Seahorses are a high-value fish species in both medicinal and aquarium trades. In China, seahorses are called ‘animal ginseng’. Since 2004, all 33 recognised seahorse species (Hippocampus) in the world have been listed on Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES 2004) due to overexploitation.

1. September | October 2013
Feeding lined seahorse juveniles with
enriched Artemia nauplii
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3. S
eahorses are a high-value fish
species in both medicinal and
aquarium trades. In China, seahors-
es are called ‘animal ginseng’. Since
2004, all 33 recognised seahorse species
(Hippocampus) in the world have been
listed on Appendix II of the Convention on
International Trade in Endangered Species
of Wild Fauna and Flora (CITES 2004) due
to overexploitation.
There arises an urgent need for breeding
seahorses to meet human demand. To meet
this demand, considerable progress in breed-
ing seahorses has been made in the past ten
years. To date, more than 10 seahorse species
have been reared successfully in captivity.
However, low survival, particularly in the early
juvenile stage, is still one of the bottlenecks
affecting the economic return in commercial
seahorse culture.
Juvenile nutrition is recognised as a major
factor that can influence juvenile survival and
growth. Furthermore, broodstock nutrition is
recognised as a major factor that can influence
fish reproduction and subsequent larval quality
of many fish species. Hence, optimising both
juvenile feeds to enhance growth and survival
of seahorse and to reduce production cost is
crucial for successful commercial culture.
Although copepods are the best food for
juvenile seahorses, mass culture of copepods
is still a challenge. Alternatively, newly hatched
Artemia nauplii have been widely used as live
food for seahorses. However, newly hatched
Artemia nauplii are deficient in DHA and EPA,
i.e. they do not provide adequate nutrition to
improve the growth and survival of seahorse
juveniles. Therefore, Artemia nauplii are usually
enriched with n-3 HUFAs prior to feeding
seahorse juveniles. However, excess HUFAs
fortification may cause adverse effects prob-
ably due to oxidative stress.
Characteristics of Artemia
nauplii
Artemia nauplii have to be
enriched with highly unsaturated
fatty acids (HUFAs) prior to feeding
seahorse juveniles. However, infor-
mation about optimized encrich-
ment for seahorse juveniles is very
limited. The enzymatic activity is a
good indicator revealing the diges-
tive and absorptive capacity of the
animal and is useful in evaluat-
ing effect of feed on survival and
growth performance.
Dietary HUFAs are able to
modify some enzymatic activities,
and moderate dietary HUFAs sup-
plementation significantly promotes
lipid metabolism and reduces lipid
peroxidation products by enhanc-
ing antioxidant defence in the juve-
niles.
However, excess HUFAs may
result in adverse effects on the
Feeding lined seahorse juveniles
with enriched Artemia nauplii
by Dong Zhang PhD and Fei Yin PhD, East China Sea Fisheries Research Institute, Chinese
Academy of Fishery Sciences, China
Figure: 1
26 | InternatIOnal AquAFeed | September-October 2013
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5. enzymatic activities in the juveniles,
which might be related to oxidative
stress. In practice, the concentra-
tion of 27.0 μl/l HUFAs is rec-
ommended for enriching Artemia
nauplii for lined seahorse juveniles.
The lined seahorse,
Hippocampus erectus (Perry), has
been reared successfully for years,
and is recognised as a good can-
didate for commercial aquaculture.
There is currently very limited
information about how HUFAs
affect the survival and growth of
the seahorse juveniles, the activities
of lipid metabolism related and
anti-oxidative stress enzymes.
Since HUFAs are able to affect
activities and gene expressions of
lipid metabolism-related enzymes,
the enzymatic activity is a good
indicator revealing the digestive and
absorptive capacity of seahorses.
Studying enzymatic activity is useful
in evaluating the effect of feed on
survival and growth performance.
