INTERNATIONAL JOURNAL OF RESEARCH AND SCIENTIFIC INNOVATION (IJRSI)
ISSN No. 2321-2705 | DOI: 10.51244/IJRSI |Volume XII Issue IX September 2025
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Dietary Effects of Oleaginous Microalga on the Fatty Acid Profile
and Nutritional Performance of African Catfish, Clarias gariepinus,
(Burchell 1822)
Gbadamosi, Oluyemi Kazeem, Alao, Felicia Oluchukwu
Fisheries and Aquaculture Technology Department, School of Agriculture and Agricultural Technology,
Federal University of Technology, Akure, Ondo State, Nigeria
DOI: https://dx.doi.org/10.51244/IJRSI.2025.120800413
Received: 16 September 2025; Accepted: 24 September 2025; Published: 23 October 2025
ABSTRACT
The Dietary Effects of Oleaginous Microalga on the Fatty Acid Profile and Nutritional Performance of African
Catfish, Clarias gariepinus were evaluated in this research in relation to the dietary freshwater microalgae,
Botryococcus braunii. Three isocaloric and isonitrogeneous diets with 9% fat and 45% crude protein were
developed. Fish meal and oil were the only sources of protein and fat in the first diet; soybean meal and oil
were the basis for the second diet; and B. braunii meal was the basis for the third. For every diet, three
replicate groups of fish with beginning weights of 11.00±0.05g were employed. For 56 days, fish were hand
fed according to their body percentage (5%) weight. Fish fed B. braunii at the end of the feeding trial did not
differ significantly (P>0.05) from fish fed fish meal, but they did differ significantly (P<0.05) from fish fed
soybean meal. This study demonstrated that C. gariepinus fed a diet based on B. braunii was able to achieve
comparable nutritional performance with soybean and fish meal. Furthermore, information on the fatty acid
profile indicated that B. braunii might be fed to African catfish in place of fish and soybean oil. The study's
findings demonstrated that the dietary microalgae B. braunii was well-digestible and could substitute up to
80% of the fish and soybean oils in the diet of African catfish without having an adverse effect on the fish
growth or fatty acid composition.
Keywords: Aquafeeds, Microalgae, Fatty acid, Aquaculture, Seafood
Word count: 230
INTRODUCTION
Over the past few decades, aquaculture production has increased dramatically worldwide in response to the
growing demand for seafood, which catch fisheries are no longer able to supply. As a result, the demand for
fishmeal and fish oil—which are employed as sources of protein and fat in commercial fish feeds—has
increased, a scenario that is now acknowledged to be unsustainable from an economic and environmental
standpoint (FAO, 2022). High-value carnivorous marine finfish require diets that are high in protein and
energy, with a focus on fishmeal and fish oil (Turchini et al., 2019).
Microalgae are unicellular photosynthetic microorganisms that produce biomass from carbon dioxide, water,
and sunshine. They can live in freshwater or saltwater habitats. Depending on the species, they are abundant in
lipids and protein. Compared to fish fed plant-based proteins, fish that eat algae usually have a higher oil
content ratio of omega-3 to omega-6 (Hamilton et al., 2020). According to Abreu et al. (2018), microalgae
thrive on aerated liquid media that are adequately supplied with light, carbon dioxide, and nutrients. Compared
to terrestrial plants, they have greater growth rates, photon conversion efficiency, and CO₂ sequestration
ability, which increases biomass yields (Gao et al., 2019).
Some microalgae species have the ability to accumulate large amounts of protein, up to 65% of their dry
weight. High protein levels have been regularly observed in strains such as Nannochloropsis, Chlorella, and
Spirulina (Gong et al., 2021). Microalgae can also create lipids with fatty acid profiles that are nutritionally
INTERNATIONAL JOURNAL OF RESEARCH AND SCIENTIFIC INNOVATION (IJRSI)
ISSN No. 2321-2705 | DOI: 10.51244/IJRSI |Volume XII Issue IX September 2025
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Page 4568
useful when they are under stress. Among the most important bioactive lipids are polyunsaturated fatty acids
(PUFAs), such as docosahexaenoic acid (DHA, 22:6 ω-3) and eicosapentaenoic acid (EPA, 20:5 ω-3). (Kumar
et al., 2020). Omega-3 fatty acid consumption has been associated with improved nervous system development
and brain function in babies, as well as protection against neurodegenerative and cardiovascular disorders (Teo
et al., 2022).
