Effect on the
growth and body composition of juvenile tilapia Oreochromis niloticus
fed raw Spirulina
T. Takeuchi, J. Lu, G. Yoshizaki, S.
Satoh-2002
Fisheries Science, 68(1): 34-40
Abstract:
In order to develop a food chain
(phytoplankton-fish) in a closed ecological recirculating aquaculture system
(CERAS), unialgal cultures of Spirulina platensis were fed to tilapia
Oreochromis niloticus (bodyweight; 1.59 ± 0.26 g, standard length;
3.4 ± 0.17 cm) for 9 weeks, using a commercial diet as the control
treatment. Water temperature was 28 ± 0.5°C. Juvenile tilapia grew
efficiently [specific growth rate (SGR) = 3.14, feed efficiency (FE) = 1.22]
and showed a high survival rate (95%) for the duration of the trial without
any nutrient supplements, although the fish fed the commercial diet had a
slightly higher growth rate. A proximate composition analysis showed that
fish fed Spirulina had a higher protein content, a higher polar lipid
content and a lower ash content than fish fed the commercial diet. The
abundance of linoleic acid and γ-linolenic acid (GLA) in the Spirulina
was reflected in the fatty acid profile of the fish. Σn-6 highly
unsaturated fatty acid (20:3n-6, 20:4n-6, 22:4n-6, 22:5n-6), which seemed to
be metabolized from linoleic acid and GLA, increased and were more
pronounced in the polar lipid fraction. On the contrary,
n-3
fatty acids, such as α-linolenic acid, eicosapentaenoic acid and
docosahexaenoic acid, decreased. No significant differences were observed in
the mineral and essential amino acid contents in the fish at the experiment
s
completion, even though there were some differences between raw Spirulina
and the commercial diet. The results suggest that it is feasible to
construct a food chain using raw Spirulina to feed transition-stage
tilapia in a CERAS.
(Department of Aquatic Biosciences,
Faculty of Fisheries, Tokyo University of Fisheries, Minato, Tokyo 108-8477,
Japan, Tel/Fax: 81-3-5463-0545. Email: take@tokyo-u-fish.ac.jp)