EFFECTS OF LIGHT CONDITIONS ON THE LARVAL DEVELOPMENT OF TWO CENTROPOMID SPECIES (Centropomus undecimalis AND C. nigrescens)

Through a series of four experimental trials two Centropomid species, common snook (Centropomus undecimalis) or black snook (C. nigrescens), larvae were exposed to two different light sources (fluorescent and LED), three light intensities (200, 500 and 1000 lux), two photoperiods (12 hr light/12 dark, 18L/6D and 24L) and three light spectrums (white, red and blue). Larvae were exposed to varying light conditions during the first 15 days post-hatch in recirculating aquaculture systems, where environmental parameters (temperature, dissolved oxygen, pH, and salinity) were controlled and maintained at optimal conditions. Survival, growth, eye diameter, swim bladder inflation and flexion were the main parameters recorded to assess treatment effects.

In terms of survival, a highly significant difference (p<0.005) was found between treatments in all the experiments, except in the LED versus fluorescent experiment. The following treatments showed the highest survival: the 1000-lux treatment at 8.32%; the 24-hour light treatment at 9.54%; the LED treatment with 13.26%; and in those maintained under the blue spectrum lighting  conditions at 5.29% survival.

There was no significant difference observed between the treatments with regards to growth, although trends in increased growth were observed.  There was no difference in eye diameter, swim bladder inflation and timing of flexion. These results can be attributed to high variability in the size distribution and also to the fact that there is less competition for food in those tanks where survival is lower (less larvae, more food).