Native Americans called the falls on the Machias River Machias, popularly translated as "bad little falls," and that name now applies to nearby towns and rivers. South of Bad Little Falls, the river becomes an estuary where tidal sea water mixes with river water, creating habitat for eagles, osprey, softshell clams, migratory fish, shorebirds, and seabirds. Upstream, tributary streams, lakes, ponds, swamps, and peatlands form the 810 square mile watershed of the Machias and East Machias Rivers. Several migratory fish species spend part of their lives in these rivers, including anadromous fish that are born in fresh water, mature in salt water, and return to fresh water to lay eggs, and catadromous fish that are born in salt water, migrate to fresh water to grow, and then return to the ocean to spawn. Wild Atlantic salmon, once common in most New England rivers, now remain in only a few Maine rivers, including the Machias; in early summer they swim upstream from the ocean to lay eggs in gravelly redds, their young parr live in the river for about two years, then become smolts able to survive in salt water, migrate to sea, and after two years return as adults to spawn, though research shows that for every 8000 eggs spawned, roughly two adults reach reproductive age. Salmon returns to Maine rivers have declined over the past several decades for uncertain reasons that may include altered river beds, human activity along rivers and at sea, predators, and environmental conditions, and federal and state governments are working with the public on hatcheries, water quality improvements, and land management plans to help wild salmon continue returning to their native rivers. American eels are born in the Sargasso Sea, drift toward land as larvae, become transparent glass eels or elvers as they approach shore, enter estuaries such as the mouth of the Machias River in late winter and early spring, and may remain in brackish or inland fresh water habitats for as long as 25 years before returning downriver to the Sargasso Sea to spawn; in the late 1900s, a commercial market for elvers in Maine led to harvests with fyke nets for export to Asia and then to state regulations because of concern over effects on these long-lived animals. Alewives are small silvery fish that return each year to the Machias and East Machias Rivers to spawn, migrate in the ocean between the Bay of Fundy and the Carolinas, usually mature at four years, may live to nine, and can spawn as many as five or six times; for centuries Native Americans and later settlers dipped them from the rivers for fertilizer or smoking, but although they still return to most Maine rivers, their numbers have declined and few people harvest them today. Starting in the 1700s, settlers built waterpowered mills at Bad Little Falls to turn logs floated down the Machias River into lumber, wharves below the falls were piled with lumber for waiting vessels, and the abundance of lumber encouraged shipbuilding, though use of the falls for power often hindered upstream passage for migratory fish.