This study relied on the day-by-day analysis of bioenergetics and prey size preference in
isolated cannibals of the African catfish Heterobranchus longifilis
(13–57 mm standard length, 3–500 mg dry body mass, n = 153) that were offered
ad libitum conspecific prey of adequate sizes in small-sized (2-L)
environments under controlled conditions (12L:12D, 30 °C). In these conditions, cannibals of
increasing body size selected preferentially prey of decreasing size relative to their
own, and increasingly closer to the optimal prey size (producing the highest gross
conversion efficiency). The role of experience in cannibalism was found of secondary
importance relative to body size, both as regards food intake and prey size selectivity.
These results indicate that in environments that minimize the escape capacities of their
potential victims, as applies to most aquacultural contexts, fish exercising cannibalism
tend to forage optimally, which has rarely been evidenced for piscivorous behaviour. The
present study further highlights that H. longifilis possesses a very high
capacity for growth, which originates from the combination of high food intake and very
high conversion efficiency, and makes this species of utmost interest for aquaculturists
wherever fast growth is desirable, but also extremely prone to cannibalism wherever
feeding schedules are inadequate.