Estrutura populacional do tetra cardinal Paracheirodon axelrodi, Schultz 1956 (Characiformes; Characidae) no médio rio Negro, Amazonas – Brasil.

Abstract

The estimation of population parameters in fish is essential for the interpretation of the life aspects of the strategy linked to its reproduction and growth, providing subsidies for the development of effective measures in the management of fishery resources. Cardinal tetra (Paracheirodon axelrodi) is a commercially important species in the ornamental fishery in the state of Amazonas, however, its dynamic population is little known. This study aimed to describe and evaluate the population structure of six streams with ornamental history fishing present on the left bank of the middle Rio Negro. The collections were carried out monthly from February 2016 to January 2017 by using three traps Cacuri for one hour in each stream. In the laboratory, the specimens were measured (SL in mm), weighed (g) and had their sex determined. The analyzes included determination of the length structure, growth parameters (L∞ and k), sex ratio, weight - length ratio, condition factor, duration of first sexual maturation (L50), reproductive period and fecundity. A total of 15.618 specimens were collected, females reached greater length than males in all streams. However, considering all collections, the mean length and recruitment period are similar for all collections in all streams. The asymptotic length of the specie was 28,35 mm and an growth rate was 0,59.year1. The sex ratio varied between 1F:1M and 1,3F: 1 M in all streams. The weight-length relation is of the positive allometric type in all the streams and the condition factor was significant in all the streams between the sexes, suggesting a better condition for the females and males in the reproductive period. The length of first sexual maturation was 14.95 mm for males and 15.44 mm for females with a period of reproduction of cardinal tetra occurring in the period of flood and fertility ranging from 234 to 1386 oocytes with total spawning. With the obtained results, it is possible to propose measures that permeate the conservation of the species, emphasizing the due care of the fishing in the period by which the reproduction takes place and the recruitment of the young that is directly connected to the seasonality.