Abstract
This study relied on the day-by-day analysis of bioenergetics and prey size preference in isolated cannibalsof the African catfishHeterobranchus longifilis(13–57 mm standard length, 3–500 mg dry body mass,n=153)that were offeredad libitumconspecific prey of adequate sizes in small-sized (2-L) environments under controlledconditions (12L:12D, 30◦C). In these conditions, cannibals of increasing body size selected preferentially prey ofdecreasing size relative to their own, and increasingly closer to the optimal prey size (producing the highest grossconversion 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 theescape capacities of their potential victims, as applies to most aquacultural contexts, fish exercising cannibalism tendto forage optimally, which has rarely been evidenced for piscivorous behaviour. The present study further highlightsthatH. longifilispossesses a very high capacity for growth, which originates from the combination of high food intakeandveryhighconversionefficiency, and makes this species of utmost interest for aquaculturists wherever fast growthis desirable, but also extremely prone to cannibalism wherever feeding schedules are inadequate