Spatial distribution and growth of Mellita Quinquiesperforata (Leske, 1778) on a sandy beach of southern Brazil

Resumo

The spatial distribution by size and its variations through an annual cycle, and the growth estimated by size-frequency analysis of Mellita quinquiesperforata are presented. Samples were taken at a subtidal exposed sandy beach located around the inlet of the Patos Lagoon, Rio Grande do Sul, Brazil, from 1986 to 1990. The distribution of the species showed that most of the adult population occupies a band immediately behind the surf-zone, with the greatest abundance at a distance of 0.5 nautical miles from shore, at 5 m depth; smaller individuals appear to be more abundant with increasing depth, probably in relation to diminished wave action. Greater density (of 50 individuals/m2) was found during the summer resulting from a characteristic gregarious behavior. The population exhibited variable annual recruitment with the presence of a dominant year class. Growth parameters estimated with different methods present small differences, varying from 63.3 to 72 mm for Loo, and from 0.33 to 0.278 for k, respectively. These parameters are smaller than those recorded for other Atlantic species of Mellita. This may be related to the preferred habitat of M. quinquiesperforata, in the proximity of breakers with heavy wave action, that requires more allocation of resources to maintenance and less to growth and reproduction.