Bioecologia do robalo-flexa, Centropomus undecimalis, em lagoa costeira tropical no norte do Brasil

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 Para State, to determine its populational biology in conjunction to environmental conditions and variations. Samples and measurements were carried out monthly along an year using a gillnet and analyzed in terms of populational structure, including length/weight measurements and their relationships, recruitment period, condition factor and gonodal stage. Environmental parameters, especially water quality, were monitored and correlated with biological data. 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 alometric growth, based on weight-length relationship (WT = 0.00088 LT 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, working as nursery area.