Bionomics of gangetic leaf fish, Nandus nandus (Hamilton, 1822), an important food fish of Assam

Nandus nandus (Ham) is a carnivorous fish. The fish is highly predatory and feeds primarily on finfish, shellfish and aquatic insects. The victual spectra trend of the gut contents of the fish has been studied through the four pronounced seasons of the year as ascertained by the index of preponderance. The relative length of gut reveals distinctly carnivorous behaviour. In males at maximum size range of 110 – 115 mm mean RLG is 1.03 whereas in females at size range of 110 – 115 mm, the RLG is only 0.903 indicating that females of the test species are more carnivorous than the males. The hepatosomatic index of the species depicts the feeding intensity of the test species. Lineament of feeding shows that the fish is a column feeder but is well competent to feed both at the surface as well as bottom level when food is supplied in the aquaria. The gill raker configuration reveal carnivorous pattern both in structure and number. The gill rakers are short and pointed backward.