A 96 hour bioassay was conducted to determine the toxicity of cassava effluents to Clarias gariepinus juveniles and its effects on the gills and liver as well as on some blood parameters such as packed cell volume (PCV), Red blood cells (RBC), White blood cells (WBC), Haemoglobin concentration (Hb) and their counts. Juveniles of C. gariepinus of the same age and size showed varying degrees of hyper-activity, mortality, stress and lesions to the organs of fish in the different concentrations of cassava effluent used (4.0, 4.5, 5.0, 5.5 ml/L). Static bioassay test revealed the 96 hour LC50 of cassava effluent as 4.28ml/L. Exposure to sublethal concentration of cassava effluents resulted in the reduction of blood parameters such as PCV, RBC and Hb however, the value of white blood cells increased at the end of the experiment. Degenerative and erosive changes were observed in the tissues of the organs of C. gariepinus. The gills of fish in the varying concentrations particularly in the higher concentrations (5.00ml/L and 5.50ml/L) showed signs of necrosis which means that at those concentrations cassava effluent was highly toxic to C. gariepinus juveniles. The liver of fish in higher concentrations also showed hydropic degenerative changes such as space formation. Water quality parameters (temperature, pH and oxygen) monitored during the experiment changed. The pH increased considerably throughout the course of the experiment, the dissolved oxygen concentration values recorded during the experiment decreases. Exposure to cassava effluent will prevent oxygen dissolution, cause destruction of breeding grounds as well as fish eggs, and ultimately, alteration of the entire aquatic environment leading to high mortality or total eradication of aquatic life.

Ariyomo TO, Jegede T, Adeniran AF, Omobepade BP (2017) Toxicity of Cassava Effluents to Catfish, Clarias gariepinus, and the Effect on Some Target Organs. Ann Aquac Res 4(2): 1034.

•    Toxicity
•    Cassava effluents
•    Histopathology
•    Haematological features
•    Clarias gariepinus

Water pollution is the contamination of water bodies such as lakes, rivers, oceans and groundwater by human activities [1]. All forms of water pollution affect organisms and plants that live in these water bodies and in almost all cases, the effect is damaging not only to the individual species and populations, but also to the natural biological communities [2]. It occurs when pollutants are discharged directly or indirectly into water bodies without adequate treatment to remove pollutants [1]. These pollutants impact certain strategic ecological habitats and directly or indirectly affect human population [3]. Contaminants are from different sources and one of such is farm runoff into nearby bodies of water [4]. This is a common occurrence in Ikole Ekiti, the study area, particularly with cassava waste water due to the numerous cassava processing industries in Ikole Ekiti. Relative to other agricultural products, the production and processing of cassava has increased drastically in Ikole. This has become particularly challenging given that the waste water is being released into the rivers directly or indirectly. The effluents from the cassava contains high quantity of cyanide [5], which is toxic to aquatic lives and the end consumers, when it gets into the aquatic ecosystem, the impact and effect of cyanide on the fish and the ecosystem cannot be over emphasized. Environmental problems from cyanide may negatively affect young stages of plants as well as sensitive stages of fish [6]. Cyanide prompts certain alterations in the naturally occurring chemical composition of aquatic phase and consequently affects the behaviour, biochemistry, haematology and general physiology of aquatic faunas [7]. Aside from cyanide being acutely toxic to animals (especially fish) and humans, exposure of plants to cyanide can inhibit respiration and consequently lead to death. Furthermore, the presence of cyanide can leave aquatic ecosystems in a very bad condition leading to water pollution and cause detrimental effect on the fisheries resources. Moreover, water from all dug wells around the cassava processing factories may be unfit to drink because of the level of cyanide in it. The presence of cyanide may make the environments unfit for cultivation of any crop and cause detrimental effect on the fisheries resources and all this is a major concern in fisheries [8].

Pollution is now the major cause of losses in fisheries resources and the improper managements of our water bodies. For more profitable yield from aquatic products, more attention should be paid to the effect of different pollutants and contaminants on the aquatic ecosystem and organism as a whole. Fish have been widely documented as useful indicators of environmental water quality because of their differential sensitivity to pollution. In this study, Claris gariepinus was used as the test species given that it has a wide geographical distribution, it is hardy and can adapt to almost all environment due to the possession of accessory breathing organs [9]. It is therefore important to access the concentration of cassava effluent that causes changes to the histological and the haematological characteristics of Clarias gariepinus. The objectives of the study were to determine the 96 h LC50 value of C. gariepinus juveniles exposed to varying concentrations of “cutback” bitumen, and determine the effects of sub-lethal concentrations on the histology of gills and liver cells and some haematological features of C. gariepinus.

