Evaluation of dietary protein and lipid requirements of two-banded seabream (Diplodus vulgaris) cultured in a recirculating aquaculture system

Abstract

The objective of this study is to investigate the effects of dietary protein and
lipid levels on the growth performance and bioeconomic benefits of two-banded seabream
(Diplodus vulgaris) juveniles, a candidate species for aquaculture sector. Eight experimental
diets were formulated with four protein (50, 45, 40 and 35 %) levels for each of the
two lipid levels (15 and 10 %). Triplicate groups of juvenile fish with an average initial
body weight of *3.64 g were reared in a recirculating aquaculture system and hand fed
twice a day until satiation for a period of 60 days. In the experiment, no difference in
survival rate was found between the different groups. Relative growth rate (RGR), specific
growth rate (SGR), feed conversion ratio (FCR) and daily feed intake were not significantly
affected by increasing protein and/or lipid treatments in this present study. However,
the RGR, SGR and FCR values showed slightly better efficiency in the experimental group
(35/15) fed with lower protein content (35 %) and higher lipid level (15 %) compared with
those fed other diets. According to bioeconomic analyses results, the diet with the 35 %
protein and 15 % lipid generated the best profit. The results suggest that two-banded
seabream can be accepted as a promising alternative species for the aquaculture industry
and optimum growth of two-banded seabream fingerlings can be obtained when they are
fed a diet containing 35 % crude protein and 15 % crude lipid.

Full text

Evaluation of dietary protein and lipid requirements
of two-banded seabream (Diplodus vulgaris) cultured
in a recirculating aquaculture system
Musa Bulut •Murat Yig
˘it •Sebahattin Ergu
¨n•
Osman Sabri Kesbic¸ •U
¨mit Acar •Nejdet Gu
¨ltepe •
Mustafa Karga •Sevdan Yılmaz •Derya Gu
¨roy
Received: 2 May 2013 / Accepted: 24 October 2013
ÓSpringer Science+Business Media Dordrecht 2013
Abstract The objective of this study is to investigate the effects of dietary protein and
lipid levels on the growth performance and bioeconomic benefits of two-banded seabream
(Diplodus vulgaris) juveniles, a candidate species for aquaculture sector. Eight experi-
mental diets were formulated with four protein (50, 45, 40 and 35 %) levels for each of the
two lipid levels (15 and 10 %). Triplicate groups of juvenile fish with an average initial
body weight of *3.64 g were reared in a recirculating aquaculture system and hand fed
twice a day until satiation for a period of 60 days. In the experiment, no difference in
survival rate was found between the different groups. Relative growth rate (RGR), specific
growth rate (SGR), feed conversion ratio (FCR) and daily feed intake were not signifi-
cantly affected by increasing protein and/or lipid treatments in this present study. However,
the RGR, SGR and FCR values showed slightly better efficiency in the experimental group
(35/15) fed with lower protein content (35 %) and higher lipid level (15 %) compared with
those fed other diets. According to bioeconomic analyses results, the diet with the 35 %
protein and 15 % lipid generated the best profit. The results suggest that two-banded
seabream can be accepted as a promising alternative species for the aquaculture industry
and optimum growth of two-banded seabream fingerlings can be obtained when they are
fed a diet containing 35 % crude protein and 15 % crude lipid.
M. Bulut M. Yig
˘it S. Ergu
¨nS. Yılmaz
Department of Aquaculture, Faculty of Marine Science and Technology, C¸anakkale Onsekiz Mart
University, 17100 C¸ anakkale, Turkey
O. S. Kesbic¸ N. Gu
¨ltepe M. Karga
Sea and Port Management Program, Inebolu Vocational School, Kastamonu University,
37500 Inebolu, Turkey
U
¨. Acar (&)
Department of Aquaculture, Faculty of Fisheries, Mugla SıtkıKoc¸man University, Mug
˘la, Turkey
e-mail: umitacar@mu.edu.tr
D. Gu
¨roy
Department of Aquaculture, Armutlu Vocational School, Yalova University, 77500 Yalova, Turkey
123
Aquacult Int
DOI 10.1007/s10499-013-9720-z

