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Patterns of ichthyofaunal diversity and distribution across Jebba Hydro-Electric Power (HEP) dam, Jebba, north-central Nigeria

Padrões de diversidade e distribuição da ictiofauna na barragem de hidroelétricas (HEP) de Jebba, Jebba, Nigéria norte-central

Abstract

The ichthyofauna diversity of the Jebba Hydroelectric Power (HEP) Dam, Jebba, North-central Nigeria was studied. Fishes were sampled for 24 months using gill net, hook and line, and cast net. Individuals were identified using morphological and molecular (mitochondrial Cytochrome c Oxidase subunit I) data. A total of 9605 freshwater fishes were recorded during the sampling period. The use of an integrative taxonomic approach enabled the identification of 83 species belonging to 42 genera. Additionally, the study recorded three unidentified species – Ctenopoma sp, Malapterurus sp., and Protopterus sp. Analyses showed that individuals belonging to families Cichlidae and Mochokidae dominated the dam. The diversity analyses revealed relatively high fish diversity during the rainy season at the downstream section of Jebba HEP dam compared to the upstream section. The study, therefore, showed the presence of a diverse fish community comprising high species richness and diversity across the Jebba HEP dam. Finally, we recommend proper biodiversity monitoring and assessment of freshwater fish diversity across Nigeria. In addition, the use of an integrated taxonomic approach is recommended for appropriate species’ identification and studies of freshwater fishes from Nigeria.

Keywords:
diversity; fisheries management; DNA barcoding; Nigeria

Resumo

A diversidade da ictiofauna da hidrelétrica de Jebba (HEP), Jebba, centro-norte da Nigéria foi estudada. Os peixes foram amostrados por 24 meses, utilizando rede de emalhar, anzol e linha, e rede de arrasto. Os indivíduos foram identificados usando a abordagem combinada morfológica e molecular (citocromo c Oxidase mitocondrial subunidade I). Um total de 9605 peixes de água doce foram registrados durante o período de amostragem. A identificação das espécies utilizando a abordagem taxonômica integrada possibilitou a identificação de 83 espécies pertencentes a 42 gêneros. Além disso, o estudo registrou três espécies não identificadas - Ctenopoma sp, Malapterurus sp e Protopterus sp. Análises mostraram que indivíduos pertencentes às famílias Cichlidae e Mochokidae dominaram a barragem. As análises dos índices de diversidade revelaram uma diversidade de peixes relativamente alta durante a estação chuvosa na seção a jusante da barragem Jebba HEP em comparação com a seção a montante. O estudo mostrou, portanto, a presença de diversas comunidades de peixes, que incluem alta riqueza e diversidade de espécies através da barragem Jebba HEP. Finalmente, recomendamos o monitoramento adequado da biodiversidade e a avaliação da diversidade de peixes de água doce em toda a Nigéria. Além disso, recomenda-se o uso de abordagem taxonômica integrada para a identificação adequada das espécies e estudos de peixes de água doce da Nigéria.

Palavras-chave:
diversidade; gestão pesqueira; DNA barcoding; Nigéria

1. Introduction

Nigerian freshwater ecosystem spans over 14 million hectares (FDF, 2008FEDERAL DEPARTMENT OF FISHERIES – FDF, 2008. Fisheries statistic of Nigeria human population; fish demand and supply in Nigeria, 2000-2015. Lagos: FDF, 56 p.). Amongst its freshwater ecosystem is the Niger River, with its tributaries extending across the country (Olaosebikan and Raji, 1998OLAOSEBIKAN, B.D. and RAJI, A., 1998. Field guide to Nigerian freshwater fishes. New Bussa: Federal College of Freshwater Fisheries Technology.). Over the years, several development projects have been constructed on this river. Notable among them is the construction of hydro-electric power (HEP) plants, which led to the development of the Jebba HEP dam. The Jebba HEP dam extends from Jebba to the southern Kainji dam with tributaries stretching across Awun, Eku, Moshi, and Oli rivers. It has good potential for the fish catch with an estimate of 909-1818 tons/annum (Adelakun et al., 2017ADELAKUN, K.M., MUSTAPHA, M.K., AMALI, R.P. and MOHAMMED, N., 2017. Seasonal variation in nutritional quality of Catfish (Clarias gariepinus) from Upper Jebba Basin, Nigeria. Journal of Nutrition & Food Sciences, vol. 7, no. 5, pp. 1-4.).

