Environmental factors are critical factors influencing fish growth and reproduction. We hypothesized that optimizing these factors can stimulate endocrine systems, enhancing growth and reproduction. Our focus was on the Malabar grouper, a valuable species in Asian markets, and our goal was to understand how environmental factors affect its growth and reproduction for improved aquaculture. This study investigated synergistic effects of light wavelengths and salinity on this fish juvenile growth physiology .
Juveniles reared under various experimental conditions utilizing LEDs with different salinities (11psu blue - 463nm, 11psu red - 623nm, 34psu blue - 463nm, and 34psu red - 623nm) over a two-week period. Compared to red light, blue light increased condition factor (CF) at both 34psu and 11psu salinity, indicating potential lipogenesis promotion. Juveniles under blue light showed higher specific growth rate (SGR) than red light, suggesting consistent light wavelength impact across salinity levels. Best growth occurred under 11psu blue light, while diencephalon opsins expression levels varied under different salinities with the same light, emphasizing synergistic effects of light wavelength and salinities. Juveniles were reared under varied conditions using LEDs (11psu blue - 463nm, 11psu red - 623nm, 34psu blue - 463nm, and 34psu red - 623nm) for two weeks. While Feed conversion ratio (FCR) responded to salinity, npy transcript levels hinted at appetite promotion contributing to enhanced growth with blue light. The GH/IGF-1 axis didn’t influence observed growth, suggesting complexity in blue light and salinity interaction.
The results emphasize the importance of considering both light wavelengths and salinity levels in optimizing the rearing conditions for aquaculture, offering valuable insights for the sustainable cultivation of Malabar grouper and potentially other marine species.