Heterobranchus bidorsalis

The piscicidal potential of water-extract mesocarp of Azardirachta indica was investigated in static biossay experiment with continuous aeration to determine its acute toxicity. The 96-hLC50 was 97.42mg/l while the threshold value was 31.12mg/l. The extract led to an initial increase in opercula ventilation rates which then decreased significantly. The computed regression equation (y) = 4.624 + 6.352 Logc. (r=0.72) and the fish exhibited respiratory distress, loss of balance and erratic swimming prior to mortality. The usefulness of A. indica as piscicidal plant is discussed.

The effect of feeding frequency on the growth and feed efficiency of Heterobranchus bidorsalis was investigated at two feeding rates (10% and 40% of body weight) in a 2x2 factorial experiment. The study was conducted in twelve 2x2x1m outdoor concrete ponds supplied with aeration with three replicate ponds for each treatment. Fish averaging 80 ± 4.5 mg were fed either two times or four times daily at two different feeding rates using practical diets for ten weeks. The percentage weight gain ranged from 55.25% to 95.13%.