Economic impact of predatory piscivorous birds on small-scale aquaculture farms in Kenya

•Pond fish damage by piscivorous birds account for over 10% of seasonal production.•Hammerkop was the most common piscivorous bird, but it was not the most destructive.•Proper pond siting and vegetation management are key to reducing bird depredation. This study assessed the economic loss due to pond-fish predation by piscivorous birds in small-scale aquaculture systems in western Kenya. Piscivorous birds were surveyed in the field through daily focal scan sampling to record abundance and species richness. Overall fish damage by birds was quantified from known daily feeding rates, and economic-loss estimates were projected for a six-month production season. The influence of farm habitat features on bird diversity and frequency was also evaluated. These features included hedgerow characteristics, size of fallow areas, presence of woodlots, tree density and pond proximity to dwellings. Thirteen piscivorous bird species were identified. Their abundances increased with increasing tree density and pond distance from houses, except when exotic hedgerows were present. Total seasonal fish damage by birds, mainly large waders, across all farms was estimated at 2.141 tonnes per production season valued at USD 12,845, representing 15% of the projected production. This corresponded to an average loss of 33 kg of fish (worth USD 165) per pond, and is a substantial and challenging setback for rural aquaculture. Urgent action through habitat management and capital support is required as a necessary step for reducing investment losses and sustaining the local food supply while at the same time protecting wildlife.