Latitudinal variation in reproductive behavior in the pearl oyster, Pinctada albina sugillata

Increased interest in periculture in New South Wales (NSW), Australia, encouraged an assessment of the changes in the reproductive condition of pearl oyster, Pinctada albina sugillata. Over a 2-year period, macroscopic and histological observations were made of oysters collected monthly from Port Stephens. In contrast to more northerly populations, P. albina sugillata in NSW were found to have a truncated breeding season. Reproductive activity was greatest from late spring to early autumn with oysters in poor reproductive condition during winter. Peaks in reproductive indices occurred in October 1998, March 1999, January 2000 and April 2000. Spat collectors deployed at two sites in Port Stephens found spat fall to be restricted to the months of November-January, indicating that the autumnal peaks (March and April) in the reproductive activity did not result in subsequent recruitment. These results supported previous observations of latitudinal change in the reproductive behavior of pearl oysters in which populations at higher latitudes have truncated breeding seasons that tend to occur during the warmer months. Recruitment to spat collectors was low and variable, discouraging the collection of wild spat for culture, yet the spring increase in reproductive activity was coincident with the likely time for hatchery propagation. Infestations of shell-boring organisms were found among wild oysters although the degree of shell damage was almost invariably low. Most common were infestations of spionid polychaetes, present in 30% of the shells collected, with several larger oysters showing shell damage typical of boring sponges.