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Euastacus australasiensis (Family Parastacidae)

Sydney Crayfish

Distribution:

Euastacus australasiensis was thought to have been widespread in the Sydney region before European settlement, collection records show that it remains in coastal bushland areas north and south of Sydney and in the Blue Mountains.

Features:

The Australian Crayfish varies in colour but is usually brown to black with spots or blotches of red, especially on the lower sides or claws. The males and females are similar. Their total body length (including the abdomen) is about 140mm, the carapace may be up to 70mm long. When they are startled they raise and outstretch their claws, aside from backing away, escape may be accelerated by flicking the tail several times.

Ecology/Way of Life:

The Australian Crayfish lives in small shallow streams with rock, gravel or sand bottoms and some logs or decomposing leaf litter present; the banks are often steep and shaded by overhanging vegetation. This crayfish also inhabits swamps adjacent to streams as well as high moist areas of heath on coastal peninsulas or headlands. These crayfish are most active at night and forage from dusk until after midnight. Details of the diet are unknown, but it is thought to include leaf litter and other plant material.

Their burrows vary in structure from short simple burrows in steep stream banks to long deep tunnels with elevated cone-like entrances in moist high heathlands. Like other members of this family, individuals of this species are thought to have small home ranges. Both sexes are mature when 60–80mm long and females breed once each year. Mating occurs in Autumn when water temperatures are falling. Between 45 and 160 small, oval–shaped eggs are attached to the swimmerets under the abdomen and are incubated for 4–5 months before hatching. After hatching the young remain attached to the female for about 4 weeks before being released in Spring to early Summer, when water temperatures exceed 22°C. There is no parental care and individuals apparently survive for a number of years.

Interaction with Humans/Threats:

The Australian crayfish is one of the most abundant and important macro-invertebrates in the small waterways and associated swamps of the Sydney region. Although the habitat modifications due to urban development have caused some fragmentation of populations, at present this crayfish is not considered to be threatened, but the survival of existing populations is dependent on conservation action, especially control of water quality and introduced pests as well as fire protection.

Other Comments:

Euastacus australasiensis was named by Milne Edwards in 1837.

Further Reading:

Merrick, J.R. 1998. Endemic crayfishes of the Sydney Region. Distribution, biology and management options. Graduate School of the Environment Research Report, No. 9812, pp. 1–118. Macquarie University, Sydney.

Acknowledgments:

Text and Distribution map by J.R. Merrick. Photograph by J. Cann.

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