Aspects of the Biology and Ecology of the Australian Freshwater Crayfish, Euastacus urospinosus (Decapoda: Parastacidae) Adrian Borsboom (Communicated by J.R. Merrick) Resource Sciences Centre, Queensland Department of Natural Resources, PO Box 631, Indooroopilly, Qld 4068 Borsboom, A. (1998). Aspects of the biology and ecology of the Australian freshwater cray-fish, Euastacus urospinosus (Decapoda: Parastacidae) Proceedings of the Linnean Society of New South Wales 119, 87-100. The range of the upland freshwater crayfish, Euastacus urospinosus, has been extend-ed to the Conondale Ranges (southeastern Queensland) where it occurs in creeks as well as bank burrows in rainforest at 450-550 m altitude. During sampling and trapping from 1982-1994 a total of 685 individuals were examined and aspects of reproduction, population structure, growth and habitat usage investigated. Breeding females range from 33.8-51.8 mm ocular carapace length (OCL), appear to breed annually, carry a mean of 51 (3—1 19) eggs and average 31 (3-93) young. Mating appar-ently commences in April with males moving considerable distances (>20 m) to burrows housing mature females to pair with them. Eggs are laid about May or June, incubated for four to five months, hatch in late October or November and young released in December in the creeks. Adults only live in bank burrows and immature individuals occur predominantly in the creek. The mean OCL for crayfish in the creeks is 11.2 mm (n = 492) and 30.3 mm (n = 162) in bank burrows. The smallest free-living individual had an OCL of 5.5 mm and the largest, a male, measured 54.1 mm OCL and weighed 84.5 grams. It is estimated that females take approximately six years to reach breeding size. A simple trapping method using black plastic tubing inserted at entrances, enabled regular capture of crays in burrows. The resulting mark-recapture program has shown that burrows are normally only occupied by one individual, except during mating in April; howev-er, trapping success is correlated with water temperature, with least success in winter. OCL has also been demonstrated to increase with burrow entrance diameter. Manuscript received 14 October 1997, accepted for publication 15 January 1998. KEYWORDS: breeding seasonality, burrows, Euastacus urospinosus, growth, maturation, population structure, reproduction, trapping . INTRODUCTION There has been no detailed account of any aspect of the biology and ecology of the Australian crayfish Euastacus urospinosus since its description by Riek (1956), and, prior to these studies, no mature females had been collected (Morgan 1988, 1991). Morgan (1988) provided a comprehensive morphological description of the species, and the maxi-mum ocular carapace length (OCL) of specimens examined was 36.7 mm. Morgan (1988) reported that E. urospinosus was restricted to tributaries of Obi Obi Creek in the Mary River Drainage Basin between Maleny and Mapleton in south-eastern Queensland, where it was found in sub-tropical rainforest above an altitude of 240 m; however, Morgan (1989) believed that the distribution of E. urospinosus might also extend to the Conondale Ranges. The studies reported here originated as part of a broader research program on the impacts of forestry on water quality and aquatic faunas. The area under investigation was state forest until incorporated into the Conondale National Park in 1995. Gold prospect-ing and mining had occurred along the creeks and selective logging has taken place in Proc. Linn. Soc. n.s.w., 119. 1998
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