Population structure and reproductive aspects of Corydoras aeneus (Siluriformes, Callichthyidae) in streams of the River Ivinhema Basin, Upper Paraná River

ABSTRACT

Despite of increase of studies about biology of small fish species, the knowledge of basic aspects of biology great portion of species still is incipient. Thereat, the aim of this study was analyze the population structure and the reproductive aspects of Corydoras aeneus (Gill, 1858) in streams of the Ivinhema River Basin, Upper Paraná River. The samplings were performed from 2008 to 2011 at fifty seven sites distributed in basin. They were analyzed 684 individuals, including 213 females, 190 males and 281 obtained only the dada of standard length. The maximum standard length registered for analyzed population was 50.19 mm for females and 45.24 mm for males, so females were larger than males. The sex ratio was 52.7% females and of 47.1% males, no significant variation (^_Χ2= 1.313; p = 0.252) between sex. How much the Length-weight relationship both sexes presented isometric growth. The highest proportion of mature females was observed in from October to December, although were observed mature females in others months of year. It was observed that 50% of females were sexually mature at 33.54 mm. Mean fecundity was estimated 359.47 eggs, and presented total spawning. The recruitment pattern no presented a unimodal period, although the more intensity was observed from October to December. The asymptotic length was estimated at 54.59 mm and growth rate at 1.1 year^-1. The growth performance index was estimated to 3.51, the longevity at 2.72 years and the mortality rate at 1.48 year^-1.

KEYWORDS
Length-weight relationship; fecundity; mortality; sex-ratio