Annual cycles of macro-invertebrates of a river in southern Ghana
The results of a quantitative study of the benthic invertebrates of a riffle area in the upper reaches of the Pawmpawm River in the forest of southern Ghana are presented. The investigation was carried out over a period of 17 months with a Surber Sampler. The seasonal fauna changes are discussed in relation to changes both in water flow and in the vegetational substrate, and a model for the succession of recolonization of the river after the resumption of flow is outlined. The earliest colonizers of the river were primary consumers, Chironomidae, Centroptilum and Simulium., which were followed after a few weeks (once a mat of vegetation had become established) by the carnivorous Cheumatopsyche (Trichoptera) and Centroptiloides (Ephemeroptera). After 2 to 3 months, the attached vegetation matured and was able to support a greater diversity of fauna. The strategy of survival in intermittent tropical rivers is discussed and it is concluded that recolonization from eggs laid by flying adults is the most important method.