The effect of the hanging ratio on the catchability of the gill net on Lake Victoria: a case study of Nile tilapia fishery

Abstract

Lake Victoria ecosystem is source of food, incomes, and livelihoods to over 200000 fishermen and 3 million people within the East African region. Over the years, fish gillnet has been the popularly used fishing gear targeting Nile perch and Nile tilapia which are most dominant fish commercial species on Lake Victoria. Several interventions have been done anchored on ensuring sustainable fishing with most recent directive of the deployment of Uganda fisheries protection unit (UFPU). However, there is prevalence of immature fish with the captured targeted landings even when legal gears are applied by the fishermen, gear maintenance and repairs affect the mesh sizes and overall hanging ratios which was anticipated to immensely affect the gear selectivity and catchability. Therefore, the study assessed the impact of hanging ratio on catchability specifically the Nile tilapia fishers at Port bell Luzira landing site. Sample nets were measured to determine the hanging ratios and fish catch composition landed by the different nets of different hanging ratios were assessed for numbers of fish and weight of fish to get mean weight and mean numbers of fish landed and tested for variance using One-way Anova at 0.05 level of significance. Results found out that fishermen used fish gillnets nets of hanging ratios 0.5,0.6 and 0.7, the fish weight landed significantly increased with increase in the hanging ratios of gillnets whereas the numbers or quantity of fish landed was significantly higher for fish nets with hanging ratio 0.7 and lower for 0.5 and 0.6, varying slightly. Results affirmed that increase in the fish net hanging ratio increased mean weight of fish landed and numbers of fish with a desirable selective range attributed to the full opening and shaping of the meshes compared to hanging ratio of 0.5,0.6 whose numbers were similarly high but of lower mean weight than 0.7 hanging ratio. The study recommended use of fish nets of higher hanging ratio of 0.7 or at least 0.6 to capture fish of higher biomass (weight) preferable in the desirable selection range to ensure sustainability of fisheries stocks with in Lake Victoria