The concentration of cadmium (Cd), Lead (Pb), Manganesse (Mn) and Iron (Fe) in fish species gills and flesh of both Tilapia, Synodontis, Clarias from river Bunza in Kebbi State, Nigeria, were determined by atomic absorption spectrophotometer. The concentration of Pb in flesh of tilapia (0.179mg/l) is higher than the gills (0.003mg/l) and concentration of Pb in Synodontis flesh (0.262mg/l) is higher than the gills and concentration in flesh of clarias is higher than the gills and both concentration of flesh and gills are higher than the WHO limit (0.01mg/l). 

The concentration of Cd in flesh of tilapia (0.013mg/l) is higher than the gills (0.004mg/l) and concentration in flesh (0.005mg/l) of clarias is lower than the WHO limit (0.03mg/l). The concentration of Mn in flesh of tilapia (0.007mg/l) is higher than the gills (0.003mg/l) an concentration of Cd is synodontis flesh (1.591mg/l) is higher than the gills (0.0042mg/l) and concentration in flesh (0.021mg/l) of clarias is lower than the gills (1.035mg/l) and both concentration of flesh and gills are higher than the WHO limit (0.5mg/l). 

The concentration of Fe in flesh of tilapia (0.670mg/l) is lower than the gills (0.672mg/l) and concentration of Cd synodontis flesh (7.760mg/l) is higher than the gills (0.638mg/l) and concentration in flesh (0.471mg/l) of clarias is lower than the gills (17.82mg/l) and both concentration of flesh and gills are higher than the WHO limit (0.3mg/l). ThereforeTherefore, this indicated that the concentration heavy metals (Pb, Cd, an Mn) in flesh is higher than in gills of fishes, while Fe is higher in gills than in flesh of fishesfishes species.




