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Characterization of growth and biochemical composition of
sterlet, Acipenser ruthenus L., juveniles from the Dniester
population reared in RAS
Oleksyi Khudyi, Ryszard Kolman, Lidia Khuda, Mykhailo Marchenko, Larisa Terteryan
Received – 19 September 2014/Accepted – 25 October 2014. Published online: 31 December 2014; ©Inland Fisheries Institute in Olsztyn, Poland
Citation: Khudyi O., Kolman R., Khuda L., Marchenko M., Terteryan L. 2014 – Characterization of growth and biochemical composition of sterlet,
Acipenser ruthenus L., juvenile from the Dniester population reared in RAS – Arch. Pol. Fish. 22: 249-256.
Abstract. A broodstock was created with individuals from the
diminishing natural sterlet, Acipenser ruthenus L., population
in the upper area of the Dniester basin. Selects and spawners
were reared in flow-through tanks with natural thermal
regimes. This is the first time artificial reproduction has been
performed with this species, followed by incubation and larval
rearing. The experimental rearing was conducted in tanks in
a recirculating aquaculture system, in which the basic
environmental quality parameters were controlled, including
water temperature, oxygen saturation, and levels of ammonia
and nitrite. During rearing, growth rates and proximate
composition of larvae and then juvenile were examined. It was
confirmed that during the period of endogenous feeding there
was a two-fold decrease in the contents of protein and lipids in
the bodies of the larvae. The effects of feeding the sterlet
juvenile two different types of commercial feed were
compared, and it was confirmed that the feed had a significant
impact on sterlet growth rates. The mean daily increase in the
body weight of sterlet juvenile fed Skretting feed was 1.91%,
while that in the group fed Aller feed was 0.97%. Additionally,
the juvenile from the former group was characterized by
higher contents of protein and lipids in both the liver and
muscle and the fatty acid profile was more varied.
Keywords: Acipenseridae, intensive rearing, growth rate,
biochemical composition
Introduction
Developing practical methods for the conservation
and restoration of stocks of rare fish species threat-
ened with extinction requires performing compre-
hensive biological studies of individual populations
and the conditions in which they occur naturally, the
creation of selected broodstocks in aquaculture, and
the development of technologies for artificial repro-
duction and rearing stocking material (Kolman et al.
2011, 2014). Sterlet, Acipenser ruthenus L. is catego-
rized as a fish that is both economically and environ-
mentally valuable. Its meat and roe are particularly
highly valued for their nutritional and organoleptic
properties. However, current resources of this fish in
Ukrainian waters have been greatly diminished
(Khudyi and Khuda 2014). Declining abundance of
sturgeon populations and, in extreme instances, their
extirpation, have been caused by overfishing, con-
structions to effect river regulation, degraded
hydrobiological conditions, and habitat loss (Pikitch
et al. 2005). Sterlet is categorized as threatened with
Arch. Pol. Fish. (2014) 22: 249-256
DOI 10.2478/aopf-2014-0026
RESEARCH ARTICLE
O. Khudyi [+], L. Khuda, M. Marchenko, L. Terteryan
Department of Biochemistry and Biotechnology
Chernivtsi National University, Ukraine
e-mail: khudij@email.ua
R. Kolman
Department of Ichthyology
Inland Fisheries Institute in Olsztyn, Poland
extinction in Ukraine (Akimov 2009) and throughout
its range of occurrence (Gesner et al. 2010).
Sterlet can form potadromous populations in up-
per river courses, and one such population has survived
in the aquatic system of the upper Dniester River
(Skilsky et al. 2007). No sturgeon from alien popula-
tions have been introduced in this region. Thus, the ge-
netic purity of this autochthonous population remains
intact, which renders the sterlet of the upper Dniester
particularly valuable ecologically. The abundance of
the population is, however, very low. This has
prompted work to be undertaken to develop
biotechnologies for the artificial reproduction and rear-
ing of stocking material. The program to restore the Bal-
tic Sea population of Atlantic sturgeon, Acipenser
oxyrinchus Mitchill, is a positive example of how to-
day’s aquaculture technologies can be exploited for
conservation measures (Kolman et al. 2014).
