A great flow of tropical water pushes southwards alongA great the flow edge ofof Westerntropical Australia’s water pushes continental southwards shelf,along sending the edge giant of Western swirling Australia’s eddies into continental coastal watersshelf, and sending out to giantsea. This swirling is the eddies Leeuwin into Current coastal waters– the longestand out boundary to sea. This current is the inLeeuwin the world, Current and– an the enormous longest boundary influence current on the inlife the cycle world, and Wyndam anddistribution an enormous of many influence WA marine on the species.life cycle and Wyndam distribution of many WA marine species.

Photo: Shannon Conway

Carried within the warmer waters of the Leeuwin Current are the Photo: Shannon Conway Rowley eggs, larvae and juveniles of various tropical fishes, invertebrates Shoals andCarried corals. within the warmer waters of the Leeuwin Current are the Rowley Derby At Ningalooeggs, larvae Reef and in autumnjuveniles each of various year there tropical is a fishes, mass spawninginvertebrates of Shoals corals.and Shortlycorals. after the spawning some coral larvae settle on the Derby reef,At while Ningaloo other Reef larvae in autumnare swept each up yearby a therestrengthening is a mass Leeuwin spawning of Currentcorals. and Shortly transported after the down spawning the coast. some coral larvae settle on the Thisreef, explains while theother existence larvae are of theswept coral up reefby a systems strengthening at the Leeuwin Broome AbrolhosCurrent Islands and transported and further down south the around coast. Rottnest Island, as well This explains the existence of the coral reef systems at the Broome as the presence of tropical marine life along the temperate south Some corals release eggs and larvae into the Abrolhos Islands and further south around Rottnest Island, as well coast of WA. water in a coordinated event, called a mass as the presence of tropical marine life along the temperate south spawning.Some corals At Ningaloo release Reef eggs this and occurs larvae in into the coast of WA. autumnwater each in a coordinatedyear, influenced event, by called the full a massmoon. Thespawning. Leeuwin CurrentAt Ningaloo begins Reef to strengthenthis occurs atin thisautumn time – andeach any year, eggs influenced or larvae bythat the have full notmoon. The Leeuwin Current begins to strengthen at 80 Mile settled on the reef are likely to be swept up by Beach thethis current time and – and transported any eggs ordown larvae the thatcoast. have not 80 Mile settled on the reef are likely to be swept up by the current and transported down the coast. Beach The mass spawning of corals at Ningaloo Reef sparks a feedingThe mass frenzy spawning that includes of corals at Ningaloo Reef sparks a Dampier the massive whale shark – the Archipelago Port Hedland largestfeeding fish frenzy in the that world. includes More Dampier of thesethe massive filter feeding whale sharksharks – the Archipelago Port Hedland arelargest seen in fish years in whenthe world. the More Leeuwinof these Current filter is feeding stronger. sharks Karratha are seen in years when the Leeuwin Current is stronger. Karratha Photo: Henrique Kwong The Leeuwin Current is a warm, low nutrient ocean current that originates near North West Cape and flows southwards North West Photo: Henrique Kwong downThe the Leeuwin WA coast Current before is aturning warm, eastlow nutrientat Cape oceanLeeuwin current and Photo: Matthew Pember Cape continuingthat originates across