DISTRIBUTION AND POPULATION-DYNAMICS OF 3 POPULATIONS OF SIPHONARIA ON ROCKY INTERTIDAL SHORES IN HONG-KONG

The pulmonate limpets Siphonaria japonica and Siphonaria sirius occur over a wide range of local habitat types in terms of exposure to wave action and salinity. This is a study of these two species on three different shore types in Hong Kong, ranging from an extremely exposed, high salinity (32-35 parts per thousand) shore at Cape d'Aguilar to a sheltered, low salinity (16-33 parts per thousand) shore at Tai Lam Chung. Both species are restricted to the low shore, year round. S. japonica is a winter breeder and recruitment occurred between October and January. The recruitment of S. sirius could not be recognised from the size-frequency histograms. The algal standing crop at Tai Lam Chung was higher than at Wu Kwai Sha during the winter period, i.e., be tween October and April. Seasonal fluctuations in growth rate were recorded for both Siphonaria species with the time of fastest growth occurring in winter. S. japonica grew faster at Tai Lam Chung than at Wu Kwai Sha. Food availability is thought to he an important factor affecting growth.