The Effect of Birbira, Milletia Ferruginea (Hochst.) Baker on Some Barbus Spp. (Cyprinidae, Teleostei) in Gumara River (Lake Tana), Ethiopia

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Date

2004-02

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Addis Ababa University

Abstract

To assess the possible effect(s) of birbira, Milletia ferruginea (Leguminosae) on the barbs, Barbus spp. (Cyprinidae) from Gumara River (Ethiopia), aquarium and field study was conducted during August to September, 2002. The effects of birbira at concentrations of 0.02, 0.04, 0.1, 0.2, 0.3 and 0.4 g/l were studied to conduct experiments on different species, sizes and sexes of fish. The amount of crude powders of birbira seeds actually applied by the fishermen at Dukalit stream (a tributary of Gumara River) was estimated to be about 0.4 g per liter of water. This amount was found to be excessive as only 0.02 g/l (a 5% dilution) was enough to bring about total fish kills in about an hour. It was observed that the amount of oxygen in the birbira solution remained almost intact after all of the fish died, supporting the idea that rotenone does not deplete oxygen dissolved in the water but affects mechanism of oxygen uptake by fish. The findings of the study revealed that when using birbira concentrations of 0.02 to 0.4 g/l, all of the fish died in about 30 to 60 minutes. Comparison of different species showed that B. brevicephalus and juvenile ‘large’ barbs (weighing < 50 g) had relatively better tolerance than had another close relative, Varicorhinus beso of similar weight. Female B. brevicephalus (usually ≥ 100 g) with running (ripe) gonads of tolerated the poison better than their male (usually < 100 g) counterparts. Fertilized eggs, presumed to have been spawned by B. brevicephalus, were collected from Dukalit stream and poisoned with 0.4 g/l birbira for 15 minutes, and then incubated in clean water. None of these eggs hatched while all of the controls (unpoisoned eggs) did after 3 days of collection from the river. The findings of this study are believed to lay a basis for further research and consequently to solve problems related to poisoning fish with birbira and/or other herbs on Gumara River and other waters. Key words/phrases: birbira (Milletia ferruginea); Gumara River (Lake Tana); ‘large’ Barbus spp.; survival time.

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Keywords

birbira (Milletia ferruginea); Gumara River (Lake Tana); ‘large’ Barbusspp.; survival time.

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