Although Jebba HEP dam was constructed to improve the populace standard of living, increased rate of anthropogenic activities poses threats to the aquatic ecosystem as well as the biotic community (Oladipo et al., 2018a)OLADIPO, S.O., NNEJI, L.M., ANIFOWOSHE, A.T., NNEJI, I.C., IYIOLA, O.A., ADEOLA, A.C. and MUSTAPHA, M.K., 2018a. Growth pattern and condition factor of seven freshwater fish species from Jebba Lake, north-central Nigeria. Iranian Journal of Ichthyology, vol. 5, no. 2, pp. 167-172.. This has led to habitat destruction and, ultimately, the disruption of spatio-temporal pattern of water discharge. Overexploitation, continuous, and indiscriminate fish harvest, and pollution are also common challenges to fishery resources in the area (Oladipo et al., 2018aOLADIPO, S.O., NNEJI, L.M., ANIFOWOSHE, A.T., NNEJI, I.C., IYIOLA, O.A., ADEOLA, A.C. and MUSTAPHA, M.K., 2018a. Growth pattern and condition factor of seven freshwater fish species from Jebba Lake, north-central Nigeria. Iranian Journal of Ichthyology, vol. 5, no. 2, pp. 167-172.). The resultant effects of these threats could lead to a reduction in population size, and fish landed trawl, and loss of gene pool (Poff and Allan, 1995POFF, N.L. and ALLAN, J.D., 1995. Functional organization of stream fish assemblages in relation to hydrological variability. Ecology, vol. 76, no. 2, pp. 606-627. http://dx.doi.org/10.2307/1941217.
http://dx.doi.org/10.2307/1941217...
; Meldgaard et al., 2003MELDGAARD, T., NIELSEN, E.E. and LOESCHCKE, V., 2003. Fragmentation by weirs in a riverine system: a study of genetic variation in time and space among populations of European grayling (Thymallus thymallus) in a Danish river system. Conservation Genetics, vol. 4, no. 6, pp. 735-747. http://dx.doi.org/10.1023/B:COGE.0000006115.14106.de.
http://dx.doi.org/10.1023/B:COGE.0000006...
; Odo et al., 2009ODO, G.K., NWANI, C.D. and EYO, J.E., 2009. The fish fauna of Anambra River Basin, Mageroa Species abundance and morphometry. Revista de Biología Tropical, vol. 57, no. 1-2, pp. 177-186.; Aliko et al., 2010ALIKO, N.G.G., DA COSTA, K.S., DIETOA, Y.M., OUATTARA, A. and GOURENE, G., 2010. Caractéris-tiques de la population de Distichodus rostratus Günther, 1864 (Pisces: Distichodontidae) du lac de barrage de Taabo (bassin du Bandama, Côte d’Ivoire). Implications pour une gestion rationnelle du stock. Tropicultura, vol. 28, pp. 50-56.). Thus, a critical survey of its ichthyofaunal diversity is important for an improved management plan for the fishery resources and its associated habitat.

Most studies on the Jebba HEP dam have focused exclusively on the upstream section of the dam (KLRI, 1983KAINJI LAKE RESEARCH INSTITUTE – KLRI, 1983. Pre-impoundment studies of Jebba Lake. New-Bussa: Kainji Lake Research Institute.; Ita et al., 1983ITA, E.O., OMORINKOBA, W.S., BANKOLE, N.O. and IBITOYE, B., 1983. A preliminary report on the immediate post-impoundment fishery survey of the newly created Jebba Lake, Nigeria. New-Bussa: Kainji Lake Research Institute, pp. 67-74. Annual report., 1984ITA, E.O., OMORINKOBA, W.S. and BANKOLE, N.O., 1984. Second post-impoundment fishery survey of Jebba Lake. New-Bussa: Kainji Lake Research Institute, pp. 62-75. Annual report.). To date, comprehensive information on the diversity and distribution of freshwater fishes is lacking. Hence, there is a need for an exhaustive inventory of the ichthyofaunal diversity of both up and downstream sections of the dam. Herein, a complete inventory of the fish diversity of the Jebba HEP dam was provided. The objectives of our study are to (1) present a comprehensive checklist of freshwater fishes in the Jebba HEP dam, and (2) compare the patterns of species abundance and distribution across seasons and localities. This study provides baseline information on fish diversity, abundance, and distribution within the Jebba HEP dam. Further, we discussed the environmental challenges affecting the ichthyofauna of the Jebba HEP dam.

