Aspects of life-history strategy of Marcusenius senegalensis (Pisces: Osteoglossiformes: Mormyridae; Steindachner, 1870) from Niger River in Northern Benin

Abstract

Marcusenius senegalensis (Steindachner, 1870) is the dominant mormyrid in Niger River in Northern-Benin where this fish species constitutes an important component of artisanal fisheries. The current study documented the reproductive biology of M. senegalensis in order to contribute to management and sustainable exploitation. Monthly samplings were conducted between February 2015 and July 2016 using gillnets, cast net, and seine. Males dominated the population with a sex ratio of 1:0.96 in favor of males. Sizes at first sexual maturity were 167.89 mm-TL for males and 163.81 mm-TL for females. Monthly gonadosomatic index (GSI) averaged 0.12 ± 0.09 for males and 1.32 ± 1.56 for female and peaks recorded indicated that spawning occured from June to September. Fecundity were moderate to low (844 – 12,643 eggs) and significantly (p < 0.05) increased with total length and body weight. Thespecies showed egg diameters varying between 0.21 and to 1.77 mm and ovaries comprised oocytes at all stages of maturation indicating that M. senegalensis displayed a multi-spawning behavior. Marcuseniussenegalensis exhibited a demographic strategy between r and K, yet more inclined towards K-selected strategy. In Niger River, reproduction grounds were being severely degraded affecting recruitment and stocks. The current findings are valuable data to design a species management scheme that should includes spawning ground protection, species conservation and valorization and fisheries/aquaculture development.