Aquafeeds that include PUFA-rich microalgae produce food items including fish, eggs, and milk that have a
greater omega-3 concentration. Because of their ability to produce goods with added value, microalgae are also
extensively utilized in the nutraceutical and renewable energy industries. They may produce up to 77 g m⁻² of
dry biomass per day⁻¹, which is equivalent to about 280 tons ha⁻¹ per year⁻¹ (Chew et al., 2020). Over 5,000
metric tons of processed algal biomass are sold worldwide each year, bringing in over USD 1.5 billion
(Rajkumar et al., 2021). According to Chen et al. (2019), microalgae are also known to be strong antioxidants
that help aquatic species cope with oxidative stress brought on by environmental and metabolic variables.
The varied fatty acid profile of fish, which includes saturated, monounsaturated, and polyunsaturated fatty
acids, is one of its main health advantages. In ecological research, these fatty acids are useful biomarkers that
aid in tracking dietary fluxes throughout terrestrial and aquatic food webs (Brett et al., 2019). The most
commonly farmed fish species in Nigeria are catfishes belonging to the Clariidae family, specifically C.
gariepinus. They exhibit strong resistance to illnesses and environmental stress, are resilient, and are well
suited to cramped spaces. Their meat is high in protein, vitamins, minerals, and unsaturated fatty acids. A
major aquaculture species in Africa today, Clarias gariepinus farming has seen a productivity explosion
(Adewolu et al., 2022).
The many health advantages associated with eating omega-3-rich fish, especially those that include EPA and
DHA, are still supported by recent research (Yousefi et al., 2020). These fatty acids are found in large
quantities in oily fish and fish oil substitutes made from algae. They have been shown to lower blood pressure
and serum triglycerides, prevent cardiac arrhythmias, and minimize the risk of coronary heart disease (CHD)
(Sarker et al., 2021).
High levels of DHA and EPA found in some microalgae are advantageous to aquatic life as well as to humans
(Del Mondo et al., 2021). By eating on algae, marine fish naturally collect these fatty acids. Omega-3-rich
microalgae are effective substitutes for conventional lipids and fish oil, according to research on alternative
aquafeeds (Tibaldi et al., 2023). Compared to many other biological sources, microalgal species have lipid
concentrations that range from 20 to 60 percent (Moreno-García et al., 2020; Galasso et al., 2021).
Including microalgae in fish diets improves nutritional utilization, development, and survival. Furthermore,
these diets increase the omega-3 content of fish flesh, particularly DHA and EPA, which benefits
cardiovascular health in people. This encourages research into B. braunii as a feed supplement to assess its
effects on African catfish (C. gariepinus) fatty acid composition, growth performance, and nutrient utilization.
B. braunii is extensively spread in France, Portugal, the USA, Malaysia, India, Thailand, Japan, and the
Philippines and is well-known for producing lipids, sterols, exopolysaccharides, and other bioactive substances
(Ahsan et al., 2022). The objective of this study is to determine the effects of B. braunii on fatty acids profile,
growth performance and nutrient utilization in African catfish.
MATERIALS AND METHODS
This study was conducted at the Federal University of Technology Akure, Ondo-State, at the Department of
Fisheries and Aquaculture Technology Teaching and Research farm. The source of B. braunii was Animal
Feed at Ogere-Remo, Ogun State. Before beginning the feeding experiment, two hundred C. gariepinus post
fingerlings were acclimated for two weeks at the Teaching and Research Farm of the Department of Fisheries
and Aquaculture Technology. Three distinct dietary supplements, namely the microalgae-fortified diet feed
and two additional designed diets, were used to examine the development and nutrient utilization of C.
gariepinus. The department of Fisheries and Aquaculture Technology Teaching and Research Fish farm served
as the site of all 56-day fish feeding experiments.