2. Material and Methods

2.1. Study area

The Jebba HEP dam lies within the middle belt region of Nigeria between longitude 4°34’12”-4° 43’48”E and latitude 9°10’- 9°55’N (Figure 1). The dam falls within the Guinea savanna eco-region of Nigeria and is characterized mainly with two seasons: dry (November to March) and rainy (April to October) seasons (Adelakun et al., 2017ADELAKUN, K.M., MUSTAPHA, M.K., AMALI, R.P. and MOHAMMED, N., 2017. Seasonal variation in nutritional quality of Catfish (Clarias gariepinus) from Upper Jebba Basin, Nigeria. Journal of Nutrition & Food Sciences, vol. 7, no. 5, pp. 1-4.). The total annual rainfall ranges between 1270-1524 mm, with the highest rainfall observed in August. Monthly temperature is highest (about 30°C) in March, and lowest (about 25 °C) in August (Adelakun et al., 2017ADELAKUN, K.M., MUSTAPHA, M.K., AMALI, R.P. and MOHAMMED, N., 2017. Seasonal variation in nutritional quality of Catfish (Clarias gariepinus) from Upper Jebba Basin, Nigeria. Journal of Nutrition & Food Sciences, vol. 7, no. 5, pp. 1-4.). The dam has a total length of 134 km, the maximum width of 24.1 km, mean and maximum depth of 11 m and 60 m respectively, the surface area of 1270 km2, a volume of 13 × 109 m3, and catchment’s area of 1.6 × 106 km2 (Obot, 1989OBOT, E.A., 1989. The macrophytic flora of the draw - down area of Lake Kainji, Nigeria. African Journal of Ecology, vol. 27, pp. 173-177.). Our study covered the entire Jebba HEP dam, including the upper (Station 1; Jebba North) and downstream (Station 2; Jebba South) stations of the dam. These stations are notable for fishing and are about 8.7 km apart.

Figure 1
Map showing different sampling points within Jebba Hydro-Electric Power, North-central Nigeria.

2.2. Sample collection and species identification

Sampling followed ethical approval number UERC/ASN/2017/991 from the University Ethical Review Committee (UERC), University of Ilorin, Nigeria. Fish samples were collected from January 2017 to December 2018 with the help of local fishermen. Fishes were collected using gill nets, hook and line, and cast net. On collection, representative specimens (2-3 individuals per species) were packed in a box containing ice blocks and transported to the Zoology Laboratory of the Department of Bioscience and Biotechnology, Kwara State University (KWASU), Malete, Nigeria. Specimens were identified following the checklist and keys of the fish identification guide by Olaosebikan and Raji (1998)OLAOSEBIKAN, B.D. and RAJI, A., 1998. Field guide to Nigerian freshwater fishes. New Bussa: Federal College of Freshwater Fisheries Technology., Idodo-Umeh (2003),IDODO-UMEH, G., 2003. Freshwater fishes of Nigeria: taxonomy, ecological notes, diet and utilization. Benin-City, Nigeria: Idodo-Umeh Publ., 232 p. and the FishBase databases (Froese and Pauly, 2017FROESE, R. and PAULY, D., 2017 [viewed 22 April 2019]. FishBase [online]. Available from: http://http://www.fishbase.org
http://http://www.fishbase.org...
). Fishes were individually imaged using digital scanning and later deposited in the Museum of the Department of Bioscience and Biotechnology, KWASU, Malete, Nigeria. To carry out the DNA barcoding of individuals with uncertain species-level identification, tissue samples (tail fin) were collected and preserved in 95% ethanol (Sigma-Aldreich, Germany) and subsequently stored under −80 °C. Vouchers were fixed with 4% formalin and kept in 70% ethanol for long-term storage. Procedures for DNA barcoding for species identification followed the methodology described by Iyiola et al. (2018)IYIOLA, O.A., NNEJI, L.M., MUSTAPHA, M.K., NZEH, C.G., OLADIPO, S.O., NNEJI, I.C., OKEYOYIN, A.O., NWANI, C.D., UGWUMBA, O.A., UGWUMBA, A.A.A., FATUROTI, E.O., WANG, Y.Y., CHEN, J., WANG, W.Z. and ADEOLA, A.C., 2018. DNA barcoding of economically important freshwater fish species from north‐central Nigeria uncovers cryptic diversity. Ecology and Evolution, vol. 8, no. 14, pp. 6932-6951. http://dx.doi.org/10.1002/ece3.4210. PMid:30073057.
http://dx.doi.org/10.1002/ece3.4210...
.

