EFFECT OF THE LEEUWIN CURRENT ON THE RECRUITMENT OF FISH AND INVERTEBRATES ALONG THE WESTERN-AUSTRALIAN COAST

The relatively high catch of invertebrate species compared with finfis h off Western Australia is in sharp contrast to other regions of the w orld, where finfish production usually dominates. This low level of fi nfish production is primarily due to the Leeuwin Current, which consis ts of warm, low-nutrient waters flowing south along the edge of the co ntinental shelf of the Western Australian coast. In contrast, the othe r eastern boundary currents in the Southern Hemisphere (Humboldt and B enguela) are associated with upwelling of cool, nutrient-rich waters f lowing north and the high rates of primary production resulting in a l arge finfish production. The Leeuwin Current, being the dominant ocean ographic feature off Western Australia, has a major influence on the a bundance of many species. The larval phase is the stage mainly affecte d by the current, but not always with the same result. For example, th e strength of the Leeuwin Current has a significant positive influence during the larval stage of the western rock lobster (Panulirus cygnus ). However, the current has a negative influence during the larval lif e of the scallop, Amusium balloti, in Shark Bay. Similarly for the pel agic finfish species, the current has a negative effect on larval surv ival of pilchards (Sardinops sagax neopilchardus) but a positive impac t for whitebait (Hyperlophus vittatus). Possible mechanisms for the ef fect of the current include transportation of larvae and temperature e ffects on spawning success and on survival and growth of larvae.