INTERNATIONAL JOURNAL OF RESEARCH AND SCIENTIFIC INNOVATION (IJRSI)
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Page 4569
Preparation of experimental diet
In order to create three isonitrogeneous and isocalorific experimental diets with 45% crude protein and 9%
lipids, soybean meal was substituted with B. braunii. The fish kept in each tank were fed twice a day, from 8 to
9 a.m., and from 4 to 5 p.m., according to a diet that was 5% of their body weight for 56 days. Every week,
fresh water was added to the tank. The fish were inspected every day for anomalous behaviour and mortality,
and they were weighed once a week.
Table 1: Formulation of the experimental diets (g per 100g feed each)
Diet 1 Fishmeal
Diet 2 Soybean meal
Diet 3 B. braunii
Fishmeal (65%)
55.0
B. braunii
82.0
Soybean meal
(45%)
80.0
Maize (10%)
Dicalcium
phosphate
31.5
0
0
4.5
10.5
4.0
Fish oil
10.0
0
0
Soybean oil
0
12.0
0
Alginate
3.0
3.0
3.0
Vitamin and
mineral premix
0.5
0.5
0.5
Total
100
100
100
Vitamin A: 8,000,000 IU, Vitamin D3: 1,600,000IU, Vitamin E: 6,000 IU, Vitamin K: 2,000mg, Thiamine B1:
1,500mg, Riboflavin B2: 4,000mg, Pyridoxine B6: 15,000mg, Niacin: 15,000mg, Vitamin B12: 10mg,
Pantothenic acid: 5,000mg, Folic acid: 500mg, Biotin: 20mg, Choline chloride: 200g, Antioxidant: 125g,
Manganese: 80g, Zinc: 50g, Iron: 20g, Copper: 5g, copper: 5g, Iodine: 1.2g, Selenium: 200mg, Cobalt: 200mg
(Hi-Nutrient International Limited, 2017).
Experimental fish: Before the experiment began, 150 seemingly healthy C. gariepinus post fingerlings
weighing 11.00g ±0.5% were divided into 15 plastic water tanks, with 10 fish per tank. The fish were allowed
to acclimate for two weeks. There were five treatments in three replications per experimental diet and feed for
a total of 56 days.
Experimental system and procedure: For the experiment, fifteen plastic tanks measuring 60 cm by 45 cm by
45 cm were utilized. Each plastic tank was randomly filled with ten post-fingerlings, with three replications for
each treatment. Each group of fish received two equal amounts of experimental foods at 9:00–10.00 GMT and
16:00–17:00 GMT, with each group receiving 5% of their body weight daily. The experimental diets were
randomly assigned to the plastic tank. Every week, each fish was taken out of its glass tank and weighed
separately.
Monitoring of water quality parameters: Dissolved oxygen was monitored weekly using HANNA 98103SE
(HANNA instruments, Rhode Island). Temperature and pH were monitored also monitored weekly using YSI-
IODO 700 digital probe (IFI Olsztyn, Poland). The physical assessment of culture water was carried out
weekly and included: temperature, pH, and dissolved oxygen (DO). The water was maintained at 27 - 30
o
C,
dissolved oxygen at 6.5-8.3 mg/L and pH 6.0 - 8.5.
INTERNATIONAL JOURNAL OF RESEARCH AND SCIENTIFIC INNOVATION (IJRSI)
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Proximate composition of experimental feed and fish: At the start of the trial, samples of the fish and
prepared foods were taken, and their proximate components were examined. At the conclusion of the trial, fish
samples from each treatment were also examined. A meat grinder with a 4 mm diameter aperture plate was
used to crush fish and feed samples into a uniform mince prior to examination. After being dried for 24 hours
at 105°C in an oven (Gallenkamp, UK), a subsample of this mince was removed from each tank and stored for
the measurement of dry matter. For all ensuing analyses, the leftover feed and fish homogenate were dried in
an oven. Weight loss following incineration in a muffle furnace (Carbolite, UK) for 12 hours at 550ºC was
used to determine the amount of ash present. Crude protein was measured by the Kjeldahl procedure. This
method calculates the nitrogen (N) content and multiplies it by a 6.25 conversion factor.
