Natural mortality of the cockle Cerastoderma edule (L.) from the Ria of Arousa (NW Spain) intertidal zone

The cockle Cerastoderma edule (L.) settles preferably in intertidal estuarine zones, buried under the uppermost centimetres of the sediment. Owing to this specific environment, the density of its populations is affected not only by biotic interactions, but also by meteorological phenomena, especially during low tide. A study was conducted over the course of seven years on the population dynamics and fishery of the cockle in two intertidal beds of the Ria of Arousa (NW Spain). The relationship between mortality and the population total density, precipitation and atmospheric temperature was analyzed during this period. The multiple regression model that includes the four variables under study provides a satisfactory explanation for the mortalities observed during the periods being compared. This model allows us to estimate the natural mortality by using variables that are relatively easy to obtain. It also proved to be a useful computational tool for readjusting the estimations of stock sizes in light of the meteorological conditions recorded.