PISCICIDAL PROPERTIES OF AQUEOUS AND ETHANOLIC BARK EX- TRACTS OF FLOATING TIMBER LOGS IN A TROPICAL OPEN LAGOONL.O. Chukwu and O.H. Okeowo
The acute toxicity of aqueous and ethanolic bark extracts of Khaya grandifoliola against Oreochromis niloticus fingerlings was investigated in laboratory bioassays. On the basis of the 96hrs LC50 values the ethanolic extracts were more toxic than the aqueous extracts of K.grandifoliola. Computed toxicity factor (ratios of 96hr LC) values) revealed that the ethanolic extract was 251.8 times more toxic than the aqueous extract when tested against 0. niloticus. The randomized analysis of variance (ANOVA) for toxicity of the bark extracts against 0.niloticus showed that there were significant differences between all treatments (P<0.05). Student Neuman Keuls test showed the statistical differences between all the concentration pairings (P=0.05). The implications of these findings on the management of logging activities on the Lagos lagoon ecosystem are highlighted.
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