 round goby (photo from Great Lakes for All) |
compiled from several sources
Once again, mid summer, the Lake Michigan shore, particularly in Leelanau County, is littered with dead seagulls. For years it's been known that they have died of botulism.
But the story has a deep twist, tied to invasive species.
At the bottom of the lake reside a blanket of invasive mussels: the zebra mussels, long known for their problematic clogging of water intake pipes, and the large quagga mussels. Along came the round goby, another invasive species. The fish eat the zebra mussels. So this should be a good thing, right? Maybe not. They also ingest and concentrate the Type E botulism toxins that the zebra mussels filter from the sediments.
Sport fish, particularly walleye, eat the gobies, and the toxin is carried farther up the food chain. Seagulls feed on the fish, and the result is occasional spectacular die-offs of the birds. Last year, nearly 2900 gulls died from this effect.
This year, as the St. Lawrence Seaway celebrates its 50th year, some people blame that engineered waterway for the entrance of the invasive species to the Great Lakes.
See Zebra Mussels and Round Goby: A Dangerous Combination
See A wake would be fitting for seaway's 50 years
See Type-E Botulism Confirmed in Waterfowl Deaths
See 330 Trillion Quagga Mussels Can't Be Right
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