Until their severe diminution because of dams, pollution and over-fishing, the 11 native sea-run fish of the Kennebec River were well known to Native Americans and European settlers alike. Each species has its own unique spawning behavior and growing habits, and migration cycle. Below are thumbnail sketches of each.

Atlantic sturgeon: The largest sea-run fish in eastern North America. Atlantic sturgeon may reach 800 pounds, 12 feet long and live for 50 years or more. They spawn in the Kennebec River in late June and July at age 15 or older. Adults live along the continental shelf at depths of over 600 feet. The species is practically extinct in the United States except for severely depleted populations in the Delaware, Hudson and Kennebec Rivers. Adults are often seen leaping out of the water near Augusta in early summer.

Shortnose sturgeon: Much more common in the Kennebec than the Atlantic sturgeon, but listed as an endangered species in the United States. Shortnose sturgeon reach three to four feet long and may live for 80 years or more. Females do not spawn until 20 years old and may stop feeding for up to a year before spawning. Unlike Atlantic sturgeon, shortnose rarely travel beyond their home river estuary.

Atlantic salmon: Nearly extinct from the Kennebec River and the United States. Eight to 15 pound Atlantic salmon spawn in lower Kennebec tributaries near Augusta in late fall and are observed leaping in the river from late May to September. The lower Kennebec holds the southernmost population of wild Atlantic salmon in North America.

Striped bass: Because of its large freshwater tidal estuary, Merrymeeting Bay, the Kennebec holds the only spawning population of striped bass in New England. Stripers in Maine have reached up to 67 lbs. They feed voraciously on river herring and eels in the Kennebec from spring to late fall. They spawn in early July in the river near Augusta and now have free access to Waterville, 60 miles from the sea.

American shad: The largest member of the river herring family, shad can grow to 10 pounds and over two feet in length. The Kennebec once hosted a run of a million or more shad, which spawned throughout the drainage in June. Adults spend up to five years at sea before returning to their home river to spawn. Dam construction and pollution nearly destroyed the Kennebec's shad population, which is now being restored.

American eel: Unlike most sea-run fish, eels spawn in salt water, migrate as tiny juveniles to freshwater and live for 30 years or more in rivers and ponds before completing their lifecycle by returning to the ocean. They grow to be three to four feet long.

Alewife: One of the most abundant fish of the Kennebec River. Alewives are born in upriver lakes and ponds, migrate to sea after a few months in freshwater and return three to five years later in May and June as 10-14 inch adults. They are eagerly devoured by striped bass, eagles, osprey and great blue heron. The Kennebec once hosted runs of over 6 million adult alewives. Today, the run is over one million and growing.

Blueback herring: Nearly identical to the alewife in appearance, the blueback herring differs by spawning in fast-flowing river reaches instead of lakes and ponds. They are devoured in great numbers by stripers and fish-eating birds during their early summer migration up the Kennebec.

Rainbow smelt: Enters the lower Kennebec River in early winter to feed on small fish and crustaceans; spawns soon after ice-out in rocky stream beds. Grows to one foot in length. Rainbow smelt are subject to a popular commercial and recreational fishery in Hallowell, Randolph, Bowdoinham and Dresden. The current population in the Kennebec is estimated in the tens of millions.

Tomcod: A close relative to the Atlantic cod, except much smaller (rarely over a foot long), with a life history very similar to rainbow smelt. Tomcod are called "frostfish" because they appear in the Kennebec only after ice begins to coat the river. They spawn in December near or above head of tide and are frequently caught by smelt fishermen in the lower river and estuary.

Sea lamprey: Juvenile lamprey live for up to eight years in freshwater, eating organic debris, and live in saltwater for two years, attaching themselves to large ocean fish. They enter the Kennebec to spawn in late May and early June where they dig nests in shallow gravel beds of the river. Like Pacific salmon, sea lamprey die immediately after spawning and their carcasses provide important nutrients to local stream environments.