Keywords Two-banded seabream (Diplodus vulgaris)Protein Lipid Growth
performance
Introduction
The increase in production and supply of seabream and sea bass, the main two marine
species for the Turkey aquaculture industry, has caused a decline in the market price for
these two species. In order to solve the problem with the market demand, fish culturists
have tended to work on new alternative marine fish species. The alternative species in
aquaculture provide the diversity for extending the market opportunity for their product.
Two-banded seabream is a sparid fish, a candidate for aquaculture sector due to both
high market value, and adapts easily to production system (Jug-Dujakovic and Glamuzina
1988). Diplodus vulgaris has a broad range of salinity tolerance compared with other
marine fish (Horta et al. 2004). Guidetti (2004) and Pallaoro et al. (2006) investigated the
stomach contents of two-banded seabream to reveal the feeding habits, and they pointed
out that algae and sea urchin were important prey for this species. D. vulgaris is an
omnivorous sparid species. Omnivorous species need less animal-based protein in their
diets; therefore, the diet costs are lower. These characteristics make the two-banded sea-
bream a good candidate for the aquaculture industry (Ozo
´rio et al. 2009). Nutrient
requirements of this species are still unknown and not well studied. Nutritionally balanced
diets contribute to high growth performance.
A well-balanced diet in terms of protein-to-lipid ratio is one of the keys for the suc-
cessful and effective feeding in fish nutrition. Furthermore, well-balanced diets are
important to support growth performance, fish welfare and fish health. Among nutrients,
protein and lipid are given more attention as main nutrients affecting fish growth. Proteins
are the most expensive nutrient sources in fish diets and may cause to increase in N
excretion, when they are over of requirement level (Wagner et al. 1995; Brunty et al. 1997;
Yigit et al. 2002). Optimization of protein and lipid levels in fish diets in terms of eco-
nomic and environmental perspective is also an important factor for an environmental
friendly aquaculture industry (Ozo
´rio et al. 2009; Yigit et al. 2002,2004).
The aim of the present study is to evaluate the suitable levels of dietary protein and
lipids for maximum growth, feed utilization and cost of feed production for two-banded
seabream (D. vulgaris).
Materials and methods
A total of 480 two-banded seabream (D. vulgaris) with a mean initial weight of
3.64 ±0.016 g were captured in the Strait of Canakkale (formerly Dardanelles)
(C¸ anakkale, Turkey) and kept at the Marine Aquaculture Research and Development
Center of Faculty of Marine Science and Technology (formerly, Faculty of Fisheries) of
Canakkale Onsekiz Mart University (Dardanos, Canakkale, Turkey). Fish were held in two
circular tanks for 15 days to adapt to the new rearing conditions (750 L max volume) and
during the adaptation stage; fish were fed to satiety twice a day, for 7 days a week with
commercial gilthead seabream diets (49 % crude protein; Bioaqua, Turkey). After the
acclimatization period, 20 fish were weighed and distributed into each of 24 aquariums of
Aquacult Int
123

