The experimental system used was a flow-through flume
composed of two parallel sections 10 m long, 1 m wide and 0.8 m
high. The flume was subjected to a 12 L/12 D photoperiod with
30 min of dawn (7:00e7:30) and dusk (18:30e19:00). Light
intensity was maintained at 27 mW cm2 during the L period (day)