Bioecology of common snook, Centropomus undecimalis, in a tropical lagoon at the Brazil north coast

Abstract

The aim of the study was to investigate the bioecology of the common snook Centropomus undecimalis captured in the so-called Salina Lagoon, at the mangrove coast of Pará State, to determine its populational biology in conjunction to environmental conditions and variations. Samples and measurements were carried out monthly along one year using a gillnet and analyzed in terms of populational structure, including length/weight measurements and their relationships, recruitment period, condition factor and gonadal stage. Environmental parameters, especially water quality, were monitored and correlated with biological data. A total of 344 specimens were captured and their length ranged from 3.4 to 29.6 cm, within a weight range from 0.4 to 209.31 g. Histological analysis revealed that the captured specimens were immature males. The species presented a negative allometric growth, based on weight-length relationship (W_T = 0.00088 L_T^2.94). The time distribution showed that the common snook is on recruitment during March, May, September/2007 and January/2008. The relative condition factor values indicate that in general the specimens presented good nutritional condition, with exception of October. Among the analyzed environmental aspects, only salinity, pH and conductivity presented substantial seasonal variations as well as extreme values. However, common snook presented a good development, proving its ecological plasticity. Furthermore, the results show that Salina Lagoon is an important ecosystem to the species life-history and works as nursery area.