First study on habitat ecology, biometric parameters and biology of Rita rita (Hamilton, 1822) from tropical perennial River Burhi Gandak, India

This study presents the first comprehensive assessment of habitat ecology, biometric parameters, and biological traits of Rita rita (Hamilton, 1822) in the Burhi Gandak River, a tropical perennial tributary of the Ganga Basin, India. Monthly sampling conducted from November 2022 to October 2023 revealed significant seasonal variations in hydrological parameters, with river width expanding from 63.39 m (pre-monsoon) to 166.13 m (monsoon), depth ranging from 4.8 m to 14.4 m, and flow rates peaking at 1.19 m/sec. Water quality parameters (DO: 4.2–6.0 mg/L; BOD: 4.5–7.0 mg/L) supported aquatic life, with PCA identifying river morphology (width, depth, flow) and TDS as key environmental drivers (PC1: 52.8% variance). The biometric analysis demonstrated strong length–weight relationships (r²: females = 0.95, males = 0.92; positive allometry) and favorable condition factors (K: females = 1.16, males = 1.03), indicating a healthy population. Gut content and gastro-somatic index (GaSI) analyses revealed an omnivorous diet, with bivalves, Puntius spp., and insects as predominant food items, reflecting trophic plasticity. Reproductive biology assessments identified peak gonado-somatic indices (GSI: males = 3.32%, females = 6.47%) and maximum fecundity (32,051 ± 1,513 eggs per fish) in August, aligning with monsoon flows, underscoring hydrological cues for spawning. Principal Component Analysis (PCA) identified river width, depth, and flow as primary environmental drivers influencing water quality and reproductive dynamics. These findings offer novel insights into the ecological adaptability and life-history strategies of R. rita, emphasizing its resilience in a seasonally dynamic freshwater ecosystem. The study underscores the species reproductive synchronization with hydrological cycles, reinforcing the necessity for conservation measures that integrate seasonal habitat variations. By establishing a baseline for sustainable fisheries management, this research contributes to long-term conservation strategies aimed at preserving both R. rita populations and the ecological integrity of the Burhi Gandak River.