BOLETIM DO INSTITUTO DE PESCA
ISSN 1678-2305 online version
Scientific Article
TILAPIA CULTIVATED IN A LOW-SALINITY BIOFLOC SYSTEM
SUPPLEMENTED WITH Chlorella vulgaris AND DIFFERENTS
MOLASSES APPLICATION RATES
ABSTRACT
The aim of this study was to evaluate the effect of supplementation with Chlorella vulgaris and
molasses application rates on water quality, zootechnical performance, proximate composition and
Priscilla Celes Maciel de Lima1
health status of Nile tilapia (Oreochromis niloticus) fingerlings cultivated in low-salinity (10 g L-1)
Luis Otavio Brito da Silva1
biofloc systems. Four treatments were tested in a factorial design (supplemented with microalgae
and molasses application rates): BFT-C30 (Biofloc supplemented with C. vulgaris and molasses
Jéssika de Lima Abreu1
application rates of 30% of the total daily feed); BFT-30 (Biofloc with molasses application rates
of 30% of the total daily feed); BFT-C50 (Biofloc supplemented with C. vulgaris and molasses
Suzianny Maria Bezerra Cabral da Silva2
application rates of 50% of the total daily feed) and BFT-50 (Biofloc with molasses application
William Severi3
rates of 50% of the total daily feed), for 70 days. Fingerlings of O. niloticus (initial mean weight of
3.15 ± 0.5 g) were stocked at a density of 680 fish m-3 in experimental units (50L), where 50% of
Alfredo Olivera Gálvez1
this volume was biofloc previously matured. Throughout the experiment, they were supplemented
with C. vulgaris every five days at the concentration of 5x104 cells mL-1. A significant interaction
between supplementation with C. vulgaris and molasses application rates for final weight and
length, survival, feed conversion ratio, specific growth rate, water consumption, protein efficiency
ratio, sedimentation time, planktonic community and hematological indices were observed.
1Universidade Federal Rural de Pernambuco - UFRPE,
The results indicated that the high molasses application rates (50%) in the biofloc system affects the
Laboratório de Maricultura Sustentável, Rua Dom
zootechnical performance, water consumption, sedimentation time and the hematological indices
Manoel de Medeiros, s/n, Dois Irmãos, CEP 52171-900,
of the Nile Tilapia fingerlings, hampering their development. Therefore, molasses application rates
Recife, PE, Brasil. E-mail: pri.c.maciel@hotmail.com
of 30% of the total daily feed for the tilapia fingerlings culture in low-salinity biofloc system is
(corresponding author).
recommended.
Key words: microalgae; carbohydrate; proximate composition; zootechnical performance;
2Universidade Federal Rural de Pernambuco - UFRPE,
hematological indices.
Laboratório de Sanidade de Animais Aquáticos,
Rua Dom Manoel de Medeiros, s/n, Dois Irmãos,
CEP 52171-900, Recife, PE, Brasil.
CULTIVO DE TILÁPIA EM BIOFLOCO EM BAIXA SALINIDADE
3Universidade Federal Rural de Pernambuco - UFRPE,
SUPLEMENTADO COM Chlorella vulgaris E DIFERENTES TAXAS DE
Laboratório de Limnologia, Rua Dom Manoel de
Medeiros, s/n, Dois Irmãos, CEP 52171-900, Recife,
APLICAÇÃO DE MELAÇO
PE, Brasil.
RESUMO
O objetivo deste trabalho foi avaliar o efeito da suplementação com Chlorella vulgaris e taxas de
aplicação de melaço na qualidade da água, desempenho zootécnico, composição centesimal e saúde
de alevinos de tilápia do Nilo (Oreochromis niloticus) cultivados em sistemas de biofloco com baixa
Received: February 19, 2019
salinidade (10 g L-1). Quatro tratamentos foram testados em um delineamento fatorial (suplementado
Approved: June 30, 2019
com microalgas e taxas de aplicação de melaço): BFT-C30 (Biofloco suplementado com C. vulgaris e
aplicação de melaço de 30% da alimentação diária); BFT-30 (Biofloco com aplicação de melaço de
30% da alimentação diária); BFT-C50 (Biofloco suplementado com C. vulgaris e aplicação de melaço
de 50% da alimentação diária) e BFT-50 (Biofloco com aplicação de melaço de 50% da alimentação
diária), por 70 dias. Alevinos de O. niloticus (peso médio inicial de 3,15 ± 0,5 g) foram estocados
na densidade de 680 peixes m-3 nas unidades experimentais (50L), onde 50% deste volume foi de
biofloco previamente maturado. Durante todo o experimento, as inoculações com C. vulgaris foram
a cada cinco dias na concentração de 5x104 células mL-1. Foi observada interação significativa entre
a suplementação com C. vulgaris e as taxas de aplicação de melaço para peso final, comprimento,
sobrevivência, fator de conversão alimentar, taxa de crescimento específico, consumo de água, taxa
de eficiência proteica, tempo de sedimentação, comunidade planctônica e índices hematológicos.
Os resultados indicaram que a alta taxa de aplicação de melaço (50%) no sistema de biofloco afeta o
desempenho zootécnico, consumo de água, tempo de sedimentação e os índices hematológicos dos
alevinos de tilápia do Nilo, prejudicando seu desenvolvimento. É recomendada a taxa de aplicação
de melaço de 30% da alimentação diária para o cultivo de alevinos de tilápias em sistema de biofloco
com baixa salinidade.
Palavras-chave: microalga; carboidrato; composição centesimal; desenvolvimento zootécnico;
índices hematológicos.
Lima et al. Bol. Inst. Pesca 2019, 45(4): e494. DOI: 10.20950/1678-2305.2019.45.4.494
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TILAPIA CULTIVATED IN A LOW-SALINITY…
organisms (Jung et al., 2017). When cultured under mixotrophic
INTRODUCTION
conditions, Chlorella sp. showed higher lipid productivity
In 2016, world aquaculture production reached 80 million tons
(67-144 mg L-1 day-1) (Yeh and Chang, 2012).
excluding aquatic plants, with inland fish aquaculture production
In this context, this study evaluated the effects of supplementation
representing 59.3% (FAO, 2018), among which the main species
with C. vulgaris and two molasses application rates on planktonic
of fresh water aquaculture were the Nile tilapia Oreochromis
community, zootechnical performance, proximate composition
niloticus. This fish is one of the most important species (4.2 million
and hematological indices in low-salinity biofloc systems.
tons, representing 8% fish aquaculture) (FAO, 2018) due to their
environmental resistance, rapid growth and salinity tolerance
between 0 and 25 g L-1 (El-Sayed, 2006; Pereira et al., 2016).
