Effects of Extracts of Dried Leaves of Erythrophleum suaveolens as Anesthetics on Clariid Catfish

Abstract

ABSTRACT The effects of crude extract, pure extract, aqueous fraction of pure extract and lipid fraction of pure extract of air-dried leaves of Erythrophleum suaveolens as anesthetic on African sharptooth, Clarias gariepinus, and the African vundu catfish, Heterobranchus longifilis, fingerlings were studied. They were exposed to various doses of the extracts in tanks. The time for each fish to reach anesthesia were recorded. The two clariids were anesthetized in up to 3.5 g/L crude extract and recovered in the fresh water. Soaking the leaves for 24 hours or 48 hours produced no significant difference (P> 0.05) in the time to reach anesthesia for the African vundu catfish. These fingerlings reached anesthesia in significantly shorter time (P<0.05) (24.5 minutes at 2.4 g/L concentration) in the pure unseparated extract than in the crude extract (70.5 minutes at 2.4 g/L concentration). All fingerlings exposed to 4 g/L extracts did not recover. Those exposed to less than 3.5 g/L of plant material were anesthetized and recovered only to die later within 24 hours. The time to reach anesthesia decreased with an increase in concentration of the plant extract. Of the two fractions, only the lipid fraction had anesthetizing effect on fish. It, however, took longer to produce the effect than the unseparated pure extract. The aqueous fraction of the pure extract and the control produced no observable anesthetic effects on the fish within 180 minutes. This suggests that the anesthetizing active ingredient resided in the lipid fraction but some factor in the aqueous layer was necessary to quicken its action. Similar results were got with the sharptooth catfish. Since the fingerlings died after recovering from anesthesia it was concluded that the safety margin of E. suaveolens for fingerlings was very narrow at the concentrations used. It is, therefore not recommended for use on the fingerlings of the clariid catfishes.