Predatory diversity of finfish species inhabiting the same ecological niche

Abstract

A total of 211 specimens of Nemipterus japonicus (Bloch, 1791) and 169 specimens of Saurida tumbil (Bloch, 1795) were
examined for different morphological traits and stomach contents. N. japonicus has a laterally compressed and deep body,
small mouth opening and villiform teeth only on the jaws, soft gill rakers with bristles, small stomach and long intestine.
These adaptations are suited for predation on small preys. S. tumbil has an elongated cylindrical body, with wide mouth
opening, different types of sharp depressible teeth, small spine-like gill rakers, well developed stomach and short intestine,
which are again the adaptations to feed on larger preys. Both the fishes are cannibalistic and asynchronous feeders. However,
N. japonicus seems to be an opportunistic feeder, predating on crustaceans (80%), fishes, cephalopods, gastropods and
polychaetes while S. tumbil is more like a selective feeder, predating on fishes (90%), crustaceans and cephalopods. The
study reveals that though these predators inhabit the same ecological niche of demersal waters and have the opportunity to
utilize similar food resources, they are entirely different in morphology which is attributed to the difference in their diet.