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African Journal of Food Science Research ISSN 2375-0723 Vol. 7 (1), pp. 001-005, January, 2019. Available 
online at www.internationalscholarsjournals.org © International Scholars Journals 

 

Author(s) retain the copyright of this article. 
 
 

 

Full Length Research Paper 

 

Comparative effects of crude oil on juveniles Clarias 
gariepinus and Clarias anguillaris 

 
Awoyinka O. A.1*, Atulomah E.1 and Atulomah N. O. S.2 

 
1
Department of Biochemistry,  Babcock University, Ilisan-Remo, Nigeria. 

2
Public and Allied Health Unit, Babcock University Ilisan-Remo, Nigeria. 

 
Accepted 21 October, 2019 

 
This study was based on biochemical assessment of the effect of crude oil spillage on marine life. Hence, life 
sustaining indices such as pH, dissolved oxygen (DO), and free CO2 were analyzed in aquaria. However, a 96 h 
static acute toxicity test was also investigated on the juveniles Clarias gariepinus (African catfish) and Clarias 
anguillaris (mudfish) on exposure to different concentrations of crude oil polluted water. Over the period of the 
experiment there was an overall decrease in pH of the test vessel from 8.64 ± 0.03 to 5.50 ± 0.08. Decrease trend 
was also found in dissolved oxygen from 6.28 ± 0.07 to 3.01 ± 0.06 and free CO2 levels from 8.35 ± 0.55 to 11.25 
± 0.17. However as the concentration of crude oil increases the haematological parameters such as red blood 
cell (RBC), packed cell volume (PCV), and white blood cell (WBC) reduced significantly (p ≤ 0.05) in both fish 
species. After 96 h, probit analysis showed the LC50 of crude oil for C. anguillaris to be 1.22 mg/L while that of 
C. garieinus was 2.19 mg/L. Overall, less insults was observed from the crude oil on C. gariepinus compare to 
C. anguillaris that tend to elicit a low tolerance to the crude oil. 
 

Key words: Clarias gariepinus, Clarias anguillaris, crude-oil, LC50, and static-acute. 

 
INTRODUCTION 

 
The activities of man have been responsible for 
introducing contaminants into the environment in the last 
few decades. The resulting pollution has led to serious 
consequences on aquatic life (Clair et al., 2003). Apart 
from the presence of industrial wastes that are sources of 
constant threat to marine life, the ecological disasters 
caused by the oil industry while exploring crude oil and 
accidental discharge of crude oil on high seas is a serious 
cause for concern (Speight, 1999). The main threat 
posed to living resources by the persistent residues of 
spilled oils and water-in-oil emulsions (“mousse”) is one 
of physical smothering that may consequently lead to 
depletion of biodiversity in the aquatic environment if 
adequate remediation is not provided (Cooney et al., 
2001). The animals and plants most at risk are those that 
could come into contact with a contaminated sea surface 
(Longhurt, 1961). These  
 
 

 
*Corresponding author. E-mails: woyinka@yahoo.com, 
oawoyinka@babcockuni.edu.ng. 

 
 
 

 
include aquatic mammals, reptiles and birds that feed by 
diving or form flocks on the sea as well as aquatic lives 
on shorelines ( Suchanek, 1993).  

Juvenile Clarias anguillaris and Clarias gariepinus were 
selected as the aquatic organisms for this experiment 
due to the fact that their response and sensitivity to 
toxicants is high (Sunmonu and Oloyede, 2006). Both are 
species of the family Clariidae, the air breathing 
catfishes, found throughout Africa and the Middle East. 
They live in freshwater lakes, rivers, swamps, as well as 
human-made reservoirs, such as ponds or even urban 
sewer systems (Teugels, 1986). C. gariepinus commonly 
refer to as African Catfish is a large, eel-like usually of 
dark gray or black colouration on the back, fading to a 
white belly. It has a slender body, a flat bony head and 
abroad terminal mouth with four pairs of barbell (Andrews 
and Matsuda, 1975). However, C. anguillaris otherwise 
known as Mudfish have an oval-shaped to rectangular in 
dorsal outline with a broadly rounded snout (Teugels, 
1986). Previous studies have shown that crude oil can 
have both lethal and sub-lethal effects on a wide range of 
organisms. These include the observation reported by in 



 
 
 

 

juvenile pink salmon (Oncorhyncusgorbuscha) (Wang et 
al., 1994); while drastic changes in liver enzyme activities 
of catfish (C. gariepinus) were reported following 
exposure to crude oil ( Sunmonu and Oloyede, 2006). 
Against the foregoing this work was set to carried out 
comparative study on the effect of crude oil exposure on 
some physical parameters, haematological parameters 
and lethality in C. gariepinus and C. anguillaris under 
experimental conditions. 
 

