Determining the diversity and distribution of macroinvertebrates in Tende Sub-Bay of Murchison Bay, Lake Victoria (Pearl Aquatics Cage Fish Farm)
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Growing fish in cages is practiced in many parts of the world but has in the last 20 years become a popular fish farming practice in Africa specifically in Ghana, Kenya, Malawi, Uganda, Zambia, and Zimbabwe. Aquaculture as an industry is capital intensive and this can be in terms of purchasing quality feeds so to achieve a lower Feed Conversion Ratios (FCRs). This raises a lot of worry on the effect of cage farming to the quality of water in the lakes and the associated effect on the biodiversity mostly the macro invertebrates. Due to the threats raised by cage fish farming to the ecological biodiversity of water, measures are in place to monitor the effects associated and one them is bio monitoring. This study sought to assess the effect of cage fish farming on the biodiversity and abundance of benthos and water quality at pearl aquatics cage fish farm Tende sub-bay, Garuga on Lake Victoria. The objective which guided the study was to: Assess the impact of cage fish farming on the distribution and diversity of benthic macro-invertebrates at Tende bay of Lake Victoria. The study will consist of four sampling sites (cage sites and non-cage sites) along a transect sampling, cage sites (A, B) and non-cage sites (C, D) will be (0, 200, 400 and 800 Meters) randomly around the fish cages respectively. Control site was 800m away from the cages and a simple and stratified random sampling system was used.Selected water physico- chemical parameters from different depths of the column and benthic macro-invertebrates community parameters (i.e. numerical abundance, Shannon-Weiner diversity Index and modified Hilsenhoff Biotic Index) determined at both cage and non-cage sites. Mann-Whitney U test was used to test differences in the Shannon-Wiener Diversity Index and Hilsenhoff Biotic Index values between the cage and non-cage sites. Differences in benthic macro-invertebrates numerical abundance between the cage and non-cage sites were tested using Kruskal-Wallis and Mann-Whitney U tests. Water quality parameters between cages and non-cages sites were analyzed using one-way ANOVA. No significant differences were observed in physico-chemical parameter values, benthic macro-invertebrates’ numerical abundance and Hilsenhoff Biotic Index between cage and non- cage sites. On the other hand, Benthic macro-invertebrate species diversity differed significantly between the reference site and cage site 2 (P<0.05). Pollution tolerant Chironomus sp. and Melanoides sp and hirudines were significantly higher at the cage sites than the non-cage sites (P<0.05). These results suggest that cage fish farming significantly changed water quality.