                                                               CHAPTER ONE



Heavy metals are defined as members sub-set of elements that exhibits metallic properties with high density and toxicity. They may include transition metals metalloids, lanthanides and actinides. They occur naturally as they are components of the lithosphere and are released into the environment through volcanism, soil erosion, dissolution of water soluble salts and leathering of rocks (Fergusson, 1990). Living organisms require trace amount of some heavy metals such as lead cadmium manganese, and iron normal growth, and metabolism but excessive level of essential metals however can be detrimental to health (WHO, 2011). Over 200 years following the beginning of industrialization, huge changes in the global budget of critical chemicals at the earth’s surface have occurred, challenging those regulatory systems which took millions of, years to evolve (Wood and Wang: 1983) However, large-Scale release or heavy metals to the aquatic environment is often a result of human activities (Mance, 1987). Heavy metals are high priority pollutants because of their relatively high toxic and persistent nature in the environment. Therefore, knowledge of the changing concentration and distribution of heavy metals and their compounds in various compartments of the environment is of a high priority for good environmental management (Don-Pedro et al., 2004). However, water doing the most abundant and familiar liquid widely distributed in nature has its stake in heavy metal pollution, although the ability of fish and vertebrates to adsorb metals depends largely on the physical and chemical characteristics of the metal (Kennish, 1992). Deposition of heavy metals in the water bodies have been exploited been exploited due to increase in population, urbanization, industrialization, Deforestation, modem agricultural concepts, increase in human standards, and a broad sphere of human activities (Sadik, 1990 and Jimoh et al, 2005). Hence, water bodies are potential carriers of toxics, organic and inorganic materials, non-biodegradable matters and pathogenic microbes which can endanger health of both human and animals and the biosphere in general. Dumping wastes into rivers contribute to the largely problem of river pollution, which can seriously damage the marine environment and cause health hazards to people in some areas, (Botkin and Keller, 1998). Landill sites and toxic wastes dumps, many of them in poorly constructed, managed and controlled are a matter of great concern especially with respect to Ground water contamination (Lisk, 1991). Run-off from roads maybe another source of chemical deposition to water bodies, particularly. Venous hydrocarbons and metals (Malbty et al, 1995). Insecticides are also applied directly to watercourses to control mosquito larva and some fisher of Poachers uses poisons to illegally obtain fish whereby depositing toxic chemical to the water body, while waste pesticides and their empty containers are carelessly dumped into the. River by farmers. The river also receives copious amount of waste from abattoir site, increase in the amount of heavy metals will cause disruption in the ecological balance of the river (Ogimtoyinbo, 1982). Allochthonous and autochthonous influences could make concentrations of heavy metals in the water high enough to be of ecological significance. Moreover, bio concentration and bio magnifications could lead to toxic, levels of these metals organisms, even when the exposure level is low (Pickering. 1980). The proven toxicity of high concentrations of heavy metals in water to fish and other aquatic life poses the problem of an ultimate dies-equilibrium in the natural ecological balance (Cain et al, 1980). Toxicity of a moderately 10XIC metal could be enhanced by synergism (Okayed, 1991). And, as a result, fish populations may decline (Ezeronye and Ubalua 2004). Apart from stabilizing the ecosystem, the accumulation of these toxic metals in aquatic food is a potential threat to public health. However, human are high level consumers. (Ndaruga et., al 1988). Suggested that over one billion people are currently exposed to elevated concentrations of toxic metals and metalloids and several millions may be suffering from sub-lethal metal poisoning. The minamata .By epidemic in Japan remains a classic example of this phenomenon. This epidemic was a neurological syndrome caused by severe mercury poisoning. The symptoms were -ataxia, numbness in the hands and feet, general muscle weakness, narrowing of the field of Vision and; damage to hearing and speech. In extreme cases, insanity. Paralysis. Coma, and death followed within weeks of the. Onset of symptoms. AA Congenital form of the disease can also affect fetuses in the womb. Minamata disease was first discovered in Minamata city in Kumamoto prefecture, Japan, in (OloWu, et al., 2010). It was caused by the release of methyl mercury in the industrial wastewater from the Chis so Corporation’s chemical factory, which continued from 1932 to 1968. This highly toxic, chemical bi o- accumulated in shellfish and fish in Minamata Bay and the Shiranui Sea, which when eaten by the local populace resulted in mercury poisoning. Cat, dog, pig, and human deaths Continued over more than 30 years (Christopher, 2009). Hence, aquatic pollution can have major impacts on the physiochemical parameters of the river such as pH, Total Dissolved Solids, Temperature, hardness etc and the general ecology of the water Contaminated water and aquatic organisms may transmit toxic elements of diseases to people who consume them. Therefore, water monitoring practices through researches are most useful to prevent disease outburst, hazards and As well check the resource from further pollution At Suitable concentrations some heavy metals are essential for enzymatic activity but they also form an important group of enzyme inhibitors when natural concentrations are exceeded (Obasohan and Eguavoen, 2008). Consequently most heavy metals, whether essential or not, are potentially toxic to living organisms. Fish are widely used as sentinels of contamination in aquatic environments (Evans Dodo and Hanson. 1993) Contaminant accumulation in various fish tissues is used as a measure contaminant exposure and effects. According to the mechanisms of absorption, regulation, Storage and excretion of trace metals, different tissues have different roles in these processes (Bryan. 1987.).A lot of elements are recognized to perform essential functions in the body of fish, for instance, calcium. Phosphorus. Sodium, potassium, selenium, molybdenum, chlorine, magnesium, iron, Sulphur, iodine, manganese, copper, cobalt, zinc, fluorine, nickel, vanadium Silicon, chromium, and tin. The proof that each of these elements is essential rests upon experiments with one or more species of fish, but this experimental work will only be limited to determining manganese, lead, cadmium and iron contents in different species of fish. Like all other animals fish require as essential factors in their metabolism and growth.


Like in other organisms, heavy metals are not destroyed by humans (Castro-Gonzeza, 2008). Instead, they tend to accumulate in the body and can be stored in soft and hard tissues such as flesh and gills threaten the health of humans. Therefore, the heavy metals are among most of the pollutants, which received attention in various countries and considered the most dangerous category of pollutants in the sea (Hassan el al, 2007).An early example of an environmental problem due to heavy metal occurred in 1952. In the vicinity of the Japanese fishing harbor of Minimata. This disease (Minimata disease) was a result of Consuming fish and shrimps contaminated by methyl mercury and non- organic mercury rom the wastewaters discharged by Chlor-alkali factories. Another example is the Ita-lta Disease in Fugawa, Japan in 1955 (Dural, et al., 200/). It was the result of consuming rice, fish and bivalves that were Cd-contaminated from waste waters discharged by nearby mining (Abader, 2008). 