MATERIAL AND METHODS
Tilapia culture in brackish water is an alternative to Brazilian
semi-arid zones, where water resources are limited and saline
Experimental conditions
groundwater is the unique source of water available, with salinities
All procedures were previously approved by the Ethics Committee
between 1.1 and 10.0 g L-1 (Andrade Júnior et al., 2006; Brasil,
on Animal Use of UFRPE under license number 129/2016. A 70-day
2012). Moreover, the desalination technology used for brackish
indoor trial was conducted at the Sustainable Mariculture Laboratory
groundwater results in highly saline residual water, which has a
(LAMARSU) of the Department of Fisheries and Aquaculture
potential use for aquaculture (Soares et al., 2006).
(DEPAq) of the Federal Rural University at Pernambuco (UFRPE),
Although aquaculture is considered a suitable alternative system
Recife, Brazil. The experiment had a 2 × 2 factorial design
for the increasing demand for animal-based protein, this activity
(Supplemented with C. vulgaris and molasses application rates)
has limitations in relation to water and land use. Therefore,
with the following treatments: BFT-C30 (Biofloc supplemented
intensive culture systems, such as biofloc technology (BFT), is a
with C. vulgaris and molasses application rates of 30% of total
promising alternative (Emerenciano et al., 2017). BFT is based on
daily feed); BFT-30 (Biofloc with molasses application rates of
carbon:nitrogen ratio management and minimum water exchange
30% of total daily feed); BFT-C50 (Biofloc supplemented with
for production of microorganism biomass (Azim and Little, 2008;
C. vulgaris and molasses application rates of 50% of total daily
Avnimelech, 2012; Emerenciano et al., 2017), which results in
feed) and BFT-50 (Biofloc with molasses application rates of
higher productivity compared to conventional systems due to the
50% of total daily feed), all in triplicate.
elevated stocking density used (Avnimelech, 2015).
Five days prior to fish stocking, water from an indoor biofloc
The carbon:nitrogen ratio is maintained through the addition
matrix tank (TAN 0.19 mg L-1, N-NO2 0.12 mg L-1, N-NO3
of a source of organic carbon, which is used by bacteria to
0.89 mg L-1, alkalinity 160 mg CaCO3 L-1, pH 7.93, orthophosphate
convert TAN (Total Ammoniacal Nitrogen) to bacterial biomass
1.76 mg L-1, TSS 366 mg L-1, SS 25 mL L-1 and salinity 10 g L-1)
(Ebeling et al., 2006). Among the various sources of carbon,
was mixed and equally distributed to fill twelve experimental
molasses is widely used because it stains water, reducing light
black-plastic rectangular tanks (50 L) up to ~50% of the volume,
penetration and associated algal growth, however, may present
with the remaining volume filled with clean water (10 g L-1 salinity).
high level of impurities and content variability (Samocha et al.,
The experimental units were maintained under constant aeration
2017). In addition, molasses is an inexpensive source of carbon
by using three cylindrical air stones (diameter 2.4 cm and length
used for various industrial fermentations (Miranda et al., 1996;
2.6 cm) per tank. No water exchange was carried out during the
Najafpour and Shan, 2003).
experimental period, except for the addition of dechlorinated
Some authors reported successfully culturing Nile tilapia in BFT
freshwater to compensate for evaporation losses. Light intensity
(Long et al., 2015; Miranda-Baeza et al., 2017; Zapata-Lovera et al.,
was at ~ 1000 lux with a 12h light/12h dark regime.
2017), including a study in brackish water (8 g L-1) (Brol et al., 2017;
Sugarcane molasses (30% organic carbon) was applied daily
Lima et al., 2018). However, due to the high stocking densities and
(10:00 a.m.) to each tank as a source of carbohydrates to promote
minimal water exchange, nutrients accumulate, mainly nitrogen
the growth of heterotrophic bacteria. Molasses inputs were based
and phosphorus, in the biofloc culture (Krummenauer et al., 2011).
on a percentage of the daily feed allotments (by weight) with
About 60% of the nitrogen and 65% of the phosphorus that enter
application rates of 30% (C:N - 12:1) and 50% (C:N - 20:1) of
in the system are not converted into shrimp biomass (Silva et al.,
the total daily feed. Calcium hydroxide (Ca(OH)2) was added to
2013). An alternative used to overcome the disadvantages is the use
maintain the alkalinity (> 100 mg L-1) and the pH (> 7.5) in all
of microalgae in this system, due to their highly efficient removal
treatments.
of nitrogen and phosphorus (80-100%) in aquaculture, livestock
and industry as have been reported by Prajapati et al. (2014),
Supplemented with C. vulgaris
Posadas et al. (2015), Kuo et al. (2016) and Singh et al. (2017).
In addition, although the use of bioflocs serves to feed
The microalgae C. vulgaris were obtained from Live Food
aquatic animals, it has low lipid content and therefore requires
Production Laboratory of DEPAq-UFRPE and cultures in a
supplementation with natural foods, such as microalgae (Jung et al.,
Provasoli medium. The culture was maintained at 25 ± 1 °C,
2017; Marinho et al., 2017). Inoculation of C. vulgaris together
salinity of 10 g L-1, pH 7.9 and light intensity of ~2000 lux using
with Scenedesmus obliquus, in the culture system without water
a fluorescent lamp with a 24-h light photoperiod. The microalgae
exchange, may improve the survival and development of cultured
were supplemented every five days in the BFT-C30 and BFT-C50
Lima et al. Bol. Inst. Pesca 2019, 45(4): e494. DOI: 10.20950/1678-2305.2019.45.4.494
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treatments at a concentration of 5x104 cell mL-1, corresponding to
with the purpose of reducing the amount of suspended solids
an addition of approximately 250 mL of microalgae to the tanks,
in the sample) and then it was filtered with a 15 µm mesh, for
regardless of the waste from unconsumed C. vulgaris.
phytoplankton and cyanobacteria retention. The phytoplankton and
cyanobacteria were fixed with formalin (4%), buffered with borax
(1%) and stored in 2.5-mL plastic recipients. A Sedgewick-Rafter
Water quality
chamber and binocular optical microscope (Olympus CH30) with
Dissolved oxygen, temperature, salinity and pH (YSI model
magnification of 400x were used for identification at the genus
556, Yellow Springs, Ohio, USA) were monitored twice a day
level, with the aid of identification keys (Hoek et al., 1995; Bicudo
(at 08:00 a.m. and 04:00 p.m.). Total ammonia nitrogen (TAN)
and Menezes, 2006), and quantification of the phytoplankton and
(Koroleff, 1976), nitrogen-nitrite (N-NO2) (Golterman et al., 1978),
cyanobacteria samples (Pereira-Neto et al., 2008).
nitrogen-nitrate (N-NO3) (Mackereth et al., 1978), orthophosphate
(PO4-3) (APHA, 2005), alkalinity (mg CaCO3 L-1) (Felföldy et al.,
Proximate composition
1987), total suspended solids (TSS) (APHA, 2005 - 2540D) and
volatile suspended solids (VSS) (APHA, 2005 - 2540E) were
Analysis of crude protein, crude lipids, moisture content and
monitored weekly in the Limnology Laboratory of DEPAq-UFRPE.