 
MATERIALS AND METHODS 

 
Collection of crude oil 
 
The crude oil was obtained from Chevron depot site, Lagos Nigeria. 

 

Collection of test organism 
 
Juvenile C. anguillaris and C. gariepinus were collected from a 
fresh water fish farm in Iperu Remo and Ilishan Remo respectively. 
The acute toxicity test was carried out at the Department of 
chemical and environmental Sciences Animal Laboratory, Babcock 
University Nigeria. 

 

Experimental methods 
 
Modified method of American Public Health Association (APHA, 
1992) was used to carry out the static bioassay procedure. This 
involved carefully controlled environmental conditions to define the 
response of the test organism to crude oil.  

Twelve rectangular glass tanks of the dimension 50 × 30 × 45 cm 
and capacity of 100.5 L were used as aquarium. The test organisms 
were brought into the laboratory and the weight of the fishes was 
taken. This ranged between 1.6 and 1.87 g and the length of the 
fishes ranged between 5.5 to 7.3 cm. The length and weight of the 
biggest was not more than twice that of the smallest, to avoid errors 
due to size. The stock populations were held for one week in the 
laboratory, inside these aquaria, filled with 30 litres of unchlorinated 
borehole water. The animals were held at a temperature range of 
26 to 28°C. The water in the tanks was changed once every three 
days in order to avoid the accumulation of toxic metabolites and 
wastes secreted by the fishes. Juvenile C. anguillaris and C. 
gariepinus of fairly equal length and weight were taken randomly 
from the stock population using a hand net and carefully transferred 
to the glass test vessel containing the test solution. 
 

 

Static acute toxicity study 
 
Preliminary studies carried out using several concentrations 
provided the basis for the spread of test concentrations along pre 
determined toxicity range of test samples. Reference chemical used 
as a negative control is Sodium Dodecyl Sulphate (Gulley and 
West, 1996). Fish tanks filled with only freshwater were used as 
positive control. Concentrations of crude oil prepared as 0.6, 1.0, 
1.4 and 1.8 mg/L were added to the C. anguillaris labelled aquarium 
while 1.2, 2.0, 2.8 and 3.6 mg/L were added to the C. gariepinus 
labelled aquarium for two hours to allow aeration. Thereafter, a total 
number of twenty of the fish species were added to each test vessel 
and covered with wire mesh to prevent the organisms from jumping 
out of the tanks. Mortalities of the test organisms were recorded at 
24, 48, 72 and 96 h according to 

 
 
 
 

 
OSPAR offshore Industries Committee (OIC, 2002). The 
experimental animals were taken as dead when there were no 
opercula and other forms of body movements even on prodding 
with a glass rod. 

 

Determination of physico- chemical parameters 
 
Samples of the test solutions were taken from each vessel for the 
determination of physico-chemical parameters. The following 
parameters were measured after the placement of each test 
solutions in each tank: pH, dissolved oxygen and temperature using 
the HORIBA U10 and the dissolved oxygen meter. The level of 
carbon dioxide in each aquarium was determined by the titrimetric 
method (Maissonneuvve and Larose, 1988). 

 

Determination of hematological parameters 
 
The method of Dacie and Lewis (1975) as modified by Alexandra 
and Griffiths (1993) was used in the determination of the 
haematological parameters. After harvesting from the aquaria, the 
fishes were allowed to stay in a dissecting tray for about ten 
minutes to reduce the slime on their bodies. They were thereafter 
dissected and blood sample was collected with a disposable 
syringe and needle and immediately transferred into sterile 
ethylene diamine tetra-acetic acid (EDTA) embedded vials for 
haematological analysis. The Automated Haematologic Analyzer 
(Sysmex KX – 21, UK) was used to analyze the haematological 
parameters namely packed cell volume (PCV), white blood cell 
(WBC) and red blood cell (RBC). 
 

 

RESULTS AND DISCUSSION 

 

One of the major problems of the inhabitants of the Niger 
Delta region of Nigeria is contamination of water and 
aquatic lives by crude oil spillage (Sunmonu and 
Oloyede, 2008).  

The severity or degree of the problems in the 
inhabitants of the area is dependent upon the point of 
contact with the polluted water (Omoregie, 1998). This 
observation is reflected in the physico- chemical 
parameters of this study. There were overall decreases in 
pH of all the test solutions after a 96 h period of the 
experiment (Tables 1 and 2). The decrease in pH which 
poses a lethal effect on the marine life is indicated to be 
from the organic pollution from the fishes (Swingle, 1961; 
GodsWill, 1989). However, similar trends were also 
observed in the values of Dissolved oxygen (DO) in all 
the aquaria. A significant decrease (P ≤ 0.05) in dissolved 
oxygen over 96 h period of the study was recorded. It is 
known that low DO causes anaerobic decomposition of 
organic matter in water, forming noxious and toxic 
substances such as hydrogen sulphide and methane 
which ultimately would have deleterious effect on the 
aquatic life (Mason, 1991; DPRM, 2000). There was a 

corresponding increase in free CO2 in the aquaria 

containing C. anguillaris from 8.35 ± 0.23 to 11.25 ± 0.17 
over a period of 96 h. and 8.69 ± 0.33 to 11.48 ± 0.15 for 
aquaria containing C. gariepinus. This observation can be 
attributed to the oil film formation that reduces the 



  
 
 

 
Table 1. Physico- chemical parameters determined in test solutions with crude oil sample containing Clarias anguillaris (mudfish) 24 to 96 h into 
the experiment.  

