Residues of Mirex and Photomirex in Eggs and Fillets of Lake Ontario Coho and Chinook Salmon

Abstract

Coho (Oncorhynchus kisutch) and chinook (O.tshawytscha) salmon collected from Lake Ontario during the fall of 1986 were analyzed by gas chromatography for mirex and photomirex residues. Mirex in fillet tissue (n=24) ranged from 0.015 to 0.41 mg/kg (mean= 0.19 mg/kg). Photomirex concentrations ranged from nondetectable (in two samples) to 0.18 mg/kg (mean= 0.080 mg/kg). Mirex in egg samples (n = 5) ranged from nondetectable to 0.21 mg/kg (mean = 0.10 mg/kg), while photomirex ranged from nondetectable to 0.38 mg/kg (mean= 0.11 mg/kg). Analysis of variance revealed no statistical difference (P > 0.05) between the value of 0.19 mg/kg reported here and either the 0.22 mg/kg reported by Insalaco et al. (1982) for salmon collected in 1977, or the mean residue of 0.18 mg/kg observed by Makarewicz (1985 unpublished data) for salmon collected in 1982. However, analysis of covariance revealed a decrease of 26% (P < 0.01) in mirex levels in 1982 and 1986 relative to 1977 levels after removal of the confounding variable weight. The data suggest the need for more rigorous statistical analyses than are typically applied in studies attempting to elucidate trends in mirex contamination in Lake Ontario.