Abstract
This study was conducted to evaluate nutritional composition and heavy metals concentration of smoked and raw edible fish species from Ologe lagoon (freshwater) and Lagos lagoon (marine). The fish species from Ologe include: Chrysichthys nigrodigitatus (Catfish), Monodactylus sebae (African moony), Pomadasys jubelini (Buro), Sphyraena barracuda (Great barracuda), and Pseudotolithus elongatus (Croaker), while that of Lagos lagoon include Chrysichthys nigrodigitatus (Catfish), Caranx hippos (Crevalle jack), Liza falcipinnis (Sicklefin mullet), Pomadasys jubelini (Buro), and Monodactylus sebae (African moony). The nutritional composition ranged in the following trend moisture (43.24 - 76.79 %) > carbohydrate (3.16 – 63.45 %) > protein (0.80 - 31.55 %) > fibre (1.07 – 2.8 %) > ash (0.81 – 1.88 %) > fat (0.40 – 1.30 %). In this study, these fishes are generally low in fats (lean fish), and fish smoking tend to reduces their nutritional composition. Heavy metals concentration trend thus Zn (2.4 – 7.75 mg/kg) > Ni (0.80 – 1.925 mg/kg) > Cr (0.20 – 0.550 mg/kg) > Pb (0.025 – 0.50 mg/kg). In all the samples, all the metals of interest were detected except cadmium which was not found in any of the samples analysed. Pb (0.025 - 0.5 mg/kg) values in the fishes were lower than the maximum standard level reported to be 0.5 mg/kg dry weight by FAO except in the raw Pomadasys jubelini where the value is 0.5mg/kg. The fresh water fishes showed higher concentration of heavy metals than marine water fishes but not statistically significant (p>0.05). Although, smoked fishes showed higher concentration of heavy metals than the raw fishes, it was only significant for zinc (p<0.05). In view of this study and the importance of fish in human diet, it is recommended that biological monitoring of fishes meant for consumption from these two water bodies be carried out regularly to ensure human safety.Keywords: Nutritional composition, heavy metals, fresh water fishes, marine water fishes, lagoons
Highlights
Fish is an important component in the diets of many Nigerians
Nutritional composition of fish samples: Table 1 high. It shows that all the fish species are good sources shows the values for the proximate composition of the of protein
The highest moisture content crude protein may be attributed to the fact that fishes was found in Liza falcipinnis with value of 76.79 % are good source of pure protein, but the variations while the lowest was recorded for Monodactylus sebae observed in values obtained could be as a result with 43.24 %
Summary
Fish is an important component in the diets of many Nigerians. It is a good source of protein for humans and animals (Holma and Maalekuu, 2013). Fish is an important source of poly-unsaturated fatty acids and contains omega-3, calcium, iodine, phosphorous, iron, trace elements like copper and a fair proportion of the B vitamins known to support good health (Tucker, 1997; USDA, 2010). An increasing amount of evidences suggest that, fish and fish oil (contain high amount of polyunsaturated fatty acids) are valuable in decreasing the serum cholesterol to prevent a number of coronary heart diseases and increase neurological development (Turkmen et al 2005). Eating of fish can reduce the risk of heart diseases and lower the risk of developing dementia, including Alzheimer’s diseases (Kelly and Knopman, 2008). Fish contains significantly low lipids and higher water than beef or chicken and is favoured over other white or red meals (Grant, 1997)
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