Michigan Department of Natural Resources
Fisheries Research Report No.1878, 1979

Introduction of Chlorinated Hydrocarbons Into Stream Fishes by Spawning Salmon


James W. Merna


      Abstract.-The extent of contamination with chlorinated hydrocarbons of trout resident in two small streams by spawning coho and chinook salmon was determined. An attempt was made to trace PCB, DDT, and dieldrin through the aquatic system following their release from decaying salmon carcasses.

No retention of contaminants within the food chain was found. Analysis of stream sediments and crayfish failed to reveal measurable concentrations. However, trout, and to a lesser extent sculpins, accumulated PCB and DDT as a result of eating contaminated salmon eggs. Eggs constituted as much as 87% (by weight) of the total stomach contents of trout collected during the salmon spawning season. The PCB level in salmon eggs ranged from 0.46 to 9.50 ppm, and they were found in trout stomachs from early October to early January. Thus the diet of trout carried a significant level of contamination for a period of at least 90 days. Utilization of eggs was highly variable among individual trout, and there was a strong correlation between numbers of eggs in the stomachs and PCB levels in the fillets. Concentrations of chlorinated hydrocarbons in trout fillets ranged from 0. 20 to 4.63 ppm of PCB and 0. 11 to 2.52 ppm of DDT. These materials were never detected in samples from the control stream.