When fish are foul

Salmon are famous for their mass migration from the sea to their freshwater spawning grounds. Sockeye salmon (Oncorhynchus nerka) live most of their lives in the North Pacific Ocean, where they accumulate 95% of their biomass. On reaching reproductive age, they can migrate as far as 1000 km up North American rivers to spawn in lakes, dying soon afterward and subsequently releasing their constituents into the freshwater ecosystem. In a brief communication the September 18 Nature E.M. Krümmel and colleagues at the University of Ottawa report that this complicated life history means that sockeye salmon can act as bulk transport vectors for pollutants from the ocean to freshwater systems (Nature, 424:255-256, September 18, 2003).

Krümmel et al. focused on polychlorinated biphenyls (PCBs), which are produced by industrial processes such as waste incineration and which can be dispersed directly into the atmosphere or can be washed into aquatic environments. Seawater typically ...