International Journal of Aquaculture, 2013, Vol.3, No.22, 126
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132
http://ija.sophiapublisher.com
127
attributed at least to some extent poor larval nutrition
(
Rutaisire, 2013,
Personal communication
,
Aquaculture
Research and Development Centre, Uganda) which
implies that
Artemia
may not meet all the basic
nutritional requirements of African catfish larvae.
Globally, several reports indicate declining yield of
Artemia
cysts from the main wild source, the Great
Salt Lake in Utah, USA, (Lavens and Sorgeloos, 2000).
This trend, combined with likely climatic change
impacts and increasing demand for aquaculture,
necessitates deliberate efforts in mass production of
alternative high quality live starter feeds for sustainable
aquaculture development.
Research in marine fish larval nutrition is not new.
Findings by Shields et al. (1999) indicated that
Copepods provide better nutritional benefits to marine
fish larvae than
Artemia
and Rotifers. The superior
nutritional value of copepods has usually been
attributed to their high polyunsaturated fatty acids
(
PUFA) and unsaturated fatty acids (HUFA) content
essential to fish nutrition (Bell et al., 2003; Conceica
et al., 2010). Molejo and Alvarez-Lajonch
è
re (2003)
therefore recommends culture of small pelagic
copepod species using high-yield semi intensive
technologies. Research on larval nutrition of
freshwater larvae remains limited. Tocher (2010)
argues that the initial assumption that freshwater fish
are generally large enough to accept formulated feeds
has hampered research initiatives in freshwater larval
nutrition. It follows therefore that Information on the
suitability of utilizing copepods as alternative starter
live food in freshwater fish larvae is quite limited.
The present study compared fatty acid profiles and
growth of African
catfish
larvae fed on freshwater
Cyclopoid copepods and decapusulated
Artemia
in an
attempt to present Cyclopoid copepods as alternative
starter feed to
Artemia
,
partially or in totality for the
culture of African catfish larvae.
1
Results
1.1
Growth of Catfish Larvae Fed on Different
Starter Diets
The impact of the three test diets on the growth of
African catfish larvae was significantly different
(
F=25.94, P<0.05; Figure 1). Cyclopoid-
Artemia
-
fed
African Catfish larvae fed indicated best overall
growth performance (9.1±0.89) mm followed by
Cyclopoids-fed larvae (8.8±0.92) mm and
Artemia
(8.6
±0.79) mm. A similar trend was observed for each
day of feeding on the experimental diets.
Figure 1 Impact of test starter diets on growth of African catfish
larvae
Note: Mean total length (mm) of African catfish larvae fed on
three experimental diets (
Artemia
,
Cyclopoids, and a mixture of
Artemia
and Cyclpoids) from day 1 to day 3 following
commencement of exogenous feeding
1.2
Fatty Acid Profiles of Catfish Larvae Fed on
Different Starter Diets
Variation in percentage composition of fatty acids of
larvae fed on different starter diets was observed
(
Table 1). Palmitic acid (16:0) and stearic acid (18:0)
were predominant among total saturated fatty acids
(
SFA) recorded for African catfish larvae fed on the
different diets. Cyclopoid-fed larvae registered much
lower total monounsaturated fatty acids (MUFA)
(12.55
±0.31)% as compared to
Artemia
-
fed larvae and
Cyclopoid-
Artemia
-
fed larvae (21.30±0.3)% and
(21.57
±0.28)%, respectively). Oleic acid (18:1n9) and
Vaccenic acid (18:1n7) were the most dominant
MUFAs across diets. Composition of total polyunsaturated
fatty acids (PUFA) was highest in Cyclopoid-fed
larvae (45.83±0.38)% followed by Cyclopoid-
Artemia
-
fed
larvae (40.95±0.91)% and slightly lower in
Artemia
-
fed
larvae (37.85±2.14)%.
Of the essential fatty acids, variation in composition
was similarly observed across diets (Figure 2). Fish
larvae fed on Cyclopoid copepods indicated
significantly high percentage composition of
docosahexaenoic acid (DHA, 22:6n3; F=101.9,
P=0.002) and Arachidonic Acid (AA, 20:4n6; F=12.1
P=0.037). On the other hand,
Artemia
-
fed larvae, had
slightly higher levels of Linoleic Acid (LA, 6.5%) and
Eicosapentaenoic Acid (EPA, 3.71%), than Cyclopoid
copepod - fed larvae. Consequently, larvae fed on a
combination of
Artemia
and copepods had
significantly higher percentages of three of the
essential fatty acids: Linoleic acid (LA, 18:2n6; F=24.1,