Ecology of the intertidal pulmonate limpet Siphonaria diemenensis Quoy et Gaimard. I. Population dynamics and availability of food

Seasonal variations in the size structure, patterns of growth and mortality of the intertidal pulmonate limpet Siphonaria diemenensis Quoy et Gaimard were examined in two zones on a rocky intertidal shore. Food supply in the upper zone (Zone 1) showed strong seasonal variation whereas in the lower zone (Zone 2) food supply was more constant. Limpets in Zone 2 were larger, grew faster, and had smaller annual adult mortality rates than those in Zone 1. In Zone 1, reduced growth and increased mortality were correlated with the seasonal reduction in food supply. Field experiments demonstrated that the availability of food, particularly in Zone 1, was a major determinant of growth rate. Starvation was a likely cause of the great seasonal mortality in Zone 1, and the growth of shell and tissue were variable characteristics in these limpets, changing quickly in response to changes in food supply.