfish species. Many of the exploited northern hemisphere species have high rates of natural mortality associated with overwintering in a torpid state, or short life cycles with high mortality after one or two seasons of breeding. Exploitation of these species substitutes for natural mortality, and does not appear to have negative effects on population size if it occurs after the brooding season. Euastacus bispinosus, however, is long lived and reproduces annually for many years. The species has not evolved a life history strategy to cope with high mortality rates and even moderate fishing pressure may not be supported.

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