Evaluation of microdiets
versus live feeds on growth, survival and fatty acid composition of larval
haddock (Melanogrammus aeglefinus)
T. Blair, J. Castell, S. Neil, L. D'Abramo, Ch. Cahu, P. Harmon, K. Ogunmoye-2003
Aquaculture, 225(1-4): 451-461
Abstract:
Two newly developed microdiets for the culture of
marine fish larvae were compared to the control ICES Standard Weaning diet
and the traditional live foods, rotifers (Brachionus plicatilis) and Artemia
nauplii, in a feeding study with larval haddock. Haddock larvae were reared
from hatch to 20 days post hatch (dph) in a 5000-l tank and fed
algae-enriched rotifers. Between 21 and 24 dph, 1000 larvae were transferred
to each of the 20 tanks. From 25 until 45 dph, the larvae were fed five
different diets: (1) B. plicatilis enriched with mixed algae species;
(2) Artemia nauplii enriched with Algamac 2000 (Aquafauna-BioMarine,
California, USA); (3) ICES Standard Weaning Diet; (4) IFREMER-INRA
microdiet; and (5) microdiet produced by Louis D'Abramo, Mississippi State
University, MS, USA. Survival was significantly higher (P<0.001)
in the rotifer and Artemia nauplii treatments (mean±S.E.; 24.9±4.2%
and 21.3±6.3%, respectively) than in the microdiet treatments (ICES, 2.2±1.1%;
IFREMER-INRA, 4.3±1.8%; and D'Abramo, 4.0±1.2%). Survival was not
significantly different (P<0.05) among the microdiet treatments.
Mean larval weights were significantly different (P<0.001) between
rotifer (1.61±0.12 mg) and Artemia nauplii (2.14±0.14 mg)
treatments. The weights of larvae fed microdiets (ICES, 0.75±0.05 mg;
IFREMER-INRA, 0.85±0.04 mg; and D'Abramo, 0.86±0.05 mg) were not
significantly different from each other; however, all microdiet treatments
were significantly smaller than the live feed treatments (P<0.01).
There were also significant differences in the fatty acid composition of the
larvae fed the different diets although no correlation was found between
dietary fatty acid composition and growth or survival of the larvae. The
highly unsaturated fatty acid (HUFA) 22:6n-3 showed a dramatic proportional
increase in larval tissue relative to its proportional composition in both
the live and formulated diets. Dietary proportions of the HUFA 20:4n-6 were
similar among the Artemia, ICES and D'Abramo diets (average
1.2–1.3%); however, the proportions of 20:4n-6 in the larvae were
significantly higher in larvae fed Artemia (mean±S.E.; 5.4±0.11%)
compared to larvae fed either ICES or D'Abramo diets (mean±S.E.; 4.0±0.04%
and 4.4±0.08%, respectively). Proportional increases of other HUFA,
specifically 20:5n-3 and 22:5n-6 in larvae relative to dietary HUFA, suggest
important physiological roles for these fatty acids. It appears that under
the current rearing conditions, none of the microdiets examined is a
suitable replacement for live feeds in the culture of haddock larvae from 25
to 45 dph and factors other than fatty acid composition must be considered.