A total of 200 apparently healthy Clarias garipienus juveniles of mean weight and mean total length 9.73g and 12.5cm respectively, were bought live from Federal Polytechnic AdoEkiti fish farm, located on coordinates 70 371 160 N, 50 131 170 E, Ekiti State, Nigeria. The fish were transported live in oxygenated plastic bags to the Fisheries Laboratory of the Federal University Oye-Ekiti, Ekiti-state. Acclimation of fish was done in fresh water by gradually changing the water in the rectangular glass tanks (75 x 40 x 40cm) from 100% holding water to 100% dilution water for over five days. The fishes were fed daily to satiation during the first one week of acclimation, with a pelleted commercial feed (35% crude protein) in order to remove any problem that could arise as a result of starvation. Thereafter a range finding test was done. One hundred (100) juveniles of C. garipienus were used for the range finding test. Cassava effluent that was used as toxicant was collected from Ikole cassava processing factory Ikole- Ekiti. Feeding was discontinued during this period to reduce the production of waste in the transparent cylindrical containers thus minimizing the chances of ammonia production. Both the ranging finding and definitive tests were conducted under standard bioassay procedures [10]. The range-finding test was carried out using ten transparent cylindrical plastic containers of 21 litre capacity, each filled with 10 litres of water prior to the introduction of cassava effluents. Four varying concentration used were 3.00ml/L, 4.00ml/L, 5.00ml/L and 6.00ml/L. Each of the four varying concentrations (3.00ml/L, 4.00ml/L, 5.00ml/L and 6.00ml/L) were duplicated; two replicates of the control treatment without a cassava effluent were also prepared.

A hundred (100) juveniles of C. gariepinus were used for the definitive test. Ten transparent cylindrical plastic containers of 21 litre capacity, each filled with 10 litres of water were used for definitive test, prior to the introduction of cassava effluent. Four varying concentrations used in the Definitive experiment were 4.00ml/L, 4.50ml/L, 5.00ml/L and 5.50ml/L. Each of the four varying concentrations and the control were duplicated. During the 96-h exposure, water temperature, dissolved oxygen concentration and pH were determined at 09.00h every 24 hours, using standard methods. Fish mortality was recorded every 24 hours. The behaviour of the fish was monitored. Data on mortality was subjected to Probit and Logit transformation and the LC50 value was determined accordingly. Gills and liver of C. gariepinus were excised and fixed in 10% formalin for three days, dehydrated in graded levels of alcohol (50%, 70%, 90%, 100%), cleared in 50/50 mixture of alcohol and xylene for three hours, embedded in molten wax, thinned, sectioned using a microtome to 7µm, and stained in haematoxylin and eosin. The stained specimens were observed under a light microscope fitted with a camera. Photographs of the stained specimens were finally taken and interpreted accordingly. Blood samples were collected from fishes in both tested and control treatments by caudal puncture into 2.5ml heparinised syringes already treated with Ethylene diamine tetra acetic acid (EDTA) to prevent coagulation. Packed cell volume (PCV), haemoglobin concentration (Hb), red blood cells, white blood cells and the counts were estimated using various methods described by Svobodova et al., [11]. The data collected on haematological characteristics were subjected to the one-way analysis of variance (ANOVA) test or regression analysis in R statistical software, version 3.2.2 [12].

The water parameters monitored were temperature, dissolved oxygen and pH. The values of the water parameters during the 96 hour period are shown in Table (1). The parameters were measured at 9h each day and at 24 hours internal. The temperature increased as the concentration increased. Similarly, pH increased as the concentration increased. However, dissolved oxygen increased greatly as the concentration increased.

