Abstract

The gross chemical composition from four populations of Clarias gariepinus, obtained from different geographical sites in the Sudan was determined. The proximate analysis of the specimens of the four populations showed significant differences (p<0.05) in protein, moisture and ash contents but not in fat contents (p>0.05). Khor Abu Gassaba and Tordat Al Rahd populations had the highest calorific contents (185.81 and 178.64kcal/100g) respectively. Analysis of variance of the chemical composition from the four sites revealed highly significant difference (p<0.01) in protein, moisture and fat, and insignificant difference (p>0.05) in ash. The calculated caloric values were high in all populations, but the fat: protein ratio was low which is indicative of high digestibility. The correlation coefficient between body weight and chemical composition percentage of C. gariepinus, from the four locations ranged from weak to high, and from positive to negative correlations. It is concluded that C. gariepinus contain adequate quantity of animal protein, fat and ash that would support and promote human health.

Keywords:Clarias gariepinus; Chemical composition; Sudan

Introduction

Clarias gariepinus (Actinopterygii) belongs to a diverse group of ray finned fish found in most of the African countries [1,2]. In the Sudan, it is the second commercial fish after the Nile Tilapia (Oreochromis niloticus) in commercial importance. It is consumed as fresh or a processed dry fish product [3,4].

Fish is a highly nutritious source of animal food made up of 70-84% water, 15-24% protein, 0.1-22% fat, and 1-2% minerals, depending on the species, seasonality and habitat. The protein of fish is of particularly high nutritive value, rich in all essential amino acids in balanced proportions and exhibits high digestibility compared to many terrestrial animal proteins [5,6]. Fish is a rich source of several essential vitamins (A, B-complex, D, E and K) and minerals (Calcium, Phosphorus, Iron, Zinc, Iodine, Selenium, Magnesium and Potassium) important for human health [4,5].

The chemical composition of fish varies considerably among species and among the individual fishes of the same species depending on factors such as age, sex, abiotic and biotic features of its environment as well as seasonal changes [3,7]. Clarias gariepinus are considered as highly nutritious and an excellent source of high-quality protein, and other dietary essentials [7,8]. Clarias gariepinus has drawn the consideration of fish culture practitioners because of its tolerability to harsh environmental conditions, high growth rate, and diseases resistance [9]. Therefore, it has been widely introduced globally for aquaculture since the 1970s/80s [10,11].

The objective of this study is to determine and compare the gross chemical composition (protein, moisture, fat, ash, and calorific value) of four geographically distinct populations of Clarias gariepinus in Sudan, and to evaluate the variation in nutritional quality among these populations that can be used in the planning and development of aquaculture fish industry in the country.

Material and Methods

Material

Out of 123 specimens of C. gariepinus, 21 specimens were selected randomly from four sites (Figure 1). The sites were: Site 1 (Sinnar Dam area, the Blue Nile), Site 2 (Khor Abu Gassaba, a seasonal stream fed from the Western Bank of the White Nile), Site 3 (Tordat Al Rahd an ephemeral water body in Northern Kordofan) and Site 4 (Khashm Al Girba, Atbara River). All specimens were purchased from fishers at the site, chilled and immediately transported to the laboratory.

Methods

Fish were identified following [1,12]. The body weight of each specimen was recorded in gm using a Docebel Braun balance.

The proximate chemical analysis followed the Association of official analytical chemists [13]. Each analysis was made in triplicates, and an average was calculated and recorded.

The calorific values were calculated using [5] equation as follows:
Calorific value (Kcal/100g) = 4.1× Pr otein + 9.3× Fats

Fat to protein ratio was computed according to the equation used by [5] as follows:
Fat: Protein = Fat%÷Protein%.

Statistical analysis

The data was subjected to Excell Programme Version 2016. The means of chemical composition were compared using Least Significant Difference (LSD) to test any significant differences (p<0.05) between the 4 fish population; as well as estimating the correlation coefficient (r) between the different traits.

