Do stocking density and feed
reward level affect growth and feeding of self-fed juvenile European sea
bass?
M.
Paspatis, T. Boujard, D. Maragoudaki, G. Blanchard, M. Kentouri-2003
Aquaculture, 216(1-4): 103-113
Abstract:
Survival, growth, nitrogen (N) and phosphorus (P)
budgets and feeding behaviour were studied in groups of sea bass, Dicentrarchus
labrax L., that fed using self-feeders with different feed reward and
maintained at different densities (up to 35 kg m-3 or 500 fish
tank-1). The experiment was conducted in 500-l indoor tanks under
ambient conditions of light and temperature during two successive years. In
the first year (experiment I), fish (5.5±0.1 g) were separated into five
groups according to stocking density (50, 200 or 500 fish tank-1)
and reward (R=0.6 g trigger-1) level: 50:R, 200:R,
200:4R, 500:R and 500:10R. Both increases in stocking
density and in feed reward affected negatively all the studied parameters
concerning growth and feed efficiency (FE). In the second year (experiment
II), the experiment was repeated with fish of similar weight (5.3±0.0 g),
which were held under the following four feeding protocols: 50:0.5R,
50:R, 500:0.5R and 500:R. The lowest feed reward fish
groups presented better tendencies in growth and feed efficiency independent
of stocking density. Survival was high in all feeding regimes in both
experiments, but at high density (500 fish tank-1), some
mortalities (<4%) were observed. Also in both experiments, feeding rhythm
was affected by stocking density, but not by reward levels. Thus, although
fish presented a typical diurnal activity, they restricted their feed
demands at the first and late hours of daylight (08:00–09:00 and 19:00 h)
when held in the lowest stocking density, while in high density they did
not.
It is concluded that a stocking density of up to 35
kg m-3 (or 500 fish tank-1) does not affect self-fed
sea bass kept in tanks, provided that feed reward is set to a low value (0.3
g).
(Institute of Marine Biology of Crete, P.O. Box 2214,
GR-71003, Heraclion, Crete, Greece, Tel.: +30-81346860; fax: +30-81241882;
email: mpaspati@imbc.gr)