84 L (35 cm 945 cm 960 cm deep) in a recirculation seawater system equipped
with aeration and filtration systems. Fish were kept under a constant photoperiod of
12 h light/12 h dark period. The experiment was conducted in three replicates per treat-
ment. Water quality parameters were periodically measured throughout the study, and the
following parameters were recorded: temperature 23.1 ±0.4 °C, salinity 29.8 ±0.4 ppm,
pH 8.19 ±0.3, pH 8.19 ±0.3, dissolved oxygen 7.08 ±0.37 mg L
-1
, nitrite 0.08 ±
0.02 mg L
-1
and total ammonia 0.4 ±0.1 mg L
-1
.
Experimental procedures and analyses
Eight fish meal-based diets with decreasing protein levels of 50, 45, 40 and 35 % at two
lipid levels of 15 and 10 %, respectively, were formulated using commercially available
ingredients (Table 1).
All ingredients were well mixed using a laboratory food mixer. The mixtures were
primed with water to yield a suitable pulp. Wet diets were made into 2-mm pellet size
using a meat grinder and dried at 40 °C in a drying chamber. The diets were stored at
-20 °C until use.
During the feeding experiment, fish were hand fed twice a day until satiety for 60 days.
Feeding was carefully monitored in order to ensure an even distribution of the feed offered
among all experimental fish. Feeding activity in one tank was continued for about 20 min,
and special attention was given to avoid overfeeding. Feed intake data were recorded daily
by subtraction of feed distributed from the initial feed weight. Fish were accepted as
satiated when they refused feeding.
Growth performance, feed utilization and protein utilization of two-banded seabream
fed with different dietary protein and lipid levels were evaluated by calculating relative
growth rate (RGR), specific growth rate (SGR), feed conversion rate (FCR) and protein
efficiency rate (PER), using the following equations:
RGRð%Þ¼½ðfinal weight(g) initial weight(g)Þ=initial weight(g)100
SGR(%day1Þ¼½ðlnfinal weight(g) lninitial weight(g)Þ=days100
FCR ¼feed intake(g)=weight gain(g)
DFI(daily feed intake) ¼ðair dry feed intake/number of fishÞ=days
DPIðdaily protein intakeÞ¼ðfeed intake crude protein in diet=100Þ=days
PER(protein efficiency rate) ¼wet weight gain=protein intake
Experimental fish were individually weighed at the beginning and at the end of the
experiment. The fish were weighed in mass every 20 days during the trial. Prior to sam-
pling in each period, fish were deprived of feed for 1 day. In order to avoid stress during
handling, fish were anesthetized with a benzocaine solution of 5 %; 100 mL ethyl alcohol
(94 %) was mixed with 5 g crystalline benzocaine, and 1 mL of the solution was made up
to 1 L with water (Allen 1988; Allen et al. 1994).
All experimental diets were analyzed for proximate composition according to AOAC
(2000). Samples were frozen at -20 °C prior to analyses. Dry matter was detected after
drying at 105 °C until a constant weight was achieved. Ash content was measured in a
muffle furnace at 525 °C for 12 h. The amount of crude protein was analyzed by the
Kjeldahl method. Lipid extractions were determined by the SOXTEC system.
Aquacult Int
123

Statistical analysis
Results were expressed as mean ±standard deviation (SD), and group mean differences
were compared using one-way ANOVA. Data in percentage were arc-sin transformed prior
to analysis. A significant level of p\0.05 was employed at all cases.
Results
During the experiment, survival rate was 100 % in all experimental groups, showing that
all fish were acclimated to experimental conditions and trial diets well. Overall, the growth
performance and feed utilization were lower in the low-lipid diets compared to the high-
lipid diets at all protein levels. When fish meal inclusion levels were decreased in order to
produce low-lipid diets, NFE incorporation levels increased 5 % in all low-lipid diets
compared to the high-lipid ones (Table 1).
Table 1 Feed ingredients (g/100 g) of experimental diets
Ingredients (g/100 g) 50/15 45/15 40/15 35/15 50/10 45/10 40/10 35/10
Experimental diet
Fish meal
a
80 73 64 56 80 73 64 57
Corn starch 9.6 15.6 22.6 30.6 14.6 20.6 28.6 35.6
Fish oil 6 7 9 9 1 2 3 4
Vit-C 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3
Vitamin
b
1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5
Mineral
c
1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.1
Binder (CMC)
d
11111111
Cholin chloride 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5
Total 100 100 100 100 100 100 100 100
Nutritional composition (%dry matter, except for moisture)
Moisture 8 8 8 8 8 8 8 8
Crude protein 50.1 45.08 40.05 35.06 50.07 45.01 40.06 35.03
Crude lipid 15.06 15.1 15 15.05 10.09 10.1 10.1 10.1
Crude ash 11.6 10.6 9.1 8.2 11.4 10.4 9.2 8.1
NFE 15.24 21.22 27.85 33.69 20.44 26.94 32.73 38.77
GE (kJ/g diet)
e
20.36 20.21 20.11 19.94 19.27 19.19 19.00 18.84
P:E (mg/kJ)
f
2.46 2.23 1.99 1.76 2.60 2.35 2.11 1.86
a
Produced by Sibal Fish Feed and Fish Meal Company, Sinop, Turkey
b
Per mg mixture: vitamin A, 65,000 IU; vitamin D3, 45,000 IU; vitamin E, 25 IU; vitamin K3, 5 mg;
vitamin B1, 12.5 mg; vitamin B2, 12.5 mg; vitamin B6, 15 mg; vitamin B12, 0.025 mg and ascorbic acid,
120 mg
c
Per mg mixture: Ca, 100 mg; P, 50 mg; K, 30 mg; Na, 20 mg; Mg, 10 mg; Fe, 22 mg; Zn, 3 mg; Mn,
3 mg; Cu, 1.8 mg; Co, 0.15 mg; I, 0.12 mg; Se, 0.05 mg; DL-calcium pantothenate, 40 mg; niacin, 50 mg;
folic acid, 2.5 mg; biotin, 0.08 mg and inositol, 75 mg
d
Carboxymethhyl cellulose
e
Energy values are estimated based on 23.6 kJ/g for protein, 39.5 kJ/g for lipid and 17 kJ/g for NFE
f
Protein-to-energy ratio in mg/kJ
Aquacult Int
123