Results

The chemical composition of C. gariepinus meat (Table 1) showed insignificant difference (p ≥0.05) between fat in the 4 sites. Site 1 was significantly different (p<0.05) from the other sites in moisture and ash. The highest mean % of moisture (80.038) was from site 4 and the lowest (69.85) was from the samples of site 3. The highest value, for ash, was 1.66 in site 3, and the lowest value was 1.02, in site 4. Sites 2 and 3 were significantly different (p<0.05) from the other sites in protein content, calorific value and fat to protein ratio. The highest mean protein value 43.05 was recorded in site 3 and the lowest 25.23 was from site 1. Sites 2 and 3 were significantly different from sites 1 and 4 (p < 0.05). The calorific value was highest in Tordat Al Rahd samples and the lowest fat to protein ratio was obtained from the same site.

Superscripts with different letter in a column indicate significant differences.

Analysis of variance (Table 2) of the chemical composition from the four sites revealed highly significant difference (p<0.01) in protein, moisture and fat. The calculated F exceeded the tabulated F_3,17 at p=0.01 which was 5.185. Insignificant difference (p>0.05) was found in ash, as the tabulate F_3,17 at p=0.05 was 3.197. which is higher than the calculate F value.

**= highly significant (p<0.01), NS =not significant.

The correlation between body weight and chemical composition of the fish samples from the four locations is given in (Table 3). High negative correlation coefficient was in ash content from Sinnar and Khor Abu Gassaba. Moderate +ve correlation was recorded for fat from Sinnar and moderate -ve correlation in moisture form Tordat Al Rahd samples. The rest of the correlates are weak.

**high correlation r>0.65, *moderate correlation r≥0.649 to p<0.401, weak correlation r<0.40.

Discussion

Clarias gariepinus is an economically important widely distributed fish species in the Sudan [4]. The proximate analysis of fish refers to the quantitative determination of moisture, crude protein, crude fat and ash [14]. The chemical composition of fish varies within and between species depending on its age, sex, environment and season [3]. In this study, the ranges of moisture (69.85% to 80.04%); protein (25.23% to 43.05%); fats (1.0% to 3%); and ash (1.02% to 1.66%) are well within the ranges given by [5,14,15]. The Kcal/100g exceeded 150/Kcal/100g in all studied sites except Sinnar. This valued indicated that C. gariepinus is of a high nutritional value. This in agreement with the findings of [15] in the same species from Egypt. The chemical composition of fish flesh is a reliable predictor of its quality and nutritive value [16] and an important attribute in fisheries industry [17].

The four populations showed significant differences (p<0.05) in protein, moisture and ash contents but not in fat contents (p>0.05). Khor Abu Gassaba and Tordat Al Rahd populations, with the highest protein contents, suggests that the slow current in both sites is among the environmental factors affecting the chemical composition of the fish. Fish samples from the fastflowing Khashm Al Girba and Sinnar have the lowest protein contents. Hagar [4] studied C. gariepinus and claimed that in fast flowing water bodies, the fish use the protein to supplement the needed energy.

According to [18] fish with lower moisture content has a higher lipid and protein content, as well as a higher calorie density. The insignificant differences in moisture and ash contents explains the high protein contents in the four populations. The low fat to protein ratio indicates the flesh of these four populations has a high degree of digestibility. Similar findings were obtained by [4,19]. Also, the four populations have high quantities of protein of edible mater [5,20,21]. The correlation coefficient between body weight and chemical composition percentage of C. gariepinus, from the four locations ranged from weak to high, and from positive to negative correlations.

Claris gariepinus fish are good source of protein, with low fat and a delicious commodity [22,23]. According to [24] carbohydrates and are present in a small percentage of wet mass that is typically assumed to be negligible (p<0.5%).

In conclusion, C. gariepinus could be the fish of choice to start proper fish product industry in Sudan because of its adaptability to the different habitat conditions, its high nutritional value and acceptability as food by the population, but this needs in-depth investigations.

Ethics

Ethics approval and consent to participate, human and animal rights, consent for publication, availability of data and materials are not applicable.

Funding

This study was funded by the Ministry of higher Education and Scientific Research.

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