Annual production by the slimy sculpin, Cottus cognatus Richardson, was estimated at 59.4 kg/hectare wet weight for the period July, 1970, to July, 1971, in Valley Creek, Minnesota. Mark-and-recapture population estimates made by electrofishing and aging with otoliths were the bases for determining mean biomass and instantaneous growth rates. Annual turnover ratio, i.e., ratio of annual production to mean standing crop, was 1.2. Unusual silt and turbidity conditions, occurring in 1971, reduced the 1971 year class drastically, but had less serious effects on total production by all age groups. Food of the sculpins was similar in most respects to that of the brook trout inhabiting the same stream. Young sculpins fed heavily on small dipterans, mainly chironomids; older sculpins fed mainly on Gammarus and Trichoptera larvae. Comparisons with annual production estimates for brook (Salvelinus fontinalis) and rainbow trout (Salmo gairdneri), made previously in Valley Creek for comparable time periods, suggested a normal total annual production for all fishes of about 200 kg/hectare, with sculpins contributing about 1/3 and trout about 2/3.