Light boosts fish fertility
long hours of daylight enhance fertility of female adult Catla catla, a major freshwater Indian carp, claim researchers from West Bengal's Visva-Bharati University. They found exposing the fish to long photoperiods during the pre-spawning phase (April-May) increased the activity of vital chemicals and steroid enzymes known to aid ovarian growth. Exposure to short photoperiods, on the other hand, inhibited sexual maturity during pre-spawning and spawning (July-August) phase.
"Given the commercial importance of this fish, a regimen of artificial long photoperiods may be used during the pre-spawning phase to advance its sexual maturation and spawning time,' says Soumen Kumar Maitra, the lead researcher. "This should enable fish farmers to produce fish of desirable size and quality when its demand is very high in the markets,' Maitra adds. The findings were published in the Journal of Biological Rhythms (Vol 20, No 2).
For the study, 24 adult female carp grown on balanced fishmeal were exposed to long (16 hours) and short (8 hours) photoperiods, through a combination of artificial and natural light. On dissecting the fish, the team found increased activity of vitellogenin (a chemical that causes egg enlargement) and growth of ovary in fish exposed to long photoperiods. But long photoperiods didn't have any effect during the post-spawning phase.