Abundance, distribution, and diversity of fishes in Ribb Reservoir, Lake Tana basin, Ethiopia

Abstract

The abundance, distribution, and diversity of fishes in Ribb Reservoir were studied based on a total of 1629 fish samples collected from February to October 2021. Fish samples were collected using gillnets of different stretched mesh sizes. Except for temperature and pH, most physico-chemical variables revealed significant spatial variation (ANOVA, p < 0.05). Fishes were highly correlated with the concentration of dissolved oxygen (r ≈ 0.8, p < 0.01) and electrical conductivity (r ≈ 0.89, p < 0.01). Three fish species include Oreochromis niloticus (Linnaeus, 1758), Clarias gariepinus (Burchell, 1822) and Labeobarbus intermedius (Rüppell, 1835) were identified (H' = 1.06). The diversity indices did not show variations among seasons (H' = 0.98–0.907) and sites (H' = 1.04–1.07). All the fish species occurred in all sampling sites and seasons. Oreochromis niloticus (41.9%) was the most important and abundant fish species followed by C. gariepinus (38.2% by %IRI). The relative importance index showed O. niloticus (45.4%) was the most abundant species in the dry season. However, C. gariepinus (73.3%) was the most abundant species in the wet season. Before the construction of the Ribb Dam, the Ribb River was dominated by about eight species. However, in the current study (after the construction of the Ribb Dam), only three species were found. Results revealed that the diversity of fishes has decreased primarily due to the dam effect followed by anthropogenic impacts such as poor land management systems, high sedimentation load, excessive irrigation and illegal fishing. Therefore, an appropriate dam design with a fish ladder and effective watershed management setup is needed to sustain fish resource utilization in the country for food security.

Keywords:

• abundance
• diversity of fishes
• fish ladder
• Ribb Reservoir
• Tana basin

Public interest statement

Irrigation activities are important to feed the fast-growing world population. However, these activities can affect fish distribution and diversity. For instance, along the Lake Tana Sub-basin, the construction of dams and weirs are expanding within the rivers without considering fisheries aspects. In Ethiopian drainage basins, there are more than 200 fish species are inhabited. However, this fish resource is not well utilized due to the scientific knowledge gap. Based on this, the present finding was focused on the abundance, distribution, and diversity of fishes in the Ribb Reservoir. The Ribb River is one of the tributaries of Lake Tana. The movement of spawning Labeobarbus fish species was impacted by the damming of Ribb River. The results revealed that the diversity, distribution, and abundance of fishes are highly impacted by the Ribb Dam followed by anthropogenic activities such as high sedimentation load, poor land management systems, excessive irrigation practices, and fishing pressure.

Acknowledgements

We would like to extend our gratitude to Guna Tana Integrated Field Research and Development Center, Debre Tabor University that provided funds and logistics. We also duly acknowledged Natural and Computational Sciences; Debre Tabor University provided logistics separately. We also acknowledged the fishermen from Ribb Reservoir during data collection. Moreover, we are happy to extend our gratitude to all individuals who contributed their effort to us during data collection.

Author’s contribution

Agumassie Tesfahun and Sale Alebachew: Conceptualization, Methodology, Software: Sale Alebachew and Agumassie Tesfahun: Data curation, Writing – Original draft preparation. Negese Kebtieneh: Visualization, Investigation, Supervision. Agumassie Tesfahun: Software, Validation. Sale Alebachew and Agumassie Tesfahun: Writing – Reviewing and Editing.

Data availability

All data sets and the materials used in this manuscript are confidentially available.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Statement of ethical approval

Ethics approval and consent to participate permits for this research were issued by the Ethiopian Wildlife Conservation Authority (EWCA), Debre Tabor University, and Farta District Livestock and Fisheries Office. Fish sampling was conducted in accordance with the Ethiopian Wildlife Conservation Authority proclamation number 41/1993.

Additional information

Funding

There is no direct fund for this research

Notes on contributors

Sale Alebachew

Sale Alebachew pursued his MSc dDegree in Animal production from Debre Markos University, Ethiopia. Presently, he is a lecturer and researcher at the Department of Animal Sciences, Debre Tabor University, Ethiopia.

Agumassie Tesfahun has an MSc degree in Fisheries, Limnology, and Aquatic-ecotoxicology from Hawassa University, Ethiopia. Currently, he s the Assistant Professor at the Department of Biology, Debre Tabor University, Ethiopia.

Negesse Kebtieneh

Negesse Kebtieneh has an MSc degree in Fisheries, Limnology, and Aquatic-ecotoxicology from Hawassa University, Ethiopia. Currently, he is an assistant professor at the Department of Biology, Debre Tabor University, Ethiopia.