2.3. Diversity analyses

Fish species abundance were determined using the following criteria, ≥10% = dominant, 1-9% = Subdominant, <1% (but caught more than once) = Occasional, <1% (caught only once) = Rare adopting the formula by Benech et al. (1983)BENECH, V., DURAND, J.R. and QUENSIERE, J., 1983. Fish communities of lake chad and associated rivers and flood plains. In: J.P. CARMOUZE, J.R. DURAND and C. LÉVÊQUE, eds. Lake Chad: ecology and productivity of a shallow tropic system. The Hague: Dr. W. Junk Publishers, pp. 293-356. The relative frequency, Simpson’s, Shannon-Wiener diversity index, and Margalef’s index methods using PAST (Hammer et al., 2001HAMMER, Ø.H., DAVID, A.T. and PAUL, D.R., 2001. PAST: paleontological statistics software package for education and data analysis. Palaeontologia Electronica, vol. 4, no. 1, pp. 4-9.).

3. Results

3.1. Species composition and identification

A total of 9605 freshwater fish belonging to 83 species, 43 genera, 24 families and 11 orders were recorded and identified using combined morphological and genetic approaches (Table 1). The combined molecular and morphological approach enabled accurate identification of the following to species-level: Auchenoglanis occidentalis (Cuvier and Valenciennes, 1840), Bagrus bajad (Forskal, 1775), Bagrus docmac (Forskal, 1775), Brienomyrus niger (Günther, 1866), Citharinus citharus (Geoffrey, 1809), Clarias gariepinus (Burchell, 1822), Clarotes laticeps (Ruppel, 1829), Distichodius rostratus (Gunther, 1864), Gymnarchus niloticus (Cuvier, 1829), Hemichromis bimaculatus (Gill, 1862), Heterotis niloticus (Cuvier, 1829), Hydrocynus vittatus (Boulenger, 1898), Labeo senegalensis (Cuvier and Valenciennes, 1842), Lates niloticus (Linnaeus, 1758), Mormyrops anguilloides (Linnaeus, 1758), Mormyrus macrophthalmus (Gunther, 1866), Sarotherodon galilaeus (Linnaeus, 1758), Parachana obscura (Gunther, 1861), Schilbe mystus (Linnaeus, 1758), Synodontis clarias (Linnaeus, 1758), Synodontis membranacea (Geofrey, 1809), Synodontis nigrita (Cuvier and Valenciennes, 1864), Synodontis obesus (Boulenger, 1898), Tetraodon lineatus (Linnaeus, 1758), Coptodon zillii (Gervals, 1848), Malapterurus electricus (Gmeli, 1789), Polypterus senegalus (Cuvier, 1829), and Xynomystus nigri (Gunther, 1868).

Table 1
Checklist of Freshwater Fishes from Jebba Hydroelectric Power Dam, North-Central Nigeria.

Individuals morphologically identified as Chrysichthys nigrodigitatus (Lacepede, 1803), Oreochromis aureus (Steindachner, 1864), Synodontis schall (Bloch and Schneide, 1801) and Protopterus annectens (Owen, 1839) clustered with Chrysichthys sp, Sarotherodon galilaeus, Synodontis aff. bastiani, Protopterus sp respectively (https://minio.scielo.br/documentstore/1678-4375/rwWR4zPQkBvzdcRPRvw7sXG/5fc2027df6ae6060f81896b85a4139773d10df17.pdfAppendix A of the supplementary material), following this, we changed the species’ names as Chrysichthys sp, Sarotherodon galilaeus, Synodontis aff. bastiani, Protopterus sp pending further identification. Further, individuals identified as Ctenopoma sp, Malapterurus sp, and Protopterus sp could not be assigned to species-level using both morphology and genetic data (Appendix A of the supplementary material), thus, referred to genera. Further, we observed that individuals morphologically identified as Dasyatis garouaensis (Stauch and Blanc, 1962) showed a similarity match of 83.10% with Dasyatis microps (India) (Appendix A of the supplementary material). Given the unavailability of sequences for Dasyatis garouaensis, our species identification could be taken as tentative, pending further revision.

3.2. Variation in species composition

Family Mochokidae had the highest number of species (number of species (n) = 17) and fish catch (Number of fish catch (N) = 2439; Relative Frequency (r) = 25.40%; https://minio.scielo.br/documentstore/1678-4375/rwWR4zPQkBvzdcRPRvw7sXG/462b2dcad7ae7f9a91ad2c9b3f588a51351834d6.pdfAppendix b of the supplementary material). Low fish catch (N = 1) and relatively lower frequency of occurrence (r = 0.01%) were recorded for family Anabantidae, Dasyatidae, Notopteridae and Protopteruridae. Moderate population density and frequencies were recorded for other families (Table 1 & Appendix B of the supplementary material) including Characidae (N = 1050; r = 10.93%), Claroteidae (N = 914; r = 9.57%), Cyprinidae (N = 678; r = 7.06%), Citharinidae (N = 592; r = 6.16%), Mormyridae (N = 519; r = 5.40%), Bagridae (N = 447; r = 4.65%), Dischodontidae (N = 356; r = 3.71%), Schilbeidae (N = 327; r = 3.40%), Cetropomidae (N = 302; r = 3.14%), Ariidae (N = 98; r = 1.02%), Clariidae (N = 49; r = 0.51%), Gymnarcidae (N = 36; r = 0.38%), Tetraodontidae (N = 23; r = 0.24%), Malapteruridae (N = 8; r = 0.08%), Polypteruridae (N = 6; r = 0.06%), Osteoglossidae (N = 4; r = 0.04%) and Clupeidae (N = 3; r = 0.03%).