The growing human population has increased the need for food Supply. Because they are good protein sources, the demand for fish and shellfish products has increased. Worldwide, people obtain about 25% of their animal protein from fish and shellfish. (Bahnasawy, et al 2004). In 2004, about 75% (105.6 million tonnes) of estimated world fish production was used for direct human Consumption (FAO) food and agriculture organization it has been predicted that fish consumption in developing countries will increase by 57 percent, from 62. million tons in 19 to 98.6million in 2020 (Retnam, and Zakaria, 2010).The real importance of fish in human diet is not only in its content of high-quality protein, but also to the two Kinds of omega-3 polyunsaturated fatty acids eicosa pentenoic acid (EPA) environmental protection agency and docosa hexenoic acid (DHA). Omega-3 (n-3) fatty acids are very important for normal 9rowtn where they reduce cholesterol levels and the incidence of heart disease, stroke, and preterm delivery (Burger, et al, 2005). Fish also contain vitamins and minerals which play essential role in human health. Since diet is the main route of exposure to heavy metals, and s represent a part of human diet, it is not surprising that polluted fish could be a dangerous dietary source of certain toxic heavy metals (Bogut, 199/).n the last two decades there has been a growing interest in assessing the levels of heavy metals in food including fish (mainly concerned with commercial species). Such interest aimed at ensuring the safety of the food supply and minimizing the potential hazardous erect on human health. 


Under regular consumption habits, it is important to assess the Daily intake of metals from fish and compare it with the total values set by world health organization (WHO 2011) 


i. Long term exposure to cadmium 1s associated with renal dysfunction. Cadmium is bio persistent and once absorbed remains resident tor many years. High exposure can lead to Obstructive lung diseases and has been linked to lung cancer. Cadmium may also cause bone defects in humans and animals. The average daily intake for humans is estimated as 0.15ug from air and 1ug rom water, Iron plays an important role in the cellular respiration process through its Oxidation, reduction activity and electron transport (Haver,1989) there is relatively little information on absorption and metabolism of iron in fish and other aquatic organisms. It appears that mechanisms of iron absorption from the digestive tract, storage, and excretion may be similar to those in other vertebrates. Some absorption of iron take place across the membrane, however, the intestinal mucosa is considered as the major source of iron for metabolic purposes. In rainbow trout iron is absorbed from the peritoneal cavity and stored in greater concentrations in flesh, gills. There is little endogenous iron lost in urine and, fasces. (Momtaz, 2002).         

ii. Exposure to lead. (Pb) can lead to a wide range of biological defects in human dependin9 on duration and level of exposure. The developing fetus and infants are tar more sensitive than adults. High exposure can cause a problems in the synthesis of hemoglobin’s, damage to the kidneys gastrointestinal tract, Joints, reproductive system and the nervous system Studies have suggested that exposure to lead can cause up to a loss of points. (Yylmaz, et al, 2007)  Manganese is known to block calcium channels and with chronic exposure results in central nerve system (CNS) dopamine depletion. Manganese is known to block calcium channels and with chronic exposure results in central nerve system (CNS) dopamine depletion. This duplicates almost the entire symptom logy of Parkinson’s disease. (Schoeters et al, 2006). 


Anthropogenic activities are the major Causes or water pollution. These activities had been observed to be concentrated at the river bank probably due to its proximity to the town, thus, there are possibilities of the presence of abundant heavy metals in the fish body. 