The mortality of C. gariepinus was observed in all concentrations (4.00ml/L, 4.50ml/L, 5.00ml/L, 5.50ml/L) of cassava effluent used in the control. Mortality was recorded at 24hours interval and this varied significantly amongst the different concentrations. C. gariepinus exhibited distress behavioural responses due to the effects of the cassava effluent. These behavioural responses were the sudden change in the organism’s response to the environment such as erratic swimming, occasional gasping for breath and frequent surfacing which increased as the concentration increased. All these are indications that the concentrations had become hypoxic and as a result induced brain dysfunction in the test organisms due to low oxygen supply. As the experiment progressed, some of the test organisms got weaker as evident by the reduction in movement; their ventral surfaces were subsequently turned upward while those that couldn’t tolerate the concentrations any longer became motionless. Normal behaviour was however observed in the control. Upon addition of cassava effluent fish showed rapid opercula movements especially in higher concentrations (5.00ml/L and 5.50ml/L). Movement of fish in the control experiment (0ml/L) was observed to be generally in different directions, while movements of fish in the varying concentrations of cassava effluent were sporadic and vertical i.e. surfacing; this was particularly evident in plastic containers with higher concentrations

The LC50 obtained using Probit and Logit for fish exposed to cassava effluent was 4.28 ml/L (Figure 2).

The presence of cyanide on the gills could reduce the surface area where respiration could take place in the fish, resulting in mortality due to severe stress and discomfort. The values of the haematological characteristics are presented in Table 2. The value of the packed cell volume (PCV) in fish not exposed to cassava effluent was the highest (27.00 ± 0.58). However, PCV in African catfish exposed to 4.00ml/L and 5.50ml/L or 4.00ml/L and 5.50ml/L were not significantly different (p?0.05) from each other (22.00 ± 0.58 and 22.00 ± 0.58 respectively). The lowest PCV (10.00 ± 0.58) was recorded in test fish exposed to 4.50ml/L of cassava effluents and it was significantly different (p?0.05) from other concentrations. The value of Red blood cells (RBC) in the control fish (0.13 ± 0.04) was not significantly different (p?0.05) from fish treated with 5.00ml/L (0.2 ± 0.58) and 5.50ml/L (0.1 ± 0.58) of cassava effluent respectively. However, RBC increased in the blood sample analysed in fish exposed to 4.00ml/L (2.3 ± 0.58) and 4.50ml/L (1.2 ± 0.58) respectively. The highest RBC (2.3 ± 0.58) was recorded in fish exposed to 4.00ml/L while the lowest (0.1± 0.58) was recorded in the fish exposed to 5.50ml/L of cassava effluent. The quantity of White blood cell (WBC) recorded in test organisms were significantly similar (p?0.05) in fish exposed to 4.50ml/L (11000 ± 577.35) of cassava effluent and the control (10000 ± 577.35). The lowest (2000 ± 577.35) was recorded in catfish exposed to 4.00ml/L of the effluent, this was however different (p<0.05) from WBC recorded in fish exposed to 5.50ml/L (5000 ± 577.35).

The Haemoglobin concentration (Hb) of test organisms were not significantly different (p?0.05) in fish exposed to 4.00ml/L (7.00 ± 0.58) and 4.50ml/L (7.00 ± 0.58) of cassava effluent. Similarly, the quantity of Hb in African catfish exposed to 5.00ml/L (4.00 ± 0.58) and 5.50ml/L (3.00 ± 0.58) were not significantly different (p?0.05). However, Hb was highest in the control and lowest in 5.50ml/L (3.00 ± 0.58).Blood count differentials showed that neutrophils were significantly different (p<0.05) in all the fish exposed to the varying concentrations of cassava effluent. The highest neutrophils was recorded in 5.00ml/L (63.00 ± 0.58) while the lowest was recorded in the control (40.00 ± 0.58). Lymphocytes equally showed significant differences (p?0.05) in blood samples collected from the varying concentrations with the lowest (12.00 ± 0.58) recorded in the control while blood Lymphocytes was high (31.00 ± 0.58) in C. gariepinus exposed to 5.00ml/L. Eosinophil was similar (p?0.05) in fish exposed to 4.50ml/L (0.30 ± 0.06), 5.00ml/L (0.20 ± 0.06) and 5.50ml/L (0.77 ± 0.33). However, eosinophil in the control (8.10 ± 0.55) and 4.00ml/L (4.20 ± 0.55) were different (p?0.05) from the ones recorded in 4.50ml/L, 5.00ml/L and 5.50ml/L.Basophil were similar (p?0.05) in fish treated with 5.00ml/L (0.20 ± 0.06) and 5.50ml/L (0.30 ± 0.06) respectively. This was however different (p?0.05) from the basophils value in the control (15.00 ± 0.58), 4.00ml/L and 4.50ml/L. The highest (25.00 ± 0.58) was recorded in fish treated with 4.50ml/L while the lowest was recorded in 5.00ml/L (0.20 ± 0.06). The results obtained from the haematological analysis indicate that, the value of the blood indices decreased with increasing concentrations of cassava effluent

