Population structure of Trachelyopterus albicrux (Siluriformes, Auchenipteridae) from the Ibicuí River, Rio Grande do Sul, Brazil

Abstract

This study aimed to determine some of the biological aspects of Trachelyopterus albicrux by analyzing its population structure. The study focused on sex proportion, length and the relation of weight/length. Samples were taken every two months, from December 1999 to January 2002, in lotic and lentic environments along the Ibicui River between the cities of São Vicente do Sul and Itaqui, in Rio Grande do Sul. The following nets were used: 10m nets with 1.5, 2.0, 2.5 and 3.0cm mesh; 20m nets with 4.0, 5.0, 6.0, 8.0 and 10.0cm mesh; and 4.0/20.0, 5.0/20 and 6.0/20.0 sweep nets (all mesh sizes were in cm and measured between adjacent knots). The nets stayed in the water for 24 hours, and were checked every 6 hours. A total of 122 males and 112 females were captured, which had a standard average length (Ls) of 13.27cm and a total average weight (Wt) of 95.95g. There was no significant difference between the males and females. The weight/length relation was calculated using the equation Wt = 0,0224 × Ls3,1691 for males and Wt = 0,0127 × Ls3,4 for females. Trachelyopterus albicrux showed isometric growth, with the coefficient value of the linear regression equation equal to 3.1691 for males and 3.4 for females.

Keywords

• Ibicuí
• Populational structure
• Sexual proportion
• Trachelyopterus