In the Lake Tana Sub-basin, the expansion of irrigation development is increasing without considering fisheries; particularly Labeobarbus spp., spawning migrates from Lake Tana to its tributaries during the rainy season. This study investigated the impact of irrigation infrastructure and practices on the spawning migration of these species and proposed potential mitigations. Data were collected from July 2019 to May 2020 through fish sampling above and below the Ribb Dam and Gilgel Abay Weir, interviews with key informants and experts, secondary data collection, and impact significance matrix analysis. The findings revealed that existing irrigation systems disrupt fisheries by blocking spawning migration routes. For instance, fish catches below the Gilgel Abay Weir were significantly higher than those upstream (Shannon Index, P < 0.001). Observations also confirmed that even large fish could not jump over the 2-meter-high Gilgel Abay Weir and the Ribb Dam. Local reports indicated that the Ribb River has become seasonal since 2007 due to excessive water abstraction for irrigation, resulting in mass fish killing and a decline in juvenile recruitment to Lake Tana. In one sampling case, over 837 adult fish and numerous juveniles were found dead in the Ribb River and its tributaries. The reduced water volume has also led to non-fishers harvesting fish from pools, while fishers target spawning migratory species at weirs, exacerbating the problem. The study also noted a decline in species diversity compared to earlier records, potentially due to changes in reproductive strategies, sampling inefficiencies, interbreeding, or altered breeding behaviors. Habituat restoration, replacing weirs with environmentally friendly technologies, and constructing fish ladders to mitigate the negative impacts on fisheries.