Temporal and Age-Related Trends in Levels of Polychlorinated Biphenyl Congeners and Organochlorine Contaminants in Lake Ontario Lake Trout (Salvelinus namaycush)

Temporal and spatial trends of organochlorines and mercury in fishes from the St. Clair River/Lake St. Clair corridor, Canada

“…Further, point sources of total-PCB, mercury, OCS, and HCB have been detected in the St. Clair River (King and Sherbin, 1986;Marsalek, 1986) and DDT was a heavily used pesticide in this largely agricultural area prior to being banned in the United States and Canada in 1972 (Myers et al, 2000;Wong et al, 1995). For all contaminants, non-detect values were substituted with one half of the detection limit, allowing consistency with previously published temporal trend studies (Bhavsar et al, 2007;DeVault et al, 1996;Huestis et al, 1996;Suns et al, 1993).…”

“…First, we used the common first-order exponential decay model (C t =C 0 e k2t ), where C 0 and C t are the concentrations initially and at time t (year), respectively, and k 2 is the apparent first-order rate constant, which allows direct comparison of our results with those who have used a similar model in temporal trend studies in the Great Lakes (DeVault et al, 1996;French et al, 2006;Huestis et al, 1996;Paterson et al, 2005). This model is intrinsically linear when log-transformed and was estimated by ordinary least-squares linear regression (lnC t =lnC 0 + k 2 t).…”

Trends of legacy and emerging-issue contaminants in Lake Simcoe fishes

“…Use of the decay model allows direct comparison of our results with those who have used a similar model in temporal trend studies in the Great Lakes (DeVault et al, 1996;French et al, 2006;Huestis et al, 1996;Paterson et al, 2005). This model is intrinsically linear when log-transformed and was estimated by ordinary least-squares linear regression (lnC t = lnC 0 + k 2 t).…”

“…However, mercury concentrations were also available for cisco, largemouth bass, northern pike, smallmouth bass, walleye, whitefish, and yellow perch. For all contaminants, non-detect values were substituted with one half of the detection limit, allowing consistency with previously published temporal trend studies DeVault et al, 1996;Huestis et al, 1996;Suns et al, 1993) and the Guide to Eating Ontario Sport Fish (OMOE, 2009). The frequency of detection for each chemical/species combination was, on average, 99%, and in all cases was greater than 75% (Table A1).…”

“…This model is intrinsically linear when log-transformed and was estimated by ordinary least-squares linear regression (lnC t = lnC 0 + k 2 t). Individual concentration data for each time point were included to incorporate the variability of each year in our regression analysis, as recommended by Zar (1984), consistent with several previous studies (Hickey et al, 2006;Huestis et al, 1996;Paterson et al, 2005). However, temporal trend analysis using arithmetic means was also performed (DeVault et al, 1996;French et al, 2006), which led to similar results except that both r 2 and p-values were generally greater because the use of mean values does not incorporate variability within years and lowers the power associated with the tests.…”