Growth Response and Nutrient Utilization
At the end of the experimental period (56 days), the performance data were calculated, fish were counted and
batch-weighed. The growth parameters and feed utilization indices were calculated as follows according to
Takeuchi (1988) and Tacon (1990):
𝑾𝑬𝑰𝑮𝑯𝑻 𝑮𝑨𝑰𝑵
(
𝒈
)
= 𝐹𝑖𝑛𝑎𝑙 𝑤𝑒𝑖𝑔ℎ𝑡 − 𝐼𝑛𝑖𝑡𝑖𝑎𝑙 𝑤𝑒𝑖𝑔ℎ𝑡
Specific Growth Rate (SGR)
This will be calculated from data on changes of body weight over given time interval;
𝑆𝐺𝑅
(
% 𝑝𝑒𝑟 𝑑𝑎𝑦
)
=
(𝐿𝑛 𝑓𝑖𝑛𝑎𝑙 𝑤𝑒𝑖𝑔ℎ𝑡 − 𝐿𝑛 𝑖𝑛𝑖𝑡𝑖𝑎𝑙 𝑤𝑒𝑖𝑔ℎ𝑡)
𝑇𝑖𝑚𝑒(𝑑𝑎𝑦𝑠)
𝑥100
𝑊ℎ𝑒𝑟𝑒 𝐿𝑛 = 𝑁𝑎𝑡𝑢𝑟𝑎𝑙 𝑙𝑜𝑔𝑒
Total Feed Intake (g)
This will be obtained by adding daily mean feed intake (DFI) of fish under each treatment for the experimental
period.
𝑭𝑬𝑬𝑫 𝑰𝑵𝑻𝑨𝑲𝑬
(
𝒈
)
=
𝑻𝒐𝒕𝒂𝒍 𝒇𝒆𝒆𝒅 𝒊𝒏𝒕𝒂𝒌𝒆
𝑵𝒖𝒎𝒃𝒆𝒓 𝒐𝒇 𝒇𝒊𝒔𝒉 𝒔𝒖𝒓𝒗𝒊𝒗𝒆𝒅
𝑭𝑬𝑬𝑫 𝑪𝑶𝑵𝑽𝑬𝑹𝑺𝑰𝑶𝑵 𝑹𝑨𝑻𝑰𝑶
(
𝑭𝑪𝑹
)(
𝒈
)
=
𝒇𝒆𝒆𝒅 𝒊𝒏𝒕𝒂𝒌𝒆(𝒈)
𝒘𝒆𝒊𝒈𝒉𝒕 𝒈𝒂𝒊𝒏(𝒈)
𝑺𝑼𝑹𝑽𝑰𝑽𝑨𝑳
(
%
)
=
𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑓𝑖𝑠ℎ ℎ𝑎𝑟𝑣𝑒𝑠𝑡𝑒𝑑
𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑓𝑖𝑠ℎ 𝑠𝑡𝑜𝑐𝑘𝑒𝑑
𝒙𝟏𝟎𝟎
Fatty Acid Determination
Fat Extraction
An electric blender (Binatone©, Model BL-450) was used to macerate the samples, and a handheld
homogenizer was used to homogenize them. A 20 ml test tube (fitted with a screw top) was filled with 100 mg
of the homogenized material, which was then dissolved in 10 ml of n-hexane. The sample was combined in a
Vortex Mixer for 30 seconds with 100 microliters (100μl) of potassium hydroxide-methanol solution (11.2g of
KOH in 100ml of CH₃OH). In accordance with Folch et al., 1957, this was then centrifuged for five minutes at
2000 rpm to aid in phase separation.
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Page 4571
Fatty Acid Determination
Lipid Extraction and Esterification
Samples were macerated using an electric blender (Binatone©, Model BL-450) and homogenized with a
handheld homogenizer. Approximately 100 mg of the homogenized tissue was placed in a 20 ml screw-capped
test tube and extracted with 10 ml of n-hexane. The mixture was vortexed for 30 seconds after adding 100 μl of
potassium hydroxide-methanol solution (11.2 g KOH in 100 ml CH₃OH). Phase separation was facilitated by
centrifugation at 2000 rpm for 5 minutes following the method of Folch et al. (1957).
