Biological and ecological aspects of Palaemonetes argentinus (Nobili, 1901)(Crustacea, Decapoda, Palaemonidae), in the Felizardo arroyo, medium Uruguai River, Uruguaiana, Rio Grande do Sul, Brazil

This work presents aspects of density, biomass, reproduction and growth of Palaemonetes argentinus. Captures were made seasonally in the period between July 2001 and May 2002, in three distinct spots of the Felizardo stream, an affluent of the medium Uruguai River, through the electric fishing technique. The results obtained refer to the four seasons of the year, throughout which a total of 551 individuals were captured out of an expected 604. The period of higher density and biomass was the Spring season with 5,982 ind./ha and 2,057 g/ha, respectively. The weight-length relation obtained for the P. argentinus population was Wt= 0.145252*L2.679. The fecundity (NO) length relation obtained for the same population was NO= exp. (1.64908 + 0.528255)* Lt and the fecundity (NO) weight relation was Wt= exp. (-1.95674 + 0.0311)*NO. The curve determined for the growth in length of Palaemonetes argentinus indicated Lt= 5.7 (1-e -0.373082 (T -0.400498)) and Wt= 1.608 (1- e -0.172389 (W -1.052659)). The reproductive period occurs with greater intensity in the spring and proceeds in a reduced manner in summer, having a rest period in the autumn and winter. The number of eggs in the spawnings varied between 18 and 84, with an average of 39.88 eggs per egged female