Summary
The scale-eating Serrasalmid fish Catoprion mento (Characoidei) eats mostly insects when young, then about an equal percentage of insects and scales of other fishes at a medium size, and has a distinct preference for scales when adult. At the same time, the intestine tract, the body depth and the width of the head (as represented by the interorbital space) show a strong positive allometry. with a critical point of growth for the depth. The head length has a negative allometry. The differential growth phenomenons and the food preferenda are possible related.