The gills and liver (plates 1-10) of the fish were examined to assess the histological effect of cassava effluent on them. Examination of gills and livers of fish in the varying concentrations showed varying degrees of damage to the tissues. Examination of the gills of fish in the control revealed a normal gill filament consisting of primary lamella with arrays of delicate secondary lamella, primary epithelium and secondary epithelium covering the primary and secondary lamella respectively, this was no vacuolation. Plate 2 of 4.00 ml/L cassava effluent concentration shows slight degeneration in the gill architecture and there was also slight congestion of the gills, with slight vacuole information in gills of the fish in that concentration. There was degeneration of the gills filament and the lamella of the fish in 4.50 ml/L concentration; it also shows erosion of the gills filament. However at higher concentrations 5.00 ml/L and 5.50 ml/L (plates 4 and 5 respectively) there was high level of degeneration in the filament, fragmentation of the lamella, vacuolation of the filaments, erosion of the gills and they showed the sign of necrosis (the cells were already dying because of too little oxygen reaching the cells via the blood).

Histological studies on the liver revealed that the control (Plate 6) had normal liver architecture (normal hepatocellular architecture). Plate 7 of 4.00ml/L concentration showed a slight/ hydropic degeneration (evidence of leaching/vacuolation), also plates 8 & 9 of 4.50ml/L & 5.00ml/L concentrations, respectively, showed hydropic degeneration of the liver and at high concentration (5.50ml/L), the liver were dying (signs of necrosis). The cellular arrangement of liver cells were distorted, lesions were also present on the tissues of the liver. The results obtained from the experiments indicate that cassava effluent had a direct impact on the tissues of the gills and livers of Clarias gariepinus.

The mortalities recorded in the course of this study are an indication that the toxic effect of cyanide in the cassava effluent had disrupted the physiological system of the fishes to the extent that death was inevitable. The fish in the higher concentrations were affected the most and this shows that, the higher the concentration the higher the effect of the cyanide on the fish behaviour. This corresponds with the finding reported by Adewoye et al. [13], in a similar study where it was observed that lethal effect occurred quickly and this lead to death of fish. Catfish juveniles exposed to varying concentrations of cassava effluent were stressed progressively with time before death. The stress signs included erratic swimming, increased opercular ventilation, air gulping, and increased mucus secretion on the skin and gills. These behavioural changes have also been reported in other studies where fish were exposed with various toxicants [14-16]. The excessive mucous secretion was a protective response of the exposed fish to coating the absorptive surfaces and preventing the continuous entry of the toxicant [17]. The respiratory distress may have also been due to gill epithelial damage as reported by Fafioye et al. [18], when C. Gariepinus was exposed to extracts of Parkia biglobosa stem bark. Air gulping and surfacing observed during the study were attempts by the exposed fish to cope with the increasing demand for oxygen [19,11]. The irregular, erratic and darting movements coupled with the observed loss of balance and the adoption of different postures by the exposed fish might be due to the stress caused by the cyanide content of the cassava effluent. Similar signs were reported in C. gariepinus exposed to the aqueous extract of Nicotiana tobaccum leaf dust [20]. The marked deviation in the rate of behavioural changes from reference (control) suggests an adjustment in physical fitness as a result of the stress condition [21]. The agitated behaviours were attempts to escape from the toxic aquatic environment. Similar signs were reported in C. gariepinus exposed to the aqueous extract of Carica papaya seed powder [22]

The value of 96hrs LC50 of 4.28ml/L (Figure 1) reported in this study is much higher than those earlier reported by Fafioye et al. [21], (Parkia biglobosa - 2.8 ppm, Raphia vinifera - 3.4 ppm) and Oshimagye et al. [23], (Parkia biglobosa - 656.05µl/l) for C. gariepinus. This observation implies that cassava effluent is more toxic to C. Gariepinus than Parkia biglobosa and Raphia vinifera. Moreover, differences in the LC50 values could be due to treatment, the nature of the toxicity bioassay and methods of the LC50 determination as well as differences in the types and concentrations of the treatment used [24].

