Vol. 9, Special Issue 7, Part D (2025)

This study investigated the effects of different photoperiod regimes on the growth and development of juvenile guppy fish (Poecilia reticulata) under controlled laboratory conditions. The experiment was conducted at a research facility in South West Khasi Hills District, Meghalaya, India, over a 90-day period. Newly hatched guppy juveniles were randomly assigned to five experimental groups with different light exposure durations: 24 hours continuous light (24 h LED), 18 hours light (18 h LED), 12 hours light (12 h LED), 6 hours light (6 h LED), and 24 hours darkness (24 h dark). Each treatment was replicated in separate 20-liter aquaria with standardized feeding and water quality management protocols. Growth parameters including body weight, total length, specific growth rate (SGR), and survival rate were measured at 0, 45, and 90 days. Water quality parameters (temperature, pH, dissolved oxygen, and alkalinity) were monitored throughout the experimental period. Results showed that fish exposed to 18 hours of LED light (Setup B) exhibited the highest growth performance with weight gain of 0.35±0.0026 g, length gain of 18±0.53 mm, and 100% survival rate. Fish maintained under continuous darkness showed the poorest growth performance. These findings suggest that an 18-hour photoperiod provides optimal conditions for juvenile guppy growth and development, balancing metabolic stimulation with adequate recovery periods.