Some reproductive and biometric features of the endangered Gangetic Leaf Fish, Nandus nandus (Hamilton, 1822): Implication to the baor fisheries management in Bangladesh

Abstract This study reflects the biometric characters of the endangered species Nandus nandus (Hamilton, 1822) including sex ratio, length-length relationships (LLRs), and length-weight relationships (LWRs) utilizing the sum of 14 linear variables, various meristic measurements, reproductive biology, and condition factor from the Borni Baor, a large wetland ecosystem of southwestern Bangladesh. A total of 579 specimens of N. nandus have been periodically collected from the Borni Baor throughout the year (January–December, 2019) using different traditional fishing gears. Highly significant LLRs (r2 > 0.90) values indicate that length parameters are profoundly associated with one another. In the LWR formula (W = aLb), higher exponent b values (b > 3.0) were demonstrating a positive allometric growth with a high correlation coefficient (r2 > 0.94). Moreover, monthly gonadosomatic index and dobriyal index fluctuations suggest the primary breeding season of this fish is from March to July. Data revealed the breeding time was associated strongly with the rainfall and air temperature (p