Trends in Mirex Residue Levels in Lake Ontario Salmon – 1977 to 1992: Also Included Levels for Photomirex, DDT, DDD, DDE, PCB and Dieldrin

Abstract

Chinook salmon (Oncorhynchus tshawytscha) collected from Lake Ontario during the fall of 1992 were analyzed for mirex, photomirex, DDT, DDD, DDE, PCBs and dieldrin. Mirex in fillet tissue ranged from 0.095 to 0.48 mg/kg (mean= 0.24 mg/kg). Analysis of variance (ANOV A) revealed no significant difference (P=0.285) between mean mirex residue values for fish collected in 1977, 1982, 1986 and 1992. However, analysis of covariance (ANCOVA), considering the covariate weight, indicated a statistically significant difference between 1977 and 1982, 1986 and 1992 mirex levels (P=0.001). Comparison of 1982, 1986 and 1992 by ANCOVA revealed no significant decrease in mirex levels. The following chlorinated hydrocarbons were also detected in fish tissue: photomirex (mean = 0 .10 mg/kg), DDT (mean= 0.17 mg/kg), DDD (mean= 0.071 mg/kg), DDE (mean= 0.82 mg/kg) and PCB (mean= 0.85 mg/kg). Dieldrin was only detected in the egg samples.