Initiating regular restocking with Dniester sterlet
juvenile produced in aquaculture is urgent because
of the range of anthropogenic and natural factors that
could cause the extinction of this fish population in
the upper Dniester River. Introducing the Dniester
sterlet to aquaculture is not only important for con-
servation efforts, it is also of economic consequence
because of the high commercial value of the species.
The factors affecting meat quality and its nutritional
value include the contents of protein, lipids, and cho-
lesterol, and the fatty acid profile. This is why much
of the focus of the current study was on the effect
rearing conditions had on the biochemical composi-
tion of the fish. The aim of this study was to deter-
mine the impact feeding had on sterlet larvae and
juvenile growth rates and on the proximate body
composition and fatty acid profile. The assumption
was that these results could serve to optimize the nu-
trition of juvenile sterlet in future
Materials and methods
The study material comprised sterlet larvae and juve-
nile of the Dniester population bred using domesti-
cated spawners caught in the wild. Artificial
spawning, egg incubation, and initial rearing were
conducted at the Ishkhan fishery enterprise on the
Cheremosh River in the Chernivtsi Oblast, Ukraine.
The juvenile specimens were reared during two ex-
periments performed in tanks in a recirculating
aquaculture system at the Department of Biochemis-
try and Biotechnology, Chernivtsi National Univer-
sity and at the Department of Ichthyology, Inland
Fisheries Institute in Olsztyn.
Artificial reproduction, egg incubation, and ini-
tial rearing of juvenile were performed in accordance
with methods developed for sturgeon (Kolman
2010). The controlled larval rearing period was from
hatching until the beginning of intense exogenous
feeding. Initially, the larval sterlet were fed Artemia
nauplii, and then Perla Larvae pro Activ (Skretting,
Norwey) was introduced gradually according to tech-
nology developed for sterlet (Kolman et al. 2011).
Experimental larval rearing was conducted in tanks
with bottom surface areas of 0.5 m2each at an initial
stocking density of 2500 fish m-2. At the beginning of
the experiment the water temperature was kept at
16°C, and was then gradually increased to 18°C.
During larval rearing, the concentrations of oxygen
and toxic ammonia and nitrite remained within
ranges optimal for sturgeon juvenile (Kolman 2010).
During the first experiment, ten sterlet larvae were
weighed and measured daily.
The next phase of rearing was performed in recir-
culating systems at the Department of Biochemistry
and Biotechnology, Chernivtsi National University.
Three-hundred and twenty individuals were stocked
into square tanks with volumes of 1.6 m3each (200
fish m-3). The sterlet were fed during this period with
Nutra TT (Skretting). The water temperature ranged
from 19 to 22°C, and the oxygen concentration did
not decrease below 70% saturation. The final stage of
the experiment focused on the comparison of the im-
pact different feeds had on the proximate body com-
position and fatty acid profile. Juvenile aged six
months were fed commercial feeds manufactured by
Aller Aqua (Poland) and Skretting. According to
manufacturer declarations, the Aller Aqua feed con-
tained 45.0% total protein, 15.0% lipids, 21.8% car-
bohydrates, 6.9% ash, 3.3% fiber, 0.2% sodium,
0.8% calcium, 1.0% phosphorus, 10000 IU vitamin
250 Oleksyi Khudyi et al.
A, and 1000 IU vitamin D3. The corresponding feed
from Skretting had the following composition: 47.0%
total protein, 14% lipids, 7.5% ash, 2.6% fiber, 0.4%
sodium, 1.0% calcium, 1.1% phosphorus, and 5000
IU vitamin A.
Biochemical analysis
Larval sterlet were collected daily for biochemical
tests to determine the contents of total protein and
lipids (n = 10). The specimens used for this were col-
lected for evaluations of growth rate. The compara-
tive biochemical tests were performed on a sample
comprising juvenile collected once from both groups
(n = 8). The mean body weight of the two groups dif-
fered with fish fed Aller Aqua feed weighing approxi-
mately 130 g, while fish reared on the Skretting feed
weighed approximately 160 g.
