Distribution patterns and diversity of riverine fishes of the Lake Victoria Basin, Kenya

Abstract

The Lake Victoria Basin (LVB) is a global hotspot of aquatic biodiversity, but aquatic ecosystems are under threat from multiple stressors. Most studies on fish have focused on Lake Victoria, while patterns of fish diversity, distribution, and assemblage structure in influent rivers remain poorly understood. To assess threats and conservation status of riverine fishes, we used sampling surveys and searches of published and gray literature to compile data on diversity, distribution, and abundance. In total, 72 fish species were found to inhabit Kenyan rivers and associated wetlands and lakes (excluding Lake Victoria). Low‐order streams (first to third order) in headwaters of rivers are species‐poor and dominated by small‐bodied cyprinids (Enteromius spp.) and clariids (Clarias spp.). A small number of fishes are endemic to rivers, and species turnover across river basins is low. Species dominance is high, with 10 species accounting for >90% of all individuals and weights. Two cyprinid species (Labeobarbus altianalis and Labeo victorianus) account for >65% of all individuals and weights (biomass) per unit effort. Most species occur in small numbers and low biomass is insufficient to sustain a commercial riverine fishery. A review of the literature continues to indicate a reduction in migratory runs of potamodromous fishes from Lake Victoria into influent rivers, although some species, such as L. victorianus and L. altianalis, also maintain stenotopic populations in rivers. Most of the exotic fishes introduced in Lake Victoria, such as Oreochromis nilotics, Oreochromis, Coptodon zillii, Coptodon rendalli, and Gambusia affinis, have invaded and established themselves in rivers, thereby posing a threat to riverine populations. Although this study focuses on Kenyan rivers, the distribution patterns of fishes reflect other rivers of the LVB and have broad implications on threats to riverine biodiversity in other regions undergoing development around the world.

Exploring the potential of small water bodies as an integrative management tool for fisheries production

“…The differences in contribution of fish abundance in both regions were linked to better water quality in the central region than the western region. Water quality is a key determinant of biota occurrence in aquatic systems, with fish also used as an indicator of water quality due to their sensitivity to pollution (Masese et al, 2020; Mora et al, 2003, 2008).…”

“…The dominance of Nile tilapia in both regions despite differences in ambient water quality could partly be due their high tolerance to poor quality conditions (Masese et al, 2020). This resilience, combined with its fast growth rate, tolerance for overstocking (high stocking densities), adaptability to differing culture systems, and its high market value, makes this fish ideal for restocking in SWBs where it is already endemic (Musa et al, 2014).…”

“…The differences in contribution of fish abundance in both regions were linked to better water quality in the central region than the western region. Water quality is a key determinant of biota occurrence in aquatic systems, with fish also used as an indicator of water TA B L E 2 Water quality parameters for the sampled small water bodies for both western and central regions of Kenya F I G U R E 4 Concentrations of phytoplankton abundance (Ind/L) in the surveyed small water bodies of western and central regions of Kenya quality due to their sensitivity to pollution (Masese et al, 2020;Mora et al, 2003Mora et al, , 2008.…”

Citizen Science for Bio-indication: Development of a Community-Based Index of Ecosystem Integrity for Assessing the Status of Afrotropical Riverine Ecosystems

“…This underscores the application of citizen science into perspective. The riverine community benefits from a river site in their neighborhood in terms of anthropogenic activities such as fishing, water abstraction, waste disposal, and other socioeconomic and cultural activities that can be quantified into a measurement of a parameter or value, herein referred to as a metric (Aura et al, 2017;Masese et al, 2020). As a result of these practices and changes, this study aims to determine the role of the riparian communities in assessing the status of riverine systems.…”

“…These rivers constitute over 45% of the total discharge to the lake (Twesigye et al, 2011). The rivers represent the major river catchments with a gradient of disturbance, and most notable biodiversity hotspots around Lake Victoria (Masese et al, 2020). These rivers support an artisanal fishery, particularly during the rainy seasons (Balirwa et al, 2003) and act as a source of water for livestock, irrigation, industries, and domestic uses.…”