Naugatuck River and roadways, through the time of development of Connecticut Route 8. The river enters a forested, hilly area between Connecticut Route 118 and Thomaston. The largely industrialized cities of the Naugatuck River Valley were developed on each side of the river, with periodic sections of forested areas, before it enters the Housatonic River at Derby, at about above sea level. As part of the Housatonic River watershed, the Naugatuck River historically hosted the southernmost Atlantic salmon ("Salmo salar") migrations. Historical runs of anadromous fish also included native American shad ("Alosa sapidissima", Connecticut's state fish), alewife ("Alosa pseudoharengus") and blueback herring
Mattapoisett River mill purposes" and featured three herring weirs; the "Upper Herring Weir" in Rochester, the "Middle Weir" or "Church's Weir", and the "Lower Herring Weir" at the entrance to Mattapoisett Harbor. Fish populations drastically declined during the twentieth century until they were almost extinguished, but local restoration efforts from the 1980s onwards have fostered a slow recovery. The principal restoration tactic has been to remove snags and other obstacles from the river that serve to impede fish migrations. The Lower Herring Weir is one of the few rivers emptying into Buzzards Bay that has electronic fish counters installed. Reports from Alewives