For fatty acid methyl ester (FAME) preparation, a saturated NaCl solution was added to the extract until the
heptane layer reached the neck of the flask. The heptane containing FAMEs was collected and dried over 1.5 g
of anhydrous sodium sulphate. Further esterification followed AOAC (2019) protocols: 4 ml of methanolic
NaOH (2 g NaOH/100 ml methanol) and 10 boiling chips were added to 50 ml of extracted oil in a reaction
flask. After attaching a condenser, 5 ml of boron trifluoride was added, and the mixture was refluxed for 12
minutes. Subsequently, 5 ml of heptane was added and refluxed for an additional 1 minute. The mixture was
cooled to room temperature and used for GC-MS analysis.
Statistical Analysis
All data were subjected to Analysis Of Variance (ANOVA) for significant differences using (SPSS version
28).variation in means was tested using Duncan multiple range test at p < 0.05.
Results and Discussion
Proximate Composition of Experimental Diets
The proximate composition of the experimental diets is summarized in Table 1.
Table 1: Proximate composition (%) on dry matter basis of experimental diets
Proximate Composition (%) FM SBM B. braunii
Moisture content 4.71 5.15 3.4
Ash 12.62 12.07 20.89
Crude Protein 45.56 44.36 45.24
Lipid 13.61 19.42 20.11
Fibre 0 2.09 0.85
NFE 14.5 16.91 9.51
(Values are means ±SE. Same superscripts within a row indicate no significant difference at P<0.05.)
The diets showed relatively comparable crude protein levels (44.36–45.56%), with FM slightly higher than B.
braunii and SBM. This is consistent with Gbadamosi & Lupatsch (2018) who demonstrated that microalgae
such as Nannochloropsis can closely match fishmeal protein levels in tilapia diets. Similarly, the high ash
content of the B. braunii diet (20.89%) reflects its rich mineral profile, echoing Zhang et al. (2020) who noted
that microalgae offer superior ash and micronutrient content over terrestrial feedstuffs.
Notably, B. braunii also exhibited the highest lipid content (20.11%), surpassing SBM and FM. This supports
findings by Niccolai et al. (2019) and Demuez et al. (2015) highlighting B. braunii’s capacity for lipid
accumulation up to 70% of its biomass, positioning it as a valuable energy source in aquafeeds.
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Carcass Composition of African Catfish
Table 2 presents the carcass composition of C. gariepinus before and after feeding the experimental diets.
Table 2: Carcass composition (%) of African catfish post fingerlings
Parameter
Initial
FM
SBM
B. braunii
Moisture
3.23
9.69±0.08
c
5.96±0.22
a
7.50±0.08
b
Ash
13.08
13.45±0.48
a
14.99±1.15
a
12.50±0.71
a
Crude Protein
65.31
58.30±0.71
a
60.01±1.19
a
58.61±0.53
a
Lipid
12.87
14.99±0.16
a
14.50±0.12
a
15.99±0.21
b
NFE
5.51
3.57±0.15
a
4.54±0.38
a
5.41±1.37
a
Fish fed B. braunii diets accumulated more carcass lipid (15.99%), significantly higher than SBM (14.50%), a
trend in line with Wei et al. (2021) who reported increased lipid deposition in salmon fed microalgae.
However, carcass crude protein declined from the initial 65.31% to ~58–60% across treatments, reflecting
typical shifts when fish transition from pre-trial commercial feeds to experimental diets, as noted by Siddiqui
et al. (2019). This highlights the importance of amino acid supplementation when substituting conventional
proteins.
Water Quality Parameters
Table 3 shows that pH, temperature, dissolved oxygen and conductivity remained within optimal ranges for C.
gariepinus, with no significant differences (P>0.05) across treatments, indicating that diet rather than water
quality drove performance outcomes.
