Trends in Mirex Concentration in Lake Ontario Salmonines and Sediments

Abstract

Chinook (Oncorhynchus kisutch) and coho (0. tshawytscha) salmon and sediment cores collected from Lake Ontario during the summer and fall of 2003 were subsequently analyzed for mirex and photomirex. Mirex in fish tissue ranged from 0.011 mg/kg to 0.094 mg/kg (mean 0.048 mg/kg). Photomirex in fish ranged from 0.005 mg/kg to 0.045 mg/kg (mean 0.020 mg/kg). Analysis of variance (ANOVA) was performed to test for differences between mirex concentrations among all sampling years. A significant difference occurred between all sampling years (p=0.000). Temporal trends in mirex concentration were determined by testing for differences in the slope of the regression line of mirex concentration versus weight using analysis of covariance (ANCVOA). The 2003 sampling year was significantly different than all other sampling years (p=0.000) except 1999 (p=0.081). A comparison of the elevation of each regression line determined that the elevation lines for 2003 and 1999 were significantly different than all years (p=0.000). There was no significant difference between the elevations lines among the 2003 and 1999 sampling years. Mirex detected in sediment cores from Lake Ontario had a mean concentration of 134.01 µg/kg. A paired t-test indicated no significant difference in mirex concentration between correlating sample intervals of the cores.