Salinity influence on development and weight-length relationship of the fat snook

Abstract

It was investigated if the seasonal changes in salinity, temperature, pH and water transparency contribute to Centropomus parallelus development in estuaries. The study was performed in 2007 and 2008 at the Guaratuba Bay, Southern Brazil, where individuals 15.0 to 214.0 mm long occupy shallow waters along the year. No relationship between fish abundance and salinity, temperature, pH or water transparency levels was observed, however, salinity was related to the individual sizes. Because each level of salinity coincides with a particular length of fish, it is concluded that both temporal and spatial environmental changes are favorable to the C. parallelus growth in the headwaters of the estuary. Comparing the seasonal distribution of individual sizes with data on the C. parallelus growth in aquaculture, it is estimated that in Guaratuba the fat snook spawns in late summer/early autumn, when the marine influence is stronger; their eggs hatch in high salinity; and juveniles develop simultaneously to the summer salinity decline, during the rainy season, when the rivers influence increases. Data on juveniles added to those coming from recreational fishing performed around the Bay, males plus females originated the weight/length relationship TW = 0.00002 TL^2.85 (n = 1,125); considering males only, TW = 0.00001 TL^2.97 (n = 185); and considering females only, TW = 0.000007 TL^3.04 (n = 445). Different coefficients between sexes are due to the gonads weight changes, higher in females than in males.