Water Hyacinth (Eichhornia crassipes) infestation, interactions with nutrients, aquatic biota and a control weevil in Winam Gulf, Lake Victoria, Kenya

Lake Victoria just like many other lakes is affected by water hyacinth which resides in several bays for the better part of the year. This weed affects several economic activities of the locals and denies the government revenue every year from blue economic activities related to the lake. This paper explores the interaction of water hyacinth with biotic and abiotic factor and the efficiency of the introduced weevils in its control with an aim of advising on the best way to tackle the menace of the weed. Water quality samples were collected and compared from the time of water hyacinth arrival and sinking within Winam gulf. Water hyacinth was collected and damages resulting from the weevils as well as the number of weevils recorded. Fish samples were also collected using experimental gill nets. Water quality was analyzed for Ammonium, Soluble Reactive Phosphorus, Nitrates and Nitrates. Data was then analyzed using R- package. Results indicated that the weevils inhibits nutrient uptake by17% within the first four weeks, hyacinth increase the nutrient levels in the gulf almost three fold after decaying and sinking. Weevils also increased the sinking rate of water hyacinth through destruction of the petioles and leaves. There was a significantly higher fish numbers during the weed infestation than when the weed was absent. In conclusion water hyacinth impacts both biotic and abiotic factor and the weevils alone cannot be depended upon to eradicate the weed.