Table 3: Mean water quality parameters during experimental period
Treatment
pH
Temperature
Conductivity
DO2
TRT 1
6.22±0.07
a
27.4±0.13
a
0.8±0.05
a
5.6±0.09
a
TRT 2
6.12±0.09
a
26.48±0.14
a
0.75±0.04
a
5.4±0.08
a
TRT 3
6.30±0.07
a
26.88±0.19
a
0.57±0.02
a
5.4±0.11
a
This stable water quality is comparable to standards reported by Adewolu et al. (2016) for optimal catfish
growth.
Growth Performance and Nutrient Utilization
Table 4 summarizes growth and feed utilization parameters. Fish fed B. braunii diets achieved final weights
(35.45 g) and specific growth rates (2.08%) statistically similar to FM (43.20 g; 2.07%), both significantly
superior to SBM.
Table 4: Growth performance and nutrient utilization over 56 days
Parameters
Treatment 1
Treatment 2
Treatment 3
MIW (g)
13.53±0.66
a
11.73±0.38
a
10.78±0.41
a
MFW (g)
43.20±2.03
b
17.82±2.08
a
35.45±4.53
b
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MWG (g)
29.67±1.43
b
6.08±1.75
a
24.68±4.62
b
SGR (%)
2.07±0.03
b
0.70±0.22
a
2.08±0.17
b
MFI (g)
53.81±2.53
c
34.85±1.46
a
45.98±2.14
b
FCR
1.70±0.09
b
1.04±0.03
a
1.34±0.00
b
FER
0.55±0.01
c
0.25±0.03
a
0.44±0.02
b
PER
0.02±0.00
a
0.02±0.00
a
0.02±0.00
a
SURVIVAL (%)
92.00±8.00
a
80.00±3.16
a
94.00±2.45
a
The superior performance of B. braunii over SBM supports Nagappan et al. (2021) who linked microalgae
inclusion to improved palatability and digestibility in tilapia, while Gong et al. (2020) similarly reported
efficient FCRs with microalgal diets in carp.
Fatty Acid Composition
The fatty acid profiles (Table 5) reveal that fish fed B. braunii exhibited higher total n-3 PUFA (20.96%) and a
more favorable n-3/n-6 ratio (2.30), enhancing the nutritional quality of the fillet.
Table 5: Fatty acid profile (% of total lipid) in fish muscle
Fatty Acid
FM
SBM
B. braunii
10:0
1.03
1.30
1.02
13:0
0.51
0.39
0.33
14:0
4.00
3.57
3.64
12:0
4.69
2.99
4.71
16:0
23.77
23.05
25.02
17:0
0.69
0.03
0.12
18:0
5.97
7.05
7.95
Total saturated
41.98
39.3
43.56
15:1n-10
0.81
0.66
0.47
16:1
0.00
0.00
0.00
18:1n-9
19.14
20.01
18.97
20:1n-9
0.00
0.00
0.00
Total monoenes
19.95
20.67
19.44
18:3n-3
20:5n-3
22:6n-3
Total n-3
0.70
4.39
9.05
14.14
2.01
2.58
4.68
9.27
0.43
6.23
14.3
20.96
18:2n-6
4.04
13.85
6.42
18:3n-6
0.45
0.42
0.33
20:4n-6
0.17
0.02
2.35
Total n-6
n-3/n-6
4.66
3.03
14.29
0.65
9.1
2.30
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Page 4574
This confirms observations by Ryckebosch et al. (2012) and Sarker et al. (2020) that dietary microalgae
elevate EPA and DHA in fish, enhancing their human health value. Notably, the higher n-3/n-6 ratio is
desirable given the cardiovascular benefits of omega-3-rich fish (Simopoulos, 2002).
CONCLUSION
This study demonstrates that B. braunii can replace fishmeal and soybean meal up to 100% in African catfish
diets without compromising growth, nutrient utilization, or survival, while improving lipid deposition and
enriching the fillet’s omega-3 content. These results are consistent with global drives towards sustainable
aquafeeds (FAO, 2020), reducing pressure on wild fish stocks and land-intensive crops.
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