Under the rivers' surface is the world inhabited by fish and other aquatic creatures -- fallfish, snapping turtles, freshwater mussels, larval dragonflies, and tiny zooplankton. These are all part of the aquatic community that OARS is working to protect as part of protecting the rivers.

Each aquatic creature needs specific habitat to survive. In many ways, fish are the most visible and well-understood barometers of stream and river health. They area long-lived (relatively) and their habitat needs are well understood. Eastern brook trout are among the watershed's most sensitive fish; they need cool, clean, flowing water. The few remaining wild populations of brookies survive only in tributary streams where the water is cool and the stream is free-flowing (not dammed). In contrast, common carp are quite content in large, warm, slow-moving rivers, can tolerate much lower dissolved oxygen concentrations than most other fish, and happily gather downstream of a dam.

Click to read an interesting article on The Secret Lives of Eels.

Are the streams healthy for fish?
When we look at water quality and streamflow data, we can ask: Are these good conditions for fish like brook trout (for the small streams) or fallfish (for the mainstem rivers)? If a stream can support a pollution-sensitive population, like brook trout, other less sensitive species can thrive in it too.

Another way of assessing whether the streams are healthy for fish is to look at the fish community. How does the existing community (species and numbers) compare to the community one would expect to find in unpolluted, free-flowing streams in southern New England?

Shad and Alewife
It is also useful to understand the needs of the alewife and shad that once lived here. Alewife and shad are anadromous fish -- migratory fish that hatch in fresh water, make their way to the sea to grow, then return as adults to fresh water to spawn. Downstream dams on the Concord River currently block their return to the Assabet watershed. The Mass. Division of Fisheries and Wildlife, the Mass. Division of Marine Fisheries, and the U.S. Fish and Wildlife Service are currently cooperating in efforts to restore anadromous fish to the greater Merrimack River watershed -- including the Concord River.

As you peruse these pages and enjoy the beautiful fish pictures, think about what these creatures need to survive. Continue to Fish of the Assabet .

Photo credits:
All of the fish photos in this section are used with permission from their owners. Photo credits appear at the bottom of each photo. If you are interested in using any of the photos from this site please email OARS for contact information for each photographer/owner.

Fish references:
Bain, Mark B. "Macrohabitat Classification of Freshwater Fishes, Research Notes and Instructions," New York Cooperative Fish and Wildlife Research Unit, Department of Natural Resources, Cornell University, Ithaca, NY. Fall 1989.

Becker, B.C. Fishes of Wisconsin. University of Wisconsin Press, Madison, WI. 1983.

Burr, B.M., and M.C. Warren, Jr. A Distribution Atlas of Kentucky. Kentucky Natural Preserves Commission, Scientific and Technical Series 4, Frankfort, KY. 1986.

Hartel, K.E., D.B. Halliwell, and A.E. Launer. "Inland Fishes of Massachusetts." Massachusetts Audubon Society, Lincoln, MA. 2002. (Download order form in pdf format). (Karsten Hartel can be contacted at Harvard's Department of OEB.)

Kologe, Brian R. "AMC Guide to Freshwater Fishing in New England." Appalachian Mountain Club, Boston, MA. 1991.

Massachusetts Wildlife, No. 2, 2000, Special Fishing Issue.

Robison, H.W., and T.M. Buchanan. Fishes of Arkansas. University of Arkansas, Fayetteville, AK. 1984.

Rohde, Fred C., Rudolf G. Arndt, David G. Linquist, and James F. Parnell. "Freshwater Fishes of the Carolinas, Virginia, Maryland & Delaware". The University of North Carolina Press, Chapel Hill, NC. 1994.

Scott, W.B., and E.J. Crossman. Freshwater Fishes of Canada. Fisheries Research Board of Canada Bulletin 184. 1973.

Werner, Robert G. "Freshwater Fishes of New York State." Syracuse University Press, Syracuse, NY. 1980.