Reproduction of the turban shell Turbo torquatus Gmelin 1791 (Mollusca : Gastropoda), in New South Wales, Australia

Abstract

The Sydney turban shell Turbo torquatus is the focus of a small-scale commercial fishery in New South Wales. Effective management requires knowledge of the reproductive biology, yet this is lacking for NSW waters. The reproductive cycle was investigated at three localities on the southern New South Wales coast. Samples of T. torquatus were collected monthly at Wollongong, Ulladulla and Eden from February 1996 until August or December 1997. The reproductive cycle was investigated by three methods: monthly determination of a gonadosomatic index, estimation of oocyte size-frequency distributions and classification of female gonads into developmental stages following histological sectioning. Males and females within a population underwent synchronous gonad development and spawning. Spawning events were often protracted over a period of several months with females in various stages of gonadal development. Two spawning events occurred each year, with a spawning event in autumn–winter and another in spring–summer. These events were asynchronous among the three localities, and partial spawning appeared to be a common occurrence. Owing to variation in the timing of spawning between populations separated by a distance as small as 15 km, seasonal closures to protect spawning stocks are unlikely to be effective.