Invasion of Nile Tilapia (Oreochromis niloticus Linnaeus 1758) and its Effects on Indian Major Carp Production in Singotam Reservoir, Telangana, India

Abstract

Telangana is predominantly an inland fisheries state, with abundant lakes, reservoirs, dams, rivers, backwaters, and irrigation tanks. Indian major carps (IMCs) are widely consumed and cultured because of their texture and characteristic taste and their contribution to rural fisher livelihoods. In recent years, invasive fishes have entered open water bodies and adversely affected fisheries-dependent communities. This study was conducted from January 2023 to December 2025 to assess the association between Nile tilapia (Oreochromis niloticus) invasion and IMC catch composition in Singotam Reservoir, Nagarkurnool District, Telangana, India. Monthly fish-landing data were collected at the landing centre, and catches were graded by species and size with the assistance of local fishers. Nile tilapia accounted for approximately 76% of the cumulative catch, whereas IMCs accounted for 24%. The annual contribution of Nile tilapia increased from 63.26% in 2023 to 82.81% in 2025, while the IMC contribution declined from 36.74% to 17.19%. Catch composition differed significantly between fish categories and sampling years (p < 0.001). The decline in the IMC contribution despite periodic seed stocking suggests possible interspecific competition, although the landing-based design does not establish causality. The findings indicate a shift in reservoir catch composition towards Nile tilapia dominance and support the need for integrated catch monitoring, scientifically planned IMC stocking, targeted tilapia removal, and habitat-based management to sustain IMC productivity.