BIRD AND FISH POISONING SPREADS IN GREAT LAKES

View slideshow Botulism is killing fish and the shorebirds that eat them. The cause is likely due to a disruption in the ecosystem by invasive zebra and quagga mussels. (Photo by Lester Graham) 

A deadly toxin is killing fish and birds along the Great Lakes shoreline. Researchers think type-E botulism works its way up the food chain from the bottom of the lake through several invasive species. Bob Allen reports:
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