Effect of light intensity on initial survival of fat snook (centropomus parallelus, pisces: Centropomidae) Larvae

Abstract

Different light intensities were tested during the larval rearing of fat snook (Centropomus parallehis) to evaluate its influence on sun'ival and functional swim bladder rate. Newly-hatched larvae were obtained by stripping of Iwniwnally induced broodstock, and were stocked in 32-liter tanks at densities from 30 to 50 L'1. Four experiments were carried out testing six light intensities: 50, 100, 200, 500, 1500, and 2500 Ix, and total darkness as a control. Mean survival ranged from 0.06 to 16.0% and were significantly influenced by light intensity. Complete darkness resulted in 100% mortality after one week, larvae appeared to have stan'ed since they had empty stomachs. The species has the characteristics of a visual-feeder. Survival was the highest at 200 Ix, while at 500 Ix was higher than at 50, 100, and 2500 Ix. Frequency of functional swim bladder ranged from 36.8 to 100%, but it was not significantly correlated with light intensity. Based on this study, a medium light intensity, 200 to 1500 Ix, is recommended for rearing fat snook larvae. Extreme values must be avoided, mainly in the first two weeks after hatching.