In addition, fewer number of species (n = 1) were recorded for families - Gymnarcidae, Citharinidae, Malapteruridae, Centropomidae, Channidae, Tetraodontidae, Protopteruridae, Osteoglossidae, Dasyatidae, Anabantidae, Notopteridae, Polypteridae and Clupeidae (Table 1). Other families were represented by modest number of species as follows: Cyprinidae (n = 9), Ciclidae (n = 8), Mormyridae (n = 8), Characidae (n = 7), Claroteidae (n = 7), Schilbeidae (n = 4), Clariidae (n = 4), Bagridae (n = 3), Dischodontidae (n = 2); and Ariidae (n = 2) (Table1).

3.3. Overall patterns of species distribution and abundance across sampling stations

Generally, high fish catch frequency was recorded at the upstream (N = 5075) compared to the downstream (N = 4530). The family Cichlidae dominated the upstream (N=1379), while Mochokidae dominated the downstream (N = 1823). Upstream, we recorded high fish catch for O. niloticus (N = 375), T. zilli (N = 309), S. galileaus (N = 141), O. aureus (N = 69), L. niloticus (N = 219), A. bisculatatus (N = 209), B. filamentosus (N = 106), B. docmac (N = 133), C. citharus (N = 405) and D. rostratus (N = 114) (Table 1). Downstream, higher frequency of occurrence were recorded for B. bensoda (N = 267), H. membranaceus (N = 252), S. budgetti (N = 157), S. eupterus (N = 134), S. schall (N = 226) and H. vittatus (N = 118) (Appendix B of the supplementary material). While three (3) species (L. branchypoma, B. lagoensis and C. lazera) were restricted upstream, 16 species were found only downstream of Jebba HEP dam - B. intermedius, M. occidentalis, G. waterloti, R. senegalensis, P. pelucida, S. vemiculatus, S. sorex, S. thomasi, C. batesii, P. annectans, H. niloticus, D. garouaensis, X. nigri, C. kingsleyae, P. senegalus senegalus and L. dekimpel (Table 1).

3.4. Patterns of distribution across seasons

During rainy reason, we observed high fish catch (N = 2434; r = 25.34%) from downstream section compared to upstream (N = 2387; r = 24.85%) (Appendix B of the supplementary material). Comparatively, we recorded relatively higher fish catch from upstream (N = 4688; r = 27.99) during the dry season compared to downstream (N = 2096; r = 21.82). Out of 83 species captured, 61 species (r = 97.60%) were common to both dry and rainy season. However, a total of 62 species (r = 97.88%) were recorded during the dry season, while 82 species (r = 99.74%) were recorded during the rainy season (Appendix B of the supplementary material) from the Jebba HEP dam. During the dry season, an equal number of species (n = 47) were observed at the upstream and downstream sections of the dam. However, during the wet season, we recorded 59 and 79 fish species at the upstream and downstream sections, respectively.

The diversity analyses (Table 2 and Figure 2) showed a significantly higher level of diversity during the rainy season at the downstream compared to the upstream section. At the upstream, high species diversity in rainy season (Margalef = 7.47; H=3.58; 1-D=0.96) was recorded compared to the dry season (Margalef = 5.81; H = 3.37; 1-D = 0.96) (Table 2). Similarly, at the downstream, high species diversity was recorded during the rainy season (Margalef = 9.73; H= 3.95; 1-D=0.98) compared to dry season (Margalef = 6.26; H=3.37; 1-D=0.96) (Table 2).

Table 2
Diversity Indices for the Seasonal Distribution of Freshwater Fishes from the Jebba Hydroelectric Power Dam, North-central Nigeria.
Figure 2
(A) Shannon-Weiner and (B) Margelef’s richness indices showing seasonal changes in fish species richness and diversity in the Jebba Hydro-Electric Power, North-central Nigeria.

