Life-history features of the marine intertidal limpet Notoacmea scutum (Gastropoda) in central California

Growth of individually marked specimens of Notoacmea scutum (Rathke) was followed for 15 months (April, 1978 to June, 1979) at a field site in central California, USA. Growth rates were highly seasonal, being highest from late spring through early summer and lowest during winter. Growth rate also varied significantly with intertidal height: limpets lower in the intertidal zone grew faster. Both relationships may have been related to the relative abundance of food or to the amount of time available for foraging. Recently settled limpets, which were present throughout the year, grew to approximately 17 mm in length by the end of their first year; by then, they had also reached the size at which mature gonads were consistently found (16 mm). Limpets were almost 26 mm long by the end of the second year. Substantial mortality occurred throughout the year, but it was particularly severe during winter, when a large portion of the reproductive population was lost. This pronounced winter mortality was probably not caused by invertebrate predators such as seastars. Most limpets at the study site were less than 2 yr old.