Abstract

The use of aqueous and alcoholic extracts of tobacco as an anesthetic for fish handling procedures was investigated using the Nile tilapia, Oreochromis niloticus.An effective concentration of the anesthetic was defined as one giving a sure state of anesthesia for 75% of the fish after an exposure time of less than 5 min. The effective concentration of the aqueous extract was 4/4.5 g/l. For the alcoholic extract it was 6/7 ml/l. There is a highly significant correlation (r = -0.98, p < 0.01) between concentration and recovery time with the aqueous extract. Recovery times with both preparations were short, 2 - 5 min with the aqueous extract and an average of 10 min with the aqueous extract. Anesthesia with the aqueous extract was recommended over the alcoholic extract as it had a lower effective dose and a comparable recovery time.

Key words: Anesthetic, recovery time, effective dose, tobacco.