The blueback herring were spawning at the base of the breached Union Gas Hydro-Electric Dam in Waterville, Maine.
More than 1,000 blueback herring were observed at this location on 10 June 2004.

Because of radical alterations (blasting) of the natural ledge drop at this site during construction of the dam in 1900,
blueback herring and other native fish are prevented from migrating any farther upstream.