Effect
of stocking density on the dynamics of cannibalism in sibling larvae of Perca
fluviatilis under controlled conditions
E.
Baras, P. Kestemont, Ch. Mélard-2003
Aquaculture, 219(4): 241-255
Abstract:
The
effect of stocking density (10, 31.6 and 100 larvae l-1; 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, 20.0±0.5 °C, O2>/=6.0 mg l-1;
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-1.
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.
(Ethology
and Animal Psychology, University of Liège, Belgium, e-mail: E.Baras@ulg.ac.be)