ash contents whole body fish, biofloc samples and commercial
Alkalinity and dissolved nutrients were analyzed from effluent
feed were performed at the beginning and at the end of the
samples filtered with HAWP Millipore membranes of 0.45 µm
experiment, in triplicate using standard methods (AOAC, 2012)
pore size. For suspended solids the samples were filtered, dried
at the Laboratory of Physical-Chemical Analysis of Foods of the
(at 105 °C) and incinerated (at 550 °C) for inference of volatile
UFRPE. Ten fish, at the beginning, and three fish in each tank, at
suspended solids (volatile suspended solids = total suspended
the end, were randomly selected and macerated for the analyses.
solids - inorganic suspended solids). The settleable solids
The biofloc samples (30g) were collected with cylindrical mesh
(SS) were monitored three times per week by an Imhoff Cone
net of 50 µm for retention of solids. The commercial feed (30g)
(Avnimelech, 2012) and when its volume in the experimental
were randomly selected and macerated for the analyses. Crude
tanks reached 50 mL L-1, a settler was used in order to maintain
protein was determined by measuring nitrogen (N·x 6.25) using
SS values under this limit. The total time of use of the settler
the Kjeldahl method and crude lipids was by the ether extraction
(ST) was also evaluated, using the equation:
method with the Soxhlet apparatus. The moisture content was
determined by drying it at 105 °C for 18 hours until a stable weight
1
ST
(
h Kg
)
=
Total time use of settler chamber h)/ Final biomass
(
Kg
)
(1)
was attained and the ash content was determined by incineration
in a muffle at 550 °C.
Microbial activity
Fish stocking, feeding and monitoring
The methods used to estimate microbial activity were those
The sex reversed male fingerlings of Nile tilapia O. niloticus
described by Vinatea et al. (2010). Once weekly, water from the
(with 1.1 ± 0.4 g mean weight) were from commercial hatchery
tanks was collected at a depth of 10 cm and placed in triplicate
(Piscicultura Vale da Mina, Paulista, Pernambuco, Brazil), and
sets of 200 mL glass bottles (clear or black). Initial and final
stored in plastic bags with water for transportation to the laboratory.
oxygen concentrations were measured with an YSI 556 digital
The fish were acclimatized for 5 days before being placed into
oxygen meter (Yellow Springs, Ohio, USA). Once initial oxygen
experimental units. The fish were stocked in a 350 L tank with
was recorded, the bottles were sealed with glass stoppers held in
clean freshwater, at density of 625 fish m-3 and fed at 10% of fish
place by plastic lids of the same color as the bottle.
wet biomass with commercial feed (36% crude protein) adjusted
The bottles were attached to a rotating table (QUIMIS Q225M)
daily according to the estimated fish consumption. Each day 2 g L-1
and incubated for 2 h, 2000 lux and at 200 rpm, a rotation
of salinity was increased with marine water for acclimatization
sufficient to keep the particles of flocs in the water column.
from freshwater until 10 g L-1 salinity within 5 days. After this
Gross primary production (GPP), net ecosystem production
acclimatization all fish were maintained at desired salinity for
(NEP) and water column respiration (R) rates were recorded
ten days.
by the classic dark and light bottle method using the following
The experimental units were stocked with Nile tilapia
formulae: gross primary production (GPP) (mg O2 L-1 h-1) = final
(3.15 ± 0.5g initial weight) at a density of 680 fish m-3 (34 shrimp
O2 of light bottle - final O2 of dark bottle/time (h); net ecosystem
per experimental unit). The fish fingerlings were fed four times a
production (NEP) (mg O2 L-1 h-1) = final O2 of light bottle -
day (at 08:00 a.m., 11:00 a.m., 2:00 p.m. and 4:00 p.m.), with a
initial O2 of light bottle/time (h): water column respiration rate
commercial fish feed (36% crude protein, 4% crude fat, 5% crude
(R) (mg O2 L-1 h-1) = initial O2 of dark bottle - final O2 of dark
fiber, 12% moisture and 3.276,1 kcal kg-1 of digestible energy).
bottle/time (h) (Strickland, 1960).
The daily feeding rate was 8% of body weight at the start of the
experiment, gradually reduced to 5% of body weight at the end
Cyanobacteria and phytoplankton monitoring
of the 70-day experiment based on the weekly biometrics.
Vertical water sampling was performed at the start and weekly
Fish weight (BEL Engineering M503 - 0.001g) and length
using plastic bottles of 500 mL for collection. The water was
(ichthyometer) were monitored weekly (30% of population) in
filtered through a cylindrical-conical 70 and 50 µm net mesh
each experimental unit to determine biomass and survival. All fish
Lima et al. Bol. Inst. Pesca 2019, 45(4): e494. DOI: 10.20950/1678-2305.2019.45.4.494
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TILAPIA CULTIVATED IN A LOW-SALINITY…
were counted weekly in each experimental unit for available
RESULTS
survival. At the end of the experiment, biomass gain, final mean
weight (W), final length, survival, feed conversion ratio (FCR),
Water quality
specific growth rate (SGR), protein efficiency ratio (PER), nitrogen
The water quality variables temperature (27.7-27.9 °C),
retaining, yield, water consumption (WC) and sedimentation time
dissolved oxygen (5.3-5.4 mg L-1), pH (7.7-7.8), orthophosphate
(ST) were calculated, based on the following equations:
(1.16-1.36 mg L-1), TAN (0.44-0.48 mg L-1), N- NO2 (0.12-0.13 mg L-1)
and N- NO3 (0.19-0.21 mg L-1), were not significantly affected
Biomass gain g)
(
Final weight g) *
)
=
Final population
(p > 0.05) by supplementation with microalgae and molasses
(2)
application rates (Table 1). However alkalinity levels significantly
(
Initial weight g) *
Initial population
)
affected (p=0.01) by molasses application rates and their interaction
(supplemented with microalgae and molasses application rates).
Among the treatments, BFT-50 (165.08 ± 12.47 mg L-1) and
1
Ln Final weight g)
-
SGR
(
%
day
)
=
100
x
/Time
days
(3)

(
)
BFT-C50 (154.75 ± 9.94 mg L-1) were higher compared with BFT-30
Ln Initial weight g)
(120.48 ± 8.89 mg L-1) and BFT-C30 (125.31 ± 10.33 mg L-1).
