The most common anthropogenic disturbance on exposed sandy beaches are recreational activities and destruction of sand dunes. To take decisions on manegment of this ecosystems, we must have effective environmental tools, to reduce impacts. The numbers of open burrows of the ghost crab Ocypode quadrata (Fabricius, 1787) should indicate the presence of animals, and in recent years it had been shown that this species is usefull as a tool in rapid assessment of human impacts. To test the hypotesis that anthropogenic impact on sandy beaches reduce the abundance of ghost crabs, the relative abundance (number of burrows/m2; N = 60) of the ghost crab O. quadrata were compared in three beaches of Santa Catarina Is., southern Brazil. In each one of the beaches, low and strong conditions of human impact were selected. Two levels in the intertidal were analysed, lower and upper midlittoral. The samples were taken in winter/2002 and summer/2003. In winter and summer there were significantly fewer burrows on that beaches with the higher levels of impact. Ingleses beach showed the higher abundances of the ghost crab in both winter and summer. In winter and summer there were significantly fewer burrows at Barra da Lagoa beach. In the summer the lower intertidal showed significantly higher abundances of the ghost crab. The results evidenced that Ingleses beach with high recreational impact had more ghost crabs, probably due to the nocturnal behavior and the fortuitous use of the food detritus left in the beach. In the beach with strong impact of cars and fisheries activities there were no ghost crabs. This study discuss the utility of the world-wide genus Ocypode for a rapid assessment tool of human impacts on exposed sandy beaches.
Anthropogenic impacts; burrows; density; ghost crab; management
