Salmon acquire pollutants through the lake food chain. When they are young, they feed on invertebrates worms and insect larvae. As they grow larger, salmon consume more and more fish, such as alewives which have also picked up pollutants through invertebrates they eat, which have picked up pollutants from algae and bacteria.
Salmon are a fatty fish, and these polluting chemicals are particularly "sticky," Lamberti says. "They are lipophilic they absorb into fat tissue."
The consequence is that the salmon magnify the pollutants as they move up the food chain. "Salmon are longer lived, eat more, and the pollutants are then bio-concentrated."
The concern is that salmon are naturalized to many tributaries of the Great Lakes. "And it's a one-way street for them," Lamberti says. "They spawn, die in the stream where they spawn, and then leave their contaminant load in the stream. Stream fish eat salmon eggs, and may also eat carcass tissue as they decompose."
Fish in streams and tributaries with large salmon runs fish that never go out into the lake, he notes show contaminant levels very similar to that of Great Lakes salmon.
"Let's keep in mind," he adds, "there are FDA advisories for pregnant women and children on the risks of eating large Great Lakes fish, because of the danger of chemical contaminants.
"But there are no warnings for stream fish that's the specter. If you're eating fish from a stream with a lot of salmon, you might as well be eating the salmon. I would err on the side of caution when eating any fish from a salmon river. Either that or harvest fish only upstream of where salmon spawn."
For comparison purposes, Lamberti's research analyzed the tissue of fish upstream from where salmon spawn and die.
"The upstream section of the same river was not contaminated. Below the salmon, the ri
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University of Notre Dame