Are Crab-collectors in Mangroves of Northern Brazil (PA) Optimal Foragers?

Abstract

Intensive harvesting of the mangrove crab Ucides cordatus provides subsistence for food and main or additional income to many inhabitants of mangrove areas in Northern Brazil. In order to better understand the spatial patterns of use of this natural resource as basis for sustainable resource-management, we used a combination of GPS-tracking, field observations, semi-structured interviews and participatory mapping with crab-collectors. We quantified daily working hours, traveling distance and time to, as well as collecting time inside, the patches where crabs are collected. Based on preliminary findings for three different types of transportation to the fishing grounds, we conclude that crab-collectors in our study area act in accordance with the central place optimal foraging concept in that they invest more time in traveling to areas with higher catch. We hold these findings will prove relevant for sustainably managing the use of mangrove crabs as natural resource. The parallel occurrence of different collecting-behaviours possibly releases pressure from crab stocks in the potentially depleting fishing grounds adjacent to villages, and thus, may render crab-collecting in these areas more sustainable. Detailed studies are needed to quantify the catch from different mangrove areas and to make these data useful for the sustainable management of natural resource-exploitation in mangroves.