Best growth performance was recorded in the group fed with 35 % CP and 15 % CL
diet, while the poorest growth rate was obtained in the fish fed with diets with lowest
protein level (35 % CP) and lower lipid diet (10 % CL) (Fig. 1). However, these differ-
ences were visible differences and not significant between groups (p[0.05) (Table 2).
Although there were no significant differences, better FCRs were obtained for high-lipid
diets compared to the low-lipid ones. DFI values were similar in all experimental groups;
this led to increasing DPIs with the increase in dietary protein levels in both high- and low-
lipid diets. In the high-lipid groups, a general improvement in PERs was recorded with the
decline in dietary protein levels. However, this was not obtained in the low-lipid diets,
where PER value was best in the low-protein–low-lipid diet. Furthermore, in the high-lipid
diet groups, higher DPIs did not improve PERs; in contrast, PERs improved when DPIs
declined. This was reflected by a better RGR and SGR in the lowest dietary protein (35 %)
with high lipid level (15 %). Fish growth performance and feed utilization data are shown
in Table 2.
As expected, the cost of diets was increased with the increase in dietary protein level
(Table 3). Overall, the gross income (GI) values in the low-lipid groups were lower than
the high-lipid groups. The highest GI was obtained in the group with lowest dietary protein
(35 %) and high lipid level (15 %). Similarly, profit and feeding cost as percentage of
profit was also highest in the 35 % protein and 15 % lipid groups. Even though the
differences were not significant among all experimental groups, economic analyses
(Table 3) also confirmed the growth-related experimental results in terms of best profit
obtained with the 35 % protein and 15 % lipid inclusion diet.
Discussion
Two-banded seabream is a potential marine fish species to be used as an alternative
commercial species in aquaculture industry. Nevertheless, the nutritional requirement of
this species is scarce.
In the present study, survival was 100 % in all experimental groups in contrast to other
sparid studies (Sa
´et al. 2008; Zhang et al. 2010). From the present results, diet containing
35 % crude protein had shown maximum growth of juvenile two-banded seabream. Car-
nivorous species such as gilthead seabream (Sparus aurata), sea bass (Dicentrarchus
labrax) and rainbow trout (Onchorhynchus mykiss) require 45–55 % protein (Sabaut and
Luquet 1973; Hidalgo and Alliot 1988; Kim et al. 1991). The optimal protein level in fish
diet is influenced by the amino acid composition of the test proteins (Wilson 1989). In the
present study, fish meal was the main protein source.
The optimum dietary protein results in the present study agreed with Ozo
´rio et al.
(2009); for the best growth performance two-banded seabream need 36 % protein and
18 % lipids in its diets. Our results were compared with Diplodus puntazzo,Dentex dentex
and Pagrus pagrus due to the existence of very limited data on D. vulgaris. Atienza et al.
(2004) expressed that diet containing 47 % protein is needed to obtain the maximum
growth performance for D. puntazzo, and this value is higher than D. vulgaris. Espino
´s
et al. (2003) and Schuchardt et al. (2008) indicated that the dietary protein demand of
D. dentex and P. pagrus was 50 %. Similarly, it is higher than D. vulgaris. In this study, the
best FCR was obtained in high-lipid group. On the other hand, SGR and RGR decreased
with decreasing lipid level.
Not significantly, but a general decrease was observed in PERs as dietary protein level
increased in both high- and low-lipid groups. Similar results were reported in European eel
Aquacult Int
123

