Our waterways are teeming with life—mammals, fish, birds, reptiles, amphibians and many smaller creatures.
Fish and wildlife populations have gradually increased since the Clean Water Act of 1972 prohibited the discharge of raw sewage and industrial pollution into rivers, but many populations are still far below their historic levels.
Fish biologists are particularly interested in populations of American shad, striped bass, blueback herring, and other fish that spawn in the river and grow and mature in the ocean. These fish, known as anadramous species, are vulnerable to threats in both of these habitats.
These migratory species have increased recently in the Delaware River but have been largely missing from the Millstone River because of old dams that were constructed in the 18th, 19th, and 20th centuries.
The Watershed Institute and other conservation organizations are working with federal and state wildlife agencies to remove old dams and allow the recovery of migratory fish. In August 2017, the Weston Mill Dam near Manville was removed from the Millstone River. Watershed scientists are working closely with U.S. Fish & Wildlife Service and the NJ Department of Environmental Protection to monitor the ecological response to the dam’s removal and have already witnessed the return of shad and other migratory fish.
In addition to American and gizzard shad, blueback herring and striped bass, more than 50 other species of fish can be found in the Millstone River, include largemouth and smallmouth bass, American eel, bluegill, and a number of species of sunfish.
The Watershed Institute staff and volunteer scientists also carefully monitor area streams for various kinds of benthic macroinvertebrates—insect larva and other invertebrates that live at the bottom of streams. Some of these species, such as caddisflies, stoneflies, and mayflies–are highly sensitive to pollution, while others, such as leeches and worms, are tolerant of pollution. The relative abundance of pollution tolerant and intolerant species lets us know the extent of pollution in that waterbody.