Diel periodicity of Metanephrops australiensis and other deep-water crustaceans of northwest Australia

The diel patterns in catch rate and, by inference, activity of eight deep-water crustacean species have been assessed by repeated trawling at a location with a depth of 430 m on the continental slope of northwest Australia. The patterns of catch rate identified show that, despite the depth, one highly valued commercial species, Metanephrops australiensis, had peaks of catchability near dusk and dawn. In general, male M. australiensis of all sizes displayed similar diel patterns in catch rate, while the females were more variable. Four species, including Metanephrops andamanicus, showed no detectable diel changes in catch rate. Two caridean shrimps and a penaeid prawn were caught in greater numbers during daylight hours, which suggests a substantial nocturnal vertical migration.