Seasonal variations in the benthos of a chalk trout stream, the River Samson, Belgium

摘要: Seasonal variations in the benthos of a Belgian chalk stream were investigated. Total biomass varies extensively over year (30 to 100 g wet wt. m−2). In summer, however, it is smaller than fish biomass. Densities range from 30 000 50 individuals m−2, but actual number taxa always near 60. Diversity indices (Shannon-Weaver and Pielou) exhibit slight fluctuations. Numerical are minimal winter when flood. Gravimetric spring maximal. Species-abundance curves almost indicate fauna with many rare species, with, also, some indication second maximum moderately abundant species. Six dominate: Oligochaeta, Gammarus fossarum, Ephemeroptera, Coleoptera, Trichoptera Diptera. There great fluctuations their relative importance year. Thus, there seems be succession peaks densities individual permitting more efficient utilization resources. However, depend on species involved. As general rule, precedes density.