Density and spatial distribution of the crab Ocypode quadrata (Fabricius, 1787) (Crustacea, Ocypodidae) on three sandy beaches of Espírito Santo, Brazil

Abstract

The relative density (number of burrows/m2) and spatial distribution of the crab Ocypode quadrata were evaluated on three sandy beaches of Vila Velha-ES: Itaparica, Itapoã and Praia da Costa. These beaches were sampled on 05/25, 06/13, 06/26 and 07/11/2006. On each day, two 5m width transects were randomly distributed on each beach, perpendicular to the waterline and divided into 2 x 5m rectangles. Within each transect, all burrows were counted, the diameters were measured (mm), and their locations in relation to the waterline were recorded. Itaparica beach presented a greater mean density of burrows (mean = 0.33, SD = ± 0.26), followed by Praia da Costa (0.16 ± 0.14) and Itapoã (0.08 ± 0.02). Regarding the burrow diameters, Itaparica and Itapoã showed greater values (16.2 ± 8.88 and 16.2 ± 8.91, respectively) than Praia da Costa (12.6 ± 6.40). The density of burrows and the burrow diameters differed significantly among the beaches. A greater abundance of small burrows occurred near the waterline and a greater abundance of large burrows were situated on the upper beach. The flux of people and the passage of the urban cleansing vehicles apparently had an influence on the density and spatial distribution standards found for the O. quadrata crabs