Introduction pathways and ecological impacts of Nile tilapia in a large tropical reservoir of India: implications for management

This study examines the early invasion of Nile tilapia (Oreochromis niloticus) in Panam Reservoir, Gujarat, marking the first record of an exotic fish species establishing itself in this large reservoir system. Using Rapid Rural Appraisal and participatory approaches, the introduction pathway was traced to an accidental escape from cage culture initiated in 2018, with a major loss event in 2019. Initially seen sporadically until 2022, tilapia quickly expanded its presence, accounting for over 20% of the total catch by 2023 and ranking third among landed species. Ecological evaluations showed significant dietary overlap with native fishes, an association with eutrophic conditions, and traits such as trophic plasticity and high reproductive rates, indicating strong invasive potential. Although tilapia has increased overall fish biomass and contributed to local protein supply through higher landings, it presents ecological and economic threats by displacing native species and reducing the value of indigenous fisheries. The study highlights the need for strict biosecurity measures, regulated enclosure culture, and integrated management strategies to balance productivity with biodiversity conservation.