Mucus production and accumulation on the gills may have contributed immensely to the increase in the opercular ventilation and mortalities recorded in this study. Konar [25], reported that accumulation of mucus on the gills reduces respiratory activity in fishes. This might be due to inability of the gills surface to actively carry out gaseous exchange. This study revealed that cyanide in cassava effluent is highly toxic to the catfish. It acts as respiratory poison possibly affecting the gills, impairing respiration and the various abnormal behaviours and eventually death. These effects on fish are directly proportional to the toxicant concentrations. Fish mortality increased with increasing concentration, but later decreased with time. This shows that mortality is dosedependent. No mortality was recorded in the control experiment during the toxicity test. This is also an indication that toxicity is dose-dependent and varies within the time of exposure of aquatic organisms to toxicants [26]. Hence, the release of this toxicant into aquatic environment needs proper control to avoid reduction in fish production and non-target aquatic fauna. The abnormal behaviour in relation to fish stress included erratic swimming, mucus secretion, gasping for air, discoloration; which are indications of effect of cassava effluent. The abnormality observed could also be due to nervous disorder to impaired metabolism, but could in addition be due to nervous disorder as earlier reported by Agbon et al. [17], and [27].

In this study, rapid opercula movement and rapid release of bubbles indicate stress; this will further lead to the reduction of available oxygen which could result in fish mortality [16]. The values of the physico-chemical parameters of both the control and the other concentration used during the experiment are shown in Table 1. The values revealed that there is significant difference between the control and varying concentrations. Death/mortality of fish could have resulted from changes in the water quality particularly the pH values because the treatment is acidic; the pH increases based on the concentration and also the DO decreases accordingly as the temperature increases. Rapid opercula movement and rapid release of bubbles indicate stress, which could have resulted in the reduction of oxygen, during the 96hour exposure period, this conforms with the report of Enujiugha and Nwanna [3], that reduction of oxygen levels can severely affect fish life, when dissolved oxygen values fall below minimum oxygen requirement for a particular species of fish, they are subjected to stress, which can result in mortality.

pH values increased during the exposure period and layers of mucus were seen on gills, particularly on gills of fish in the higher concentration (5.00ml/L and 5.50ml/L), this could have caused reduction in oxygen intake and resulted in the death of fish. This is in line with the findings reported by Korwin-Kossakowksi [28], who found that reduction in fish respiration is mainly due to mucus coagulation in the gills which was caused by high pH to which Cyprinus carpio larvae were subjected, which led to lowered oxygen consumption of carp fry at high pH. However, Adesina et al. [3], indicated that dissolved oxygen, pH and temperature during their acute-lethal toxicity test were 3.3- 6.2mgl-1, 7.05-7.75, and 23.0 0C respectively. These values are within acceptable ranges for culturing Tilapia fish in the tropics [29,30]. Adesina et al. [26], stated that mortality was highest (77%) at 200.0 mgl-1 and lowest, (20%) in 19 mgl-1 after 96-h of exposure but this does not apply to catfish as seen in the present study.

Fish mortality increased with increasing concentration, but later decreased with time. This study showed that the cassava effluent used caused the pH to increase and lowered the dissolved oxygen (DO) content of the water. This indicates that the effluent is toxic and should not be discharged indiscriminately into the immediate environment. Furthermore, the observed characteristics features may have resulted from the organic loads in the wastewater [13]. The abnormalities (gasping for breath and frequent surfacing) observed prior to mortality are indications of depleted oxygen content (hypoxia) due to higher demand for oxygen. There was an observed positive correlation between concentration and response of the test organisms. The concentration-dependent nature of fish mortality in this study agrees with the work of Fafioye et al. [18], who exposed C. gariepinus to extracts of P. biglobosa bark. Oxidative biodegradation of the cassava effluent over time as suggested by Kela et al. [31], might be responsible for the subsequent reduction in the toxicity of the effluent as the exposure period increased. However, the findings in this study did not agree with the work of Fafioye et al. [18], who reported an increase in toxicity with increasing exposure period. This may be due to the static nature of the present toxicity bioassay compared to the non-static nature of the previous work by Fafioye et al. [18]. The investigation further showed that fishes can tolerate low concentrations of pollutants with reduced mortality as suggested by Oyedapo and Akinduyite [32], who found that the abnormal behaviour observed in fish subjected to Morinda lucida increased with increasing concentration of the pollutant used.