 

 Concentration Duration Positive Negative 1.2 2.0 2.8 3.6 
 (mg/L) (h) control control 0.6 1.0 1.4 1.8 

 pH 24 7.86 ± 0.02
a
 7.25 ± 0.04

b
 7.96 ± 0.03

c
 8.20 ± 0.02

d
 8.43 ± 0.05

e
 8.64 ± 0.03

f
 

 pH 96 6.23 ± 0.03
a
 6.89 ± 0.02

b
 5.68 ± 0.06

c
 5.50 ± 0.08

d
 5.63 ± 0.04

e
 6.42 ± 0.07

f
 

 Dissolved oxygen 24 6.17 ± 0.1
a
 6.28 ± 0.0

a
 6.18 ± 0.1

a
 6.21 ± 0.1

a
 6.28 ± 0.1

a
 5.96 ± 0.1

a
 

 Dissolved oxygen 96 3.27 ±0.04
a
 5.46 ± 0.05

b
 3.27 ± 0.07

c
 4.81 ± 0.04

d
 4.28 ± 0.06

e
 3.01 ± 0.06

f
 

 Carbon (iv) oxide 24 8.53 ± 0.1
a
 8.45 ± 0.1

a
 8.35 ± 0.2

a
 8.46 ± 0.3

a
 8.67 ± 0.5

a
 8.35 ± 0.5

a
 

 Carbon (iv) oxide 96 11.00 ± 0.14
a
 9.25 ± 0.15

b
 10.86 ± 0.22

c
 10.00 ± 0.25

d
 9.69 ± 0.37

e
 11.25 ± 0.17

f
 

 
Values are means ± SEM for 20 catfish. 

a,b,c,d,e,f
 column values with different superscript are significantly different (P ≤ 0.05). 

 
 

 
Table 2. Physico- chemical parameters determined in test solutions with Crude oil sample containing Clarias gariepinus (African catfish) 24 to 96 h 
into the experiment.  

 

 Concentration Duration Positive Negative 1.2 2.0 2.8 3.6 
 (mg/L) (h) control control 0.6 1.0 1.4 1.8 

 pH 24 7.34 ± 0.05
a
 7.34 ± 0.07

a
 9.50 ± 0.02

b
 9.44 ± 0.05

c
 9.68 ± 0.02

d
 9.70 ± 0.08

d
 

 pH 96 5.43 ± 0.08
a
 6.34 ± 0.06

b
 6.28 ± 0.06

c
 5.87 ± 0.08

d
 6.43 ± 0.02

e
 6.67 ± 0.04

f
 

 Dissolved oxygen 24 6.21 ± 0.28
a
 6.16 ± 0.24

a
 6.20 ± 0.13

a
 5.96 ± 0.13

a
 6.00 ± 0.23

a
 6.36 ± 0.33

a
 

 Dissolved oxygen 96 3.59 ± 0.15
a
 4.06 ± 0.14

b
 3.29 ± 0.23

c
 3.76 ± 0.10

d
 3.64 ± 0.09

e
 3.36 ± 0.12

c
 

 Carbon(iv) oxide 24 8.36 ± 0.34
a
 8.27 ± 0.23

a
 8.69 ± 0.33

a
 8.45 ± 0.25

a
 8.56 ± 0.23

a
 8.76 ± 0.25

a
 

 Carbon(iv) oxide 96 11.45 ± 0.12
a
 10.67 ± 0.14

b
 11.50 ± 0.09

a
 11.23 ± 0.10

c
 11.36 ± 0.12

c
 11.48 ± 0.15

a
 

 
Values are means±SEM for 20 fishes. 

a,b,c,d,e,f
 column values with different superscript are significantly different (P≤0.05). 

 
 

 
Table 3. Hematological parameters determined from Clarias gariepinus and Clarias anguillaris exposed to vary concentrations 
of crude oil.  