4. Discussion

A total of 83 fish species belonging to 24 families recorded in this study presents a more comprehensive inventory of ichthyofauna of the Jebba HEP dam when compared with previous studies (e.g., Ita et al., 1983ITA, E.O., OMORINKOBA, W.S., BANKOLE, N.O. and IBITOYE, B., 1983. A preliminary report on the immediate post-impoundment fishery survey of the newly created Jebba Lake, Nigeria. New-Bussa: Kainji Lake Research Institute, pp. 67-74. Annual report.; Ita, 1993ITA, E.O. 1993. Inland fishery resources of Nigeria. Rome: FAO. CIFA Occasional Paper, no. 20.). This current record was higher when compared to 51 species (12 families) recorded by Abiodun and Odunze (2011)ABIODUN, J.A. and ODUNZE, F.C., 2011. Fish composition of Jebba Lake, Nigeria. Nigerian Journal of Fisheries and Aquaculture, vol. 8, no. 2, pp. 284-290.. The present study benefits from having broader coverage and a more comprehensive sampling across the Jebba HEP dam than the other studies and, thus, it marks the beginning of a better understanding of ichthyofaunal diversity and distribution across the Jebba HEP dam. In addition, most of the fish species recorded in this present study have been reported to be present in Nigerian inland waters (Ita et al., 1983ITA, E.O., OMORINKOBA, W.S., BANKOLE, N.O. and IBITOYE, B., 1983. A preliminary report on the immediate post-impoundment fishery survey of the newly created Jebba Lake, Nigeria. New-Bussa: Kainji Lake Research Institute, pp. 67-74. Annual report., 1984ITA, E.O., OMORINKOBA, W.S. and BANKOLE, N.O., 1984. Second post-impoundment fishery survey of Jebba Lake. New-Bussa: Kainji Lake Research Institute, pp. 62-75. Annual report., 1985ITA, E.E., SADO, E.K., BALOGUN, J.K., PANDOGORI, A. and IBITOYE, B., 1985. Inventory survey of Nigerian inland waters and their fishery resources: a preliminary checklist of inland water bodies in Nigeria with special reference to Ponds, Lakes Reservoirs and major Rivers. New-Bussa: Kainji Lake Research Institute. Technical Report Series, no. 14.; Akinyemi et al., 1986AKINYEMI, O., ITA, E.O. and SADO, E.K., 1986. A preliminary assessment of the post impoundment fisheries of Lake Eleiyele and Lake Asejire, Oyo State, Nigeria. New-Bussa: Kainji Lake Research Institute, pp. 44-50. Annual Report.; Ita, 1993ITA, E.O. 1993. Inland fishery resources of Nigeria. Rome: FAO. CIFA Occasional Paper, no. 20.; Olaosebikan and Raji, 1998OLAOSEBIKAN, B.D. and RAJI, A., 1998. Field guide to Nigerian freshwater fishes. New Bussa: Federal College of Freshwater Fisheries Technology.; Sikoki et al., 1998SIKOKI, F.D., HART, A.I. and ABOWEI, J.F.N., 1998. Gill net selectivity and fish abundance in the lower Nun River, Bayelsa State, Nigeria. Journal of Applied Science & Environmental Management, vol. 1, pp. 13-19.; Abiodun and Odunze, 2011ABIODUN, J.A. and ODUNZE, F.C., 2011. Fish composition of Jebba Lake, Nigeria. Nigerian Journal of Fisheries and Aquaculture, vol. 8, no. 2, pp. 284-290.; Allison and Okadi, 2013ALLISON, M.E. and OKADI, D., 2013. Gill net selectivity, seasonal, tidal and photoperiod variation in catch in Lower Nun River, Niger Delta, Nigeria. Scientific Research and Essays, vol. 8, no. 3, pp. 108-114.; Oguntade et al., 2014OGUNTADE, O.R., OKETOKI, O.T., UKENYE, E.A., USMAN, B.A. and ADELEKE, M.T., 2014. Survey of the present and fast disappearing fish species along two rivers in Niger Delta, Nigeria. Su Ürünleri Dergisi, vol. 9, no. 5, pp. 352-358.; Oladipo et al., 2018bOLADIPO, S.O., MUSTAPHA, M.K., SULEIMAN, L.K. and ANIFOWOSHE, A.T., 2018b. Fish composition and diversity assessment of Apodu Reservoir, Malete, Nigeria. International Journal of Fisheries and Aquatic Studies, vol. 6, no. 2, pp. 89-93.; Mustapha, 2010MUSTAPHA, M.K., 2010. Fish fauna of Oyun reservoir, Offa, Nigeria. Journal of Aquatic Sciences, vol. 25, no. 1, pp. 106-114.). Also, the use of combined morphological and molecular approaches enabled us to unravel species identity as well as discover possible potential new species (Ctenopoma sp, Malapterurus sp and Protopterus sp) from the area. Studies involving combined molecular, morphological, and ecological data are needed to ascertain if these species represent new species or sub-species for the area.