The high WBC count recorded in this study could be due to an attempt by the fishes to fight against the antigens (pollutants) and this led to the production of more antibodies (WBC) to improve the health status of the organism. Similar findings were reported by Ates et al. [33], that the increase in WBC during acute and sublethal treatment may be due to stimulated lymphomyeloid tissue as a defence mechanism of the fish to tolerate the toxicity. The increase in lymphocytes count indicates the stimulatory effects of the toxicant on the immune system. The gradual reduction in the values of WBC at 4.0ml/l and 5.0ml/l concentrations may be due to the breakdown of vital metabolic activities as a result of possible blockage in the metabolic pathway which then lowered the toxic production of WBC. The observed reduction in haematocrit (PCV) percentage and haemoglobin concentration of the fish exposure to the effluent was as a result of uncontrolled hemolysis of the RBC due to the toxicity level of the effluent; while the decrease in haematocrit compared to the haemoglobin standards may be attributed to shrinkage of the erythrocytes [34], which may be an indication of severe anaemia [33,15]. Relative to the control, there was a significant increase in the RBC of fish with increasing concentration of the toxicant to a point (4.00ml/L). Subsequently, RBC decreased as concentration of the effluent increased. There was a drastic reduction in the WBC of fish at 4.00ml/l of cassava effluent compared with the control. However, WBC increased at 4.50ml/L, decreased at 5.00ml/L and increased at the end of the exposure period (5.50ml/L); however, Musa & Omoregie [35], reported that no significant changes were observed in the lymphocytes of C. gariepinus exposed to Malachite green but Sampath et al. [36], recorded an increase in the lymphocytes of Oreochromis niloticus exposed to toxic environment, this they attributed to the stimulation of the immune mechanism of the fish to eliminate the effects of the pollutants which correlate with this present study.

Histological examination of the gills as presented on plates 4 and 5, from fish in 5.00 ml/L and 5.50 ml/L of cassava effluent showed the gills were covered with a layer of slime (mucus). Furthermore, there were degeneration of the gills tissue, gill enlargement at the end of the experiment, and signs of necrosis. Similar observations were made by Aderiye [37], who found that the gill structure of the fish O. niloticus treated with petrol and engine oil mixture was fused together and that there was extensive hyperplasia and separation of the epithelial layer from the supportive tissues. Onwumere [38], also reported that the histology of the organs (livers and gills) of O. niloticus fingerlings exposed to 30, 40, and 50% effluent from the NNPC Refinery at Kaduna showed that the gills were swollen and this bulged the opercula. Histological examination of the liver as presented on plates 9 and 10 (i.e. 5.00ml/L and 5.50ml/L) showed vacuolation, hydro degeneration, large space formation on the tissues of the liver, and necrosis. These agree with the report by Wong et al. [39], and Kothari & Suneeta [40], when disintegration and necrosis occurred in the liver of Cyprinus carpio due to zinc toxicity. John et al. [41], also stated that livers of channel catfish (Ictalurus punctatus) exposed to chlorinated effluents from a wastewater treatment plant were enlarged and showed histological lesions.

Death in fish is the end product of the various effects caused in the various tissues and organs. When these tissues collectively stop functioning due to the toxin, the fish dies. For instance, the degeneration of gills causes a dysfunction of its gas exchange ability causing an anoxic internal environment [42]. The blood is a homeostatic organ in fish. Any attack made on it, if intense, may cause a damage that will result to outright death of the organisms. Its reduction of the hepatosomatic index is in line with destruction of the liver tissue. The liver is a target organ given that it is used for poison modification or detoxification [43]. Therefore, as the liver is overwhelmed, it starts to degenerate and consequently there is unhindered access of poison to the liver as a result it becomes easier for points to attack other tissues.

1. Agrawal A, Pandey R, Sharma B. Water pollution with special reference to Pesticide Contamination in India. J Water Res and Protec. 2010; 2: 432-448.

2. Saiyed HN, Bhatnagar VK, Kashyap. Impact of Pesticide use in India. Electronic Journals: Asaia Pacific Newsletter. 1999-2003.

3. Enujiugha VN, Nwanna LC. Aquatic oil pollution impact indicators. In: J Appl Sci Environ Mgt. 2004; 8: 71-75.

4. Environmental Protection Agency (2003) Natural Management Measure to Control Non-Point Source Pollution from Agriculture, July 2003. Document No: EPA 841- B-07- 002.

5. Arguedes P, Cooke RD. Cyanaide concentrations during extraction of cassava starch. Food Technol. 1982; 17: 251-262.

6. Ehiagbonare JE, Adjarhore RY, Enabulele SA. Effect of cassava effluent on Okada natural water. Afri J of Biotech. 2009; 8: 2816-2818.

