FAQs on the Carillon Dam and the American eel

In the fall of 2020 it was announced that the Carillon Dam, the most significant barrier to American eel migration into the Ottawa River watershed, would be undergoing major renovations. We’ve assembled a series of questions and answers to bring you up to speed on the relationship between the dam and this endangered fish species in our watershed.

What and where is the Carillon dam?

Carillon is a run-of-river power plant operated by Hydro-Québec. It is located on the Ottawa River, just over 100 km downstream from the National Capital Region, and just upstream of Rigaud and Oka, Québec. The dam is transboundary; its turbines are located on the Québec side of the river, while the spillway is located on the Ontario side.

Carillon has the most generating capacity of any dam in the Ottawa River watershed, with its 14 units generating 753 MW, enough to power about 150,000 households. As it sits near the mouth of the Ottawa River, the dam sees an immense volume of water pass through it, with a mean flow rate of 2,000 m3/s, which can reach levels up to and beyond 8,000 m3/s during the spring freshet.

When was the dam built?

The dam was completed in the early 1960s, at a time when fish passage was rarely taken into account in the construction of these structures.

Carillon Dam, summer 2006 – taken by AerialPhotographs.ca

What impact did the dam’s construction have on the American eel population in the watershed?

Since the construction of the dam, the Ottawa River’s eel population has collapsed dramatically, by as much as 99%. There are many factors that have contributed to this collapse, but experts agree that dams, in particular the Carillon dam as it relates to the Ottawa River population, are the primary culprits.

Why are dams having such an impact on eels?

American eels are migratory, catadromous fish; they spawn in the ocean (the Sargasso sea) and live their adult lives in freshwater. Dams impact fish migrating in both directions. In the downstream direction, a portion of the fish migrating back to the ocean are killed when they are struck by turbines. It is difficult to know exactly how many in the case of the Carillon dam, but estimates hover around 20%.

Perhaps even more dramatic is the impact the dam has had in the upstream direction, on young eels attempting to migrate into the Ottawa River. In short, they can’t. The dam is the very first one eels encounter as they enter the Ottawa River, and it acts as a practically impassable barrier, due to the absence of eel passage infrastructure (i.e. an “eel ladder”).

Has anything been done to try to mitigate these impacts?

Yes, but not nearly enough. We need to do more.

For several years, the Québec and Ontario governments, in conjunction with Hydro-Québec and other collaborators (including Ottawa Riverkeeper) have been conducting a “trap and transfer” program, which involves capturing approximately 400 eels in the St. Lawrence, tagging them, then physically transporting them around the dam to be released upstream in the Ottawa River. We recognize that this is an important measure, but it is a stop-gap approach at best. It cannot be considered a permanent solution, and it does not allow for passage of sufficient numbers that would lead to a significant population recovery.

American eel trap and transfer, summer 2017

Moreover, for several years the Québec government has been promising an ‘action plan’ to guide recovery efforts. This plan has yet to be published, and we look forward to seeing what measures are being proposed to respond to the dramatic collapse of the American eel.

Ontario published their American Eel Recovery Strategy several years ago, and it offers insight into their plans for the protection and recovery of this species, including to “Strategically restore access to habitat within the historical range of the American Eel”, which  specifically mentions the Ottawa River.

Knowing that an eel ladder would mitigate the dam’s impact on migration, why hasn’t one been constructed yet?

We have been asking ourselves that question, too! Here are three reasons that are often cited by authorities.

  1. Cost.
    Installing eel ladders can be costly, into the millions of dollars for a large structure. While the cost argument is frequently brought up, to our knowledge, there has never been a costing exercise by Hydro-Québec to put a price tag on an eel ladder at Carillon. 
  2. Invasive species.
    We’ve heard from authorities that the dam’s “barrier effect” also has a positive impact because it blocks invasive species such as Asian carp from entering the Ottawa River system. While we don’t disagree with that fact, it’s certainly not an argument to oppose an eel ladder! As good luck would have it, eel biology is such that ladders can be custom-made to allow for eel passage, while not allowing invasive species to make it through. (For example, eels can climb at a much steeper angle than other fish). 
  3. A contested need for it.
    To date, the Québec government has questioned the need to allow eel migration back into the Ottawa River system. We’ve heard many arguments to this effect. One is that the number of eels attempting to migrate into the Ottawa River is now so low that it’s not worth the investment relative to other eel recovery measures elsewhere in Québec. To this we would give two responses: 
    • First, that the number of migrating eels being impeded by the Carillon dam is currently unknown – the latest data being over 10 years old. Ottawa Riverkeeper proposed to conduct – and pay for – new research on this front, but unfortunately authorization was denied by the Québec government. 
    • Second, those numbers are almost certainly low, but that is precisely because the dam has caused a population collapse! If we don’t fix the root cause of this problem, we are locking ourselves into a spiral that will lead to the extirpation of eels in the Ottawa River watershed.

Why is this the time to push for eel passage at Carillon?

The best time to add fish passage infrastructure to a dam is when it is being upgraded. Hydro-Québec is moving forward with a massive $750 million dollar overhaul of this dam. (To put that into context, the entire annual budget of Québec’s Ministry of Forest, Wildlife and Parks (MFFP) is significantly smaller, at only $564 million). This is literally a once-in-a-generation opportunity to devote a small fraction of the costs of this upgrade to adding permanent fish passage infrastructure. An upgrade such as this could help the population recover. The next time such an opportunity presents itself it may be too late.

Eel ladder to be installed at Chaudière Falls generating station, fall 2018

5 responses to “FAQs on the Carillon Dam and the American eel”

  1. Erik Pohanka says:

    Is there a government representative (MPP/MP) in Ontario or Canada in which I can submit a letter concerning the installation of an eel ladder? Are there plans to format a letter for this purpose or a petition that is planned? What can the public do to push for this proposal?

    Thank you!

    • Matthew Brocklehurst says:

      Hello Erik, great question! Please stay tuned to our newsletter and other information channels. We will be releasing information about how the public can get involved in this issue very soon.

  2. Robert Postma says:

    The rehabilitation of the Carillon Generating facility is focused on upgrading the generators over 16 years. A contract has already been let in October of 2020 for the first six units. The best time to consider an eel ladder is certainly during this disruption in dam operations. Our forefathers had the foresight to include a 20 meter high lock in the dam’s design to support commercial and recreational boat traffic, surely it is time to consider the natural traffic that has been disrupted for the past 60 years. The cost of an eel ladder could be shared between the provinces, the feds and Hydro Quebec.

  3. Erik Pohanka says:

    Thank you Matthew!

  4. raymond Marcotte says:

    i was involved in the design of this dam while working for Shawinigan Engeneering in montreal. at the time I suggested that the top of the dam could act as a bridge for cars only . of course the idea was rejected without any consideration ,

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