Improving approaches and modeling framework for assessing vulnerability of Asian leaf fish in the major river basin floodplains of India in changing climate

Asian leaf fish Nandus nandus (Hamilton, 1822) is a valued small indigenous freshwater fish (SIF) in inland waters with high food, and conservation importance but relatively less studied. We assessed the impact of regional climate variability for the first time on population attributes and breeding phenology and predicted its biological vulnerability through General Additive Model (GAM) in changing climatic scenario. We determined environmental cue, threshold biological condition and preferred climatic condition for breeding from lower Gangetic floodplains and Brahmaputra floodplain wetlands, India. We observed that female length at first maturity (LM50) was 10.5 cm for Brahmaputra basin and 10.8 cm for Ganga basin. Threshold Gonado-somatic index value for ready to spawn individuals (GSIspawn50) was estimated at 10.6 units for Brahmaputra and 8.11 units for Ganga basin. Temperature > 28 °C and rainfall >200 mm were found optimum for breeding in Ganga basin and temperature between 26 and 29 °C and monthly rainfall >150 mm were found optimum for Brahmaputra basin. Narrow GSIspawn50 temperature window indicated that the species is more vulnerable to climate change in Assam compared to West Bengal. Pearson correlation coefficient indicated a strong and significant correlation of gonado-somatic index (GSI) with rainfall and temperature in floodplain wetlands of both states. The population vulnerability ranged from moderate to highly vulnerable to climate change based on 14 designed attributes. Evidently, an innovative vulnerability framework developed for assessing the resilience of the species was an important effort in the Indian sub-continent. This will further help to quantify the climate induced risks which could serve as important database to develop the mitigation measures.