Neolissochilus hexagonolepis, the copper mahseer, chocolate mahseer or katli, is a species of freshwater ray-finned fish belonging to the family Cyprinidae, the family which includes the carps, barbs and related fishes. This species is found in Nepal, eastern India, Bangladesh, Myanmar, Thailand, Malaysia and Sumatra. It may also be present in China and Viet Nam, also the record sof this species from the easyetn part of its range is uncertain and reports may be misidentifications.

In 2021, the Indian state of Sikkim declared the copper mahseer, locally called 'Katley' as the State fish.

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