(Anguila anguila) (De La Higuera et al. 1989) and in Yellow snapper (Lutjanus argenti-
ventris) (Maldonado-Garcı
´a et al. 2012), in terms of decreasing PERs with increasing
dietary protein levels.
The lower growth performance and feed utilization in low-lipid diets compared to the
high-lipid diets in the present study could be attributed to the higher NFEs and lower GE
levels in the low-lipid diets. It is interesting to see the best performance of fish with the
lowest P:E ratio (1.76) diet (35/15). This shows that low-protein but high-energy diets
demonstrate better performance in two-banded seabream diets. In the present study, the
dietary protein requirement of D. vulgaris is considerably higher than white sea bream
Fig. 1 Variation of biomass of two-banded seabream fed with different level of protein and lipid for
60 days
Table 2 Growth performance and feed utilization efficiency of D. vulgaris juveniles fed with different diets
Groups SGR (%/day) FCR DFI (g) DPI (g) PER
50/15 2.05 ±0.06
a
1.51 ±0.03
a
0.22 ±0.005
a
2.22 ±0.050
a,b
1.32 ±0.034
a,b
45/15 2.01 ±0.03
a
1.65 ±0.12
a
0.23 ±0.022
a
2.12 ±0.200
a,b
1.35 ±0.102
a,b,c
40/15 2.03 ±0.03
a
1.53 ±0.21
a
0.22 ±0.029
a
1.64 ±0.346
a
1.82 ±0.437
c
35/15 2.10 ±0.08
a
1.50 ±0.33
a
0.22 ±0.044
a
1.60 ±0.311
a
1.73 ±0.367
b
50/10 1.97 ±0.04
a
1.80 ±0.13
a
0.24 ±0.011
a
2.47 ±0.114
b
1.56 ±0.008
a
45/10 1.98 ±0.05
a
1.66 ±0.05
a
0.23 ±0.004
a
2.07 ±0.040
a,b
1.39 ±0.092
a,b,c
40/10 1.92 ±0.12
a
1.66 ±0.12
a
0.21 ±0.009
a
1.74 ±0.075
a
1.42 ±0.052
a,b,c
35/10 1.95 ±0.03
a
1.77 ±0.28
a
0.23 ±0.031
a
1.89 ±0.009
a
1.62 ±0.123
a,b,c
Values with different superscript letters are significantly different (p\0.05)
RGR, relative growth rate (%) =[(final wet weight -initial wet weight)/initial wet weight] 9100
SGR, specific growth rate (%/day) =[(ln final wet weight -ln initial wet weight)/days] 9100
FCR, feed conversion rate =feed consumed/weight gain
DFI, daily feed intake (g) =(air dry feed intake/number of fish)/days
DPI, daily protein intake (g) =(feed intake 9crude protein in diet/100)/days
PER, protein efficiency rate =wet weight gain/protein intake
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123

Table 3 Bioeconomic analyses of two-banded seabream juveniles fed diets with different levels of protein and lipid during the course of the study (mean ±SD for triplicate
groups)
High lipid level (15 %) Low lipid level (10 %)
50 45 40 35 50 45 40 35
Feed cost ($/kg) 1.62 1.57 1.52 1.45 1.57 1.52 1.46 1.40
Price of Fish ($/kg) 4.40 4.40 4.40 4.40 4.40 4.40 4.40 4.40
FS (kg/fish) 0.01 ±0.00
a
0.01 ±0.00
a
0.01 ±0.00
a
0.01 ±0.00
a
0.02 ±0.00
a
0.01 ±0.00
a
0.01 ±0.00
a
0.02 ±0.00
a
MWG (kg) 0.18 ±0.08
a
0.17 ±0.03
a
0.17 ±0.05
a
0.18 ±0.12
a
0.16 ±0.07
a
0.16 ±0.08
a
0.16 ±0.18
a
0.16 ±0.05
a
FC ($/kg) 0.02 ±0.00
a
0.02 ±0.00
a
0.02 ±0.00
a
0.02 ±0.00
a
0.02 ±0.00
a
0.02 ±0.00
a
0.02 ±0.00
a
0.02 ±0.00
a
GI ($/fish) 0.78 ±0.04
a,b
0.75 ±0.01
a,b
0.77 ±0.02
a,b
0.81 ±0.06
b
0.73 ±0.03
a,b
0.73 ±0.03
a,b
0.70 ±0.08
a,b
0.71 ±0.02
a
TIBC ($) 0.17 ±0.00
a
0.17 ±0.00
a
0.17 ±0.00
a
0.17 ±0.00
a
0.17 ±0.00
a
0.17 ±0.00
a
0.17 ±0.00
a
0.17 ±0.00
a
TFBC ($) 0.59 ±0.01
a,b
0.58 ±0.00
a,b
0.59 ±0.01
a,b
0.61 ±0.03
b
0.57 ±0.01
a,b
0.57 ±0.01
a,b
0.55 ±0.04
a
0.56 ±0.01
a,b
Profit ($/kg) 0.40 ±0.02
a,b
0.39 ±0.00
a,b
0.40 ±0.01
a,b
0.42 ±0.03
b
0.38 ±0.02
a,b
0.38 ±0.02
a,b
0.36 ±0.04
a
0.37 ±0.01
a,b
FC as % profit 55.76 ±2.86 48.28 ±0.99 53.68 ±1.61 56.33 ±4.18 54.05 ±2.32 47.77 ±2.28 61.84 ±7.02 57.28 ±1.79
Values with different superscript letters are significantly different (p\0.05)
FC, feeding cost ($/kg) =feed supply (kg/fish) 9feed cost ($/kg)
GI, gross income ($/fish) =mean weight gain (kg) 9price of fish ($/kg)
TIBC, total initial biomass cost ($) =initial fish weight (kg) 9price of fish ($/kg)
TFBC, total final biomass cost ($) =final fish weight (kg) 9price of fish ($/kg)
Profit ($/kg) =(total final biomass cost-total initial biomass cost) -feeding cost
MWG (kg) =mean weight gain
Aquacult Int
123

