Fish scales are a surprisingly nutritional food source, containing layers of keratin and enamel, as well as a dermal portion and a layer of protein-rich mucus. They are a rich source of calcium phosphate.2 However, the energy expended to make a strike versus the amount of scales consumed per strike puts a limit on the size of the lepidophage; such fish seldom exceed 20 centimetres (7.9 inches) and most are under 12 cm (4.7 in).2 There are a number of advantages to consuming scales: scales are common, covering the body of most fish species, can be regrown relatively quickly by "prey" fish, are abundant and seasonally reliable, and their removal requires specific behaviors or morphological structures.2
A diversity of morphologies and attack behaviors are used by lepidophagous predators. The behavioral origins of scale feeding may be different for different lineages.2
^Petersen, C. C.; Winemiller, K. O. (1997). "Ontogenic diet shifts and scale-eating in Roeboides dayi, a Neotropical characid". Environmental Biology of Fishes49 (1): 111–118. doi:10.1023/A:1007353425275.
^Yanagisawa, Y. (1984). "Parental strategy of the cichlid fish Perissodus microlepis, with particular reference to intraspecific brood ‘farming out’". Environmental Biology of Fishes12 (4): 241–249. doi:10.1007/BF00005455.
^Nshombo, M. (1991). "Occasional egg-eating by the scale-eater Plecodus straeleni (Cichlidae) of Lake Tanganyika". Environmental Biology of Fishes31 (2): 207–212. doi:10.1007/BF00001022.