Role of stocking density of tilapia (Oreochromis aureus) on fish growth, water quality and tomato (Solanum lycopersicum) plant biomass in the aquaponic system

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International Journal of Environment, Agriculture and Biotechnology (IJEAB) Vol-2, Issue-6, Nov-Dec- 2017 ISSN: 2456-1878 Page | 2819
Role of stocking density of tilapia (Oreochromis
aureus) on fish growth, water quality and tomato
(Solanum lycopersicum) plant biomass in the
aquaponic system
Hijran Yavuzcan Yıldız, Süleyman Bekcan
Department of Fisheries and Aquaculture, Faculty of Agriculture, Ankara University, Turkey
Abstract The present study reports the results of the
production of Nile tilapia (Oreochromis aureus) and
tomato (Solanum lycopersicum) in the classical aquaponic
system (one-loop) with different fish density. The
experiment as the first scientific aquaponics study in
Turkey was conducted at the Ankara University, Faculty of
Agriculture, using in-door, small-scale classical
aquaponic systems. Ninety six tilapia juveniles (O. aureus)
were stocked at different ratio; 25 kg/m3 (Group I), 35
kg/m3 (Group II) and 50 kg/m3 (Group III) a nd fed with
45% raw protein feed at the level of 2% body weight for
126 days. Fish density affected the fish growth parameters
and the most densiest group showed the best results in
terms o f fish growth and feed efficiency. Water quality
parameters measured fluctated during the experiment even
the exceed of the optimal ranges for the fish. However,
tilapia tolerated the changes of water quality. Total plant
biomass was low with the various limiting factors
including insufficient lighting of in-door aquaponics
system and low level of water potassium. The results of
this study clearly illustrate the fish stocking ra te has an
impact on total biomass in the aquaponics and in one-loop
aquaponics the water quality fluctation is the main
challenging factor.
Keywords aquaponics, tilapia, tomato, fish growth.
One of the main challenges of agriculture in 21th century
to feed the growing po pulation is finding more efficient
and sustainable food p roduction systems and ad apting to
climate change. There is also a gap in the availability of
freshwater a nd land to increase the yield with minimal
environmental effect [1]. To overcome the problems that
the worls is facing with such as water scarcity, soil
degradation, climate change and the population increase
the aquaponics appear an alternative so lution as the
aquaponics are an environmental friendly and sustainable
food production system [2,3].
Aquaponics, basically, the symbiotic growing of fish and
vegetables in recirculating water systems is emerging as
one of the most important areas of sustainable agriculture.
Aquaponics is the systems that integrati ng aquaculture
recirculating production systems with hydroponics. With
aquaponics dual production o f both fish and plants is
possible by using the water fro m the fish tanks for plant
growth. T he esse ntial ele ments o f an aq uaponic system
consists of fish rearing tank, a suspended solid removal
component, a biofilter, a hydrponic component and a sump
[4]. In the aquaponic system, nutrients, which are excreted
directly by the fish or generated by the microbial
breakdown of organic wastes, are absorbed by plants
cultured hydroponically. Through microbial
decomposition, the insoluble fish metabolite and
unconsumed feed are converted into soluble nutrients
which then can be absorbed by plant [5] . Fish feed
provides most of the nutrients required for plant growth
[6]. Aquaponics work on the principle of nitrogen cycle,
where in dissolved waste generated fro m the production
system is effectively converted to plant nutrients by
beneficial nitrifying bacteria. P lants can utilize these
nutrients for their growth [6, 7, 8]. Plants in hydroponics
and aquaponics gro w more rapidly compared to their
counterparts which grow in the soil because the root
system is in direct contact with nutrients and nutrient
uptake is more efficient in an aqueous phase [9]. Water,
energy and fish feed are the three main physical inputs for
aquaponic systems although the aquaponic operations var y
in size and type of production system [10]. Palm et a l. [11]
highlighted that economic s ustainability of aquaponics
depends on a variet y of factors including system and feed
design, animal welfare and pathogen contro l. There is a
need to establish the macro- and micronutrient proportion
that fish can release in the water for a given feed in a given
system; this dep ends on fish species, fish density,
temperature, and type of plants [12]. It is clear that feed
and stocking rate of fish are directly related and to
maintain the balance between metabolic products the
International Journal of Environment, Agriculture and Biotechnology (IJEAB) Vol-2, Issue-6, Nov-Dec- 2017 ISSN: 2456-1878 Page | 2820
stocking rate is critical in the aquaponics as a reflectio n of
feed. Therefore, the present study was carried out to assess
the production of Nile tilapi a (Oreochromis aureus) and
tomato (Solanum lycopersicum) in the aquaponic system
with different fish density.
