Biodiversity and Community Structure of Mormyridae (Pisces: Teleostei: Osteoglossiformes) from Niger River in Northern Benin: Threats, Conservation and Valorization Perspectives

Kayodé Nambil Adjibade,Stanislas Pejanos Sonon,Alphonse Adite,Rachad Sidi Imorou,Hamidou Arame

doi:10.18483/ijsci.2068

Abstract

Mormyrid fishes are of great commercial and economic importance in the artisanal fisheries of the Niger River in Benin. We investigated species composition and community structure of this taxa in order to contribute to species management and sustainable exploitation. Mormyrid individuals were collected monthly from February 2015 to July 2016 using cast nets, gill nets and seines. Among a total of 6825 individuals collected, eleven (11) species belonging to 9 genera were inventoried. Numerically, Marcusenius senegalensis dominated the fish assemblages and made 43.74% of the mormyrid sub-community followed by Mormyrus macrophthalmus (14.87%), Hyperopisus bebe, (11.43%), Petrocephalus bovei (11.21%), Mormyrus rume (8.54%) and Hippopotamyrus pssittacus (4.69%). The Shannon-Weaver index of species diversity was moderate and reached H’=2.54. Overall, percentage occurrences (PO) of Mormyrids in the 5 selected sites ranged between 40 and 100%, with Marcusenius senegalensis (PO=100%) and Hyperopisus bebe (PO=100%) widely distributed in all 5 sites. In the Niger River, Mormyrid abundances significantly (r=0.70; P<0.01) increased with dissolved oxygen. The overexploitation and other antropogenic disturbances such as domestic uses (ditch cleanings, clothe washings, bathings), invasion of floating plants (Echhornia crassipes), sand dragging, human wastes dumping, the use of chemical fertilizers and pesticides for adjacent agriculture etc. constituted some major threats for the growth and survival of the Mormyrids in the Niger River. The results of this study will contribute to design a holistic species management scheme that includes habitat protection, species conservation and valorization.

Highlights

The fishes of the Mormyridae family are of high commercial and fisheries importance and display a very large distribution in tropical Africa
Marcusenius senegalensis was the most abundant species and made 43.74% of the mormyrid sub-community followed by Mormyrus macrophthalmus (14.87%), Hyperopisus bebe, (11.43%), Petrocephalus bovei (11.21%), Mormyrus rume (8.54%) and Hippopotamyrus pssittacus (4.69%) (Table 2)
Marcusenius senegalensis alone accounted for about 37% of the fish assemblages, followed by Mormyrus rume (25.11%), Hyperopisus bebe (19.03%), Mormyrus macrophthamus (9%), Mormyrops anguilloides (3.02%) and Petrocephalus bovei (2.57)

Summary

Introduction

The fishes of the Mormyridae family are of high commercial and fisheries importance and display a very large distribution in tropical Africa. These weakly electrical fishes are endemic in African riverine ecosystems and among the Osteoglossiformes, the Mormyridae is the most speciose family comprising 22 genera and about 228 species (Hopkins et al, 2007; Kisekelwa et al, 2016; Rich et al, 2017). The species of this family occurred in water bodies and streams such as Tchad (Blache , 1964), Congo, Ebrié, Kainji, Malawi, Tanganyika, Bagoé, Sassandra (Daget and Iltis, 1965), Bandama, Comoé, Bénoué (Daget, 1960; Lowe-McConnell, 1969; Hopkins et al, 2007) etc. The fishes show a nonprotrusible mouth with a snout of variable forms (see description in Adjibade, 2019)

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Discussion

Conclusion