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, Maiduguri Borno state, were studied from October 2001 to September 2002. Three patterns of seasonal abundance were found, maximal abundance during the rainy season (July-September), moderate abundance during the harmattan season (November-February) and minimal abundance in the dry hot season (March-June). Significant dif erences 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 29 86% and 27 7%. The least was from the families Lymnaci dae w h ota number of 116 and 3.44% as the percentage composi on. The abundance of the molluscs was positively and significantly correlated at 5% confidence with temperature (r = 0.675), dissolved oxygen (r = 0.832), phosphate (r = 0.528).

Seasonal Abundance and Distribution of Freshwater Snails in Different Beels of Gopalganj District, Bangladesh

“…Subsiding process is still active in this physiographic unit. Idowu [2] observed that "shallow Lake often with a well-developed littoral vegetation are often more productive than deep lakes and particularly in the tropics, they are important source for fisheries and other aquatic fauna products". Gopalganj district of Bangladesh has lots of beels with shallow water area from where people collect huge amount of Mollusca species from the time immemorial.…”