 
 

Concentration (mg/L) Positive control 
1.2 2.0 2.8 3.6 

 

 
0.6 1.0 1.4 1.8  

   
 

 PCV(%)catfish 39.0 ± 1.45
a
 36.0 ± 1.23 

a
 34.0 ± 1.46 

a
 30.0 ± 1.45 

a
 27.0 ± 1.26 

a
 

 

 PCV(%)mudfish 38.0 ± 2.18 
a
 34 ± 1.98 

b
 31 ± 1.46 

b
 27 ± 1.50 

b
 17 ± 1.31 

b
 

 

 WBC(10
9
/L)catfish 290.5 ± 2.78 

a
 285.0 ± 1.56 

a
 266.0 ± 2.25 

a
 250.0 ± 2.30 

a
 233.0 ± 2.56 

a
 

 

 WBC(10
9
/L)mudfish 286. ± 2.50 

a
 282.0 ± 2.15 

b
 256.0 ± 1.98 

b
 230.0 ± 3.50 

b
 222.0 ± 2.75 

b
 

 

 RBC(10
12

/L)catfish 2.11 ± 0.05 
a
 2.08 ± 0.02 

a
 2.00 ± 0.02 

a
 1.66 ± 0.05 

a
 1.00±0.03 

a
 

 

 RBC(10
12

/L)mudfish 2.11 ± 0.05 
a
 2.11 ± 0.07 

b
 1.85 ± 0.02 

b
 1.06 ± 0.03 

b
 0.47±0.05 

b
 

  
a,b,

 column values with different superscript are significantly different (P≤0.05). 
 

 

dissolution of atmospheric oxygen that comes in contact 
with the test solutions (Basau, 1959; Mason, 1994), 
thereby leading to reduction in the dissolved oxygen in 
the aquarium.  

Table 3 shows hematological parameters determined 
from the two fish species after 96 h exposure to different 
crude oil concentration. There was significant difference 
(P ≤ 0.05) in all the haematological parameters 
determined between the two fish species. As the 
concentration of crude oil increases the values of WBC 
(white blood cell) also increases. However, decline in the 
values of PCV (packed cell volume) and RBC (red blood 

 
 
 

cell) were observed after exposure to increasing levels of 
crude oil concentrations. There was a significant 
difference (P ≤ 0.05) in the effect of toxicant on the PCV 
of both species of fish after 96 hours of exposure to the 
toxicant. The PCV of the C. anguillaris appeared to be 
more reduced compared with C. gariepinus at double 
concentration of toxicant. The significant reduction (P ≤ 
0.05) in RBC count may be attributed to cytotoxic effect 
and suppression of erythropoiesis caused by constituents 
of the crude oil (Suchanek, 1993). This would imply 
reduction in the level of oxygen that would be carried to 
the tissues and the level of carbon dioxide returned to the 



 
 
 

 
Probit Transformed Responses  

 
 
 
 
 
 
 
 

 

P
ro

b
it
 

 
 

 
1.5 
 
 

 
1.0 
 
 

 
0.5 
 
 

 
0.0 

 
 
 
 
 
 
 
 
 

 
LC50=1.22mg/L 

 
 
 
 
 

R Sq Linear = 0.865 
 
 

 
-0.25 0.00 0.25 
 

Log of concentration 
 

Figure1Probit1. transformProbit respotransformesoftheresponses96hracutetoxicityofof thecrude96oilonhClacuteriasanguillaristoxicity. of crude oil on C.  
anguillaris.  

 
 
 
 
 
 
 
 
 
 
 
 
 

 

LC50=2.19mg/L 
 
 
 
 
 
 
 
 
 
 

 
Figure 2 Probit transform responses of the 96hr acute toxicity of crude oil on Clarias gariepinus. 
Figure 2. Probit transform responses of the 96hr acute toxicity of crude oil on C.  
gariepinus. 

 
 

 

lungs would also be reduced (Sunmonu and Oloyede, 
2008). The major functions of WBC are to fight infection, 
defend the body by phagocytosis against invasion by 
foreign organisms and to produce or at least transport 
and distribute antibodies in immune response. A 
significant reduction (P ≤ 0.05) in WBC count with 

 
 
 

 

increase in crude oil concentration may suggest that the 
species are exposed to high risk of infections with 
mudfish being most susceptible based on its comparative 
level of white blood cell count.  

Figures 1 and 2 show probit transformed response of 
the 96 h acute toxicity of crude oil on C. anguillaris and 



 
 
 

 

C. gariepinus respectively. From the probit analysis, the 

LC50 of C. gariepinus was 2.19 mg/L (P ≤ 0.05) while the 

LC50 C. anguillaris (mudfish) was 1.22 mg/L (P ≤ 0.05), 
suggesting that C. gariepinus showed better ability to 
resist adverse environmental condition than C. 
anguillaris. 
 

 

Conclusion 

 

Considering the observations on C. gariepinus in this 
study based on parameters selected. It is concluded that 
the specie is relatively more tolerant to high level of crude 
oil compared to C. anguillaris. 
 

 
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