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Is there still a problem with chemicals getting into the walleye from eating the round goby, who eat zebra mussels?
To answer your question—YES! The process you've described is called biomagnification. Some toxic chemicals found in the Great Lakes, such as DDT and PCBs, are stored in the fatty tissue of organisms, and when one organism is consumed by another, these toxins are further concentrated in the bodies of the predator. This is repeated at each step in the food chain. Biomagnification occurs regardless if non-native species are involved or not, and it occurs in every waterbody around the world.
The top predators in a food chain, such as trout or salmon, may accumulate concentrations of a toxic chemical high enough to cause serious deformities or death. Humans must also be careful about eating certain fish, because the concentrated toxins could affect our health as well. Every year, each Great Lakes state publishes a fish consumption advisory, which informs the public of what quantities of various types of fish from different waterbodies are safe to eat. For a listing of fish consumption advisories, go to GLIN's Fish Consumption Advisory page.
The Environmental Protection Agency provides a detailed look at biomagnification.
Thank you for your question!
Answered on November 15, 2000