In the spring of 2025 Fishheart Ltd. deployed one of their innovative hydraulic fishways at the Tunnel Generating Station on the Quinebaug River in Preston, CT, initiating the first year of a three-year program to assess passage of river herring and American Shad.
The purpose of the program’s first year was to collect as much information as possible about the optimal positioning of the unit, flows, and bypass spills, so that in the second year the efficiency of the Fishheart fishway can be verified. If successful, the fishway will be relocated to the Stevenson Generating Station on the Housatonic River in Monroe, CT as a permanent fish passage solution for the same species, as well as lamprey and resident fish.
FirstLight and Fishheart reached an agreement for testing at the Tunnel Project in 2024 after Fishheart completed a successful test at the Santee Dam on the Santee River in Pineville, SC where they passed a total of 4142 fish (16 different species), including river herring and American Shad, in a relatively short migration window due to a high-water event. Fishheart demonstrated an ability to avoid flood damage to its unit by removing and reinstalling the hydraulic Fishheart unit in only eight hours. The first year at Tunnel continued to showcase the fishway as one of the most mobile, adjustable, and cost-effective fish passage technologies to dam owners.
Mobility and adjustability
One of the leading factors in FirstLight’s consideration to move forward with the Fishheart fishway, aside from the significant cost savings, was the mobility and adjustability of the unit. The Fishheart system is extremely mobile, allowing it to be removed and repositioned relatively rapidly, which was especially important during the high-water event at the Santee Dam Project.
The floating unit makes it possible to adapt to site specific conditions and optimize fish passage performance through empirical observation by adjusting position and orientation. This is a major advantage when compared to planning and building requirements for conventional fishways which are permanent structures that are limited in how they can be modified if they are ineffective.
Implementation and deployment
Fishheart and FirstLight began the consulting phase of the implementation process in February of 2025. This included assessing the bathymetry and natural attraction flows at the site, as well as determining anchoring points, all to ensure the highest probability for effective fish passage.
After the deployment plan was finalized, the Fishheart unit was delivered to the site at the end of April, unloaded, and assembled in five days; it only required an additional week to deploy the unit into position for the season. This included assembling the pipeline that is connected to the fishway entry unit where fish travel from the unit to above the dam, mounting the anchoring points, and installing guiding nets.
For deployment, a crane, telehandler, and boat crew were required. The crane lifted the Fishheart unit off land and placed it into the water, where the boat crew assisted guiding it into position and then anchored the unit to its anchoring points. In this case, the unit was secured to the turbine building’s concrete wall with two high-strength ropes attached to anchor shackles and another two high-strength ropes connected to two concrete blocks placed downstream.
Throughout the deployment period, the Quinebaug river experienced heavy rains and high flows which caused the shad and herring migration to be disrupted numerous times during much of the migration season. During the peak migration period, there were 17 days that experienced river flow rates that exceeded the project’s generating capacity resulting in large amounts of spill over the dam.
High spill flows likely affected passage by attracting shad and herring away from the Fishheart, located immediately downstream of the powerhouse. Shad and herring typically follow the highest flows in the river as they migrate upstream, so competing flows such as spillways negatively affect passage effectiveness for fishways with entrances in lower flow areas. For season two, Fishheart plans to reposition the unit more downstream and next to the spillway to align its entrance with the natural attraction flows. This, together with a new guiding structure is expected to attract shad and herring into the Fishheart fishway.
Next season
With the season coming to an end, Fishheart and FirstLight began preparing for the extraction of the fishway, as the Fishheart unit was being shipped back to Finland to make adjustments for the next season. This is where Fishheart was able to showcase the incredible speed in which the fishway can be removed from the water. Fishheart and FirstLight operators decommissioned the whole Fishheart fishway in just four days; day one was removing the Fishheart unit, pipeline, and other floating items from the water; the remaining days consisted of disassembling, cleaning, and packing.
For season two at Tunnel, FirstLight and Fishheart will be conducting a passage efficiency study to assess the behavior of shad as they approach the site and the entrances to the Fishheart. The study intends to use acoustic telemetry to track fish tagged and released at a dam downstream of Tunnel. Tracking of these fish will focus specifically on when they enter the tailwater below the Fishheart unit and when they enter the fishway. More cameras will be added to the entrance of the unit as well to see how fish respond to attraction flows from inside the unit. A new mesh guiding system with rigid panels will be installed downstream of the catcher, further helping fish navigate towards the Fishheart unit.
More from Fishheart
Ecological Egg Box
The innovative Fishheart Ecological egg boxes are a conservation tool used to help revive fish populations, particularly in situations where fish species have been impacted by habitat degradation, overfishing, or environmental changes. These boxes are designed to mimic natural spawning conditions for fish and can provide a controlled environment for egg incubation, offering safety and protection from predators, sedimentation, and poor water quality during critical early life stages. Part of what makes this product so great is its biodegradable composition, allowing agencies, organizations, and different environmental groups to cause less disruption in the ecosystem. Furthermore, using the Eco egg box is simple: fill the box with 1.5 dl (2/3 of a cup) of fish eggs, place the box in a riverbed where there is constant flow, and walk away. The eggs will hatch by themselves, and the fry will stay in the box until their yolk sac runs out. This design gives them the best chance
for survival after hatching. Then the box will decompose in about
4 months.
Fisheye-AI
A primary component of the Fishheart fishway is the Fisheye-AI camera system that detects motion and records data. Each Fishheart is equipped with two that detect motion, identify the species of fish, measure the length of each fish, and record the quantity of fish in the pipe. In the Fishheart fishway applications, the AI system relays this information to an external or local server before approving or denying the system to open the fishway and pass them through the pipeline. The whole process is automated and controlled remotely using preset preferences dependent on the location and takes place in a split second. Fisheye-AI can also be used in other applications, such as in existing fishways currently using video monitoring and manual counting. With the use of the Fisheye-AI system, the counts can be done automatically and sent to the owners in a detailed report, increasing accuracy and decreasing labor. This technology can be used for upstream or downstream monitoring.