The contents of total protein in the liver and white
muscle homogenate were determined with the Lowry
method (Lowry et al. 1951). The lipid fraction was ex-
tracted from the sterlet body tissues with the Folch
method (Folch et al. 1957). The total lipid content,
cholesterol, and fatty acids were determined in the ex-
tract. The fatty acids were determined in the labora-
tory of the Institute of Biochemistry of the Ukrainian
National Academy of Sciences using the gas chroma-
tography method and a HRGC 5300 chromatograph
with a 3.5 m glass column filled with Chromosorb
W/HP with a 10% Silar 5CP liquid phase at a pro-
grammed temperature range of 140-250°C with a 2°C
min-1 gradient. The different fatty acids were identi-
fied with standards from Sigma and Serva, and their
values were expressed in percentages of the total
quantity of fatty acids. The contents of protein, total
lipids, and cholesterol were expressed in mg per 1 g
dry tissue weight mg × g-1 dry weight
MS Excel was used for statistical processing.
Student’s t-test was used to determine the signifi-
cance of differences among groups at a level of signif-
icance of P £0.05.
Results and Discussion
At the end of April when the water temperature in-
creased to 14-15°C and following hormonal stimula-
tion, sex products were collected in vivo from sterlet
spawners and the eggs were fertilized artificially. The
eggs were incubated in Weiss jars. Embryo survival
to hatching was approximately 50%.
The specific growth rate of larval sterlet reared at
optimal temperatures of 20-22°C can range from 5 to
30% of body weight daily (Gorskii and Yarzhombek
2003). The mean specific growth rate of the larval
Dniester sterlet population was 3.8 mg d-1, which
was 20.5% of the mean initial weight. The body
weight growth rate was exponential (Fig. 1); however,
the mean total body length of sterlet increased during
this period by 54.6% at 23.2 ± 0.42 mm. Increases in
total length at this stage of rearing was linear (Fig. 2).
It should be underscored that the water temperature
Characterization of growth and biochemical composition of sterlet, Acipenser ruthenus L., juveniles... 251
y = 0.4593x -1.191x + 19.653
2
R = 0.9306, P < 0.05
2
0
10
20
30
40
50
60
70
24681012
Days
Total protein content (mg x g dry weight)
-1
Figure 1. Mean body weight growth of larval Dniester sterlet (A.
ruthenus) during initial rearing in RAS tanks.
y = 0.6636x + 14.473
R = 0.7485, P < 0.05
2
14
16
18
20
22
24
024681012
Days
Mean length (mm)
Figure 2. Mean total body length growth of larval Dniester sterlet
(A. ruthenus) during initial rearing in RAS tanks.
in the tanks stocked with larval sterlet was 16-17°C,
which is lower than the optimum for quick growth.
Nevertheless, the larval growth rate was fast. During
the endogenous feeding phase, the contents of pro-
tein (Fig. 3) and total lipids (Fig. 4) decreased nearly
two fold. The larvae began exogenous feeding six to
seven days after hatching. Changes in feeding cased
rapid body weight growth, and increases in the con-
tents of protein and lipids.
The juvenile had reached a mean body weight of
3.46 ± 0.32 g by the age of two months. The sterlet
were divided into three size groups: the first group
comprised 23% of the total number of fish, and their
mean body weight was 1.28 ± 0.15 g; the second
group comprised 45% of the fish with a mean body
weight of 2.94 ± 0.19 g; the mean body weight of the
remaining fish was 5.83 ± 0.37 g. The maximum and
minimum juvenile body weights were 8.55 and 1.05
g, respectively.
By the age of four months, the mean body weight
of the fish was 22.3 g. In this same period, the mean
body weight of the sterlet reared in the tanks at
Ishkhan was just 13.5 g; this was probably caused by
the low water temperature of 16-17°C. Data in the
literature indicates that sturgeon growth rates de-
cline significantly at water temperatures below 15°C
(Alimov et al. 2007).
Feeding is a very important element of intensive
aquaculture technology. The quality of the feed, its
composition, and the technique of its delivery all
have a significant impact on fish tissue and organ
biochemical indicators (Chipinov et al. 2012). The
type of feed had a significant impact on the specific
growth rate of the juvenile sterlet (Fig. 5; P < 0.05).
252 Oleksyi Khudyi et al.
0
50
100
150
200
250
300
350
400
450
2 4 6 8 10 12
Days
Totalproteincontent(mgxg dryweight)
-1
Figure 3. Changes in total protein content in bodies of Dniester
sterlet (A. ruthenus) during initial rearing in RAS tanks.
