Uma armadilha para captura de Porcellanidae (Crustacea, Decapoda) do mediolitoral de praias rochosas

Abstract

A simple net trap for capturing agile porcelain crabs living amongst superposed stones of the midlittoral rocky shore was developed. About a hundred pebbles and boulders were dislodged from I m² area and Im depth, so that a pit was formed. A sheet net of Im² and Imm mesh size was spread on the bottom of this pit and the stones were replaced again, like the original condition. After a cicle of high tide (about 12 hours), the same stones in the pit were carefully searched by dislodging and by rinsing them. The porcelain crabs were slowly getting out from the handling stones towards the bottom until they found the net sheet. The net border was lifted and the animais captured. The density of population sampled with the aid of the net trap was about 50% higher than that collected by hand. Also, small size species and early developmental stages were adequately collected in this trap. However, the sampling by hand also showed a good performance, as all species of Porcellanidae known from Farol isle and all developmental stages of those species were registered in this collection methodology.