Influence of a new impoundment on pesticide concentrations in warmwater fish, Saylorville Reservoir, Des Moines River, Iowa, 1977-78.

Samples of seven species of warmwater fish were collected above, within, and below newly impounded Saylorville Reservoir, Des Moines River, Iowa, from October 1977 to October 1978. Whole-body analyses by gas chromatography were significantly higher in river carpsucker (Carpiodes cyanazine and for the organochlorine insecticides dieldrin, p,p'-DDE, p,p'-TDE, p,p'-DDT, and heptachlor epoxide. Only the organochlorine insecticides were detected in fish tissue. Concentrations of dieldrin and heptachlor epoxide were significantly higher in river carpsucker (Carpiodes carpio) from the reservoir than in those from the river. Other species of fish showed no differences in pesticide concentration related to locality of collection.

Organochlorine insecticide concentrations in fish of the Des Moines River, Iowa, 1977-78.

Organochlorine insecticides were measured in fish of the Des Moines River, Iowa, in 1977 and 1978 to determine whether concentrations exceeded allowable levels and to compare differences among species. Significant differences in mean concentrations of dieldrin, sigma DDT, and heptachlor epoxide in whole-body samples of seven species of fish, Dorosoma cepedianum, Carpiodes carpio, Cyprinus carpio, Ictalurus punctatus, Pomoxis annularis, Micropterus salmoides, Stizostedion vitreum, could not be adequately explained by body size, position of species in the food chain, or percent body fat.

Persistence of dieldrin water and channel catfish from the Des Moines River, Iowa, 1971-73 and 1978.

This study was conducted to determine if dieldrin concentrations in water and fish of the Des Moines River, Iowa, decreased after registration of the compound was withdrawn by the Environmental Protection Agency in 1975. Mean June concentrations of dieldrin in river water decreased from 50 ppt in 1971 to 11 ppt in 1978. Average daily transport of dieldrin was 156 g in 1971 and 70 g in 1978. July levels in channel catfish muscle were 75 ppb in 1973 and 46 ppb in 1978. Dieldrin was still present in significant concentrations in the aquatic system 3 years after registration withdrawal.

Variations in DDT concentration in muscle tissue of channel catfish, Ictalurus punctatus, from the Des Moines River, 1971.

Concentrations of DDT in muscle tissue of channel catfish, Ictalurus punctatus, from the Des Moines River, Iowa, were compared in relation to length, age, sex, and fat content. Residue concentrations were not correlated with sex. Although residue concentrations were significantly correlated with size-related factors and fat content, they varied widely. Therefore, predictions of DDT concentrations in individual catfish on the basis of length, age, or muscle fat content may be grossly inaccurate.

Seasonal concentrations of dieldrin in water, channel catfish, and catfish-food organisms, Des Moines River, Iowa--1971-73.

Concentrations of dieldrin in aquatic insects, crayfish, minnows, and small carpsuckers, and muscle tissue of channel catfish (Ictalurus punctatus) were compared with the dieldrin content of Des Moines River water in 1971-73. Monthly mean concentrations of dieldrin in river water and most aquatic organisms were highest in June and July, soon after aldrin had been applied to corn land in the watershed. Several groups of aquatic organisms also exhibited high dieldrin levels in the fall when the dieldrin content of river water was seasonally low. The influence of temperature on metabolic rate and enzyme activity and the differences in body fat content were suggested as probable causes of variations observed in the dieldrin content of aquatic organisms.