thenear Great North Australian West Cape Bight, and evenflows as southwards North West far downas Tasmania. the WA coast before turning east at Cape Leeuwin and Photo: Matthew Pember Cape Thesecontinuing clear, warmer, across nutrient-poorthe Great Australian waters support Bight, even a high as varietyfar as of Tasmania.marine species (biodiversity) but very low amounts Ningaloo Exmouth (biomass)These clear, of finfish. warmer, nutrient-poor waters support a high Thevariety current of plays marine an importantspecies (biodiversity) role in the spawning but very lowand amounts Reef Exmouth (biomass) of finfish. The Leeuwin Current can Ningaloo distribution of coral as well as that of other tropical organisms, sweep turtle hatchlings Reef in theThe life current cycle playsof western an important rock lobster role inand the southern spawning bluefin and hundredsThe Leeuwin of kilometres Current awaycan tuna,distribution and in the of distribution coral as well of asseagrass that of andother algae, tropical sea organisms, birds, fromsweep their turtlenorthern hatchlings nesting andin coastal the life scallop cycle of and western finfish rock stocks. lobster and southern bluefin sites.hundreds Combined of kilometres with winter away tuna, and in the distribution of seagrass and algae, sea birds, storms,from manytheir northernhatchlings nesting and coastal scallop and finfish stocks. becomesites. strandedCombined on with beaches winter muchstorms, further many south. hatchlings become stranded on beaches much further south. Western rock lobster larvae drift in the open ocean for nearly a year before winds and currents carry them back to the continental shelf Photo: Shannon Conway andWestern coastal rockareas. lobster A strong larvae Leeuwin drift inCurrent the open normally ocean results for nearly in higher a year numbersbefore of winds young and lobsters, currents called carry puerulus, them back settling to the on continental inshore reefs. shelf Photo: Shannon Conway Carnarvon and coastal areas. A strong Leeuwin Current normally results in higher Carnarvon numbers of young lobsters, called puerulus, settling on inshore reefs. The Leeuwin Current transports warmer waters south but does Photo: M. Jenner, Centre for Whale Research Denham not flow at the same strength during the year. Stronger in the colderThe halfLeeuwin of the Current year (April transports to September), warmer watersthe warm south water but does Photo: M. Jenner, Centre for Whale Research Shark Bay Photo: Barb Malc Denham temperaturesnot flow at maintained the same strengthby the current during throughoutthe year. Stronger winter in the Shark Bay Photo: Barb Malc enablecolder tropical half of species the year to (Aprilthrive to much September), farther south the warm of their water normaltemperatures range – and maintained further south by the than current elsewhere throughout in the winter world. As enablethey are tropical unlikely species to breed to thrivein cooler much temperate farther south waters, of theirthe continuednormal presencerange – and of thesefurther tropical south than species elsewhere in the south-westin the world. of WAAs theydepends are unlikely on the arrivalto breed of ineggs, cooler larvae temperate or juveniles waters, from the Ningaloocontinued Reef presence and the Abrolhosof these tropicalIslands, speciescarried insouth the bysouth-west the Leeuwinof WA Current. depends on the arrival of eggs, larvae or juveniles from Ningaloo Reef and the Abrolhos Islands, carried south by the Leeuwin Current.

