Effect of the Leeuwin Current on the Recruitment of Fish and Invertebrates along the Western Australian Coast

Abstract

The relatively high catch of invertebrate species compared with finfish off Western Australia is in sharp contrast to other regions of the world, where finfish production usually dominates. This low level of finfish production is primarily due to the Leeuwin Current, which consists of warm, low-nutrient waters flowing south along the edge of the continental shelf of the Western Australian coast. In contrast, the other eastern boundary currents in the Southern Hemisphere (Humboldt and Benguela) are associated with upwelling of cool, nutrient-rich waters flowing north and the high rates of primary production resulting in a large finfish production. The Leeuwin Current, being the dominant oceanographic feature off Western Australia, has a major influence on the abundance of many species. The larval phase is the stage mainly affected by the current, but not always with the same result. For example, the 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 life of the scallop, Amusium balloti, in Shark Bay. Similarly for the pelagic finfish species, the current has a negative effect on larval survival of pilchards (Sardinops sagax neopilchardus) but a positive impact for whitebait (Hyperlophus vittatus). Possible mechanisms for the effect of the current include transportation of larvae and temperature effects on spawning success and on survival and growth of larvae.

Novel algal symbiont (Symbiodinium spp.) diversity in reef corals of Western Australia

“…We suggest that the warm-water Leeuwin Current, which influences the coastal waters of Western Australia (Cresswell & Golding 1980, Legeckis & Cresswell 1981, Maxwell & Cresswell 1981, Caputi et al 1996 from the surface to 150-300 m depth (Thompson 1987), may help to supply Western Australian reefs with symbionts that are commonly found in tropical waters fur- burn 1942, Markina 1976, Marsh 1976, Maxwell & Cresswell 1981, van der Kaars & De Deckker 2003. It has also been identified as contributing to regions of biotic diversity that exhibit characteristics of both tropical and temperate areas (Markina 1976, Maxwell & Cresswell 1981, Caputi et al 1996. Long-distance dispersal (e.g.…”

“…Corals living at latitudinal extremes are particularly interesting in this respect, because they experience intense seasonal environmental changes which may promote diverse symbiont communities. Western Australian reefs span transitional (tropical to temperate) reef coral environments, and are further extended into high latitudes by the warm-water Leeuwin Current (an offshoot of the Indonesian Throughflow), allowing coral colonies to survive in areas where low temperature might otherwise be prohibitive (Cresswell 1991, Caputi et al 1996, Wijffels et al 1996. Scleractinian coral generic and species richness decreases with latitude from 57 genera (216 species) at Dampier, to 4 genera (7 species) at Dunsborough (Veron & Marsh 1988, our Table 1).…”

The Hillarys Transect (1): Seasonal and cross-shelf variability of physical and chemical water properties off Perth, Western Australia, 1996–98

“…Instead of a cool northwards boundary current (as found off the west coasts of southern Africa and South America), the dominant current off Western Australia is the 60 warm south-flowing Leeuwin Current (Godfrey and Ridgway, 1985). The lack of large-scale upwelling (which occurs in the Benguela and Humboldt Current regions) results in a generally 62 nutrient-and chlorophyll-poor ocean environment (Rochford, 1980;Pearce et al, 2000;Lourey et al, 2006), with the commercial fisheries being dominated by benthic invertebrate species 64 rather than pelagic fish (Lenanton et al, 1991;Caputi et al, 1996). The major sources of nutrients along the Western Australian continental shelf are river run-off and local inshore 66 recycling, with only a small contribution from sporadic localised upwelling (Gersbach et al, 1999;Hanson 2005a).…”

Flux of larval fish around Cape Hatteras

“…However, the wide range in monthly average water mass transport (up to eight times higher as suggested in other years by other workers), coupled with the effect on larval fish flux demonstrated here, implies that transport can strongly influence variability in recruitment at Cape Hatteras. The effect of similar conditions has, in fact, been demonstrated to affect large-scale recruitment patterns at similar points where boundary currents converge (see Cowen 1985;Caputi et al 1996). The distribution of fish larvae with depth is known to affect retention and export, and behavior affecting distribution is probably selected for on the basis of mechanisms common over a species range (Norcross and Shaw 1984;Boehlert and Mundy 1988;Govoni and Pietrafesa 1994).…”