7. Olaniyi, Christianah O, Adewoye SO, Ismail MO, Adeseun FM. Effect of Cassava Mill Effluents on haematological and biochemical characteristics of adult African catfish (Clarias gariepinus). J of Bio Agric and Healthcare. 2013; 3: 191-196.

8. International Cyanide Management Institute (2006). Environmental and Health Effects of Cyanide”. Retrieved 4 August 2015.

9. Freyhof J, FishBase team RMCA, Geelhand D. Clarias gariepinus. The IUCN Red List of Threatened Species. 2016: e.T166023A84198891.

10. American Public Health Association. American Water Works Association APHA/AWWA/WEF, American Public Health. 1977.

11. Svobodova ZD, Pravda, Palackova J. Unified methods of heamatological examinations of fish. Research Institute of Fish Culture and Hydrobiology, Vodany, (Zeechoslovakia). 1991; 49.

12. R Development Core Team 2015. R: A Language and Environment for Statistical Computing. Vienna: R Foundation for Statistical Computing.

13. Adewoye S O, Fawole OO, Owolabi OD, Omotosho JS. Toxicity of cassava waste water effluents to Africa Catfish Clarias garipenius (Burchell, 1822). Eth J Sci. 2005; 28: 189-194.

14. Davis JC. Sub-lethal effects of bleached draft pump mill effluent on respiration and circulation in stock eye salmon (Oncorhyncus mykiss). J Fish Res Board. 1973; 30: 346-348.

15. Nwanna LC, Fagbenro OA, Kayode AO. Toxicity of Gramazone and detergent to Nile Tilapia (Oreochromis niloticus) fingerlings and aquatic environments. 2003.

16. Ariyomo TO, Fagbenro OA, Bello-Olusoji OA. Toxicity of ‘cutback’ bitumen to climbing perch, Ctenopoma kingsleyae (Günther 1896) and the effects on some target organs Bio and Environmental Sci for the Tropics. 2009; 6: 83-88.

17. Agbon AO, Omoniyi IT, Teko AA. Acute toxicity of tobacco (Nicotianatobaccum) leaf dust on Oreochromis niloticus and haematological changes resulting from sub-lethal exposure. J Aquat Sci. 2002; 17: 5-8.

18. Fafioye OO, Adebisi SO, Fagade AA. Toxicity of Parkiabiglobosa and Raphiavinifera extracts on Clarias gariepinus juveniles. Afri J of Biotech. 2004; 3: 137-142.

19. Schmidt K, Staaks GB, Pfluqmacher S, Steinberg CE. Impact of PCB mixture (Aroclor 1254) and TBT and a mixture of both on swimming behaviour, body growth and enzymatic bio-transformation activities (GST) of young carp (Cyprinus carpio). Aqua Toxico. 2005; 71: 49-59.

20. Kori-Siakpere O, Oviroh EO. Acute toxicity of tobacco (Nicotianatobaccum) leaf dust on the African catfish: Clarias gariepinus (Burchell, 1822). Arch of App Sci Res. 2011; 3: 1-7.

21. Gabriel UU, Okey IB. Effect of Aqueous Leaf Extracts of Lepidagathis alopecuroides on the Behaviours and Mortality of Hybrid Catfish (Heterobranchus bidorsalis % X Clarias gariepinus &) Fingerlings. Res J of Appl ci Eng and Tech. 2009; 1: 116-120.

22. Ayotunde EO, Offem BO, Bekeh AF. Toxicity of Carica papaya Linn: Haematological and Piscicidal Effect on Adult Catfish (Clarias gariepinus). J of Fisheries and Aquac Sci. 2011; 6: 291-308.

23. Oshimagye MI, Ayuba VO, Annune PA. Toxicity of Aqueous Extracts of Parkia biglobosa Pods on Clarias gariepinus (Burchell, 1822) Juveniles. Nigerian J of Fisheries and Aquac. 2014; 2: 24-29.

24. Abalaka SE, Fatihu MY, Ibrahim NDG, Kazeem HM. Phytochemical composition and toxicity of the aqueous extract of Parkia biglobosa pods in adult Clarias gariepinus. Biokemistri. 2013; 25: 79-84.

25. Konar SK. Nicotine as a Fish Poison. The Progressive Fish-Culturist. 1970; 32: 103-104.

26. Adesina BT, Omitoyin BO, Ajani EK, Adesina OA. Acute-lethal toxicity (LC50) effect of Moringa oleifera (Lam.) Fresh Root Bark Extract on Oreochromis niloticus Juveniles Under Renewal Toxicity Exposure. Int. J. of Applied Agricultural and Apicultural Research. 2013; 9: 182-188.

