Effect of stocking density on the dynamics of cannibalism in sibling larvae of Perca fluviatilis under controlled conditions

The effect of stocking density (10, 31.6 and 100 larvae l ; three replicates per treatment) on the day-by-day dynamics of survival, growth and cannibalism was examined in sibling perch larvae reared from eyed-egg stage in 100-l cages (16L:8D, 20.0F 0.5 jC, O2z 6.0 mg l ; feeding in excess with live Artemia nauplii during the photophase) during the first 3 weeks of exogenous feeding. Larvae unable to achieve the transition to exogenous feeding died in between 7 and 11 days post-hatch. Later, mortality from causes other than cannibalism never exceeded 1% day . Cannibalism did not start before days 10–11 and first consisted in the incomplete ingestion of prey attacked tail first, exclusively. This type of cannibalism never caused losses higher than 2.0% of the initial stock, and ceased after days 16–18. From days 12–14 onwards, differential growth was apparent, and cannibals turned to complete cannibalism of small prey ingested head first, which caused greater losses (28–53% of the stock). Increasing the stocking density did not compromise growth and decreased the overall impact of cannibalism through several complementary mechanisms: (i) a postponed emergence of cannibalism, (ii) a lower proportion of cannibals in the population, and (iii) probably a lower rate of cannibalism per capita as predation was complicated and less directed at high stocking density. D 2003 Elsevier Science B.V. All rights reserved.