The use of catch predictions in the stock assessment and management of invertebrate fisheries of Western Australia

The Leeuwin Current, which brings warm, nutrient-poor waters southward on the lower west coast of Australia, provides conditions supportive of invertebrate fisheries rather than finfish.  A significant factor in the stock assessment and management of these fisheries has been the development of reliable catch prediction techniques.  These techniques include (a) abundance of puerulus (post larval stage) used in prediction of rock lobster catches 3-4 years ahead; (b) abundance of 0+ and 1+ piggyback spat of pearl oysters measured on commercial shell that predict catches 3-5 years ahead; (c) dive survey of 0+ and 1+ Roe’s abalone that predict recruit densities 4 years ahead; (d) trawl survey of prawn and scallop abundance that predicts catches 1-4 months ahead; and (e) trawl survey of 0+ crab abundance that predict catch six months ahead.  These predictions can be used in the stock assessments by providing reliable recruitment indices for future abundances.  They are used in management decision rules to ensure that fishing effort or catch quotas are set so that adequate breeding stocks are maintained.  This enables pro-active management of stocks based on predicted abundance which avoids the pitfall of heavy fishing on poor recruit classes that can lead to recruitment overfishing.