The TSS (453-473 mg L-1) and VSS (352-365 mg L-1) were
FCR = Feed supplied (g)/Biomass gain (g)
(4)
not significantly affected (p > 0.05) by supplementation with
microalgae and molasses application rates (Table 1). However,
SS levels significantly affected (p=0.02) by molasses application
Survival (%) = (Final population/Initial population) x 100
(5)
rates and their interaction (supplemented with microalgae and
molasses application rates). Among the treatments, BFT-50
3
3
Yield
kg m
=
Final biomass
(
kg
)
/Volume
m
(6)
(
)
(
)
(54.95 ± 2.57 mL L-1) and BFT-C50 (51.76 ± 2.82 mL L-1) were
higher compared with BFT-30 (43.40 ± 2.83 mL L-1) and BFT-C30
PER = Biomass gain (g)/Total protein intake (g)
(7)
(45.20 ± 2.62 mL L-1). The ST were significantly affected (p=0.002)
by molasses application rates and their interaction (Table 2).
The molasses application rates of 50% of total daily feed were
(
final body nitrogen g)
-
initial body nitrogen g))/
Nitrogen retaining
(%)
=
x
100
(8)
total nitrogen consumed
(g)
higher compared with molasses application rates of 30%.
1
WC
L Kg
=
Total water consumed L)/ Final biomass
(
Kg
)
(9)
(
)
Microbial activity
The GPP (-0.002-0.076 mg O2 L-1 h-1), NEP (-0.264-0.334 mg O2 L-1 h-1)
and R (0.274-0.350 mg O2 L-1 h-1) were not significantly affected
Hematological assays
(p > 0.05) by supplemented with microalgae and molasses
At the end of the experiment, ten animals from each experimental
application rates (Table 3). There were fluctuations for GPP,
unit were collected, anesthetized with eugenol (1.0 mL L-1) and
NEP and R, however, the NEP presented negative values in all
blood samples were collected from the caudal vessels by EDTA
the treatments, throughout the experimental period, indicating
treated syringes. The hematological assays measured: hematocrit
that the environment was dominated by bacteria, even in the
level (Goldenfarb et al., 1971); red blood cell count and mean
treatments where microalgae were added.
corpuscular volume (MCV) (Wintrobe, 1934); and blood glucose
The phytoplankton community consisted of four genera at the
levels using ACCU-CHEK ACTIVE blood glucose test meter
beginning of the experiment (Aphanocapsa sp., Chlorococcum sp.,
(Roche), performed in the Aquatic Animal Health Laboratory
Cyclotela sp. and Tetraedron sp.) and nine genera at the end
of DEPAq-UFRPE. Moreover, during the weekly biometrics,
(Aphanocapsa sp., Chlorella sp., Chlorococcum sp., Chroococcus sp.,
external symptoms such as injuries, infection and other abnormal
Cyclotela sp., Cryptomonas sp., Oscilatoria sp., Rhabdonema sp.
condition of fish body (integument and gills) were evaluated.
and Tetraedron sp.).
The Chlorella sp. was the most abundant genera in all treatments,
but due to its addition in BFT-C30 and BFT-C50 treatments,
Statistical analysis
they had higher average levels of relative abundance, 55.99%
A two-way analysis of variance (ANOVA) was used to determine
and 57.54%, respectively, followed by BFT-30 and BFT-50
the effect of supplementation with C. vulgaris and molasses
treatments, with 41.17% and 44.89%, respectively (Table 4).
application rates of 30% and 50% of total daily feed and their
Although there was no significant difference between treatments,
interaction, after confirming homoscedasticity (Cochran p < 0.05)
the supplementations with C. vulgaris added influenced the
and normality (Shapiro-Wilk p < 0.05). Water quality variables,
abundance of Chlorophyta (Chlorella sp., Chlorococcum sp.
microbial activity, cyanobacteria and planktonic community were
and Tetraedron sp.) and Cyanobacteria (Aphanocapsa sp.,
analyzed by performing repeated ANOVA measures. Tukey’s
Chroococcus sp. and Oscilatoria sp.). The relative abundance of
test was used when differences between factors and treatments
Cyanobacteria was higher in the treatments without supplemented
were detected (p < 0.05). Data analyses were performed using
with C. vulgaris, while the relative abundance of Chlorophyta
Statistica 10 software.
was higher in the treatment with supplemented with C. vulgaris.
Lima et al. Bol. Inst. Pesca 2019, 45(4): e494. DOI: 10.20950/1678-2305.2019.45.4.494
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TILAPIA CULTIVATED IN A LOW-SALINITY…
Table 1. Water quality variables of Nile tilapia fingerling cultivated in low-salinity biofloc system supplemented with Chlorella
vulgaris and molasses application rates.
¥
Treatments1
Significance (p value)
Variables
BFT-30
BFT-50
BFT-C30
BFT-C50
C
M
CxM
Temperature (°C)
27.74 ± 0.12
27.83 ± 0.11
27.90 ± 0.12
27.75 ± 0.10
ns
ns
ns
DO (mg L-1)
5.39 ± 0.04
5.45 ± 0.11
5.39 ± 0.04
5.33 ± 0.05
ns
ns
ns
Salinity (g L-1)
10.36 ± 0.11
10.29 ± 0.09
10.39 ± 0.12
10.35 ± 0.09
ns
ns
ns
TAN (mg L-1)
0.45 ± 0.06
0.45 ± 0.07
0.44 ± 0.06
0.48 ± 0.08
ns
ns
ns
N-nitrite (mg L-1)
0.12 ± 0.01
0.12 ± 0.02
0.12 ± 0.01
0.13 ± 0.02
ns
ns
ns
N-nitrate (mg L-1)
0.21 ± 0.03
0.19 ± 0.04
0.19 ± 0.02
0.19 ± 0.04
ns
ns
ns
PO43 (mg L-1)
1.21 ± 0.07
1.16 ± 0.06
1.36 ± 0.09
1.16 ± 0.08
ns
ns
ns
Alkalinity (mg L-1)
120.48 ± 8.89b
165.08 ± 12.47a
125.31 ± 10.33b
154.75 ± 9.94ab
ns
*
*
pH
7.74 ± 0.04
7.81 ± 0.04
7.72 ± 0.05
7.80 ± 0.04
ns
ns
ns
SS (mL L-1)
43.40 ± 2.83b
54.95 ± 2.57a
45.20 ± 2.62b
51.76 ± 2.82a
ns
*
*
TSS (mg L-1)
453.47 ± 30.98
463.71 ± 27.65
461.42 ± 31.77
473.46 ± 28.12
ns
ns
ns
VSS (mg L-1)
352.82 ± 25.87
359.73 ± 24.00
359.09 ± 27.21
365.81 ± 24.78
ns
ns
ns
1The data correspond to the mean of thirty replicates ± standard deviation by treatments. Mean values on the same row with different superscript letters differ significantly
(p < 0.05); C = supplemented with C. vulgaris; M = molasses application rates; CxM = supplemented with C. vulgaris and molasses application rates; ns = not-significant
(p >0.05); *p <0.05; ¥Results from split-plot two-way ANOVA and Tukey’s test; DO = Dissolved oxygen; TAN = Total ammonia nitrogen; PO43 = orthophosphate;
SS = Settleable solids; TSS = Total suspended solids; VSS = Volatile suspended solids; BFT-C30 = Biofloc supplemented with C. vulgaris and molasses application rates
of 30% of total daily feed; BFT-30 = Biofloc with molasses application rates of 30% of total daily feed; BFT-C50 = Biofloc supplemented with C. vulgaris and molasses
application rates of 50% of total daily feed; and BFT-50 = Biofloc with molasses application rates of 30% of total daily feed, all in triplicate.
