Otolith-based growth reconstruction and comparative evaluation of back-calculation methods in Reba carp, Cirrhinus reba (Hamilton, 1822)

Context Understanding growth patterns is essential for effective fisheries management and conservation of freshwater fishes, for economically important species with limited otolith-based growth studies. Cirrhinus reba, a valuable minor carp in the Ganga River, lacks comprehensive otolith-based growth studies despite its significance to subsistence fisheries and aquaculture. Aim This study establishes otolith morphometric relationships and validates back-calculation methods for growth reconstruction of C. reba from four sites along the Ganga River. Methods We analysed relationships between fish body size and otolith measurements by using linear regression and Spearman correlation on 235 specimens, and compared five back-calculation functions and three growth models by using linear mixed-effects and non-linear approaches. Key results The strongest relationships were between otolith weight and fish length (R2 = 0.76–0.78, ρ = 0.85–0.86). The Monastyrsky scale proportional hypothesis best estimated length-at-age. Von Bertalanffy and Gompertz models showed spatial variation; asymptotic length varied from 96 to 205 mm and growth coefficient from 0.44 to 0.74 year−1 across sites. Conclusion Otolith morphometric relationships and validated back‑calculation methods provide a solid foundation for reconstructing growth in C. reba. Implications This validated framework enables otolith-based size and age reconstruction, facilitating evidence-based fisheries management, including minimum catch-size regulations, seasonal fishing restrictions, and habitat prioritisation as site-specific conservation strategies for C. reba under varying environmental conditions throughout the Ganga River.