Macrognathus aral (Bloch and Schneider 1801): Growth, condition, age, mortality, recruitment and exploitation in running and stagnant ecosystems in Gandak Basin, India

Growth and fishery of Macrognathus aral were studied from an oxbow lake Matwali-Majhariyamaun and the river Dhanauti in Gandak Basin, India based on 367 and 451 specimenscollected from the oxbow lake and the river, respectively through weekly sampling fromJune 2020 to May 2021 . The length-weight relationship revealed negative allometric growth(b<3.0) as W= 0.0051*L (2.82) in lake and W= 0.0045*L (2.85) in the river. The relative conditionfactor Kn was found to be ≈1.0 in both the ecosystems. The age at length zero and themaximum age Tmax were estimated to be -0.312 year and 9.4 years in the lake and -0.328year and 8.8 years in the river respectively. Growth parameters L∞ and ‘K’ were estimatedto be 37.7 cm and 0.32 year-1 in the lake, and 34.3 cm and 0.34 year-1 in the river, indicatingslow growing nature of the species. The mortality rates ‘M’ ‘Z’ and ‘F’ were determined tobe 0.78, 0.95 and 0.17 per year in lake and 0.81, 97 and 0.16 per year in river. Recruitmentanalysis showed a single peak during August in both the ecosystems. Lopt was estimatedas 20.8 cm in lake and 19.2 cm in river. Virtual population analysis (VPA) revealed highestfishing mortality observed in the length groups above 30.0 cm in both the ecosystems. Theoptimum level of exploitation (E0.5) was found to be 0.32 in lake and 0.34 in river, which waslesser than the current level of exploitation. The above finding will be useful for sustainablemanagement and conservation of the species. Keywords:Age, Exploitation, Gandak Basin, Growth, Mortality,Macrognathus aral, Recruitment