27. Aguigwo JN. The toxic effect of cymbush pesticide on growth and survival of African catfish, Clarias gariepinus (Burchell). J Aquat Sci. 2002; 17: 81-84.

28. Korwin-Kossakowksi M. Acclimation and survival of carp (Cyprinus carpio) fry in alkaline solutions. In Larvi ’91. Fish and Crustacean Larviculture Symposium (Lavens P.P. Sorgeloos, E. Jaspers and F. Ollevier (editors). European Aquaculture Society, Special Publication No 15, Belgium Ghent. 1992.

29. Ayoola SO, Kuton MP, Idowu AA, Adelakun AB. AcuteToxicity of Nile Tilapia (Oreochromis niloticus) Juveniles Exposed to Aqueous and Ethanolic Extracts of Ipomoea aquatica Leaf. Nature and Sci. 2011; 9: 91-99.

30. Fafioye OO. Acute and sub-acute toxicities of five plant extracts on white tilapia, Oreochromis niloticus (Trewavas). Irjas. 2012; 2: 525- 530.

31. Kela SI, Ogunsusi RA, Ogbogu VC, Nwude N. Screening of some plants for molluscicidal activity. Revue d?élevageet de médicinevetérinaire des pays tropicaux. 1989; 42: 195-202.

32. Oyedapo F, Akinduyite V. Acute Toxicity of Aqueous Morindalucida leaf extracts to Nile Tilapia, Oreochromis niloticus (Linnaeus, 1857). Proceedings of the Ninth International Symposium on Tilapia in Aquaculture. Shanghai, China. April 22nd -24th. 2011. 52-59.

33. Ates B, Orun I, Talas ZS, Durmaz G, Yilmaz I. Effects of sodium selenite on some biochemical and haematological parameters of rainbow trout (Oncorhynchus mykiss, Walbaun, 1792) exposed to Pb2+ and Cu2+. Fish Physiol. Biochem. 2008; 34: 53-59.

34. Dahunsi SO, Oranusi US. Haematological Response of Clarias gariepinus. Ann Rev & Res in Bio. 2013; 3: 624-635.

35. Musa SO, Omoregie E. Haematological changes in the mudfish, Clarias gariepinus, exposed to malachite green. J of Aquatic Sci. 1999; 14: 37- 42.

36. Sampath K, Velamnial S, Kennedy IJ, James R. Haematological changes and their recovery in Oreochromis mossambicus as a function of exposure period and sublethal levels of Ekalus. Acta Hydrobio. 1993; 35: 73-83.

37. Aderiye BK. Studies on the Toxicological effects of petrol and Engine Oil Mixture on African catfish, Clarias gariepinus (Burchell, 1822) Fingerlings. M. Agric. Tech. Thesis. Department of fisheries and wildlife FUT, Akure. 1998; 65.

38. Onwumere BG. Toxicity of treated effluent from NNPC Refinery, Kaduna to Tilapia (Oreochromis niloticus, M.Sc Thesis, Ahmadu Bello University, ABU Zaria. 1986.

39. Wong MH, Luck KC, Choir KY. The effects of Zn and Cu Salts on Cyrinus carpio and Ctenopharyngodon idellus. Acta Anat. 1977; 99: 450-454.

40. Kothari S, Suneeta G. Study on the accumulation and toxicity of zinc sulphate in the liver of a cat fish, Heteropnests fossils (BLOCH). Pp 947-950. In the second Asian fisheries (Hirano R.I, Hanyu) (editors) Asian Fisheries Society. Manila, Philippines. 1990.

41. John MG, Stephen AH, Strength DR. Caged fish as Monitors of Pollution: Effect of Chlorinated Effluent from a Wastewater treatment plant In: J of American water Res Ass. 2007; 24: 951-959.

42. Ajani F, Olukunle OA, Agbede SA. Hormonal and Haematological Responses of Clarias gariepinus (Burchell, 1822) to Nitrate Toxicity. J Fisheries Int. 2007; 2: 48-53.

43. Taylor SR, Pakdae B, Klampratum D. Border method and fish culture: Synergistic effects on the yield of rice grains. In. Pullin RSO, Bhukaswa T, Tonguthal K, Maclean JI. The second International Symposium on Tilapia in Aquaculture, Manila, Philippines. 1988; 91-98.