0
0.5
1
1.5
2
2.5
Aller Aqua Skretting
Specific growth rate (% d )
-1
Figure 5. Differences in the specific growth rate of body weight in
juvenile starlet (A. ruthenus).
0
50
100
150
200
250
300
2 4 6 8 10 12
Days
Total lipid content (mg x g dry weight)
-1
Figure 4. Changes in total lipid content in bodies of Dniester
sterlet (A. ruthenus) during initial rearing in RAS tanks.
*
0
100
200
300
400
500
600
700
800
900
muscle liver
Totalproteincontent(mgxg dryweight)
-1
Aller Aqua Skretting
Figure 6. Total protein content in muscles and livers of juvenile
sterlet (A. ruthenus). *differences among groups is statistically
significant: P £0.05.
The daily growth rate of sterlet fed the Skretting feed
was nearly twice that of the fish fed Aller Aqua feed
(1.91 and 0.97%, respectively).
Rearing sterlet under intense aquaculture condi-
tions with artificial feed causes changes in the bodies
of these fish in comparison with individuals from nat-
ural environments (Kireyev 2011). Accelerated fish
growth requires intensified protein synthesis in
which the liver plays a special role. The liver is the
primary organ for processing large quantities of pro-
tein that is then transported to the body, in particular
blood serum protein (Yarzhombek 2007). The type
of feed had a significant impact on the contents of
protein in the livers of the juvenile sterlet (Fig. 6; P <
0.05), but the protein content in muscles of sterlet
fed the two feeds compared was similar (P > 0.05).
The lipid content and composition in fish from
aquaculture differs from that of wild fish. This stems
from the composition of the food and various behav-
iors that demand various expenditures of energy, and
these factors lead to increased fat content in the body
(Ovissipour and Rasco 2011, Ghomi et al. 2013).
The results of this study confirmed that the type
of feed has a statistically significant impact on the
liver lipid contents of juvenile sterlet (P < 0.05). The
fish fed the Skretting feed had higher liver total lipid
contents (Fig. 7). The muscle total lipid content was
also higher in the fish fed this feed, but the differ-
ences noted were not statistically significant (P >
0.05). Lipid content was higher in the livers than in
the muscles in both groups (Fig. 7).
Cholesterol is one of the essential structural com-
ponents of cell walls, and it is a precursor of bile ac-
ids, steroid hormones, and vitamin D3. Cholesterol is
the most commonly occurring sterol in fish tissues.
Its content in different tissues and organs fluctuates
within a wide range. The highest concentrations are
noted in the brain and adrenal glands, a little less in
the liver and gastrointestinal mucosa, and the least in
the muscles and connective tissue (Kopicová and
Vavreinová 2007). The cholesterol occurring in the
muscle tissues is mainly the free form and its compo-
sition is characterized by high levels of saturated
(palmitic acid) and polyunsaturated (oleic and
palmitoleic) fatty acids. The greatest quantity of cho-
lesterol is synthesized directly in the livers of fish.
However, the speed of sterol synthesis in the liver is
substantially slower in fish than in mammals; conse-
quently, most cholesterol is delivered to fish by the
food. This is why the cholesterol content in the liver
depends on feed quality and feeding intensity. The
results of the study indicated slightly lower quanti-
ties of cholesterol deposited in the livers and tissues
of the fish fed Aller Aqua feed (Fig. 8).
The feeding tests confirmed that the type of feed
has a statistically significant impact on the fatty acid
profile and content (Table 1). The muscles of juvenile
sterlet fed Skretting feed contained 29 fatty acids of
which 33% were saturated (SFA), 39%
monounsaturated (MUFA), and 28% polyunsatu-
rated (PUFA). The sterlet fed Aller Aqua feed were
lacking five fatty acids that were noted in the fish fed
Characterization of growth and biochemical composition of sterlet, Acipenser ruthenus L., juveniles... 253
*
0
50
100
150
200
250
300
muscle liver
Aller Aqua Skretting
Total lipid content (mg x g dry weight)
-1
Figure 7. Total lipid content in muscles and livers of sterlet juve-
nile (A. ruthenus). *differences among groups is statistically sig-
nificant: P £0.05.
