Effect of a Herbicidal Control of Water Hyacinth (Eichhornia crassipes Mart.) on Fish Composition and Abundance in the Kofawei Creek, Ondo State, Nigeria

Water hyacinth (Eichhornia crassipes Mart.) infestation of the Nigerian waterways since 1984 has created a perennial problem. This paper examines the efficacy of herbicidal control of the noxious aquatic weed and its resultant effect on the fish composition and abundance in the Kofawei creek. The result showed that Diquat and Terbutryn applied in the study succeeded in killing the weeds with 2 weeks without causing any fish mortality. The low catch recorded in the untreated area was a reflection of the deleterious effect of the presence of water hyacinth on the water quality. The fish species composition improved qualitatively and quantitatively in the treated sites. A preponderance of male to female fish species was also recorded in the creek water pre- and post-herbicidal application.