The occurrence of Macrobrachium olfersii (CRUSTACEA, DECAPODA, PALAEMONIDAE) in an affluent of the Santa Maria da Vitória river, in Santa Leopoldina, ES, southeastern Brazil

Abstract

The population studies of crustaceans provide important information on the dynamics of species and the preservation of natural biodiversity. Factors such as adverse weather conditions, over-exploitation of natural stocks, tourism and economic activities, point out how disturbing the natural regulation of these organisms. The species of the genus Macrobrachium, is included in the group that includes economically interesting species to human activity. These shrimp are widely distributed in rivers and estuaries in tropical and subtropical regions of the world. In Brazil, the genus Macrobrachium is represented by 18 species distributed in the Amazon basin, inland and coastal. Among these may be cited the Macrobrachium olfersii predominantly freshwater species that need brackish water to complete their life cycle, especially in its reproduction and larval metamorphosis. This study aims to provide information on the population structure of M. olfersii in a stretch of the Rio Santa Maria da Vitoria, verifying their distribution with respect to temporal frequency, biometrics and environmental variables. The physico-chemical data showed no significant difference over the months of collection. There was a significant correlation with total length of the weight is considered normal for the species studied and variations in length and weight throughout the work. There was the presence of predominantly M. olfersii in the samples, with the class of total length from 37.60 to 60.00 mm. During the months observed temperature and dissolved oxygen did not correlate significantly with the maturity of prawns. The river flow showed no significant correlation with the maturity of shrimps, however, was noted on the distribution of species along the stretch observed, noting that during the period of higher flow rates, a reduction of population, both in size and number individuals. The correlation of oxygen saturation with a total length of shrimps showed that the size of individuals increases with the scarcity of oxygen saturated. Therefore, it is noted that the population of M. olfersii suffers the direct influence of some physicochemical parameters and indirectly by the river flow.