Biology of the common cockle Cerastoderma edule (Linnaeus, 1758) in Ria de Aveiro (NW Portugal): Implications for fisheries management

This study reports the reproductive cycle, condition index, size at first maturity, growth and the morphometric relationships of the common cockle Cerastoderma edule in Ria de Aveiro (NW Portugal), fundamental knowledge in fisheries management planning and ecosystem conservation. The reproductive cycle was monitored for a period of two years, from January 2013 to December 2014. Spawning extended from June to October, with a peak in the summer months (July to September). The condition index showed a seasonal pattern which appear related to food availability and gametogenic cycle. Sexual maturity was attained at a shell length of 18.6 mm during the first year of life, which stands below the minimum landing size currently in force (25 mm). The von Bertalanffy growth equation was based on size-at-age data obtained from the microscopic analysis of growth rings in sectioned shells: Lt = 40.7[1-e -0.74(t-0.30)]. The morphometric relationships between shell dimensions (length, height and width) were studied in order to understand the effects of ontogenetic changes in cockles` shell morphology, an information that is useful to improve the selectivity of the fishing gears and the size-sorting devices. Some management strategies for the Ria de Aveiro cockle fishery were proposed.