Food spectrum of two co-occurring invasive fish, Cyprinus carpio Linnaeus, 1758 and Clarias gariepinus (Burchell, 1822) in Mattupetty Reservoir, Kerala, India

Abstract

The survey on fish fauna of the Mattupetty Reservoir in the Idukki District of Kerala State, India revealed the presence of four
non-native fish species viz., Clarias gariepinus (family Clariidae), Cyprinus carpio (family Cyprinidae), Poecilia reticulata
and Gambusia affinis (family Poeciliidae). Gut content analyses of Clarias gariepinus and Cyprinus carpio demonstrated
no significant dietary overlap among them, though both are omnivorous. Cannibalism was observed in C. gariepinus and
it was also found to feed on C. carpio and the latter feeds on the eggs of the former. Both the invasive fishes showed
ontogenetic shift in diet. The initially invaded C. carpio might have facilitated the establishment of C. gariepinus, with the
probable displacement of native species and currently these two invasive species are the only commercially valuable species
available in the Mattupetty Reservoir. It is hypothesised that in a resource-scarce ecosystem like a reservoir with multiple
invasive species, the invasive species not only feed on the indigenous food items available, but also feed on each other to
ensure survival.
Keywords: Alien species, Food and feeding, Melting down hypothesis, Stomach contents, Western Ghats