Environmental Factors and Genetic Diversity as Drivers of Early Gonadal Maturation: A Gonadosomatic Index Based Investigation on Indian Shad, Tenualosa ilisha Population of Bangladesh

In recent years, attaining gonadal maturation in smaller Hilsa ( Tenualosa ilisha ) has become a burning issue for fishery of Bangladesh. Causes early are not yet clearly understood. Along with environmental parameters, genetic differentiation within the population was hypothesized as main driver, and therefore, assessing correlation between gonadosomatic index (GSI) factors analyzing diversity were set objectives present study. To address these complex issues, six diverse habitats across Bangladesh chosen sample collection. For GSI, gonad dissected from fresh fish preserved Bouin’s fluid histological observation. Water quality parameters such temperature, dissolved oxygen, pH, salinity also assessed. 35 each habitat used to extract amplify DNA through PCR technique, examined. Further, draw firm conclusion, phylogenetic tree developed by unweighted pair-group method arithmetic mean based on Cyt b gene mitochondrial DNA. Results GSI studies revealed that peak spawning months T. October February, where showed highest values all habitats. Histological examination different stages development sizes ages Hilsa. Among sampling sites, no statistical difference observed value; however, sized aged being ripped evident Gaglajur Haor Kali River. water temperature correlated strongly. Increased augmentation downstream upper stream, irrespective body size age. A perplex oxygen executed. Other physico-chemical viz. pH exhibited weak moderate positive association respectively. Haplotype divided into three possible sub-populations, most distant group (Gaglajur River) subjected maturity. this study make clear conclusions regarding role maturations, pointing fingers at curse climate change anthropogenic stressors migration