THE POPULATION OF FISH AT COW GREEN, UPPER TEESDALE, BEFORE IMPOUNDMENT.

The population density, growth, biomass, fecundity and production of fish were estimated with the Tees River, England and different streams of the proposed reservoir basin. The fish species present were brown trout, bullhead and minnow. Trout were widespread throughout the study area, whereas bullhead and minnow were confined to the main river of the proposed reservoir. Trout growth was slow and compared with published estimates from other waters, whereas the minnow showed god growth. The range in numbers of O group fish was considered to be a reflection of variation in survival between time of oviposition and the period when the fry first became vulnerable to capture by electro-fishing.