THE LEEUWIN CURRENT NEAR ROTTNEST ISLAND, WESTERN-AUSTRALIA

Ship data and a satellite image in June 1987 showed the Leeuwin Curren t as a warm, low-salinity tropical stream travelling southward inshore of the 180-m isobath with near-surface speeds up to 0.9 m s(-1). Fart her offshore, where the waters became progressively more subtropical, the southward currents were also quite strong-0.75 m s(-1) above the c ontinental slope and over 0.4 m s(-1) out to 70 km beyond the shelf ed ge. Beyond this, a doming of 150 m in the temperature structure at sev eral hundred metres depth drove a cyclonic eddy that had its maximum s peed of similar to 0.5 m s(-1) in a ring at 200-400 m depth. The prese nce of the eddy was confirmed by the path of a drifter. Geostrophic cu rrents and currents measured directly with an Acoustic Doppler Current Profiler showed good agreement. The warm 'shoulder' of the Leeuwin Cu rrent between the 105-m and 135-m isobaths was a biological oasis char acterized by, inter alia, several fish schools at least 10 km long and 1 km wide and with vertical extents from 20 m to more than 100 m dept h.