Estimate of Production By a Population of Fathead Minnows, Pimpephales promelas, In a South Dakota Prairie Wetland

Estimates of production and population densities were obtained for an autochthonous population of fathead minnows, Pimephales promelas Rafinesque, in a South Dakota prairie wetland. The study was conducted from May to September of 1976. Population estimates were obtained using a Schnabel-type mark and recapture model. Fish were marked either by fin clipping or granular fluorescent pigments driven into the dermal tissue. Production estimates were derived both arithmetically and graphically. The estimated population of adult fathead minnows declined from 194 in May and June to 26 in July. Production by adults was estimated at 0.10 kg, or 0.0007 gm/m²/yr. The population of young-of-the-year fathead minnows was estimated at 21,020 in July; 126,505 in August; and 105,297 in September. Production by young-of-the-year was estimated at 174.99 kg, or 1.75 gm/m²/yr. Young-of-the-year contributed more than ninety-nine percent of the total net production, which was estimated at 175.09 kg, or 1.75 gm/m²/yr. Chapman (1967) reported that lentic waters in temperate regions have produced 2 to 15 gm/m²/yr. where a single species predominated. Production by fathead minnows in Pickering Slough was probably underestimated as a result of: 1) low initial brood stock density (less than five per acre); 2) receding water levels through the study period; 3) exclusion of sexual products form the estimate of net production; 4) exclusion of production by fry not surviving to be censused; and 5) exclusion of production in September and October