Anglers were alarmed when they stumbled upon thousands of dead, floating perch at a popular fishing spot on Lake Michigan last week. It is still not known exactly what killed the fish, but it is thought to be due to an ‘upwelling’. An upwelling is a phenomenon in nature that occurs when deep, cold water suddenly rises to the surface, displacing warm water above. It is thought that the upwelling immediately killed the perch that were already weak from the long, harsh winter.
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