(Diplodus sargus) (27 % protein; Sa
´et al. 2008), similar with two-banded seabream (D.
vulgaris) (36 % protein; Ozo
´rio et al. 2009) and lower than sharpsnout sea bream (D.
puntazzo) (43 % protein; Coutinho et al. 2012), gilthead seabream (S. aurata) (50–54 %
protein; Lupatsch et al. 2003). The recorded protein level for best growth performance of
D. vulgaris in the present study is also lower than those reported for other marine species
such as yellow tail (Seriola dumerilii, 50 % protein, Jover et al. 1999), Japanese flounder
(Paralichthys olivaceus, 50 % protein, Yigit et al. 2004) and dentex (D. dentex,50%,
Espino
´s et al. 2003). A reason for the lower protein requirement of D. vulgaris compared to
other sparid fishes or other marine species could be due to the feeding habits of D. vulgaris,
which is an omnivorous species, whereas the other fishes recorded with higher protein
requirements in earlier reports are carnivorous species.
Dietary lipids are important nutrients, and fatty acids are needed for normal growth and
development. Marine fish need eicosapentaenoic acid (EPA) and decosahexaenoic acid
(DHA) for good growth performance in the diets (NRC 1993). The lipids of the test are
obtained from fish meal and fish oil. The dietary lipid level results in this study showed
differences between 10 and 15 % levels; growth was low with 10 % lipid than 15 % lipid
which are very close to the requirements of marine species such as D. labrax 12–14 % lipid
(Pe
´rez et al. 1997), D. dentex 12–17 % lipid (Espino
´s et al. 2003), P. pagrus 15 % lipid
(Schuchardt et al. 2008).
Regarding economic efficiency of experimental diets, the reduction or increase in cost
of diets is related to fish meal levels in the diet. Overall, the experimental diets used for
two-banded seabream in the present study gave lower GI results compared to the values
reported for gilthead seabream diets in a previous study by Yigit et al. (2012). Similarly,
the profit and feed costs as percentage of profit values in the present study were also lower
than those reported for gilthead seabream diets by Yigit et al. (2012). These differences
could be attributed to the lower fish meal contents in their diets for gilthead seabream.
The economic analyses performed supported the growth parameters found in the present
study with best GI and profit obtained in diets containing 35 % protein and 15 % lipid
level. At all protein levels, the diets with higher lipid levels showed better profit compared
to those with lower dietary lipid levels. Considering the importance of profitability of fish
diets, high performance with less cost is the main target for the environment-friendly and
successful aquaculture operations.
As a conclusion, based on the results in the present study, it is recommended that the use
of practical diets containing 35 % protein and 15 % lipid provides efficient and cost-
effective production of two-banded seabream juveniles. The fact that growth performance
of fish was virtually unchanged in the present study, even when protein inclusion levels
were as low as 35 %, arises a question ‘‘what would happen with protein levels below this
value?’’ Further researches are encouraged to investigate nutritional studies on two-banded
seabream with lower protein levels and different lipid contents.
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