With recent studies revealing that people exposed to contaminated fish suffers considerable damage to cerebral function, which was not related to anxiety (Altmann, 1999) And the documentation, of some deadlier diseases like, edema of eyelids, tumor Congestion of nasal mucous membranes and pharynx, stuffiness of the head and gastrointestinal muscular, reproductive neurological and genetic malfunction caused by some of these heavy which enters the body through food as race elements. Air water, absorbed through skin when come in contact with in agriculture or manufacturing industries etc. (Roberts, 1999). yauri river which serves as a source of drinking water both to the inhabitants of the community and domestic animals, and where several other human activities such as, fishing, washing of clothes, household materials, trucks, cars, motorbikes and bathing had been observed, seems not to have received  any Scientific attention. Has studying the presence of some heavy metals like Lead, manganese, cadmium. And iron in yauri River and in the flesh and gills of some fish species there in is imperative, to ascertain its ability to Sustain the aquatic animal there in and humans who depends on the river for day-to-day activities 


The aim of this research work is to assess the level of heavy metals in different species of fish from Yauri River and compare the results with other Standard values. Thus, the objectives are, Assessment of the presence of some heavy metals in three fishes, (oreochromis niloticus, synodontis and claries ganepinus membraneceouS) of the river. 

To determine and quantify some of the heavy metals that may be present and compare with 

WHO and other international acceptable standards 


In the last decades, contamination of aquatic systems by heavy metals has become a global problem. Heavy metals may enter aquatic systems from different natural and antnropogenic (human activities) sources, including industrial or domestic wastewater, application of pesticides and inorganic fertilizers, storm runoff, leaching from landfills, shipping and harbour activities. Geological weathering or the earth crust and atmospheric deposition (Yiumaz, 2005).


In natural aquatic ecosystems, metals occur in low concentrations. As they cannot be degraded, they are deposited, assimilated or incorporated in water, sediment and aquatic animals and thus, causing heavy metal pollution water bodies (Abdel-Baki ef al., 2011). Metals entering the aquatic ecosystem can be deposited in aquatic organisms through the effects of bio concentration, bioaccumulation via the food chain process and becomes toxic when accumulation reaches a substantially high level (Huang leed, and chem 2009). In fish which is often at the higher level of the aquatic food chain substantial amount of metals may accumulate in their soft and hard tissue (Mansour and sidky 2002). Pollutant enter fish through a number of routes. Flesh, gills, oral consumption of water, food and non-food particles. Once absorbed, pollutant are transported in to the blood stream to either a storage point (i.e bone) (Obasohan, 2008).


