When you think of spring migration, birds most likely come to mind. The geese have returned, their signature V-formations cutting across the sky, and colorful warblers happily find our feeders to replenish their dwindling reserves. There are plenty of events celebrating and documenting how many and which type of birds are found along the coast. But, there’s another migration that happens on a smaller, more local scale – that of the alewife (Alosa pseudoharengus). This little silvery fish travels each spring from the ocean up into Maine’s lakes to reproduce. This offers a unique opportunity to see these otherwise ocean dwelling fish up close. They arrive in early spring and lay their eggs in freshwater. When the eggs hatch, they develop for a few months before they migrate out to sea and grow into adults. They’ll spend the next four years or so at sea before returning to freshwater to spawn.

The spring migration was once a time dedicated to alewife harvest. Native Americans and early settlers caught them using baskets and weirs as they came up the falls to spawn. They dried and smoked them for the winter. Apparently, the town of Woolwich allotted widows two bushels of alewives a year — a law that exists today. They have also traditionally been an important source of bait for the spring lobster fishery. But, alewife populations have had their challenges.

Alewives are known as anadromous fish because of the way they split life cycle between fresh and salt water. Salmon, smelt and striped bass are other familiar anadromous fish that run up the rivers to spawn. The word anadromous comes from the Greek ana for up and dromo for run. That kind of migratory life sounds quite nice – unless there are obstacles. In Maine, as in many other places, people have built structures in waterways that prevent the fish from being able to get through. Mills for products like lumber, textiles and paper in Maine built dams to harness the energy of Maine’s rivers. Even though laws dating as far back as the 1700s required mills to have chutes to let alewives through, these dams provided an additional challenge for the fish and led to a reduction in their populations. Declines in water quality in the rivers also led to poor survival. Today, water quality has improved, but alewife numbers are still far below historical levels. This has led to efforts to improve fish passageways and to monitor populations.

Fish passageways have varied in design over time, but are essentially a set of tiers going from below to above a dam. They are commonly called fish ladders. The idea is that the rungs of the ladder slow the water down. Then, the fish can jump up one level, take a rest in calm water, and then jump up to the next, and so on. These ladders were made of various materials from wood to stone to concrete and stone ­— the materials most often seen today. The ladder at the Nequasset Dam serves as an excellent example of evolving design. It was first built in the late 1800s and was a wooden structure built to create a water supply for surrounding residents from Nequasset Lake. A stone fishway replaced that in the 1920s, and then a concrete dam was constructed in 1955. The fish ladder is now owned and maintained by the Bath Water District, which has used the Nequasset Lake for its water supply for over 100 years, and is managed by the Woolwich Fish Commission. In 2014, a major effort to improve the passageway was undertaken in collaboration with the Kennebec Estuary Land Trust (KELT). The slope was decreased, aluminum baffles replaced wooden ones, and the design was changed to slow the speed of the water down.

Counting rather than fishing dominates much of the activity around places like Nequasset at this time of year, although commercial harvest is still allowed below the dam. Scientists compare the number of fish counted in the lake to the number that are harvested, allowing them to assess the health of the population each spring. This is a neat opportunity for any interested community scientist to volunteer to watch these muscular fish leap up the ladder. Armed with a clicker, clipboard, and timer, you can sit atop the falls and count the number of successful leapers. The counting effort at Nequasset is managed by KELT. It’s a fun spring activity, particularly with kids. You can sign up by contacting Ruth Indrick, Project Coordinator (rindrick@kennebecestuary.org) to get an alert at the beginning of the season letting you know when the first fish start to appear in the Lake and when they need volunteers. And, at the end of the day, you can buy some alewives from the smokehouse right there and take them home to eat.

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