CANNIBALISMIN CULTURED EURASIAN PERCH, PERCA FLUVIATILIS (ACTINOPTERYGII: PERCIFORMES: PERCIDAE)-IMPLICATION OF MATERNAL INFLUENCE, KINSHIP, AND SEX RATIO OF PROGENIES

Background. Intra cohort cannibalism is one of the main factors that affects the growth and survival of cultured fishes, especially in the larval and juvenile stages. Cannibalism is mainly influenced by extrinsic factors, but intrinsic effects cannot be excluded. As regards the family Percidae, all-female rearing can be advantageous for the fish growth, but does this solution have some impact on cannibalism? The main objective of this study was to investigate potential differences in cannibalism rate and its relation to further growth and survival between mixed-sex and all-female Eurasian perch, Perca fluviatilis Linnaeus, 1758, larvae reared in full-siblings and half-siblings groups. The additional purpose of this study was to determine whether there was some maternal influence on the cannibalism-survival-growth dynamics in cultured Eurasian perch larvae. Materials and methods. Cannibalism, survival, and growth were studied in mixed-sex and all-female progenies of Eurasian perch larvae. Ten-day old larvae (body weight of 20 mg) originating from the crosses of four parents (two females: f1 and f2; one male: ma; and one neomale: mc) were reared over 77 days at 22 degrees C under the light regime of 16 : 8 (light : dark) in replicated groups consisting of mixed-sex full siblings (f1 ma, f2 ma), all-female full siblings (f1 mc, f2 mc), or mixed-sex half-siblings (f1 ma + f2 ma) and all-female groups (f1 mc + f2 mc). Results. At the end of the experiment, there was no sexual growth dimorphism and no sex-biased cannibalism. Neither the effect of sibling versus half-sibling groups, nor effects of normal progeny versus all-female population on survival and cannibalism rate were significant. By contrast, maternal effects on cannibalism were observed, chiefly as regards type I cannibalism (partial and tail-first ingestion), and they impacted on survival, as mortality from other causes (complete cannibalism or others) was independent from maternal origin. Conclusion. There is no particular disadvantage of rearing monosex female progenies in term of cannibalism and survival, whereas this culture-management solution is prone to produce long-term advantages for the perch growth, owing to the faster growth of female fish.