Monthly dynamics of reproductive indices of Neolissochilus hexagonolepis (McClelland, 1839) and their relationship with physico-chemical parameters along the mid-reaches of Tamor River, Nepal

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Physico-chemical parameters exert influence on the reproductive biology of fish. The present study was carried out from December 2014 to November 2016 to investigate the effect of physico-chemical parameters on the reproductive indices like gonad weight and GSI of either sex of N. hexagonolepis in the mid-reaches of Tamor River. Altogether 198 fishes were sampled during the study period. The mean total body weight (TW) and mean total length (TL) of male fishes were 171.67 ± 186.78 gm and 21.21 ± 6.38 cm, respectively. Similarly, the mean TW and mean TL of female fishes were 349.23 ± 316.82 gm and 27.86 ± 9.21 cm, respectively. The trend of monthly mean GSI of both male and female sex in the present study hinted that N. hexagonolepis spawns during monsoon season with peak activity in July to August. A single well-defined peak of GSI for both male and female fish indicated that N. hexagonolepis is an annual breeder. NMDS (Non-matrix multidimensional scaling) of the physico-chemical parameters and reproductive indices of N. hexagonolepis revealed that the atmospheric temperature and water temperature exert a significantly positive influence on the gonad weight and GSI of either sex of N. hexagonolepis while the other environmental variables pH, DO, free CO2, TA and TH exert negative influences upon the reproductive indices of the fish.

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