Heavy metals are one of the serious environmental pollutants because of its high toxicity. abundance and ease of accumulation by various plants and animals (aris, e al., 2004) industrial activities, Vehicle emissions, agricultural activities and domestic waste, in addition to shipping traffic especially in and close to harbors can all act as sources of heavy metal pollution 5ub and Lester, 1991). With the rapid industrialization and economic development in coastal regions, heavy metals are continually introduced to estuarine and coaster environments through rivers, runoffs, and land-based point sources where metals are produced because of metal refinishing by-products. Therefore, heavy metal contamination is still an environmental problem today in both developing and developed countries throughout the world. Heavy metal pollution in aquatic environment and Subsequent uptake in the food chain by aquatic organism s threats human health, hence it can result in morphological abnormalities, neurophysiologic disturbances, genetic alteration of cells (mutation). teratogenesis and carcinogenesis. (Sodoumou, et al; 2005) In addition, heavy metals can affect enzymatic and hormonal activities, as well as growth rate, and increase mortality (Bubb and Lester, 1991). More than 20%% of the worlds population does not have access to safe drinking water each day, some 25, 000 children die in everyday from use of water, four million of these deaths every year are Simply from diarrhea, it is also estimated that, at any one time, halt of inhabitants of developing countries are ill with diseases caused by polluted water. Some 80% of all illness and a third of all deaths are due to unwholesome water (Lean et al. 1990). Among the inorganic contaminants of the river water, heavy metals are getting importance for their non-degradable nature and often accumulate through. Tropic level causing a deleterious biological effect (Jain, 1998) in Nigeria, a considerable amount of studies have been carried out on the effect of pollution in the water bodies affecting its physicio-chemical parameters and general ecology. The lead, copper, zinc nickel B, Chromium, cadmium iron (Adeyemi et al 2008). UUs and Adewolu et al, 2009) and (Ajlbad 2004). Eniola et al, 2010 ayinka 2004) his has continued to pose a threat on health and economic Development in Nigeria (olayinka MuUsla:ha, 2008). Several researchers have also investigated the concentration of heavy metals in the coastal river Atlantic tidal effect in Nigeria. (Egborge.1991 Correlation analysis of concentrations suggest that some of them are strongly associated. indicating a common source of chemical Similarity for the Coupled element (Ndiokwere,1984) in investigated the heavy metal content of the sediments, algae and the Nigerian causal ware his finding. be stated that all the heavy metals had higher Concentration rainy than in dry season, suggesting high concentration from external sources. this  perfect was especial strengthened by the fact that time main metal levels were higher than natural background level. (Nekim et al; 7993) reported on the distribution of race metals in the sediments of yauri River, and found out higher presence of heavy metals n the river Sediments, while (Oiuwande el al; 1983). Reported generally on the pollution levels in some Nigerian rivers. Suggesting that the major contribution to the pollution of aquatic systems comes from industrial pollutants which originate from industries requiring large volumes of water tor their operations these include textile producers, sugar production paper mills, sawmills and logging mills, petro-Chiemical works and hydro-electric power stations (Adeni Mbagwu, 1990). Although findings related to industrial pollution of water resources have been disturbing, category of pollution that has received much attention in Nigeria is sewage pollution of portable drinking water. This has been managed with the weight of such bodies as UNICEF established in Nigeria in 1952 and water Aid which began work in Nigeria in 1995. However, about 60 percent of the Nigerian populace both rural and some urban dwellers still source for domestic water and sometimes drinking water from ponds, streams and shallow wells justifying the concern for increases in the level of pollutants in surface and groundwater thus making water monitoring even more vital, (Adelegan, 2004 and Morenikeji, 2010). Low heavy metal concentration have been reported in Nigerian water bodies by earlier researchers, notable among which are (Obire et al. 2003) on lower Bonny River, (Omoigberale and Ogbeibu 2005) on Osse River, Southern Nigeria. The use of fish and invertebrates as bio indicators of water quality has been advocated by several researchers, (OgbeiDu and Victor, 1989). This is because they produce evidence of relatively stable concentration compared with water analysis that indicates only short term conditions. Fishes are lived in the water for a long time, for at least 400 million years. In their long history they have become adapted for life in all sectors of the aquatic world the sunlight ocean and its black depths, the washing surf, placid tropical rivers and mountains torrents. Fishes outnumber all other vertebrates in both numbers of individuals and numbers of species. They live in almost all the waters of the earth. Fish belong to a major group, or phylum of animals termed the chordate, a phylum that includes ourselves and as well some small, relatively sample animals that lack backbones. All forms of aquatic animals require inorganic elements, for their normal life processes Fish have the ability to absorb some inorganic elements not only from their external environment in both fresh water and sea water fish constitute an important source of protein for many people throughout the world and fish consumption has increased in importance among health-conscious people because it provides a health and low cholesterol sources of protein and other nutrients (ESurge ana loeenmEd, 2003JUsa et al, 2005). Heavy metals such as copper (Cu) Zinc Zn are essential for fish metabolism while some others such as lead Pd have no role in biological systems. For the normal metabolism of fish, the essential metals must be taken up from water, food or some however, similar the route of essential metals, non-essential ones are also taken up fish and accumulate in their tissues (Turikmen et al, 2008, Dural et al, 2007). Hunan beings have been exposed to heavy metal toxins for an in measurable amount of time. The industrialization of the World has dramatically increased the overall environmental “load of heavy metal toxics to the point that our societies are dependent on industrialization for proper functioning. In Ningana, the levels of toxic and non-prod gradable heavy metals in fish samples have been reported for some dams and lakes including Kainji Lake (Jimon et al, 2004). Oguta Lake, Asa Dam, Ilorin, Ureje Dam, EKiti State, Alau Dam, Maiduguri Kusalla Dam, Kano State (minganu, el al; 2010) among others. Thus, despite the valuable nutritional Constituents o fish, their notoriety n the ability to concentrate toxic and non-biodegradable heavy metals in their body tissues (Turkmena, el al; 2008) calls for adequate assessment of the metal levels in them at regular intervals, so as to safeguard the safety of the consumers. 


