Spatial and temporal distribution of the shellfish Anomalocardia brasiliana (Gmelin, 1791) on Mangue Seco beach, Pernambuco, Brazil

Document Type: Primary Research paper

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Abstract

This study aims to analyze the spatial and temporal distribution of the mollusc, Anomalocardia brasiliana along the Mangue Seco beach (Igarassu, PE, Brazil). The 1,800 meters beach line was divided into three sections (S) of 600 meters each; S1: 0 to 600, S2: 600 to 1200m and S3: 1200 to 1800m. Totally, 540 samples were taken at different levels, sections and during different seasons. A total of 1,016 specimen were collected during the two periods; January (summer) and August (winter) 2009. In January, 636 clams were collected of which 55% were smaller than 15 mm. In winter 380 samples were collected, 57% being of adult size, between 21 and 25 mm in length. The maximum density recorded in the summer period was 414.91 ± 82.48 ind.m-² at S3 and 323.49 ± 90.11 ind.m-²  at S1respectively, which were significantly different from S2 (156.12 ± 28.72 ind.m-²). The lowest density was found during the winter with 102.67 ± 5.07 ind.m-² and 122.37 ± 36.86 ind m-² for S1 and S2 respectively, which largely differed from S3 (296.76 ind.m-² ± 45.20). Among the stations, S3 obtained the highest rate of biomass with 1,248.47 ± 305.82 g.m-² during the summer and 1,136 ± 191.14 g.m-² during the winter, which was significantly different from two other stations' sections. The rain exerts an influence on the distribution of the bivalve A. brasiliana, which was shown through the decreasing of the molluscs’ density, however, they also increased in size (>20mm) due to increase of food availablity in the rainy season.

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