Crab gatherers perceive concrete changes in the life history traits of Ucides cordatus (Linnaeus, 1763), but overestimate their past and current catches

Abstract

The mangrove crab Ucides cordatus (Linnaeus, 1763) is an important resource for the livelihood of several poor families living on the Brazilian coast. However, this species is in the Brazilian list of threatened aquatic species, although not much is known about its stock situation. This study aimed to assess the situation of U. cordatus fisheries, comparing biological data, obtained through crab landing sampling, to information provided by crab gatherers. For that, data sampled along 12 years in a coastal municipality on the Brazilian northeast (Canguaretama, Rio Grande do Norte) were compared to interviews with 30 crab gatherers from the same municipality regarding changes in fishing and in the crab life history traits during the same 12 years. Long temporal analyses and intense data collection like these are relatively rare in developing countries. Therefore, comparing their efficiency to the data obtained through interviews could confirm the efficacy of this last method in obtaining quality data in a quick and inexpensive way. The crab landing sampling indicated an increase in catch and a decline in the Catch per Unit of Effort (CPUE), while the biological data showed an increase in male crab proportion in the sex ratio and a decrease in the carapace length of both sexes. Crab gatherers were able to provide accurate information on crab life history traits, but overestimated their catch. This suggests that information provided by gatherers and probably by resource users in general may have some limitations, although it could provide cheap and reliable information, depending on the topic investigated.