The bioaccumulation of heavy metals in tissues of marine organism indirect measure of the abundance and availability of metals in the marine environment (kuCuksezgin et al; 2016 Vmodhinsi and Narayarnan, 2008). The natural aquatic systems may extensively be contaminated with heavy metals release from domestic, industrial and other man-made activities (velez and MonterO, 1998). Heavy metals contamination may have devastating effects on the ecological balance of recipient environment and a diversity Of aquatic organisms (Ashraj, 2005, Ciman, 1992, Jankalte,and vosylene 2006). Marine organisms are characterized by a greater spatial ability to accumulate metals compared to bottom sediments. for this reason fish are widely used as bi-indicator for aquatic marine pollution by metals and have also been used to evaluate ecological risk (KUcuksezgin et al, 2006). And Szeler et a1, 2006). The studies carried out on various fishes have shown that heavy metals may alter me physiological activities and Biochemical parameters both in issues and in blood (Basa and Rani, 2003, Canii. 1995 and Tort and torres, 1988). the toxic effects of heavy metals have been reviewed, including bioaccumulation organisms developed a protective defense against the deleterious effect of essential and inessential heavy metals and other xenobiotics that produce degenerative changes like Oxidative stress in the body his observation agrees with previous findings of other researchers in the past years stated that Lead enters into the body Through gill cells and mostly accumulate in the same gill Cells but the later organs aimed at are the flesh. Zinc in the other hand is usually accumulated in bone and skin with greater amount of accumulation in flesh and gill although zinc as trace element is necessary animal body for respiratory and enzymatic activities, but this high level of zinc could cause metabolic disorders in fish (Ololade, el al, 2001). Especially the concentrations of four heavy metals (P’, Fe, Cd, Mg) in the ills and flesh of Tilapia are safer for consumption than the other parts (organs) investigated (flesh and gills) as they contain the least amount of the heavy metals determined. This reveals the adverse health effect the people in the study area could be exposed to by the consumption of the gills, flesh of Tilapia as it happens to be the most preferred and heavily consumed fish in human diet in the study area.


The concentration of fish in the body of aquatic organisms depends on food source, environment species, stage of development, and physiological status of the animal Most organisms accumulate and retain fish from the environment, however, their incorporation is highly selective An interesting (Russian) study on fist from different lakes showed that the qualities of manganese, Iron lead, cadmium in the flesh and gills of fishes reflect the geochemical characteristics of the earth surrounding the lake. Fishes absorb manganese, Iron lead, cadmium from the environment to satisfy part of their nutritional requirements (zeiton et al; 1976) demonstrated absorption of manganese, iron, cadmium, lead hatching by eggs in rainbow trout and uptake of manganese, cadmium lead chromium from the water after yolk absorption After 2-10 week, evidence of deficiency appeared in the fish, e.g poor appetite, sluggish movement. Growth retardation, hypo-chromic microcytic anemia, and certain percentage of the fish started convulsing and diet


Elements such Cd and Pb are non-essential metals and their toxic effect on human health is well Known, while metals such, Fe and Mn, and are essential metals. The toxic effect of them on human health begins when they are present in high. These elements may be added on the ecosystem through human activities or from natural sources as it was explained previously. Many studies assessed concentration of these heavy metals in fish species all over the world.