Experimental protocols
Newly hatched nauplii of Artemia sinica at
approximately 200 nauplii/mL were cultured
in 15 litre tanks, which were enriched with
four concentrations 0.0 μl/l, 13.5 μl/l, 27.0
μl/l, and 54.0 μl/l, of HUFAs (2/3 DHA, 1/3
EPA), respectively for 12 h with aeration at
temperature of 28.0±1.0 C.
Each tank (50×30×30 cm) was stocked
with twenty 20 day-old juveniles. Plastic plants
were used as the substrate and holdfasts
for the juveniles. The juveniles were fed the
Artemia nauplii enriched with four concentra-
tions of HUFAs. Each diet was fed to three
tanks of the biochemical parametres and enzy-
matic activities (Lipase (LPS), Lipoproteinlipase
(LPL), malate dehydrogenase (MDH), alkaline
Figure: 2
September-October 2013 | InternatIOnal AquAFeed | 27
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6. phosphatase (AKP), pyruvic acid (PA), lac-
tate (LD)], antioxidant defence enzymes,
superoxide dismutase (SOD), catalase (CAT),
glutathione peroxidase (GPX), and oxidative
breakdown product, malonaldehyde (MDA))
were monitored over 30 days.
The juveniles were fed twice
at 0800 h and 1500 h each day
at approximately 10 nauplii/mL.
Before each feeding, the bot-
tom of the tanks was siphoned
to remove feces and uneaten
food.
Impact of different
HUFAs concentrations
The different concentra-
tions of HUFAs significantly
affected the activities of lipase
(LPS), lipoproteinlipase (LPL)
and malate dehydrogenase (MDH) of the
lined seahorse juveniles, but alkaline phos-
phatase (AKP) (Figure 1).
The LPS activity of the juveniles in the
concentration of 27.0 μl/l HUFAs was sig-
nificantly higher than that in other three
concentrations (Figure 1). LPL activity in the
higher concentrations (i.e. 27.0 and 54.0 μl/l
HUFAs) were significantly higher than that
in the lower concentrations (i.e. 0.0 and
13.5 μl/l HUFAs) (Figure 1). MDH activity
decreased with increasing concentration of
HUFAs (Figure 1).
The different concentrations of HUFAs
significantly affected the contents of lactate
(LD) and malonaldehyde (MDA) of the
seahorse juveniles (Figure 2). The lowest
LD content of the juveniles occurred in the
concentration of 54.0 μl/l HUFAs (Figure. 2).
MDA content decreased significantly from
the concentrations of 0.0 to 27.0 μl/l HUFAs
(Figure 2). Pyruvic acid (PA) content was not
significantly different among the four concen-
trations (Figure 2).
The different concentrations of HUFAs
significantly affected activities of
superoxide dismutase (SOD),
catalase (CAT) and glutathione
peroxidase (GPX) of the sea-
horse juveniles (Figure 3). The
SOD activity in the lower con-
centrations (i.e. 0.0 and 13.5 μl/l
HUFAs) was significantly higher
than in the higher concentration
(i.e. 27.0 and 54.0 μl/l HUFAs)
(Fig. 3). CAT activity increased
significantly from the concentra-
tions of 0.0 μl/l HUFAs to 27.0 μl/l
(Figure 3). GPX activity increased
significantly with increasing con-
centration of HUFAs (Figure 3).
Conclusions
Dietary HUFAs may be used
to modify some enzyme activities
and biochemical contents, and
moderate dietary HUFAs supple-
mentation significantly promotes
lipid metabolism and reduces
lipid peroxidation products by
enhancing antioxidant defence in
H. erectus juveniles.
However, excess HUFAs may
result in adverse effects on the
enzymatic activities in the juve-
niles, which might be related to
oxidative stress.
In practice, the concentration
of 27.0 μl/l HUFAs is recom-
mended for enriching Artemia
nauplii for H. erectus juveniles,
which is consistent with the
results of growth and survival.
More InforMatIon:
Dong Zhang
Email: zd_fit@hotmail.com
Figure: 3
28 | InternatIOnal AquAFeed | September-October 2013
FEATURE
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