Table 2. Zootechnical performance of Nile tilapia fingerling cultured in low-salinity biofloc system supplemented with Chlorella
vulgaris and molasses application rates.
¥
Treatments1
Significance (p value)
Variables
BFT-30
BFT-50
BFT-C30
BFT-C50
C
M
CxM
Final Weight (g)
17.93 ± 0.20a
12.05 ± 1.12b
17.98 ± 0.85a
13.86 ± 2.10ab
ns
*
*
Final Length (cm)
9.73 ± 0.41a
8.95 ± 0.32b
9.88 ± 0.48a
8.95 ± 0.57ab
ns
*
*
Survival (%)
97.77 ± 2.22a
87.77 ± 4.00b
95.55 ± 2.93ab
92.22 ± 1.11b
ns
*
*
FCR
2.08 ± 0.03b
4.96 ± 0.88a
2.06 ± 0.17b
3.74 ± 0.65a
ns
*
*
SGR (% day-1)
2.91 ± 0.02a
2.19 ± 0.16b
2.91 ± 0.08a
2.41 ± 0.26ab
ns
*
*
PER
1.07 ± 0.01a
0.59 ± 0.10b
1.01 ± 0.06a
0.80 ± 0.16ab
ns
*
*
NR (%)
20,81 ± 0,76a
10,22 ± 0,68b
19,43 ±1,33a
12,89 ±1,47b
ns
*
*
Yield (kg m-3)
11.95 ± 0.10a
7.34 ± 0.85b
11.39 ± 0.59a
9.05 ± 1.40ab
ns
*
*
WC (L kg-1)
55.22 ± 7.13b
93.28 ± 12.89a
47.79 ± 6.41b
51.26 ± 11.85b
*
*
*
ST (h Kg-1)
23.47 ± 0.43b
38.20 ± 3.25a
24.44 ± 1.04b
31.23 ± 4.59ab
ns
*
*
1The data correspond to the mean of three ± standard deviation by treatments. Mean values on the same row with different superscript letters differ significantly
(p < 0.05); C = supplemented with C. vulgaris; M = molasses application rates; CxM = supplemented with C. vulgaris and molasses application rates; ns = not-significant
(p >0.05); *p <0.05; ¥Results from split-plot two-way ANOVA and Tukey’s test; FCR = Feed conversion ratio; SGR = Specific growth rate; PER = Protein efficiency
ratio; NR = Nitrogen retaining; WC = water consumption; ST = sedimentation time. Treatments’ abbreviations as in Table 1.
Table 3. Gross and net primary production and respiratory activity of Nile tilapia fingerling cultured in low-salinity biofloc system
supplemented with Chlorella vulgaris and molasses application rates.
Variables
Treatments1
Significance (p value)¥
(mg O2 L-1 h-1)
BFT-30
BFT-50
BFT-C30
BFT-C50
C
M
CxM
GPP
-0.075 ± 0.114
-0.002 ± 0.140
-0.076 ± 0.114
-0.027 ± 0.097
ns
ns
ns
NEP
-0.312 ± 0.196
-0.264 ± 0.253
-0.334 ± 0.231
-0.316 ± 0.319
ns
ns
ns
R
0.274 ± 0.180
0.298 ± 0.183
0.285 ± 0.115
0.350 ± 0.199
ns
ns
ns
1The data correspond to the mean of thirty replicates ± standard deviation by treatments. Mean values on the same row with different superscript letters differ significantly
(p < 0.05); C = supplemented with C. vulgaris; M = molasses application rates; CxM = supplemented with C. vulgaris and molasses application rates; ns = not-significant
(p >0.05); ¥Results from split-plot two-way ANOVA and Tukey’s test. GPP = Gross primary production; NEP = Net ecosystem production; R = Respiratory activity.
Treatments’ abbreviations as in Table 1.
Lima et al. Bol. Inst. Pesca 2019, 45(4): e494. DOI: 10.20950/1678-2305.2019.45.4.494
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TILAPIA CULTIVATED IN A LOW-SALINITY…
Table 4. Relative abundance of the planktonic community and cyanobacteria of Nile tilapia fingerling cultured in low-salinity biofloc
system supplemented with Chlorella vulgaris and two molasses application rates.
Division /Genera
Treatments1
Significance (p value)¥
Initial
(%)
BFT-30
BFT-50
BFT-C30
BFT-C50
C
M
CxM
Chlorophyta
16.70
49.82
55.92
65.51
65.47
*
ns
ns
Tetraedron
7.10
0.96
0.68
0.33
0.22
ns
ns
ns
Chlorococcun
9.60
7.69
10.35
9.19
7.71
ns
ns
ns
Chlorella
0
41.17
44.89
55.99
57.54
*
ns
ns
Bacillariophyta
54.37
18.80
15.93
11.21
12.77
ns
ns
ns
Cyclotela
54.37
18.74
15.87
11.17
12.7
ns
ns
ns
Rhabdonema
0
0.06
0.06
0.04
0.07
ns
ns
ns
Cyanobacteria
28.92
21.14
20.45
16.50
15.05
*
ns
ns
Aphanocapsa
28.93
4.72
6.68
3.78
4.26
ns
ns
ns
Oscillatoria
0
1.42
4.95
6.24
3.46
ns
ns
ns
Chroococcus
0
15.03
8.82
6.48
7.33
*
ns
ns
Cryptophyta
0
10.07
7.49
6.63
6.6
ns
ns
ns
Cryptomonas
0
10.07
7.49
6.63
6.6
ns
ns
ns
TOTAL (cell mL-1)
8.02
3535.1
1810.31
2389.614
2657.25
1The data correspond to the mean of thirty replicates by treatments. Mean values on the same row with different superscript letters differ significantly (p < 0.05);
C = supplemented with C. vulgaris; M = molasses application rates; CxM = supplemented with C. vulgaris and molasses application rates; ns = not-significant (p >0.05);
*p <0.05; ¥Results from split-plot two-way ANOVA and Tukey’s test. Treatments’ abbreviations as in Table 1.
Table 5. Proximate composition (% dry weight) of whole body fish and biofloc from of Nile tilapia fingerling cultured in low-salinity
biofloc system supplemented with Chlorella vulgaris and molasses application rates.
