Molluscan Population Of An African Arid Zone Lake

Abstract

The species composition, abundance and distribution of molluscs population together with some physico-chemical variables from five different stations in the littoral region of lake Alau, MaiduguriBorno state, were studied from October 2001 to September 2002. Three patterns of seasonal abundance were found, maximal abundance duringthe rainy season (July -September), moderate abundance during the harmattan season (November – February) and minimal abundance in the dry hot season (March - June). Significant diferences in species composition and abundance of the molluscs were found between stations studied. The total number of organisms recorded was 3368 comprising of 1924 Bivalves and 1544 Gastropoda. 8 families were recorded which includes Bithyniidae, Hydrobiidae, Lymnaeidae, Physidae, Valvatidae, Vivipariidae, Sphaeridae and Unionidae while 15 species were observed in this study. The predominant families in terms of total number collected from all stations Sphaeridae and Unionidae recording 1006 and 933 organisms with the percentage compositions of 2986% and 277%. The least was from the families Lymnacidae wh ota number of 116 and 3.44% as the percentage composion. The abundance of the molluscs was positively and significantly correlated at 5% confidencewith temperature (r =0.675), dissolved oxygen (r = 0.832), phosphate (r = 0.528).

Keywords: Molluscs, Littoral Region, Abundance, Unionidae

Animal Research International Vol. 4 (2) 2007 pp. 680-684