Population parameters of Poeciline in streams of Mato Grosso do Sul State, Brazil

Abstract

This study aimed to describe and compare the population structure of Phalloceros harpagos in Perobão and Água Boa streams, Mato Grosso do Sul State, through quantitative population parameters. Samplings were performed using electrofishing in the streams´ upper, intermediate and lower stretches (sites 1, 2 and 3, respectively), between March and November 2008. Standard length, weight and sex were used to determine the sex ratio, standard length classes’ frequency and populations’ condition at each stream. A total of 686 and 3,404 specimens of P. harpagos were captured at Água Boa and Perobão streams, respectively. Only the population of the upper stretch of the Água Boa Stream was considered in the analysis due to the inexpressive capture in intermediate and lower stretches. Males with 1.4-1.8 and 1.8-2.2 cm standard length were the most captured in both streams. Females reached greater lengths, and the most frequent were those with 2.2-2.6 and 1.8-2.2 cm in Água Boa and Perobão respectively. Females predominated significantly (2.5:1) in the Água Boa Stream and at Site 1 (1.3:1) of Perobão Stream. The sex ratio was the same in all other sites. The Kolmogorov-Smirnov test indicated significant difference in the distribution of individuals within size classes for both streams. The application of covariance analysis or of the separate slope model on data from the linearization of the length-weight relationship indicated the best condition of the P. harpagos population in Água Boa Stream and of that present in the upper stretch of Perobão Stream.