EFFECT OF LIGHT INTENSITY AND PHOTOPERIOD ON NILE TILAPIA OREOCHROMIS NILOTICUS L. SEED PRODUCTION

M.T. Ridha, E.M. Cruz-2000

Aquaculture Research, 31 : 609-617

Abstract :

The objective of this study was to compare the effect of six light intensity/photoperiod combinations (2500lux/18h, 2500lux/15h, 2500lux/12h, 500lux/18h, 500lux/15h and 500lux/12h) on seed production in the Nile tilapia Oreochromis niloticus L. Each combination represented a treatment and was triplicated in 0.4-m3 fibreglass tanks within a recirculating water system. Water temperature was maintained at 29.0 ± 1.0°C. Males and females with mean body weights of 116.8 and 91.6 g, respectively, were stocked at a rate of eight fish/tank with a male to female ratio of 1:3. Seeds (eggs, sac fry and swim-up fry) were collected every 2 weeks. The experiment lasted for a total of 120days. The results showed that the 2500lux/ 18 h treatment produced significantly greater (P < 0.05) total seed/tank (4944), seed kg-1 female day-1 (50.9), seed m-2 day-1 (40.3) and seed/ female day-1 (6.7) than treatments with medium or short photoperiods (15 and 12h day-1 respectively) or lower light intensity (5 00 lux). The degree of spawning synchrony and percentage of the sac and swim-up fry stages were significantly higher in the 2500lux/18h treatment than in the other treatments. Under the conditions tested in this study, seed production and spawning synchrony in the Nile tilapia may be improved by subjecting breeders to a light intensity of 2500lux and a photoperiod of 18 h day-1.

(Mariculture and Fisheries Department, Food Resource Division, Kuwait Institute for Scientific Research, PO Box 1638, 22017 Salmiya, Kuwait)

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