Induced Maturation of Prawn Penaeus indicus

Abstract

Viable spawns have been obtained in the laboratory from untreated prawn Penaeus indicus and from others which had one eyestalk ablated. Fecundity was shown to be dependent on spawning technique, female size and whether the spawner was wild or domestic. Using low aeration during spawning, domestic unablated female fecundity was significantly lower than it was for wild females, due to a concomitantly smaller ovary volume. During late premoult, mature ovaries are resorbed to ovarian Stage 1-2 and after ecdysis they redevelop. 52.1 O/O of spawnings occurred during early premoult, 44.4 O/o during intermoult, 3.5 O/O at premoult, while no spawns occurred during late premoult or early postmoult. Average egg numbers and hatch successes were higher for unablated females when compared with ablated females. Average spawns per moult cycle were 1.98 and 2.24, respectively. It was conservatively estimated that wild females spawn at least 7-9 times in a lifetime. There were twice the number of spawns with a black tank background as there were with a white one and the former yielded higher average egg numbers and hatch successes. General pigmentation, ovary, egg and nauplius colour was dependent on background colour. Moult-cycle duration was temperature dependent but generally shorter for ablated females. As female condition decreased, moult-cycle duration decreased accordingly for any given temperature. Spawning activity declined when the condition factor was less than 0.8. Both ablated and unablated spawning females > 39 g tended to decrease in mass and condition while females < 39 g continued to grow. Nutrition is probably the main contributory factor to this anomalous growth. Large females possibly have nutritional requirements different from females of less than 39 g. A viable F, generation of P. indicus has been reared.