Light color and ovarian maturation in unablated and ablated giant tiger prawn Penaeus monodon (Fabricius)

Abstract

The effect of light color (green, blue and white fluorescent lights, with natural light as a control) on maturation in intact and eyestalk-ablated Penaeus monodon was tested in 12-m³ broodstock tanks. Size and quality of sequential spawns from ablated females were also compared. In Experiment 1, unablated females under green light produced the highest number of spawns (5), total number of eggs (4.26 × 10⁶), total number of nauplii (2.69 × 10⁶) and mean egg counts (6537 eggs g⁻¹ female), the latter significantly higher than in the other treatments. Mean nauplii counts were higher under green (3979 g⁻¹ female) and natural (3303 g⁻¹ female) light compared to the other treatments. Mean hatch rate was highest in control (87.3%) but this was not significantly different from green light (61.8%). In Experiment 3, ablated females under natural light gave the highest total number of eggs (13.04 × 10⁶) and nauplii (9.74 × 10⁶). Mean egg and nauplii counts were significantly higher in the natural (4436 eggs and 3308 nauplii g⁻¹ female) and green (4016 eggs and 2906 nauplii g⁻¹ female) light treatments compared to white. Hatchability was similar for all treatments. In Experiment 2 (using green light), ablation increased the total number of spawns, eggs and nauplii 14 to 17 times. Rematuration data showed no significant differences in spawn size (egg counts); hatchability and nauplii counts of sequential spawns were similar in Experiment 2 but tended to decrease in Experiment 3.