LUVERNE, MINN. – Nick Utrup sat with a team of biologists in the tall grass, straining to see through the ripples of a small, unnamed pond. An approaching rainstorm from the west, already over the red ...

The fish become nearly immobile, use very little oxygen, and hardly feed at all. Native species — such as carp, roach, pike, and bream — are well adapted to these conditions. Snow and ice do not ...