.

Anaesthetic test was conducted using values of histological tissues examinations to assess the effects of Clarias
gariepinus fingerlings (9.6g) exposure to aqueous extract of promethazine hydrochloride (phenergan) under a static
bioassay system. The fishes were exposed to various concentrations of phenergan extracts (50-250mg/l). The time in
which each reached anaesthesia decreased with increase in phenergan concentrations. The fingerlings reached
anaesthesia in significantly shorter time (P<0.05) (10 minutes at 250mg/l concentration) in phenergan but never
recovered. All fingerlings exposed to 200mg/l phenergan extract reached anaesthesia within 15 minutes but only 50%
of the fish recovered while 50% died within six hours. Fingerlings exposed to 150mg/l phenergan reached anesthesia
within 18 minutes and 80% recovered within 2 hours later. It took a longer time (25-40 mins) for fingerlings in the
lowest concentrations (50mg/l and 100mg/l) to reach anaesthesia and they all recovered within 30- 60 minutes. As
the duration of exposure increased, fish showed increased weakness, they were motionless and gasped for air. The
was at 200ml concentration. Excessive mucous secretion was observed. Histological examination showed varying
degrees of gill filaments, degeneration in the lamella, cellular infiltration, vacuolation, necrosis and lesion in the
gills, liver and skin of the fish. Result of the test provided baseline information for which safe limits of using phenergan
as an anaesthetic agent in catfish ponds may be established. The safe margin for C. gariepinus fingerlings (9.6g) is
50-100ml.