Magnification and Toxicity of PCBs, PCDDs, and PCDFs in Upriver-Migrating Pacific Salmon

Abstract

The depletion of lipids associated with pre-spawning migration of Pacific salmon has the potential to magnify concentrations of hydrophobic organic contaminants (HOCs), which elevates risk of toxic effects. We present data from a field study of sockeye salmon (Oncorhynchus nerka) migrating to spawn in Great Central Lake, BC, which demonstrate that pre-spawning migration causes a magnification of PCB, PCDD, and PCDF concentrations in female gonads (1.9-2.5-fold), female soma (3.4-5.6-fold), and male soma (5.6-9.7-fold). We further develop a model of prespawning migration chemical magnification for sockeye salmon stocks as a function of migration distance. This model is shown to be consistent with available empirical data on pre-spawning magnification and predicts magnification factors ranging between 1.4 and 7.9 in gonad and between 1.6 and 10.4 in soma in seven Pacific salmon stocks in British Columbia. Post-migration (prespawning) toxic equivalent dioxin concentrations in roe were measured to be approximately 3 pg/g lipid in salmon from the Great Central Lake sockeye stock and estimated to range between 1.5 pg/g lipid for the shortest-migrating stocks and 7 pg/g lipid for the longest-migrating stocks. Concentrations in certain stocks approach or exceed the concentration of 3 pg/g lipid associated with 30% egg mortality in Oncorhynchus mykiss. This indicates the potential for population-level effects of current contaminant levels. It also suggests that historic contaminant concentrations, which were greater than current concentrations, may have contributed significantly to the decline of certain Pacific salmon stocks in British Columbia.

Life Histories, Salinity Zones, and Sublethal Contributions of Contaminants to Pelagic Fish Declines Illustrated with a Case Study of San Francisco Estuary, California, USA

“…Turbidity and conductivity increase from east (Sacramento-San Joaquin Delta) to west (San Francisco Bay). All life stages are affected by hydrologic changes in turbidity and salinity, impaired water quality from stochastic rainfall events, and wastewater inputs that impair habitat quality During migration to spawning grounds in the Delta, anadromous fish mobilize energy reserves, which releases organic contaminants from adipose tissues (Debruyn et al 2004) (Fig. 3, effect M).…”

Dioxin-like compounds in sediments from the Daliao River Estuary of Bohai Sea: Distribution and their influencing factors

“…Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/ Fs) and polychlorinated biphenyls (PCBs), which are two classical groups of dioxin-like compounds, are known to be the most hazardous to ecological and human health, and thus caused worldwide concerns and extensive research (deBruyn et al, 2004;Kubota et al, 2004). To evaluate their potential risk to environmental matrixes, consensus toxic equivalency factor (TEF) values for PCDD/Fs and PCBs have been derived (Van den Berg et al, 1998).…”

Tissue residue concentrations of organohalogens and trace elements in adult Pacific salmon returning to the Fraser River, British Columbia, Canada

“…during upstream migration [18,19]. Returning Pacific salmon generally stop feeding after entering freshwater.…”