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BIRDS and fish in North America’s Lake Erie are dying in their thousands from
a mysterious outbreak of botulism. Caused by a toxin from the bacterium
Clostridium botulinum, the deaths are puzzling experts. The toxin is
usually found in dead fish, but now it’s turning up in freshly caught fish and
in birds. Experts suspect that the round goby, an invader from the Caspian Sea,
may be picking up the toxin by eating zebra mussels which absorb it from the
lake bed, before being eaten themselves. Jeff Robinson of the Canadian Wildlife
Service in Ontario agrees that the goby might be the reason, but no one yet
knows for sure.