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River Restoration Boosts Maine’s Fishy Food Web

Sharks and humans could be eating more local fish, thanks to improving connections that allow small fish to migrate between rivers and the Atlantic Ocean. The number of river herring crossing a dam in Maine has already doubled this year, and new projects offer the same potential.

But how do ocean fish and humans benefit?

It’s the aquatic circle of life. Adult river herring (alewife and bluebacks) and shad reside in coastal ocean waters for most of their life. But they need access to rivers to spawn and complete their life cycle.

These fish, called “forage fish,” are food for larger commercial and recreational species. They once supported the largest commercial and recreational fisheries along the Atlantic coast. Today, these populations are at low levels due to habitat degradation, fishing impacts, and reduced access to spawning habitat.

Big Fish Need Little Fish

Scientists have confirmed that helping forage fish rebound supports the big fish caught at sea. A 2015 NOAA-funded study found many small, forage fish in the stomachs of more than 60,000 big fish. These big fish—such as striped bass, cod, and spiny dogfish—are important for commercial and recreational fisheries.

Little Fish Need Elevators

In 2013, a fish lift was installed on the Milford dam on Maine’s Penobscot River (a NOAA Habitat Focus Area). The lift—essentially an elevator that carries fish over the dam—is already working. In 2015, less than 600,000 river herring passed over the dam. That number has more than doubled to 1.25 million fish so far in 2016, according to the Maine Department of Marine Resources.

Fish Shall Overcome

Between now and 2020, NOAA is planning to build seven new fishways on Maine rivers, in addition to improvements to existing fish passage. NOAA’s fish passage work restores access to important fish habitat. It also contributes to the long-term sustainability of fisheries that depend on these little fish within the delicately-balanced food web.

Table: Recently completed (2007 – 2016) fish passage projects on Maine’s rivers, supported by NOAA. These projects allow migratory fish to pass dams safely.

River

Project

Year Completed

Penobscot River

Howland Dam fishway

2016

Millford Dam fish lift

2013

Stillwater dam eel passage

2012

Veazie dam removal

2013

Kennebec River

Burnham fish lift

2007

Sebasticook River

Benton Falls fish passage

2007

 

Burnham fish lift

2007

Saco River

West Buxton upstream eelway

2016

Bar Mills eelway and fish ladder

2014

 

Forage fish: These 3 fish species, called forage or “food” fish, form an important middle link in the food web. They depend on freshwater habitats to reproduce, but in the ocean they eat plankton, comb jellies, shrimp, and smaller fish. In turn, alewife, herring, and shad are fed upon by larger fish such as striped bass, weakfish, and spiny dogfish, which are targets of humans.

Images from: Maryland Department of Natural Resources

Biologists survey river herring in a holding tank full at the Millford Dam in Maine.(Photo credit: Sean McDermott, NOAA Fisheries)

American shad migrate over a dam spillway on the Saco River in Maine. (Photo credit: Sean McDermott, NOAA Fisheries)