This research was carried out in the small-scale aquaponic
system with a grow bed form, producing tilapia (O.
aureus) and tomato (S. lycopersicum) in Ankara
University, Faculty of Agriculture, Department of
Fisheries and Aquaculture. Aquaponic system was
installed in-door.
The protocol for the experiment was ap proved by the
ethics committee of t he Ankara University with the
reference number of 2014-2-9.
Experimental set up
Ninety six tilapia juveniles (O. aureus) were stocked at
different ratio; 25 kg/m3 (Group I), 35 kg/m3 (Group II)
and 50 kg/m3 (Group III). Individual fish weight was 5-7 g
at the beginning of the experiment. Fish were fed with
commercial rainbow trout feed with 45 % raw protein with
2% body weight for 126 days. Chemical composition of
the feed is presented in Table 1. The aquaponics
experimental system comprises of a nine fish tank
(80x60x50 cm) and nine plastic tanks (65x40x35 cm)
filled with hydraton for vegetable beds. Each vegetation
tank planted with 4 plantlet (30-35 days old) of tomato (S.
lycopersicum). Each fish tank was filled with 100 L of tap
water and aerated continuous ly with air stone. Nitrifying
bacteria; Nitrosomonas europaea and Nitrobacter
winogradskyi were added to the s ystem at t he initial
period. Experiments were run in three replicates. A
lighting system made o f eight Ostram HO 80w/865
lumilux cool daylight fluorescent lamps was placed above
the units. Water loss due to sampling and evaporation was
replenished with the addition of distilled water.
Analytic procedures
After 126 days of rearing the fish was harvested and their
growth performance was measured with the parameters
using the formulas as below.
i) Feed Conversion Ratios (FCR): FCR= food
intake/ weight gain
ii) Protein efficiency ratio (PER): (PER) = (Wt-
Wt0)/crude protein fed
iii) Feed efficiency (FE): FE= weight gain/feed fed
iv) Specific growth rate (SGR%): SGR%= (lnWt
lnWt0 x100) / t-t0
where, lnWt = the natural logarithm of the final weight,
lnWt0 = the natural logarithm of the initial weight, t = time
(days) between lnWt and lnWt0
v) Average daily gain (ADG): ADG% = 100[Wt-
Wt0/Wt x (t-t0)]
where, Wt =Mean final fish weight, Wt0 =Mean initial fish
weight and t-t0 = number of days on feed
vi) Daily growth index DGI (%): DGI%= (final
weight1/3 - initial weight1/3 ) ×100/day
Table.1: Chemical composition of the feed
Component (%)
Protein %
Digestible energy
Lipid %
Metabolic energy
Moisture %
Vitamin A IU/kg
Ash %
Vitamin D IU/kg
Cellulose %
Vitamin E IU/kg
Nitrogen free
extract %
Vitamin K IU/kg
GE (Gross
energy) kcal/kg
At the end of the experiment, plant (S. lycopersicum) parts
were weighted separately (as leaf, stem and root) for
determination of fresh and dry weight. For measuring dry
weight of the plant samples was dried in 65 ºC for 3 days.
Water Quality Measurements
Water quality parameters in fish tanks were routinly
measured. During the experimental period the water
temperature was kept at 23°C. Dissolved oxygen (DO),
temperature (T) and pH were measured every week with
portable equipments. Other water quality parameters;
ammonia (NH3), Nitrat ( NO3-), Nitrit (NO2-) and
potassium (K) were measured every 15 days by using
Standard Methods [13].
