From shad to sturgeon, commission named for salmon addresses barriers for many migratory fish
When an American shad encounters a strong current in its journey upstream, it faces it head-on, just as you would if paddling a canoe or kayak. Orienting into the current helps a fish or small boat hold its position in a river, rather than be swept downstream.
For a paddler, it’s a tactical maneuver. But for a shad, it’s evolution — a biological response to make sure it keeps swimming, reaches spawning ground, and passes along its genes.
Beginning in the mid-1800s, shad and other migratory fish found it increasingly difficult to follow that urge upstream in the Connecticut River because of dams that were constructed along the way.
In recent decades, fish experts have worked to let nature retake its course by removing obsolete dams, or constructing fishways that help fish bypass dams that still serve a purpose. That’s why when Brett Towler noticed shad passing more efficiently through the fishway at the Holyoke Dam — which spans the river between Holyoke and South Hadley, Massachusetts — than at other dams along the river, he wanted to figure out what was working from a fish’s perspective.
“At most dams, fishway gates move up and down vertically. When water spills over the gate, it creates a lot of turbulence on the other side, which shad aren’t really happy about,” said Towler, a hydraulic engineer for the U.S. Fish and Wildlife Service. “They will go over it, just not efficiently.”
But the fishway gate at Holyoke was designed differently. “It swings down, kind of like a tailgate on a pickup truck,” Towler explained.
He theorized that when the gate was down, it trained the water into a current that triggered the biological response in shad to stay the course.
He worked with fellow Service engineer Bryan Sojkowski on a hydraulic analysis of the fishway gate to explore the physics behind his hypothesis and presented the findings at a fisheries research forum.
The talk led to funding to test the idea at the U.S. Geological Survey’s Eastern Ecological Science Center at the S.O. Conte Research Laboratory in Turners Falls, Massachusetts. There, researchers can divert part of the Connecticut River through a building to simulate different fish-passage scenarios and compare them using real fish.
The test confirmed the hypothesis.
They published the results in a peer-reviewed journal, and the fishway design was added to the Service’s manual for migratory fish passage for the East Coast, which provides criteria for dam owners to follow when making upgrades. The design has since been implemented at dams throughout the region, to the benefit of shad and other migratory fish.
If that seems like a serendipitous series of events, it’s not. The entire process — from Towler’s observations at the Holyoke Dam, to the analysis of the fishway, to the presentation at the research forum, to the life-size simulations — played out within the context of the Connecticut River Atlantic Salmon Commission, an interstate partnership that coordinates fisheries management and restoration in the watershed.
The analysis of the fishway gate in Holyoke illustrates the role the Commission plays in connecting dots to support fish passage in a four-state watershed fragmented by centuries of dam building. And it’s just one of many examples.
A convergence
Established in 1983 by an act of Congress with Atlantic salmon as its lodestar, the Commission built upon an effort starting in the 1960s to restore populations of anadromous fish species — those that migrate up river from the sea — in the four-state watershed.
“When the first Anadromous Fish Restoration Program came about in 1967, shad and other sea-run species hadn’t been seen in Vermont or New Hampshire in more than 120 years, and only rarely in much of Massachusetts,” said Ken Sprankle, a fisheries biologist for the Service. “Both state and federal fishery agencies realized restoring and managing these species required a cooperative approach.”
The Commission is led by the state fish and wildlife agency directors of Vermont, New Hampshire, Massachusetts, and Connecticut; the regional directors of the U.S. Fish and Wildlife Service and National Marine Fisheries Service; and four public members appointed by the governors of each state.
Their decisions are guided by a technical committee of agency biologists who use available data, research, and engineering to develop and implement restoration plans. By working in concert with other agencies along the Atlantic Coast involved in population monitoring, research, habitat management and restoration, and fish passage at dams, the committee helps ensure those plans succeed.
