Michigan Department of Natural Resources
Fisheries Research Report No.1852, 1977

Results of Short-Term Exposure of Stream Organisms to Methoxychlor


James W. Merna and Paulette Queerer


      Abstract.-Experimental streams at the Saline Fisheries Research Station, Michigan Department of Natural Resources, were dosed with methoxychlor to simulate a blackfly control treatment. A series of six matched streams was used in the experiment. A 15-minute injection of methoxychlor was made into the treated streams. Two streams were treated at 200 m g/l, two at 600 m g/l, and two untreated streams served as controls.

An immediate increase in drift of benthic organisms was visually evident during treatment. Isopoda, Ephemeroptera, and Chironomidae were the most abundant organisms in the drift. Despite the significant increase in drift, the population of benthic organisms did not appear to be depleted. Hester-Dendy plate samplers showed no difference in macroinvertebrates between control and dosed streams following treatment.

Yellow perch (Perca flavescens) accumulated methoxychlor very rapidly in body tissues. Mesenteric fat samples from one of the high-level streams exceeded 200 m g/l 24 hours after dosing. The perch did not utilize the drifting benthos that were available during dosing, so it appears that the methoxychlor was not accumulated through the food chain,

Perch which were not sampled for tissue analysis remained in the streams for 3 months following dosing. The streams were then drained and all fish were collected. The perch in the high-level streams experienced a high, delayed mortality (42%) compared with perch in the low-level (18%) and control streams (8%).