Habitat use by the hymenosomatid crab Amarinus lacustris (Chilton) in two south-eastern Australian rivers
Kerrylyn Johnston A B and Belinda J. Robson AA School of Ecology & Environment, Deakin University, PO Box 423, Warrnambool, Vic. 3280, Australia.
B Corresponding author. Email: kerrylyn@deakin.edu.au
Marine and Freshwater Research 56(1) 37-44 https://doi.org/10.1071/MF04219
Submitted: 17 August 2004 Accepted: 20 December 2004 Published: 4 February 2005
Abstract
The hymenosomatid crab Amarinus lacustris is abundant in some south-eastern Australian rivers; however, little is known of its ecology. Patterns of habitat use by crabs in rivers may be affected by seasonal changes in river discharge. This study investigates population characteristics, timing of reproduction and patterns of habitat use by A. lacustris in five riffle and pool habitats from each of the Hopkins and Merri Rivers in south-west Victoria, Australia, sampled over a twelve-month period. Distribution of Amarinus lacustris was similar between the two rivers, but log-linear modelling showed that there was a strong association between crab sex, habitat occupied and time of year because female A. lacustris showed a shift from riffle to pool habitats during March and April, coinciding with the non-gravid period of the year. Male crabs also showed a change in relative occurrence, occurring most often in riffles during winter–spring (July–November) but being equally common in both habitats in summer–autumn (January–May). These patterns are probably the result of the reproductive cycle of A. lacustris, which appears to show both ontogenetic and sex-related changes in habitat use during its life cycle, taking advantage of seasonal fluctuations in flow regime that may assist egg/larval development and dispersal.
Extra keywords: Decapoda, false-spider crabs, freshwater crabs, Hymenosomatidae, log-linear modelling, pools, riffles.
Acknowledgments
We wish to thank the Glenelg–Hopkins Catchment Management Authority for providing supportive funding for this project. Thanks are also owed to Lynette Johnston, Gavin Johnston, Geoff Johnston, Andrew McIntyre, Kylie Bishop, Al Danger and Leigh Thwaites for their assistance in the field, and to Colin Magilton and David Mills for providing technical support throughout the project. Barbara Downes is thanked for discussions regarding the use of log-linear modelling.
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