In comparison, species diversity (n = 83) recorded in our work was higher compared to other freshwater bodies in Nigeria such as Asa river (n = 21; Omotosho, 1997OMOTOSHO, J.S., 1997. Icththyofauna diversity of Asa reservoir, Ilorin Nigeria. Biosciences, vol. 36, pp. 37-48.), Alau Lake (Idowu and Eyo, 2005IDOWU, R.T. and EYO, J.E., 2005. Fisheries status and fishing gears of a West African arid zone lake. Animal Research International, vol. 2, no. 2, pp. 353-357.), Anambra basin (n = 52; Odo et al., 2009ODO, G.K., NWANI, C.D. and EYO, J.E., 2009. The fish fauna of Anambra River Basin, Mageroa Species abundance and morphometry. Revista de Biología Tropical, vol. 57, no. 1-2, pp. 177-186.); Oyun reservoir (n = 18; Mustapha, 2010MUSTAPHA, M.K., 2010. Fish fauna of Oyun reservoir, Offa, Nigeria. Journal of Aquatic Sciences, vol. 25, no. 1, pp. 106-114.); Usuma reservoir (n = 11; Ataguba et al., 2014ATAGUBA, G.A., TACHIA, M.U. and AMINU, G., 2014. Fish species diversity and abundance of Gubi Dam, Bauchi State of Nigeria. Biological Diversity and Conservation, vol. 7, no. 2, pp. 1-9.) and Apodu reservoir (n = 17; Oladipo et al., 2018bOLADIPO, S.O., MUSTAPHA, M.K., SULEIMAN, L.K. and ANIFOWOSHE, A.T., 2018b. Fish composition and diversity assessment of Apodu Reservoir, Malete, Nigeria. International Journal of Fisheries and Aquatic Studies, vol. 6, no. 2, pp. 89-93.). The observation made on species dominance was lower compared to other Nigerian water bodies e.g., Eko-Ende and Owalla reservoirs (Taiwo, 2010TAIWO, Y.F., 2010. Fish diversity in two reservoirs in Southwest Nigeria. In: 25th Annual Conference of the Fisheries Society of Nigeria (FISON), 25-29 October 2010, Lagos, Nigeria, pp. 258-265.), Majidun Creek (Lawson et al., 2013LAWSON, E.O., DOSEKU, P.A. and AJEPE, R.G., 2013. Fish assemblage of Majidun Creek, Lagos, Nigeria. The Journal of Biological Sciences, vol. 13, no. 7, pp. 577-586. http://dx.doi.org/10.3923/jbs.2013.577.586.
http://dx.doi.org/10.3923/jbs.2013.577.5...
) and coastal waters of Ondo State (Bolarinwa et al., 2015BOLARINWA, J.B., FASAKIN, E.A. and FAGBENRO, A.O., 2015. Species composition and diversity of the coastal waters of Ondo State, Nigeria. International Journal of Research in Agriculture and Forestry, vol. 2, no. 3, pp. 51-58.). The differences in the observed species diversity could be attributed to the size of the river, locations of sampling, the time frame of sampling, and the combination of sampling nets. Our study, with its wider coverage, enabled recovery of fish species that would otherwise remain undetected if sampled within a limited time frame and season.

