Population biology of shrimp Macrobrachium jelskii (Miers, 1778) (Decapoda, Palaemonoidea) at the Grande River at northwest of the state of Minas Gerais, Brazil

aim: the population biology of the freshwater shrimp macrobrachium jelskii was investigated here emphasizing the length-frequency distribution, sex ratio, reproductive period and juvenile recruitment. in addition, the abundance of individuals was correlated with the abiotic factors. methods: samples were collected on a monthly basis from july 2005 to june 2007 along the river margin in shallow water of grande river, at planura region, state of minas gerais, brazil (20o 09' s and 48o 40' w), using a trawl net (1.0 mm mesh size, and 2.0 m × 0.5 m wide). the fishing gear was handled by two people along the marginal vegetation of the grande river in a course of 100 m, covered for one hour. in the laboratory, the specimens were identified, measured and sexed. results: a total of 2,789 specimens was analyzed, which corresponded to 1,126 males (549 juveniles and 577 adults) and 1,663 females (1,093 juveniles, 423 adults non-ovigerous and 147 ovigerous). the sex ratio differed significantly in favor of the females of m. jelskii (1:1.48; χ2 = 103.95; p < 0.0001). the mean size of carapace length (cl) of females (6.32 ± 1.84 mm cl) was statistically higher than of males (5.50 ± 1.07 mm cl) (p < 0.001). the length-frequency distribution of the specimens revealed an unimodal pattern and non-normal distribution for males and females (w = 0.945; p < 0.01). no significant relationship between the abundance of m. jelskii and the environmental variables was observed (p = 0.799). conclusion: the presence of ovigerous females and juveniles in the population suggests a continuous reproduction pattern and recruitment for m. jelskii at planura region.