Pineal hydroxyindole-0-methyltransferase (HIOMT) activity
was monitored over a 24 h period under three different photoperiods,
16L:8D, 8L: 16D, and 12 L:12D. It was observed that in all three
groups of fish HIOMT activity was high' during the dark portion of the
photoperiod in comparison to activity during the light portion....