Class Year

2022

Document Type

Student Research Paper

Date of Creation

Spring 2022

Department 1

Environmental Studies

Abstract

Lake Turkana, located in northern Kenya on the Ethiopian border, is the world’s largest permanent desert lake. Over 90% of its flow originates from the Omo River in Ethiopia, which causes the lake to have seasonal rises and falls in water level. The Omo River has been subject to the construction of five dams (the Gilgel Gibe dams) and several irrigation projects. These developments will impact the amount of water entering the lake, with implications for lake chemistry and productivity, littoral habitat availability, and the breeding biology of the lake’s fishes. Though ongoing upstream changes are likely to have serious impacts on the fishes and fisheries of Lake Turkana, this system remains drastically understudied. The purpose of this project was to develop an understanding of the food web and ecology of seven key fisheries species in Lake Turkana before the installation of the Gibe III dam. I used Bayesian mixing models in the statistical software R and stable isotope data (𝛿15N and 𝛿13C) collected between 2011 and 2013 at three sites in Lake Turkana to estimate key species’ diet. I found that site or site type (littoral or pelagic) was an important driver of diet for the majority of the species studied. I also found diet shifts in six species as compared to earlier research. Notably, fish declined in the diet of some larger predatory species (Hydrocynus forskallii and Lates niloticus), which may be because of declines in the lake’s small pelagic planktivores. Phytoplankton and zooplankton were an important diet item for low-trophic level fishes, including tilapias and pelagic schooling fishes. There were also clear ontogenetic dietary shifts in four species. This study highlights vulnerabilities in the diet of key fishery species in a large lake experiencing ongoing ecosystem change. Findings of this study are the first step in understanding how upstream projects will impact the fisheries of Lake Turkana by providing a baseline assessment of the food web structure.

Comments

Written for ES 460: Individualized Study Research

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

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