Abrolhos Various current systems (including the Leeuwin Current) Islands Abrolhos interact around the deep, steep-sided Perth Canyon off theVarious west of current Rottnest systems Island (includingand can cause the Leeuwin upwellings Current) of Islands nutrient-richinteract around water containingthe deep, steep-sided schools of krill.Perth A Canyon preferred off Geraldton foodthe source west offor Rottnest pygmy blue Island whales, and can they cause gather upwellings here to feed, of The Leeuwin Current acts as a ‘highway’ for Humpback Whales mostlynutrient-rich between water the months containing of December schools of and krill. May. A preferred Geraldton migrating from northern waters, where they mate and give birth, to food source for pygmy blue whales, they gather here to feed, theirThe southern Leeuwin feeding Current grounds acts as ina Antarctica.‘highway’ for Mothers Humpback and calvesWhales stop mostly between the months of December and May. to restmigrating at certain from areas northern of the waters, coast whereduring theythe longmate trek. and give birth, to their southern feeding grounds in Antarctica. Mothers and calves stop to rest at certain areas of the coast during the long trek.

Jurien Samson fish migrate from southern Australia during the summer to form spawning Jurien aggregationsSamson fish in themigrate waters from west southern of Rottnest Australia Island.during They the finish summer spawning to form when spawning the Leeuwin Currentaggregations begins to in strengthen the waters – west transporting of Rottnest Rottnest eggsIsland. and larvae,They finish and some spawning exhausted when theadults, Leeuwin IslandRottnest backCurrent to southern begins waters. to strengthen – transporting eggs and larvae, and some exhausted adults, Photo: Russell Cocker Island back to southern waters. Perth Photo: Russell Cocker Photo: Tim Leary Perth Mandurah Photo: Tim Leary Pilchards prefer to stay close to home, so Mandurah a weaker Leeuwin Current ensures their eggsPilchards and larvae prefer are to not stay transported close to home, too so Bunbury far aaway weaker from Leeuwin where theyCurrent were ensures spawned. their Esperance eggs and larvae are not transported too Cape Bunbury far away from where they were spawned. Esperance Naturaliste Cape Busselton Recherche Naturaliste Archipelago Busselton Recherche Margaret River Archipelago Margaret River Cape Albany Leeuwin NT Cape Albany RE T Leeuwin R N During the summer and autumn, big schools of salmon migrate west along CU E LE N R the southern coast of Australia to spawn in waters off the south-west corner EUWI UR of WA.During The the Leeuwin summer Current and autumn, carries thebig larvaeschools eastwards, of salmon where migrate they west settle along L C in nurserythe southern areas coastalong ofsouthern Australia WA to andspawn the incoast waters of Southoff the Australia. south-west corner EEUWIN of WA. The Leeuwin Current carries the larvae eastwards, where they settle in nursery areas along southern WA and the coast of South Australia. Between September and March, southern bluefin tuna migrate to their single known spawning ground in tropical Indian Ocean waters, between JavaBetween and northern September Western and Australia. March, southern As they bluefingrow, the tuna young migrate tuna toride their the strengtheningsingle known Leeuwin spawning Current ground southwards in tropical down Indian the Ocean WA coast waters, to thebetween Great AustralianJava and Bight northern and beyond. Western Australia. As they grow, the young tuna ride the strengthening Leeuwin Current southwards down the WA coast to the Great Australian Bight and beyond.

By the time it reaches Cape Leeuwin, the Leeuwin Current has lost several degrees in heat.By Onlythe time the toughestit reaches tropical Cape Leeuwin,eggs, larvae the An abnormally strong Leeuwin Current in andLeeuwin juveniles Current have survived has lost theseveral journey degrees this in 1999 and 2000 swept mud crab larvae An abnormally strong Leeuwin Current in far heat.– leaving Only the the waters toughest of thetropical south eggs, coast larvae 1,000 kilometres southwards into south-west 1999 and 2000 swept mud crab larvae mainlyand tojuveniles temperate have organisms. survived the journey this estuaries. Normally only found north of Shark Bay,1,000 the crabs kilometres were able southwards to grow into adultssouth-west Here,far the– leaving influence the watersof the Leeuwinof the south Current coast mainly to temperate organisms. butestuaries. the environmental Normally conditions,only found northparticularly of Shark is felt in other ways – the warmer waters Bay, the crabs were able to grow into adults Here, the influence of the Leeuwin Current Photo: Henrique Kwong water temperature, did not let them reproduce. are likely to act as a spawning trigger for but the environmental conditions, particularly temperateis felt in marineother ways species, – the carrying warmer their waters Photo: Henrique Kwong water temperature, did not let them reproduce. Copyright © 2011 DepartmentCopyright of Fisheries eggsare and likely larvae to act south as a and spawning east into trigger coastal for nurserytemperate areas. marine species, carrying their Australian herring also migrate from the southern coast of Australia to Copyright © 2011 DepartmentCopyright of Fisheries eggs and larvae south and east into coastal the south-west corner of WA to spawn. Depending on the strength of nursery areas. theAustralian current, eggs herring and alsolarvae migrate may be from carried the southernonly as far coast as the of Australiasouthern to Westernthe south-west Australia cornernursery of areas WA to or spawn. in stronger Depending years much on the further strength east of to Souththe current, Australia eggs and and Victoria. larvae may be carried only as far as the southern Photo: Clay Bryce Photo: OCEANA, Keith Ellenbogen

NMDC-024_01 MAR11 Western Australia nursery areas or in stronger years much further east to South Australia and Victoria. Photo: Clay Bryce Photo: OCEANA, Keith Ellenbogen NMDC-024_01 MAR11

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