Proximate
Treatments1
Significance (p value)¥
composition
BFT-30
BFT-50
BFT-C30
BFT-C50
C
M
CxM
Fish
Moisture
74.55 ± 0.07b
75.05 ± 0.99ab
74.81 ± 0.33b
75.77 ± 0.07a
ns
ns
*
Crude protein
71.24 ± 1.88a
64.74 ± 2.63b
61.62 ± 1.04b
63.31 ± 0.74b
ns
*
*
Lipids
20.67 ± 0.59a
16.86 ± 0.23b
20.70 ± 0.38a
16.51 ± 0.38b
ns
*
*
Ash
7.97 ± 0.57
8.32 ± 0.10
7.56 ± 0.23
8.02 ± 2.06
ns
ns
ns
Biofloc
Moisture
84.96 ± 3.11b
89.06 ± 0.13a
86.91 ± 0.11b
89.16 ± 0.19a
ns
ns
*
Crude protein
37.60 ± 1.17
34.19 ± 11.62
38.13 ± 1.42
36.81 ± 8.98
ns
*
ns
Lipids
1.75 ± 0.52
1.83 ± 0.13
1.24 ± 0.61
1.89 ± 0.07
ns
ns
ns
Ash
17.96 ± 1.05
17.18 ± 0.08
16.42 ± 0.74
17.11 ± 0.28
ns
ns
ns
1The data correspond to the mean of three ± standard deviation by treatments. Mean values on the same row with different superscript letters differ significantly (p < 0.05);
C = supplemented with C. vulgaris; M = molasses application rates; CxM = supplemented with C. vulgaris and molasses application rates; ns = not-significant (p >0.05);
*p <0.05; ¥Results from split-plot two-way ANOVA and Tukey’s test. Treatments’ abbreviations as in Table 1.
Proximate composition
Tilapia zootechnical variables
The moisture, crude protein and lipids content in fish were
All the zootechnical performance variables were significantly
significantly affected (p < 0.05) by molasses application rates
affected (p < 0.05) by molasses application rates and their interaction
and its interaction with microalgae addition (Table 5). While for
(Table 2). In the final weight, final length, survival, SGR, PER,
the biofloc content the crude protein was significantly affected
nitrogen retaining, yield in the molasses application rates of 30%
(p < 0.05) by molasses application rates. The proximal composition
of total daily feed were higher compared with molasses application
found for commercial feed (8.38 ± 1.25% moisture, 35.56 ± 1.31%
protein, 2.61 ± 0.36% lipid and 6.31 ± 0.68% of ash) was different
rates of 50%. However, FCR was lower in molasses application
from the information described on the label, especially lipids.
rates of 30% compared with 50%.
Lima et al. Bol. Inst. Pesca 2019, 45(4): e494. DOI: 10.20950/1678-2305.2019.45.4.494
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TILAPIA CULTIVATED IN A LOW-SALINITY…
Table 6. Hematological indices of Nile tilapia fingerling cultivated in low-salinity biofloc system supplemented with Chlorella
vulgaris and molasses application rates.
Significance
Treatments1
Variables
(p value)¥
BFT - 30
BFT - 50
BFT - C30
BFT - C50
C
M
CxM
Hematocrit (%)
30.69 ± 2.84a
19.20 ± 2.50b
28.08 ± 0.90a
18.46 ± 2.39b
ns
*
*
Erythrocyte (x106 μL-1)
1.69 ± 0.04a
0.76 ± 0.17b
1.52 ± 0.11a
0.78 ± 0.08b
ns
*
*
MCV (fL)
256.59 ± 26.14
233.61 ± 22.34
217.14 ± 27.09
233.85 ± 11.94
ns
ns
ns
Glucose (mg dL-1)
53.27 ± 8.30b
77.46 ± 5.03a
53.60 ± 4.47b
51.33 ± 8.3b
ns
ns
*
1The data correspond to the mean of three ± standard deviation by treatments. Mean values on the same row with different superscript letters differ significantly (p < 0.05);
C = supplemented with C. vulgaris; M = molasses application rates; CxM = supplemented with C. vulgaris and molasses application rates; ns = not-significant (p >0.05);
*p <0.05; ¥Results from split-plot two-way ANOVA and Tukey’s test. MCV- Mean corpuscle volume. Treatments’ abbreviations as in Table 1.
The WC were significantly affected (p=0.04) by supplementation
Singh et al. (2017), C. vulgaris has a high potential for reducing
with C. vulgaris and molasses application rates and their interaction
the phosphorus of effluents.
between the factors (Table 2). In the treatments BFT-50 (93 L kg-1)
In relation to alkalinity, biofloc systems lose buffering capacity and
was higher compared with BFT-C50 (51.26 L kg-1), BFT-30
require frequent corrections (Azim and Little, 2008). The alkalinity
(55.22 L kg-1) and BFT-C30 (47.79 L kg-1).
levels were affected (p=0.01) by molasses application rates and
their interaction. The BFT-50 and BFT-C50 treatments had higher
Hematological assays
alkalinity levels compared with BFT-30 and BFT-C30, probably
in higher molasses application rates there is more heterotrophic
The hematocrit levels and erythrocyte counts were significantly
microbial biomass in relation to the nitrifying bacteria. According
affected (p < 0.05) by molasses application rates and their interaction,
Ebeling et al. (2006) the nitrification process promotes a more
and glucose was significantly affected (p < 0.05) by interaction
intense alkalinity reduction compared with the conversion of
between the factors; however MCV was not significantly affected
ammonium nitrogen into heterotrophic microbial biomass. The pH
(Table 6). In the molasses application rates of 30% of total daily
and alkalinity remained within the range considered adequate for
feed the hematocrit levels and erythrocyte counts were higher
tilapia cultivated by Avnimelech (2015) due to the addition of
compared with molasses application rates of 50%. From the
calcium hydroxide.
fourth week of experiment, signs of stress were observed, such
The mean values of settleable solids varied between 43 and 55 mL L-1
excess of superficial mucus and hemorrhage at the bases of the
and were affected (p=0.02) by molasses application rates and their
pectoral and caudal fins and mouth of the animals in the BFT-50
interaction. The higher molasses application rates (50% of the total
and BFT-C50 groups.
daily feed, C:N 20:1) presented settleable solids values higher
than 50 mL L-1, in addition to denser and larger diameter bioflocs.