Statistical Analysis
This experiment were conducted as completely
randomized design with three replicates. Data were
analyzed by analysis o f variance (ANOVA) with the SAS
package. Duncan’s multiple-range test was used to
compare differences among individual means. Treatment
effects were considered significant at p<0.05. Percentage
and ratio data were transformed to arcsine values prior to
Growth and production of tilapia in the aquaponic s ystem
are given in Table 2. T he mean group weight gain was
544.1±57.9 in Group I (stocking rate: 25 kg/m3),
849.7±30.8 in the Group II (stocking rate: 35 kg/m 3) and
1003.3±49.8 for Group III (stocking rate: 50kg/m3). The
differences in mean group weight gain were statistically
significant (p < 0.05) and the highest weight gain was in
Group III with the highest fish density. Feed conversion
ratio (FCR) differed among the groups (p < 0.05) however,
International Journal of Environment, Agriculture and Biotechnology (IJEAB) Vol-2, Issue-6, Nov-Dec- 2017 ISSN: 2456-1878 Page | 2821
the FCR was similar in Group II and III. The FCR was
higher in Group I than t hat of Group II and III. Thus, feed
efficiency (FE) was lo wer in Group I. Protein efficiency
ratio (PER) showed signific ant differences among t he
groups. PER was the lowest in Group I and the highest in
Group III. Specific growth rate was higher in Group III.
Average daily growth was the highest in Group III with the
value of 1 2.833±0.829 %. Daily growth index (DGI)
differed among the groups (p < 0.05) and the minimum
DGI percentage was in Group I. Survival rate showed
significant differences among the groups (p < 0.05) and
was the highest in Group II.
Table.2: The growth parameters of tilapia (O. aureus) in the aquaponics system by the stocking ratio
Growth Parameters
Experimental groups
Group I
Group II
Stocking rate: 35 kg/m3
Group III
Stocking rate: 50
Mean group initial body weight (g)
Mean group Final body weight (g)
Mean group weight gain (g)1
Food Consumed (g)2
Feed Conversion Ratios (FCR)1
Feed efficiency (FE)1
Protein Efficiency Ratio (PER)1
Specific Growth Rate (SGR %)
Percentage average daily growth (ADG
Daily growth index (DGI %)
Survival (%)
*Values with different superscripts in a row differ significantly (p<0.05)
1 Expressed as the percent of the initial body weight after 126 days.
2 Moisture-free basis.
The tomato (S. lycopersicum) plant biomas s as fresh and
dry weight of tomato plant leaf, stem and root b ranches
were presented in Table 3. Significant differences were
observed in the fresh weight and dry weight of tomato
plant (p < 0.05). Final total weight values were the
maximum in Group III. Fresh and dry weight of total
plant correlated with fish density (R2=0.92).
Table.3: Biomass of tomato (S. lycopersicum) plants grown in the aquaponic system by fish stocking density groups.
Fresh Weight (g pot-1)
Dry Weight (g pot-1)
*Different letters in a column indicate significant differences (p < 0.05) among the groups.
Water quality parameters measured in the experiment
(DO, pH, ammonium, nitrite, nitrate, potassium) are
presented in the Fig 1. Water quality parameters except
water temperature showed significant differences by the
time (p<0.05) and the experimental groups (p<0.05).
During the experimental period the water temperature was
kept around 24-25°C. The ra nge of pH was bet ween 5.83
and 7.31 in Group I, 5.60-7.22 in Group II and 5.50-7.12
in Group III. Dissolved oxygen level providing with
artificial aeration ranged between 5.80 mg/L (min) and
7.13 mg/L (max). Ammonium levels during the
experiment varied between 0. 68 and 3.70 mg/L in Group
I, 0.15 and 3.49 mg/L in Group II and 0.40 and 2.92 mg/L
in Group III. Nitrite levels were between 0.05 and 0.80
mg/L in Group I, 0.16 and 0.90 in Group II and 0.10 and
0.53 mg /L i n Group III. Nitrate levels ranged from 1.85