                                                              CHAPTER TWO






Fume cupboard






Conical Flask   


Measuring Cylinder


x20c (MC) 100ml             



A.C 50m


Mortar and Pestle

Plastic Knife


Wash glass


Filter paper

No 42


Volumetric flask  





AD 100XB4J




1. trioxonitrate (v) acid HNOs

2. tetraoxosulphate (vi) acid H2SO4

3. Sodium hydroxide NaOH

4. Distilled Water

5. De ionized Water


This study was conducted on Yauri River in yauri Local Government Area, Kebbi State, Nigeria. Kebbi State is located in North-West Nigeria. The state is bonded by Niger State north east and, Niger State northwest, It has a total land, area of 36,129 square km and the State capital is Birnin Kebbi. Human activities around Yauri River include washing clothes, bathing, and poultry farm. yauri river which serves as a source of drinking water both to the inhabitants of the community and domes animals, and where several other human activities Such as, fishing household materials, trucks, cars, had been observed, the yauri river is a very large river that is connected with some village rivers like rofia,zamare, kasabo and also the river it comes from argungu in kebbi state. The river from the north  it also connected with some west African countries such as niger, Burkina faso, codevour, seria leon, Senegal.  yauri river from the south is connected to kainji, jabba dam,  and people from many area Come for fishing every day.


 The gills, and flesh of three common fishSpeciesTilapianilotica (oreocnromisniotcus) Clarasganepinus, (clariaslazera).Synodentis membraneceous) were collected for analysis of heavy metals



A total of three species of the fishes were obtained from yauri river these are Tilapia (nilonica) (oreochromisniloticus) Clarias gariepinus (clariaslazera) Synodontis (membraneceous), fish were bought from fisherman at the Yauri River and stored un a cooler with ice blocks. The fish where transported to the laboratory. G ills and flesh section  were removed using a plastic knife and then dried in an oven of about 105+20 for about 24 hours, after which were weighed prior to digestion, the dried gills and flesh of fish species were pounded and milled with a mortar and pestle until a powder was obtained (Usero, 1996 ).  They were then put in plastic containers and stored in desiccator until digestion 10cm3 Conc. H2SO and 5crn3 Conc. HNO, Was added. The sample was digested in fume cupboard until the solution volume was reduced to 2cm3. the digestion continued until the solution was colorless. These ensured the removal of all HNO the sample was allowed to cool, and 15cm3 of distilled water was added win gentle swirling. 1M NaOH was added drop wise until a pink- brown of colorless solution was produced the solution was filtered using a Whitman filter paper No. 42, followed by dilution to the mark in a 25cm3 volumetric flask. The water and sediment were digested according to the method prescribed by (Sreedevi, et al 1992). Following the digestion, all samples were analyze for Cd, Pd, Fe, and Mn.


After taking the measurements and Justification, fish were washed with De ionized water sealed in bucket and kept in a freezer at.20oC until chemical analysis


                                                               CHAPTER THREE


In all the fishes Lead (Pb) Concentration in their flesh is higher than in their gills and the concentrations are higher than the WHO limit (0.01mg/l). The highest Lead Pb concentration Was found in flesh of clarias fish (0.363mg/l) while lowest concentration was found in gills of tilapia fish (0.003mg/l) both of the concentrations have exceeded the standard limit. The highest Cadmium Cd concentration was found in synodontis flesh (0.057mg/l) while the lowest was found in gills of (0.004mg/l)synodontis fish and the concentration have exceeded the standard limit. The highest Manganese Mn concentration was found in flesh of synodontis (1.591mg/l) while the lowest concentration was found in tilapia flesh (0.007mg/l), both the conc. Have exceeded the standard limit. The highest Iron Fe concentration was found in gills of clarias (17.82mg/l) while the lowest concentration was found in clarias flesh (0.471mg/l), both the concentration has exceeded the standard limit.

Table 3.1 Heavy metals distribution in tilapia (niloticus) fish organs



Mean conc.ppm


Tilapia (flesh)                              



Tilapia (gills)                             



Tilapia (flesh)                          



 Tilapia (gills)                          



Tilapia (flesh)



Tilapia (gills)                          



Tilapia (flesh)                         



Tilapia (gills)                              


Tables 3.2 World Health organization (WHO) Permissible Limit











Table 3.3 Heavy Metals concentrations in (Synodontis Membraneceous) Fish Organs.