Due to the high levels of solids, the treatments with higher molasses
DISCUSSION
addition required a longer sedimentation time. Due to the use of
the settler chamber, the values of SS and TSS were maintained
During the experiment, the variables of temperature and dissolved
at ideal levels by Avnimelech (2012), between 5 and 50 mL L-1
oxygen were maintained in ideal values for the cultivated Nile
for SS and 200 and 500 mg L-1 for TSS. However, an increase of
tilapia (El-Sayed, 2006). In heterotrophic systems, such as in
these values was observed throughout the rearing time, similar to
the biofloc system, it is expected that the levels of inorganic
that found by Long et al. (2015). The high concentrations of SS
nitrogen compounds would be kept low due to direct conversion
and TSS can cause discomfort in fish such as the accumulation
into microbial biomass as found in another study (Ebeling et al.,
of organic matter in the gills, which affect oxygen diffusion and
2006). The daily addition of a carbohydrate source to stimulate
also growth (Hargreaves, 2006; Avnimelech, 2012; Arantes et al.,
the growth of heterotrophic bacteria contributed to the reduction
2017). In a study of Litopenaeus vannamei culture in biofloc,
of the nitrogen compounds of water (Emerenciano et al., 2017),
Arantes et al. (2017) found that the use of a settler chamber
furthermore, fluctuations did not occur in nitrogen (TAN, N- NO2,
promoted improved the zootechnical performance of shrimp,
N- NO3) concentrations and may be related to the fact that the
resulting in higher productivity, survival and final weight.
experiment started with a previously matured biofloc.
Based on the results of the net productivity, even supplemented
The orthophosphate levels increased throughout the rearing
with C. vulgaris the system presented negative values from the
time and ranged from 1.08 to 1.45 mg L-1. The low levels of
beginning of the experimental period. According to Avnimelech
orthophosphate compared with those found by Luo et al. (2014)
(2012), when using a C:N ratio greater than 10:1, it is possible
(~12.3 mg L-1) using the biofloc system, may be related to the
to promote the succession and dominance of bacteria on the
abundance of the genera Chlorella (41-57% phytoplankton
microalgae, thus corroborating the findings in the present study
community) in all treatments. According to Ruiz et al. (2011) and
using the C:N ratio of 12:1 and 20:1, in treatments with 30%
Lima et al. Bol. Inst. Pesca 2019, 45(4): e494. DOI: 10.20950/1678-2305.2019.45.4.494
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TILAPIA CULTIVATED IN A LOW-SALINITY…
and 50%, respectively. This high abundance of Chlorella sp.
The Zootechnical performance of Nile tilapia fingerlings
(55 - 57%) may have reduced the density of cyanobacteria in
was affected (p < 0.05) by molasses application rates and their
BFT-C30 and BFT-C50. This result is similar as observed by
interaction. However, the addition of microalgae C. vulgaris had
Turker et al. (2003) who verified that Chlorella sp. reduces the
no influence, as reported by Araújo et al. (2019), when evaluating
abundance of phytoplankton, especially cyanobacteria in Partitioned
different densities of C. vulgaris (2.5, 5 and 10x104 cell mL-1)
Aquaculture System (PAS). On the other hand, Malbrouck and
in the culture of tilapia in biofloc with stocking density lower
Kestemont (2006), mentioned that the excess of cyanobacteria in
than the present study (250 fish m-3), and found final weight of
the aquaculture system can cause problems to species. Moreover,
approximately 21 g and survival greater than 80%. The addition of
Miranda-Baeza et al. (2017) observed that the incorporation of
C. vulgaris microalgae may not have influenced fish performance
the genus Oscillatoria had a significant negative effect on the
because it is already abundant in the culture system, as we found
survival and growth performance (<90% and around 19g) of
when evaluating the phytoplankton community, where C. vulgaris
tilapia in the biofloc system, especially in treatments with greater
represented 55.99% (BFT-C30) and 57.54% (BFT-C50) in
abundance this genus.
addition treatment, and 41.17% (BFT-30) and 44.89% (BFT-50)
in treatments without addition.
The fish crude protein and lipids were affected (p < 0.05) by
molasses application rates and their interaction. Jung et al. (2017)
The final weight and length, FCR, SGR, PER and yield were
identified an influence of supplementation with C. vulgaris and
higher in BFT-30 and BFT-C30 as compared than BFT-50 and
Scenedesmus obliquus on the nutritional values (protein and lipids)
BFT-C50. Pérez-Fuentes et al. (2016), Zapata-Lovera et al. (2017)
of the tilapia cultivated in a biofloc system. However, in our study,
and Liu et al. (2018) observed a higher zootechnical performance
we did not find effects just by supplementing with microalgae.
of Nile tilapia fingerlings in C/N (10:1) ratios compared with
This result may be related to the concentration and or frequency
higher C/N (20:1) ratios, as in the present study, where treatments
of supplemented microalgae. The values for proximal composition
with 50% addition of molasses presented lower final weight at
(53-80% crude protein and 4-27% lipids of the dry weight) of
the end of the cultivation. It is probable that the lower levels of
tilapia were similar to those reported by Azim and Little (2008),
solids (Pérez-Fuentes et al., 2016) and the dominance of the mix
Luo et al. (2014) and Jung et al. (2017). The biofloc can also be
of microalgae, heterotrophic bacteria and autotrophic bacteria
is more beneficial for fish and shrimp growth (Xu et al., 2016).
used as a supplementary food source contributing close to 50% of
protein requirement for fish (Avnimelech, 2007). The values for
Moreover, in high C:N ratios there may be consumption of large
amounts of oxygen (Liu et al., 2018).
proximal composition (34-38% crude protein of the dry weight),
were close to the values of protein content suggested for the
Due to the stress and reduction of feed intake observed in fish
diet in rearing tilapia (25 and 40%) (Craig and Helfrich, 2002;
from treatments with 50% addition of molasses presented lower
El-Sayed, 2006). The lipid content of the biofloc 1.67 ± 0.33%
values of nitrogen retention, and consequently a lower rate of
of the dry matter was relatively low, as were the results found
protein efficiency when compared to the other treatments (BFT-30
by Jung et al. (2017). Several studies have reported low lipid
and BFT -C30). However, as nitrogen retention depends on the
levels in biofloc from fish (1.27 to 3.16% of dry matter) (Azim
digestible energy content of feeds (Kaushik and Oliva Teles,
and Little, 2008; Luo et al., 2014). Low lipids levels in bioflocs
1985; Einen and Roem, 1997), the values found in the present
may be related to low lipid content of the commercial feed used
study were lower than those reported by other studies with tilapia
in this experiment (2.61% crude lipids).
(>30%) (Furuya et al., 2005; Righetti et al., 2011).
Regarding the effect of salinity, there is an increase in energy
The highest WC was from the BFT-50 treatment (93.28 ± 12.89 L
expenditure as a function of osmotic regulation, since in fish,
kg-1), while in the other treatments the consumption varied between
osmoregulation requires a high demand of metabolic energy,
47.19-55.22 L kg-1, showing a significant effect (p < 0.05) by
ranging from 20 to 50% of total energy expenditure, reducing the
supplemented with C. vulgaris and molasses application rates and
energy available for growth (Boeuf and Payan, 2001). Moreover,
their interaction. A similar result was found by Jung et al. (2017)
the low nutritional content of the commercial feed used probably
where WC decreased about 82% when supplementation with two
influenced the reduced growth and higher FCR (2.03 to 5.86), due
microalgae species were used. The WC was similar (52.48 L kg-1
to the low lipid content found in the commercial feed (2.61%),
with 500 fish m-3) that reported by Lima et al. (2018) and lower
different from the information described in the label. Lima et al.
compared with 750 to 1250 fish m-3 (76.32 to 101.54 L kg-1).
