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Not AvailableReproductive biology of female amphidromous croaker Johnius coitor (Hamilton, 1822) was
studied for the first time from various freshwater stretches of Ganga river basin, India in relation to climatic
variability. The species showed high spatial variation in reproductive phenology and capable of breeding
during pre-monsoon, monsoon, post-monsoon and winter. Water temperature is the most crucial
environmental parameter influencing gonadal maturation and breeding. Generalized additive model (GAM)
models revealed water temperature near 23β25 Β°C as optimum and threshold GSI above 3 units necessary for
breeding. Pre-spawning fitness (Kspawn50) and size at 50% maturity (LM50) benchmarked through Kaplan-
Meier survival fit estimates were in the range 1.27β1.37 units and 19β24.5 cm respectively. First maturity of
females was encountered at 11.4 cm within the size range 7.2β28.5 cm. Egg parameters in mature-ripe
females ranged between 0.29β0.80mm(diameter), 0.05β0.19 mg (weight) and 5687β121 849 eggs (absolute
fecundity). Mapping of climate preferendum through LOESS smoothing technique hinted water
temperatures 32 Β°C to be detrimental for attainment of pre-spawning fitness while no
dependence on rainfall was observed. Based on the climato-hydrological influence on breeding and regional
trends of changing climate along river Ganga, we infer minimal climate driven changes in breeding
phenology of this amphidromous fish species. Results of this study may serve as baseline information for
future studies assessing climate driven changes and evolutionary adaptations in croakers from river Ganga.Indian Council of Agricultural Research (ICAR) and National Innovations in Climate Resilient Agriculture (NICRA