Mean conc.ppm


Synodontis (flesh)



Synodontis (gills)



Synodontis (flesh)



Synodontis (gills)



Synodontis (flesh)



Synodontis (gills)



Synodontis (flesh)



Synodontis (gills)


Table 3.4 Heavy metals concentrations in (Clarias Gariepinus) Fish Organ



 Mean conc.ppm


Clarias (flesh)



Clarias (gills)



Clarias (flesh)



Clarias (gills)



Clarias (flesh)



Clarias (gills)



Clarias (flesh)



Clarias (gills)





             CHAPTER FOUR 


 4.1 DISCUSSION           

Lead (Pb) concentration in flesh of Clarias species (0.363mg/l) is higher than in all other species followed by flesh of Synodontis (0.262mg/l) while the lead (Pb) conc. of Tilapia flesh (0.170mg/l) was the lowest. ThereforeTherefore, taking this fish pose health effect on human either directly or through bioaccumulation.

The concentration of Cadmium (Cd) in flesh of  tilapia (0.013mg/l) and synodontis (0.057mg/l) is higher than in their gills (0.007mg/l) and (0.004mg/l) while gills in clarias (0.008mg/l) has high concentration of cadmium than in the flesh (0.005mg/l) and all the concentrations are higher than the WHO limit (0.003mg/l). In additionaddition, cadmium (Cd) concentration. in Synodontis Species’ flesh (0.057mg/l) is higher than in all the other species, followed by Tilapia flesh (0.013mg/l), While the cadmium (Cd) conc. of Synodontis  gillsSynodontis gills (0.004mg/l) is lowest. ThereforeTherefore, taking this fishes species will pose effect on human either directly or by bioaccumulation.

The manganese (Mn) Concentration in flesh of synodontis(1.591mg/l) was higher than in their gills and clarias is having high concentration of manganese (Mn) in gills (1.035mg/l)  than) than in flesh (0.021mg/l) and the concentrations are higher than the WHO limit (0.5mg/l). The manganese (Mn) concentration in synodontis (1.591mg/l) species flesh is higher than all the other species, followed by clarias gills (1.035mg/l), while the manganese (Mn) concentration of tilapia gills (0.007mg/l) is lowest. Consuming the flesh of synodontis and clarias gills will lead infections or disorders on human either directly or bioaccumulation. 

The Concentration of iron (Fe)  in synodontis’s flesh (7.760mg/l) is higher than in its gills (0.638mg/l) while iron concentration in gills of tilapia(6.72mg/l)  and clarias (17.82mg/l) is higher than that of their flesh which was (0.670mg/l) and  (0.471mg/l) respectively  and all of the concentrations are higher than the WHO limit (0.3mg/l).Hence iron concentration(17. 82mgi/l) in gills of clarias species is higher than in all the other species, followed by synodontis flesh (7.760mg/l), while iron (Fe) concentration of clarias flesh (0.471mg/l)  is the lowest. ThereforeTherefore, taking this fishesthese fishes may be dangerous to human either directly or bioaccumulation.


This study shows that lead, cadmium, manganese and iron. Are present in all fish species collected from yauri local government area of Kebbi state. It was discovered that the flesh of fish contained higher concentration of heavy metals compared to their gills, Except for iron (Fe). it is therefore advisable not to consume the flesh of fish so as to reduce the risk of heavy metals consumption from contaminated fish. All results were above the maximum limits for fish consumption proposed by WHO Among the three fish species, higher concentrations of Pb, Cd, Mn, Fe were found in tilapia and synodontis flesh concentration of fish species have the highest concentration while gills of synodontis have the lowest concentration, and claries the highest concentration are found in gills while lowest concentration are found in flesh of clarias. Daily intake of all metals showed that in case of regular consumption there may be a harmful effect on general public health from the consumption of the studies fish in Yauri River. 


Similar studies may be performed to check contamination in those heavy metals such as cadmium, lead, iron and manganese in commercial fish species in yauri river, periodical monitoring of heavy metals level in commercial fish is needful, for tilapia, synodontis fish which showed the highest concentrations of studied metals. The Government should developeddevelop stringent regulations to monitor pollution in the aquatic system and enforce the existing laws and regulation. 


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