Fish composition and their habitat preferences in human impacted tributaries of the upper Awash River, Ethiopia
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The distribution, diversity and habitat use of stream fishes in major tributaries of the upper Awash River were assessed from May to October, 2021. We conducted field surveys at five strategically selected sites where we recorded data on fish species composition, habitat characteristics and key environmental parameters. There was significant variation in nutrient concentration (total phosphorous and nitrate), water depth and velocity (p < 0.05) highlighting the heterogeneous nature of the riverine ecosystem. A total of 1,784 individuals were recorded and the analysis of fish assemblages at the mesohabitat level revealed interesting trends with riffle habitats supporting a higher fish abundance (55%), dominated by small indigenous Garra species. Pool habitats had a relatively higher taxonomic richness compared to riffle habitats. Interestingly, only indigenous species were common between these two habitats (i.e., occurred in both habitats), while commercially exploited species were found exclusively in the pool habitats suggesting that habitat complexity plays a significant role in determining fish distribution. It has been determined that hydrological parameters such as water depth and velocity play a crucial role in determining fish distribution patterns. Additionally, human activities, such as water diversion and waste from dams, are significant factors influencing fish distribution. These results highlight the complex interaction between environmental variables and fish community structure in each habitat in the upper Awash River emphasizing the need for integrated conservation strategies that take habitat features into consideration.
Abstract
The distribution, diversity and habitat use of stream fishes in major tributaries of the upper Awash River were assessed from May to October, 2021. We conducted field surveys at five strategically selected sites where we recorded data on fish species composition, habitat characteristics and key environmental parameters. There was significant variation in nutrient concentration (total phosphorous and nitrate), water depth and velocity (p < 0.05) highlighting the heterogeneous nature of the riverine ecosystem. A total of 1,784 individuals were recorded and the analysis of fish assemblages at the mesohabitat level revealed interesting trends with riffle habitats supporting a higher fish abundance (55%), dominated by small indigenous Garra species. Pool habitats had a relatively higher taxonomic richness compared to riffle habitats. Interestingly, only indigenous species were common between these two habitats (i.e., occurred in both habitats), while commercially exploited species were found exclusively in the pool habitats suggesting that habitat complexity plays a significant role in determining fish distribution. It has been determined that hydrological parameters such as water depth and velocity play a crucial role in determining fish distribution patterns. Additionally, human activities, such as water diversion and waste from dams, are significant factors influencing fish distribution. These results highlight the complex interaction between environmental variables and fish community structure in each habitat in the upper Awash River emphasizing the need for integrated conservation strategies that take habitat features into consideration.