A quantitative study of the invertebrate fauna of the River Tees below Cow Green Reservoir

摘要: Summary Monthly samples were taken in the River Tees below Cow Green dam from four sites differing flow conditions, by means of trays containing stones river, which immersed for a period 1 month. Information on distribution, abundance and biomass benthos is given with additional data life-histories some more common species, during May 1971 to 1972. Of seventy-two taxa found, fourteen made up 95% total numbers. Hydra, Polycentropodidae, molluscs Limnaea peregra Ancylus fluviatilis most abundant animals slower-flowing water (10–26 cm s−1) Simuliidae, Orthocladiinae, Baetis rhodani dominate riffle (50–75 fauna numerically. Some organisms, Nais spp., Caenis rivulorum scambus favoured intermediate flows 20–60 s−1. The slowest-flowing contained largest number site fastest supported least. A mean monthly weight per square metre 14·56 g (95% limits 7 31) was calculated using all sites. The frequency distribution nymphal size-classes B. scambus, C. rivulorum, Ephemerella ignita, Brachycentrus subnubilus, association certain particular analysed. The composition discussed. It suggested that relative richness terms attributable organic enrichment river following building dam. regulation has allowed dense growth algae mosses, development large molluscan populations, reservoir itself provides rich source food, particularly zooplankton phytoplankton, benthos.