Alewife herring in Cecil County, Md.
Alewife swim against the current where thousands of herring gather to spawn in a tributary of the Chesapeake Bay in Cecil County, Md., on April 20, 2017. River herring like the alewife and the American shad are anadromous fish that live off the Atlantic coast as adults but journey into freshwater to spawn every spring. Often that journey ends at dams that have cut off thousands of miles of stream habitat. “Last month they were out in the Atlantic ocean somewhere,” said Jim Thompson, a fisheries biologist with the state of Maryland. “That’s why it’s really important to build these (fish) ladders or take these dams out to get them over that last little speed bump so they can spawn.” (Photo by Will Parson/Chesapeake Bay Program)