REPRODUCTIVE-CYCLE OF CENTROSTEPHANUS-RODGERSII (ECHINOIDEA), WITH RECOMMENDATIONS FOR THE ESTABLISHMENT OF A SEA-URCHIN FISHERY IN NEW-SOUTH-WALES

The reproductive cycle of the sea urchin Centrostephanus rodgersii (Ag assiz) was investigated in two populations, at Clovelly and Little Bay , in Sydney, New South Wales, Australia. C. rodgersii were collected a t monthly intervals from February 1992 through January 1993. The repro ductive cycle was determined by histological examination of oogenesis and spermatogenesis, monthly measurements of gonad index (GI), and ind uction of spawning by KCl injection. C. rodgersii has an annual reprod uctive cycle that was highly synchronous in both populations. From Feb ruary to June, gametogenesis was accompanied by a decline in the amoun t of nutritive tissue in the gonads. The urchins were mature from June to September, with peak spawning between July and August, as indicate d by a significant drop in GI. The breeding season of C. rodgersii the refore coincides with the lowest sea temperatures and the shortest day s of the year. The gonads returned to the recovering condition within a month of spawning, with a substantial thickening of the nutritive la yer along the gonad wall, and the GI returned to near pre spawning lev els. As a result, the spent phase was rarely found in C. rodgersii. Wi th the exception of a significant decrease in the GI following spawnin g of urchins from the Clovelly population, the GI measurements did not show any distinct pattern through time. Specimens spawned in response to KCl injection from mid-May to early October, with the maximum resp onse in July. Although all individuals sampled were at a similar stage of maturity at any one time, inter-site differences were seen with al l of the methods used. Gonad indices from Little Bay were consistently higher and less variable than those from Clovelly for most of the yea r. The Little Bay population could also be induced to spawn for a long er period of time than could the Clovelly population. The breeding sea son of the Little Bay population appears to be longer than that of the Clovelly population. The relationship between size and sexual maturit y was also examined. All C. rodgersii with a test diameter of > 60 mm could be induced to spawn and produced viable gametes. C. rodgersii ha s been nominated for commercial exploitation in New South Wales, and t he results of this investigation are used to make recommendations on t he timing and size limits for a fishery utilising this species.