The formal effort to restore Atlantic salmon in the Connecticut River ended in 2012 after persistently poor survival rates, likely due to changing marine environments. However, the collaborative work to reconnect and restore hundreds of miles of river habitat under the auspices of the Commission has benefited many other species: alewife, blueback herring, American eel, and of course, American shad.
The shad-friendly fishway gate at the Holyoke Dam is a case in point — it was originally designed to improve passage for salmon.
“It’s a perfect example of how the interests of different entities converge in the Commission, and how its mission helps to support the needs of all migratory fish species,” Towler said.
In fact, Towler noticed shad were passing through the fishway efficiently because he was there to inspect it anyway. The Service conducts annual inspections of the fishway, motivated in part by the shortnose sturgeon, a federally protected fish species that today has a reproducing population in the Connecticut River.
Up until the early 2000s, sturgeon couldn’t access their spawning grounds — near the Conte Research Center in Turners Falls — because they couldn’t get past the Holyoke Dam.
Safe passage
Power company dams are federally licensed for terms of 30 to 50 years. During the relicensing process, state and federal agencies assess environmental impacts from the facilities and prescribe modifications to address them.
In 2002, the relicensing of the Holyoke Dam, its canal, and associated infrastructure was completed by an agreement among the Commission agencies and other parties, resulting in greater releases of water into habitat below the dam, less manipulation of daily river flows, and structural improvements to make fish passage safer.
Because shortnose sturgeon — which are “small” compared to Atlantic sturgeon, but can still reach a whopping 4.5 feet long — faced injury risks from the turbines, or from plummeting over the spillway, technicians had been catching them in the dam’s fish lift on their way upstream and sending them back down.
That was a problem for the species because it separated the populations above and below the dam.
To support long-term recovery, the City of Holyoke, which owns the dam, worked with the Service, Conte Laboratory, the state, and the National Ocean and Atmospheric Administration’s National Marine Fisheries Service — the lead agency for shortnose sturgeon — on a multi-year redesign to improve passage. The goal was to ensure sturgeon and other species could get upstream, and back downstream.
The changes included a submerged screen to keep large fish that were returning to the ocean from swimming through the turbines. The angled screen directed the fish toward a bypass channel, providing a safe exit.
The redesign was completed in 2016, and the following year, fish-lift operators began to release sturgeon upstream. Thanks to the bypass channel, the fish can now swim safely back downstream after spawning to the rich estuary habitat at the mouth of the river.
The sturgeon have responded. In the 30 years prior to the completion of the redesign, technicians had seen an average of four sturgeon at the lift annually. The year after it was complete, they counted 84.
Big picture
Imagine a commute with no alternate routes, where bottlenecks become dead ends. For migratory fish, rivers are the only way to get where they need to go to complete their complex life cycles, and fishways are critical to ensuring a smooth journey. But like any infrastructure, fishways require maintenance and upgrades.
While compliance with regulations is the responsibility of the Service, the Commission provides a mechanism for identifying problems as they arise, and addressing them in a timeframe that matters for migrating fish, by serving as a conduit between partners.
While observations of specific fish species — shad, sturgeon, and salmon — inform constant fine-tuning to address the barriers they face, these species’ populations benefit from the improvements. The Commission is now working with Congress and the four state legislatures to reauthorize the compact as the Connecticut River Migratory Fish Commission — a change in name to better reflect its purpose.
“The Commission has always been about more than salmon, even more so now,” explained Andrew Fisk, director of the Connecticut River Conservancy and chair of the Commission. “Ecological restoration is about entire communities of species.”
That includes human communities. A healthy, intact river system is less prone to flooding and safer for recreation, and supports a suite of aquatic wildlife.
Fisk pointed out that the 410-mile Connecticut River has enormous potential for migratory fish to return. “Not just hundreds of thousands, but millions of fish,” he said.
We can imagine what that might look like from a fish’s point of view. The Commission can see the big picture from a population perspective, and figure out how to get there.
This story is part of a series on how the Connecticut River Atlantic Salmon Commission has advanced the restoration of migratory fish populations in the four-state watershed through collaboration, research, and adaptive management.