Of interest to our study are the families Cichlidae and Mochokidae. Similar to previous studies on the Nigerian freshwater ecosystem (Ita and Balogun, 1982ITA, E.O. and BALOGUN, J.K., 1982. Report of the pre-impoundment fishery survey of Goronyo Reservoir, Sokoto State, Nigeria. Nigeria: Sokoto Rima Basin Development Authority, 86 p.; Balogun, 2005BALOGUN, J.K., 2005. Fish distribution in a small domestic water supply reservoir: a case study of Kangimi Reservoir, Nigeria. Journal of Applied Science & Environmental Management, vol. 9, no. 1, pp. 93-97.; Owolabi, 2008OWOLABI, O.D., 2008. The dietary habits of the upside-down catfish, Synodontis membranaceus (Osteichthyes: Mochokidae) in Jebba lake, Nigeria. International Journal of Tropical Biology, vol. 56, no. 2, pp. 931-936. PMid:19256454.), high species diversities for families Cichlidae (N = 1754) and Mochokidae (N = 2439) were observed. Cichlids have been known to dominate dams in the Nigerian freshwater ecosystem (Mustapha, 2010MUSTAPHA, M.K., 2010. Fish fauna of Oyun reservoir, Offa, Nigeria. Journal of Aquatic Sciences, vol. 25, no. 1, pp. 106-114.). Besides, Mochokids have been reported to be abundant in the Jebba HEP dam (Ita, 1978ITA, E.O., 1978. Analysis of fish distribution in Kainji Lake, Nigeria. Hydrobiologia, vol. 58, no. 3, pp. 233-244. http://dx.doi.org/10.1007/BF02346958.
http://dx.doi.org/10.1007/BF02346958...
; Ita and Balogun, 1982ITA, E.O. and BALOGUN, J.K., 1982. Report of the pre-impoundment fishery survey of Goronyo Reservoir, Sokoto State, Nigeria. Nigeria: Sokoto Rima Basin Development Authority, 86 p.; Balogun, 2005BALOGUN, J.K., 2005. Fish distribution in a small domestic water supply reservoir: a case study of Kangimi Reservoir, Nigeria. Journal of Applied Science & Environmental Management, vol. 9, no. 1, pp. 93-97.). Similarly, Cichlidae and Mochokidae have been known to be present in high abundance in the lower River Niger basin (Oyewo, 2005OYEWO, S.D., 2005. A survey of fish species diversity and abundance in Dogon Ruwa water body of Kamuku National Park, Birnin Gwari, Kaduna State, Nigeria. Zaria: Ahmadu Bello University. M.Sc dissertation.; Atile et al., 2016ATILE, J.I., SHIMA, J.N. and AKOMBO, P.M., 2016. Food and feeding, length-weight and condition factor of the catfish Synodontis membranaceus (Etiene Geoffroy Saint Hilaire, 1809) (Osteichthyes: Mochokidae) from Lower Benue River, Makurdi, Nigeria. Agriculture. Forestry and Fisheries, vol. 5, no. 4, pp. 87-96. http://dx.doi.org/10.11648/j.aff.20160504.11.
http://dx.doi.org/10.11648/j.aff.2016050...
; Abiodun and John, 2017ABIODUN, J.A. and JOHN, P., 2017. Biodiversity and abundance of fish and some processing methods in Lower Niger River, Idah, Kogi State, Nigeria. Nigeria Journal of Fisheries and Aquaculture, vol. 5, no. 2, pp. 20-25.). The dominance of these families could be in relation to their prolific breeding capabilities and high adaptation to varying environmental conditions (Mustapha, 2010MUSTAPHA, M.K., 2010. Fish fauna of Oyun reservoir, Offa, Nigeria. Journal of Aquatic Sciences, vol. 25, no. 1, pp. 106-114.; Araoye, 1999ARAOYE, P.A., 1999. Spatio-temporal distribution of the fish Synodontis schall (Teleostei: Mochokidae) in Asa lake, Ilorin, Nigeria. Revista de Biología Tropical, vol. 47, no. 4, pp. 1061-1066.).

The diversity analyses revealed high species richness and diversity at the downstream section of the Jebba HEP dam, although all sampling localities had a high level of fish species richness. This implies that environmental conditions at the downstream section were conducive for species to thrive and reproduce effectively. In addition, the diversity indices revealed higher number of species and frequency of occurrence both in rainy and dry seasons. The result, therefore, showed Jebba HEP dam represents an important area with good potentials for fisheries and aquaculture.

In conclusion, this present study shows that Jebba HEP dam comprises a high number of fish diversity that faces challenges due to the unregulated fishing gear and poor conservation techniques. These challenges could be attributed to a low level of conservation awareness among the fishermen, inappropriate fishing laws, and lack of adequate fishing regulations in the community. Hence, the implementation of effective fishing regulations, as well as community-based conservation awareness in the area, are necessitated. For instance, conservation awareness geared towards educating the local community on the need for proper management and controlled fishing in the area will improve the understanding of the fishermen on the need for sustainable fishing activities. Finally, this study has provided vital information on the biodiversity of freshwater fishes in the Jebba HEP dam and Nigeria as a whole.

Acknowledgments

The study was funded by the Federal Government of Nigeria through TETFUND and Kwara State University, Malete. The authors thank the management of Mainstream Energy Solution for approving the fieldwork, Mrs. Roseline Adeshike Oladipo (Interpreter and field assistant) and Jebba artisanal fishermen, for their support during the field survey.

  • #Equal contribution/first authorship
  • (With 2 figures)

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Publication Dates

  • Publication in this collection
    20 July 2020
  • Date of issue
    Mar-May 2021

History

  • Received
    22 Apr 2019
  • Accepted
    27 Nov 2019
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