(2018) found similar values to those of the present study at a
A good indicator of fish health may be hematological indices
lower time (42 days), from 12.40 to 18.99g, 96.82 to 100% of the
(Martins et al., 2017). In the present study, stress caused by
survival, and lower values of FCR (1.24-1.40) when cultivating
molasses application rates of 50% (C/N 20:1) of total daily
tilapia at different densities in biofloc with 36% protein and 4%
feed (BFT-50 and BFT-C50) caused significant changes in the
lipid feed. However, the difference in the feed conversion factor
hematocrit level and the erythrocyte counts of the fish, resulting
between treatments with 30% and 50% addition of molasses is
in macrocytic anemia. The values found in the treatments with
due to the fact that the animals of the treatments with the highest
molasses application rates of 30% of total daily feed (C:N 12:1)
application of molasses showed signs of stress. Fish exposed
(BFT-30 and BFT-C30) remained in the ideal range described by
to stress situations presents changes in homeostasis, inducing
several authors (20 to 32% for hematocrit and 1.9 to 5.0 x 106 µL-1
changes in their physiological responses (Furuya, 2010). Even so,
for erythrocyte counts) (Ueda et al., 1997; Signor et al., 2010;
the yield values in BFT-30 and BFT-C30 were within the range
Costa et al., 2014; Martins et al., 2017). However, the values
recommended by Avnimelech (2015), between 10 to 40 kg fish m-3.
for treatments molasses application rates of 50% of total daily
Lima et al. Bol. Inst. Pesca 2019, 45(4): e494. DOI: 10.20950/1678-2305.2019.45.4.494
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TILAPIA CULTIVATED IN A LOW-SALINITY…
feed (BFT-50 and BFT-C50) were below the recommended level
AOAC - Association of Official Analytical Chemists. 2012. Official methods
(21-44% hematocrit level and 1.50 to 3.76 x 106 µL-1 erythrocyte
of analysis. 19th ed. Gaithersburg: AOAC. 3000p.
count) (Tavares-Dias, 2015).
APHA - American Public Health Association. 2005. Standard methods for
In addition, the values found for mean corpuscular volume
the examination of water and wastewater. Washington: APHA. 560p.
(MCV) were higher than those described by Signor et al. (2010),
Arantes, R.; Schveitzer, R.; Magnotti, C.; Lapa, K.R.; Vinatea, L. 2017. A
Salvador et al. (2013) and Tavares-Dias (2015) for Nile tilapia,
comparison between water exchange and settling tank as a method
between 113.4 and 170 fL. This increase in MCV is the first
for suspended solids management in intensive biofloc technology
response of fish in order to compensate for the decrease in the
systems: effects on shrimp (Litopenaeus vannamei) performance,
number of erythrocytes, by carrying larger amounts of hemoglobin
water quality and water use. Aquaculture Research, 48(4): 1478-1490.
(Tavares-Dias et al., 2002). Higher glycemia values were obtained
http://dx.doi.org/10.1111/are.12984 .
in the treatments with molasses application rates of 50% of total
daily feed and without supplemented microalgae. Although the
Araújo, M.T.; Braga, I.F.M.; Cisneros, S.V.; Silva, S.M.B.C.; Gálvez,
values found were within the range described by Tavares-Dias
A.O.; Correia, E.S. 2019. The intensive culture of nile tilapia
(2015), between 14.1 and 92.1 mg dL-1, the increase in glucose
supplemented with the microalgae Chlorella vulgaris in a biofloc
levels was reported in fish when associated with stressful conditions,
system. Boletim do Instituto de Pesca, 45(2): e398. http://dx.doi.
with elevated levels of cortisol and high blood glucose due to
org/10.20950/1678-2305.2019.45.2.398 .
the hyperglycemic characteristic of cortisol (Iwama et al., 1999).
Avnimelech, Y. 2007. Feeding with microbial flocs by tilápia in minimal
The low quality of the feed used in the experiment influenced
discharge bioflocs technology ponds. Aquaculture, 264(1-4): 140-147.
the performance of the fish, along with the high rate of addition of
http://dx.doi.org/10.1016/j.aquaculture.2006.11.025 .
molasses. A high amount of molasses can cause serious physiological
Avnimelech, Y. 2012. Biofloc technology: a practical guide book. 2nd ed.
problems in fish (Azim and Little, 2008; De-Schryver et al.,
2008), for these reasons, attention is needed when adding this
Louisiana: The Word Aquaculture Society. 272p.
carbon source to the system and using high C:N ratios and in the
Avnimelech, Y. 2015. Biofloc technology: a practical guide book. 3rd ed.
quality of the feed.
Louisiana: The Word Aquaculture Society. 258p.
Azim, M.; Little, D. 2008. The biofloc technology (BFT) in indoor tanks:
water quality, biofloc composition, and growth and welfare of Nile
CONCLUSION
tilápia (Oreochromis niloticus). Aquaculture, 283(1-4): 29-35. http://
dx.doi.org/10.1016/j.aquaculture.2008.06.036 .
In summary, the data of the present study show that the interactions
between supplementation with C. vulgaris and molasses application
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ACKNOWLEDGEMENTS
linhagem e densidades de estocagem. Archivos de Zootecnia, 66(254):
229-235. http://dx.doi.org/10.21071/az.v66i254.2326.
The authors are grateful to Tereza Santos (Limnology
Costa, D.V.; Ferreira, M.W.; Navarro, R.D.; Rosa, P.V.; Murgas, L.D.S. 2014.
Laboratory-UFRPE) for their contribution to this study. We are
Parâmetros hematológicos de tilápias-do-Nilo (Oreochromis niloticus)
also grateful for the financial support provided by the Brazilian
alimentadas com diferentes fontes de óleo. Revista Brasileira de
National Counsil for Scientific and Technological Development
(CNPq) for the aid granted to the Professor Alfredo Olivera Gálvez
Saúde e Produção Animal, 15(3): 754-764. http://dx.doi.org/10.1590/
(PQ 311058/2015-9), the Coordenação de Aperfeiçoamento de
S1519-99402014000300023 .
Pessoal de Nível Superior (CAPES) and Fundação de Amparo
Craig, S.; Helfrich, L.A. 2002. Understanding fish nutrition, feeds, and feeding.
à Ciência e Tecnologia do Estado de Pernambuco (FACEPE).
Virginia: Virginia Cooperative Extension. 4p. Publication 420-256.
De-Schryver, P.; Crab, R.; Defoirdt, T.; Boon, N.; Verstraete, W. 2008. The basics
of bio-flocs technology: the added value for Aquaculture. Aquaculture,
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