Morphological and Molecular Systematics of Freshwater Fish Diversity and Physico-chemical Parameters of Jebba Hydro-electric Power Reservoir, Nigeria
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Date
2021-01
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UNIVERSITY OF ILORIN
Abstract
Fishery activities in Jebba Hydro-electric Power Reservoir (JHPR) contribute to socio-economic development of Jebba town and Nigeria. There is paucity of information on fish biodiversity in JHPR, hence, this study aimed at identifying fish species and their ecology. The objectives of the study were to: (i) investigate the physico-chemical parameters in up- and down-streams of JHPR; (ii) identify fish species, abundance and diversity; (iii) determine the relationship between fish diversity and physico-chemical parameters; (iv) determine phylogenetic relationships of the barcoded fish species; and (v) determine intra- and inter-generic diversities of the barcoded fish species.
The study of physico-chemical parameters in relation to fish composition and diversity in JHPR was carried out between January, 2017 and December, 2018. The physico-chemical parameters of water in the reservoir were determined using standard methods. Fishes were collected with the aid of gill and cast nets of different mesh sizes and identified morphologically utilizing morphometric and meristic features; and molecular approach adopting DNA barcoding. Simpson’s, Shannon-Wiener and Margalef’s indices and relationship between the physico-chemical parameters and fish abundance/diversity in the sites/seasons were statistically analysed with correlation matrix and factor analysis in XLstat at p≤0.05. The phylogenetic relationships, intra- and inter-specific divergence of the barcoded fish species were determined applying MEGA 5.0.
The findings of the study were that:
(i) the range for dissolved oxygen (DO), chemical oxygen demand (COD), turbidity and nitrate concentration in up- and down-streams of JHPR was 2.0-5.5mg/L, 20.50-35.67mg/L, 1.2-375NTU and 0.2-3.4mg/L respectively;
(ii) there was a significant (p<0.05) seasonal variation in turbidity with higher mean value of 175.40±34.49NTU observed in rainy season;
(iii) eighty-three fish species belonging to forty-three genera were identified morphologically while 170 nucleotide sequences generated confirmed all the species identification except for Chromidotillapia guntheri, Ctenopoma kingsleayae, Malapterurus electricus and Dasyatis garouaensis;
(iv) fish species distribution in the family Cichlidae and Mochokidae were more abundant in up- and down-streams of JHPR, but diversity indices showed higher species richness (Margalef=9.73) and diversity (H= 3.95; 1-D = 0.98) at the downstream;
(v) positive correlations (≥0.73) between DO, nitrate concentration and fish abundance were obtained for all fish families except Claroteidae, Latiidae, and Tetraodontidae, while turbidity positively correlated (≥0.71) with the abundance of Mormyridae, Gymnarcidae, Characidae, Distichodontidae, Bagridae, Malapteruridae, Dasyatidae, Polypteridae and Schilbedae;
(vi) all the barcoded sequences showed levels of genetic distinctiveness among species in the phylogenetic tree and taxonomical hierarchy; and
(vii) a range of 0-18.83% and 0.00-0.45% were generated for intra- and inter-generic divergence respectively in the barcoded species.
The study concluded that JHPR harboured high diversity of fish species which was influenced by seasonal variations in turbidity, DO, COD and nitrate concentrations. The study recommended that morphological and molecular methods be used for fish species identification, biodiversity monitoring, ecology and management.
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Keywords
Morphological Systematics, Molecular Systematics, Freshwater Fish Diversity, Physico-chemical Parameters, Jebba Hydro-electric Power Reservoir