Reproductive response of Nile tilapia (Oreochromis niloticus) to photoperiodic manipulation; effects on spawning periodicity, fecundity and egg size

Nile tilapia (Oreochromis niloticus) has rapidly become an important species for aquaculture, although their intensive culture remains constrained by poor spawning synchrony and low fecundity, adding significant cost to hatchery production. Previous research has indicated that spawning synchrony may be improved in some fish species by photoperiod manipulation. There is limited information on the effects of photoperiod manipulation on tilapia. In this paper, the reproductive performance of 32 individually housed Nile tilapia was evaluated under four different photoperiods: short day (6L:18D), normal day (12L:12D), long day (18L:6D), and continuous illumination (24L:OD). Significantly larger eggs (P< 0.05) were produced under normal daylength (12L:1213) compared to other treatment groups. Fish reared under long daylength (18L:6D) exhibited significantly higher (P< 0.05) total fecundity (2408 +/- 70 eggs spawn(-1)) and relative fecundity (7.2 +/- 0.2 eggs g(-1) body weight) concomitant with a significant reduction in inter-spawn-interval (ISI, 15 +/- 1 days) in comparison with the rest of the trials. This investigation shows that long daylength (18L:6D) helps improve some important reproductive traits in Nile tilapia, and suggests that such methodology may be used to alleviate the production problems caused by low fecundity and poor spawning synchrony, and thus play a valuable future role in tilapia culture. (C) 2004 Elsevier B.V. All rights reserved.