Downstream changes in the composition,numbers and biomass of bottom fauna in the Tees below Cow Green Reservoir and in an unregulated tributary Maize Beck,in the first five years after impoundment

Changes in composition, numbers and biomass of benthic fauna of the Tees below Cow Green Reservoir and an unregulated tributary Maize Beck were followed between 1972 and 1975 and pre- and post-impoundment conditions were compared. Species diversity was lowest just below the dam and numbers and biomass were highest 240 m downstream of the dam. Faunal densities increased in the Tees after impoundment but in Maize Back no major changes were observed.Freshwater Biological Association, Cow Green UnitFreshwater Biological Association, Cow Green Unit