Abstract

A 96 h static toxicity bioassay was carried out to examine fish responses and to determine the median lethal concentration (LC50) of Balanites aegyptiaca stem bark extract on adults of Brycinus nurse, Labeobarbus bynni and Labeobarbus intermedius. Experimental fish were exposed to piscicide plant extract of 0.0 (control), 15.0, 17.5, 20.0, 22.5, and 25.0 mgL-1. Fish exposed to these extracts except the control showed symptoms of toxicity including darting, agitated swimming, air gulping, loss of sensitivity and knockdown before death. These responses were much frequent and faster in L. bynni and L. intermedius. The 96 h LC50 values for the different test fishes were 18.99, 20.72 and 20.72 mg L-1 for L. bynni, L. intermedius and B. nurse, respectively. Based on the present investigation, we can conclude that the application of B. aegyptiaca extract causes lethal toxic effects on different fishes even at low concentrations and hence, indiscriminate use of the plant for fishing should be discouraged and regulated in order to protect fish biodiversity lose in the Alitash National Park area.

Key words: Alitash National Park (ALNP), Balanites aegyptiaca, floodplain rivers, piscicide, toxicity, LC50.