0
5
10
15
20
25
30
35
40
45
muscle liver
Aller Aqua Skretting
Total choresterol content ( g x g dry weight)μ
-1
Figure 8. Total cholesterol content in muscles and livers of sterlet
juvenile (A. ruthenus).
the Skretting feed (Table 1). However, the total con-
tent of unsaturated fatty acids in the muscles was
higher in fish fed the Aller Aqua feed. Thirteen satu-
rated fatty acids were noted in the muscles of juvenile
sterlet fed the Skretting feed. The dominant fatty acid
was palmitic, while significant amounts of myristic,
stearic, and arachidic fatty acids were noted. The
shares of the other unsaturated fatty acids did not ex-
ceed 1%. It should be underscored that the fatty acid
spectrum in the muscles of the fish examined began
with undecanoic (C11:0), which was not noted in
other studies (Lee et al. 2012, Ljubojevic et al. 2013).
254 Oleksyi Khudyi et al.
Table 1
Fatty acid profile (%) in muscles of juvenile sterlet (A. ruthenus) fed different commercial feeds
Fatty acid Aller Aqua Skretting
Undecanoic C11:0 0.30 0.03
Tridecylic C13:0 - 0.02
Myristic C14:0 3.73 5.09
Isomyristic Ci14:0 - 0.02
Pentadecanoic C15:0 0.28 0.33
Palmitic C16:0 17.42 21.80
Isopalmitic Ci16:0 0.14 0.07
Margaric C17:0 0.57 0.83
Stearic C18:0 2.16 1.96
Isostearic Ci18:0 0.24 0.37
Arachidic C20:0 1.30 1.38
Heneicosylic C21:0 0.31 0.30
Behenic C22:0 0.31 0.29
GSFA 22.73 32. 51
Lauricoleic 0.06 0.08
Myristoleic C14:1 0.09 0.22
Palmitoleic C16:1 5.87 9.30
Margaroleic C17:1 0.53 0.74
Oleic C18:1 34.52 26.25
Gadoleic C20:1 2.20 2.24
GMUFA 43.27 38.82
Tetradecanoic C14:2 - 0.05
Hexadecanoic C16:2 T-6 - 0.15
Linoleic C18:2 T-6 12.31 10.99
Linolenic C18:3 T-3 2.52 1.15
Eicosatrienoic C20:3 T-6 0.19 0.10
Arachidonic C20:4 T-6 0.93 0.68
Eicosapentaenoic C20:5 T-3 6.45 7.64
Docosadienoic C22:2 T-6 0.20 0.24
Eicosatrienoic C22:3 T-3 - 0.11
Docosahexaenoic C22:6 T-3 6.47 6.44
GT-3 15.44 15.27
GT-6 13.63 12.13
GPUFA 29.07 27.45
MUFA comprised approximately 40% of the fatty ac-
ids in the muscles of juvenile sterlet. The greatest
fraction of MUFA was of oleic and palmitoleic fatty
acids (Table 1). The polyunsaturated fatty acids in
sterlet muscles comprised mainly linolenic,
eicosapentaenoic, and docosahexaenoic fatty acids.
The results of the present study confirmed that
feed had a significant impact on both sterlet growth
and body composition. These pilot experiments sup-
port the aim of improving feed quality through sup-
plementing missing fatty acids and protein fractions
that can have a significant impact on sterlet rearing
indicators as well as their condition and the composi-
tion of their muscle tissues. This is very important
from the standpoint of proposed restoration work
and for the development of commercial sterlet pro-
duction in aquaculture. In the first instance, optimiz-
ing feeding will increase the biological value of
stocking material, which will result in increased sur-
vival in the wild. In the second instance, the eco-
nomic outcomes of rearing these fish will improve as
will the nutritional value of the meat, which will earn
the status of a functional food.
Acknowledgements. The study was partly conducted
within the framework of the statutory research program
of the Inland Fisheries Institute in Olsztyn (No. S025).
Author contributions. O.K., R.K., L.K. and M.M. de-
signed the research; L.K. and L.T. performed the re-
search; O.K., R.K., L.K. and L.T. analyzed the data; O.K.
and R.K. wrote the paper.
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