Tropicultura (Jan 2013)
Croissance de Auchenoglanis occidentalis (Pisces, Claroteidae) dans le Delta Central du Niger (Mali, Afrique de l'ouest)
Abstract
Growth of Auchenoglanis occidentalis (Pisces, Claroteidae) in the Central Delta of Niger River Flood Plain (Mali, West Africa). Growth biology of Auchenoglanis occidentalis (Valenciennes, 1840) is studied from individuals monthly sampled on two different annual cycles (1991 and 1997) in the fishing port of Mopti. Individual age of fishes was determined by squelettochronology. Chronological follow-up of relative margin diameter (dr) of spine ray section was used for validation of the periodicity of annulus formation. Only one annulus is formed annually. Period of growth recovery shows an individual variability with an early starting up from the lowwater level, in May. The seasonal cycle of growth of this benthic fish, A. occidentalis, depends more on the availability of the trophic resources than of abiotic factors. However, the optimal period of growth always remains the high-water one in this river with flood plain. Fishes condition factor's varies between 1.97±0.27 à 2.57±0.41. Year x season interaction affects this parameter. Growth realized during the first year (189.17±4.57 and 261.25±12.19 mm) as well as the later growths depend on hydrological conditions and are influenced by fishing pressure. Presence of 3+ age class fishes shows that demographic structure is not qualitatively modified despite changes arisen in the Delta.
