Intra-cohort cannibalism in early life stages of pikeperch

Cannibalism has been described in 390 teleost fish species belonging to 104 families. In rearing conditions, intra-cohort cannibalism is one of the major bottlenecks during the early life stages of pikeperch (Sander lucioperca). This study aims to describe precisely the occurrence and the onset of cannibalism of this species during the first two post-hatching months. In a first step, the cannibalistic behaviour was analysed through observations in three experiments. In each experiment, the number of cannibalistic cases was similar. From 14 to 48 days post-hatching (dph), more than 60 % of prey ingestions were realized by tail-first, but after 48 dph, the number of prey ingestions by head-first increased. In a second step, the behavioural sequence exhibited to attack and to capture a conspecific was analysed, taking into account the size ratio between the cannibal and its prey. The behavioural sequence to capture was always the same, similar to a predatory sequence and it seems that the cannibal chose its prey about 10 s before attacking. Moreover, prey choice by a cannibal was based more on the size ratio between the cannibal and its prey than the previous activity of the potential prey. These new results could lead to solutions to decrease cannibalism in pikeperch rearing.