A unique fish ladder is helping species at risk reclaim their habitat
Heading up the river
The Copper Redhorse (Moxostoma hubbsi) is running up the Richelieu River again. This is a major victory for the unusual coppery coloured fish species, which is found only in southwestern Quebec. A dam built in 1967 hindered this endangered species’ migration to its most important spawning area upstream from the Canal-de-Saint-Ours National Historic Site. Now a fish ladder of unique design is brightening the future for the Copper Redhorse.
Like the Copper Redhorse, other denizens of the Richelieu had long been stranded below the dam. Up to 60 fish species use the river, including several species at risk. The American Eel, which had supported an important local commercial fishery before the dam was built.
Building a fish ladder, step by step
Solving the problem required diligent research and cooperation from several federal and provincial agencies and conservation groups. Parks Canada, as manager of the historic site, was responsible for species at risk on the site. Fisheries and Oceans Canada , the Ministère de l’Agriculture, des Pêcheries et de l’Alimentation and the Ministère des resources naturelles et de la faune du Québec had both fisheries and species at risk responsibilities. Transport Canada also had to be involved, as it had built the dam. “It was a financial challenge, a partnership challenge and an engineering challenge,” says Quebec Service Centre Species at Risk Coordinator Sylvain Paradis.
It all came together in 2001. Parks built a unique fishway with funding from many sources, including proceeds from Rescousse beer, a beer created to support the recovery of species at risk. They named it the Vianney-Legendre fishway, after the ichthyologist who had first officially described the Copper Redhorse in the 1950s.
Different fish – different needs
The Richelieu fishway is no ordinary fish ladder. Experts agreed that the fishway should serve multiple species, particularly at-risk species. Fishways designed for a single species such as salmon are fairly common but multi-species designs are rare and quite complex. The design had to consider the needs of species that vary widely in size and behaviour. Specific hydraulic conditions to help them find the fishway entrance and allow them to swim up the ladder were created. Different parameters such as water level fluctuations, water flow, and migration dates also had to be considered. The American Eel has such particular needs that the fishway designers made a whole separate structure tailored to eels at the side of the main fishway.
A versatile system
To save money, the fishway is designed as a compact S-shaped structure, but the complex structure still cost some $2.5 million to build. To suit a variety of water conditions and fish of different sizes, the fishway has two different entrances at or below the water surface. Also, dam operators can modify the direction of the river flow to improve the fishway’s effectiveness in attracting fish.
Experts from as far away as France advised on the design, as did biologists and engineers, who then carefully monitored its operation. There were no guarantees it would work. Over an eight-year period, the efficiency of the fish ladder was studied using different testing methods.
The results have been impressive. Of the 60 species historically known to use the Richelieu River, researchers have found 36 using the fishway so far. This includes four of the five at-risk species initially targeted, bringing hope for their populations’ recovery.
The Vianney-Legendre fishway shows that an historic site can be more than a site of Heritage significance. It can protect biodiversity and help recover species at risk.
The opportunity to observe the numerous fish species swimming up the fishway through the viewing window during the spring upstream migration, as well as the installation of information panels should raise interest in species at risk in the Richelieu. Such a successful environmental engineering project could create a tourist attraction and be useful in educating the public about this biodiversity restoration project. In fact, the fish ladder has even gained international attention. Although it has been designed uniquely for this site, other jurisdictions are interested in it as a model. “Enquiries have been coming from all over the world,” says Sylvain Paradis.
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