The role of nutritional
factors on the survival and disease tolerance of common dentex (Dentex dentex), reared under intensive aquaculture conditions
European Network for the Dissemination of Aquaculture
RTD Information (Q5CA-2000-30105) and previously FAIR-3837, Aquaflow ref. :
TL2003-183
The
common dentex is a prime candidate species for the diversification of
Mediterranean marine finfish production.
Reproduction of this species in captivity is feasible and juvenile
fish show a better growth rate than that of sea bream and sea bass. However,
intensification of its production is not feasible yet, due to (a) a high
incidence of cannibalism and low survival at the fry stage, and (b) the
non-acceptance of dry formulated commercial feed during the grow-out.
The objective of this project was to study the effect
of nutritional factors on the survival and the immune system of common
dentex. Initially, differences
in the proximate analysis between wild and reared stocks were identified.
Then, seven experimental diets and one commercial diet were tested in
order to improve feed acceptability and to check their effect on fish
cannibalism present on the fry and juveniles of common dentex.
Finally, the effect of specific nutritional factors, such as vitamin
C, E, and fatty acids, on the immunological system was studied.
The experimental diets were formulated either to
incorporate different ingredients with attractive properties (fish solubles,
krill meal, shrimp meal and meat solubles for diets 1 to 4 respectively) or
to have increased moisture (30%, for diet 5). An all fishmeal as well as one
raw fish diets were also tested as control treatments. The experiments
revealed that the common dentex showed a very limited acceptability of the
sea bream (Sparus aurata)
commercial feed. However, all the experimental diets, either in dry or wet
formulation, displayed a good acceptability. These results indicate that the
common dentex can consume dry feeds of the proper texture and taste. It was
also observed that a high incidence of cannibalism was evident in only
unhealthy individuals.
Experimental rearing of fish at both the laboratory
and the commercial scale for the evaluation of the relation between
different levels of vitamins and fatty acids and the immunological system
showed that:
the growth rate was not affected by the different
levels of vitamins and fatty acids in the experimental diets, the vitamin
content in tissues was increased only in the case of vitamin E, and the
lysozyme activity and the phagocytosis index did not show to be efficient
indicators of the no- specific immunosystem for the particular species.
Further
research is now in progress in order to define the nutritional requirements
of common dentex, reared under intensive culture conditions.
Grant:
PENED. Ministry of Development, General Secretariat of Research &
Technology.
For more information, contact:
Dr. I. Nengas
Hellenic Centre for Marine Research
Institute of Aquaculture
Agios Kosmas, Hellinico
GR-16604 Athens - Greece
Tel.: +30 1 9820213
Fax: +30 1 9811713
E-mail:
jnengas@ncmr.gr