Continuous lighting inhibits the onset of reproductive cycle in pikeperch males and females

The effect of a constant photoperiod on the inhibition of male and female reproductive cycles was studied in pikeperch Sander lucioperca. Over a 153-day period, batches of pikeperch (2 years, 950 g) breeders were kept under either under natural or artificial photoperiod conditions (24L:0D) (30-35 fish/tank, triplicate) and sampled in late June (start of the photoperiod decrease in natural conditions), late August (start of temperature decrease) and late November (exogenous vitellogenesis) (7-10 fish/tank/sampling date). Morphological parameters, sexual steroids, alkaline-labile phosphate (mu g/mL) levels and gamete developmental stages were investigated. Gonado-somatic index (%), developmental stages and sexual steroid levels (17 beta-estradiol, testosterone and 11-ketotestosterone, ng/mL) in both sexes and oocyte diameter (mu m) and plasma alkaline-labile phosphate (mu g/mL) in females were lower in response to a continuous lighting (24L:0D). In both sexes, continuous lighting applied in June for 153 days totally inhibited or delayed the onset of the reproductive cycle. In conclusion, photoperiod manipulation can be used to delay the pikeperch reproductive cycle, even if temperature decreases. This is the first report of the inhibitory effect of photoperiod on the onset of the reproductive cycle in pikeperch.