Bioecologia de Ucides cordatus Linnaeus 1763 (Decapoda: Ocypodidade) em áreas com diferentes níveis de impactos antrópicos no Golfão Maranhense, Brasil

Abstract

Bioecology studies that address reproduction and morphometry have accurate information to assist in the conservation of species. This study aimed to analyze the bioecology of Ucides cordatus in two areas with different levels of human impacts in the Maranhense Gulf, involving morphological and reproductive aspects and population structure. The first area is the Manguezal do Zé da Mata (less anthropogenically impacted) located in the municipality of Raposa and the second is the Porto Grande Manguezal (with the greatest human impact), located in the municipality of São Luís. Six collections were carried out in the period from September 2020 to December 2021. Population density was measured by counting the number of galleries in five 1m² quadrants along a 35m transect in all sampling months and calculated in G/m². Biometric data from specimens were compared between sampling sites using Student's t test; the population density data were correlated with the abiotic data pH, temperature and dissolved oxygen through a multiple regression and finally, the size at first sexual maturation (L50) was verified. The immediate (PEI) and future (PEF) extractive potential were evaluated based on the Carapace Width (LC mm) with the PEI: LC =/> 60mm and the PEF: LC =/< 60mm. In addition, sediment samples from the sampling areas were analyzed to identify the difference between the levels of anthropic impact. The abiotic data did not influence the population density of the species in the two analyzed sites. There was a significant difference between the means of LC (mm) and CC (mm) between the specimens from Zé da Mata and Porto Grande, with more robust individuals in the latter. The immediate extractive potential (PEI) was higher in the Porto Grande mangrove, as were the values of G/m² (4.93). The L50 was 51.33 mm for the mangrove of Zé da Mata and 54.42 mm for the mangrove of Porto Grande, demonstrating that the population of these places can reproduce at least once before reaching their commercial size (60 mm of LC) . The results on crabs from the two mangroves indicate stable populations, although there is greater fishing pressure in the Zé da Mata mangrove. These data point to the need for inspection of fishing activity and guidance for the Raposa community, especially regarding the closed season for the species.