Estudo da estrutura populacional do marisco Anomalocardia brasiliana (Gmelin, 1791) na praia de Mangue Seco, litoral norte de Pernambuco – Brasil

Abstract

This study aimed to analyze the spatial and temporal distribution of the clam Anomalocardia brasiliana and evaluate the stock recovery of this species in relation to the clam number and size after extraction in summer and winter in Mangue Seco, Pernambuco. In the first study, the beach (1800 m) was divided into three sections (S): S1 0 to 600m, S2 600 and 1200m and S3 1200 to 1800m. During this research a total of 1,016 specimens were collected in January (summer) and August (winter) of 2009, corresponding to 636 clams collected in the summer and 380 in the winter. The maximum density recorded in the summer period were 414.91 ± 82.48 ind.m-² at S3 and 323.49 ± 90.11 ind.m-² at S1, both were significantly different from S2 (156.12 ± 28.72 ind.m-²). In winter, the lowest densities were observed with 102.67 ± 5.07 ind.m-² and 122.37 ± 36.86 ind m-² for S1 and S2, respectively, both significantly different from S3 (296.76 ± 45.20 ind.m-²). The second study evaluated three treatments corresponding to an area of 18.75 m² each, where: the clams were removed manually by the fishers, collected using a fishing gear, and where there was no harvesting of clam. The sampling of the clams in these treatments was conducted in three moments: before extraction by fishers, after an hour and after 24 hours. Clams showed a smaller size (15.46 ± 0.86 mm) after manual collecting, but no significant difference in the size of the animals was found after the collection with the fishing gear (18.16 ± 0.92 mm). The number of the animals collected with size larger than 20 mm was greater than 80% in the winter and lower than 20% in the summer, without significant differences between the collection type tested for both seasons. The A. brasiliana showed a characteristic spatial distribution, with a greater abundance of juveniles during the summer while the adults were more abundant during the winter. The collection type and the extraction period did not influence the clam amount, as the stock of A. brasiliana in Mangue Seco is still quite dense and probably has the capacity to reconstitute itself after a period of 24 hours without clam extraction. The winter and summer seasons have a great influence on the abundance of A. brasiliana, with the largest number of animals within the recommended fishing size (> 20 mm) during the winter.