Canadian Rivers Institute (UNB) – Dr. Linnansaari

The Canadian Rivers Institute (CRI) at UNB is studying the migration and survival of smolt, post-spawning (kelt), and adult Atlantic salmon through the 96-kilometre long Mactaquac reservoir upstream of the Mactaquac Generating Station.

The CRI received a three-year grant from the Atlantic Salmon Conservation Foundation totaling $118,500. The project is a part of larger research (Mactaquac Aquatic Ecosystem Study consortium) evaluating the options for the future of the generating station which is nearing the end of its service life.

The CRI’s Dr. Tommi Linnansaari notes it is widely recognized that when a river is regulated for hydropower by building a dam spanning across a river, the migratory routes of diadromous fishes, like Atlantic salmon, will be affected.

“Multiple means to mitigate these effects exist, and often fish passage solutions are required and built at dams,” he said. “However, the location of the dam may not be the only location the focus should be on. Dams create reservoirs behind them, and depending on the size of the dam and the geography of the impounded area, a sizeable reservoir may be created that may act as a movement barrier in itself. Relatively little is understood about the role of a reservoir as a movement barrier as opposed to the dams in itself.”

“Our project tries to understand how do different migratory life stages of Atlantic salmon cope with a large reservoir; are they able to find a migratory path through it, or do they “get lost”? Does the passage through the reservoir cause a delay in their migration? If yes, is this delay ecologically significant? Are there certain areas where the fish get confused along the way?”

Linnansaari said they are also interested in a secondary problem, related to how do Atlantic salmon behave as they approach the dam in close range.

“This is important to understand so that such behavioural data can inform what engineered solutions would be helpful when trying to arrange successful downstream passage for migrating salmon at a potential new hydropower facility.”

“In short, we are trying to assess how big of a problem the mere existence of a relatively large reservoir is for Atlantic salmon migration in the St. John River. In other words, if one found a silver bullet to build an engineered passage structure that was 100% efficient at a potential future dam at Mactaquac, do we still have a problem with salmon migration due to the reservoir? This information will not only inform us, but has implications for similar large hydro regulated rivers around the world.”

Linnansaari said one challenge researchers are facing is with low numbers of salmon it has been difficult to get enough fish for their tagging program.

“We have been successful for the most part, although we may have had to tag fish with some delays. Also, we have realized we have had to tag more fish than we first anticipated due to some technical challenges. However, the data has been very informative, and we are progressing as planned.”

Some of the things being considered as part of this project include: does the reservoir create a movement barrier to different life stages of Atlantic salmon; does it cause migratory delays, and what are the ecological implications of such delays; what is the survival of different life stages through the reservoir; are there certain locations along the reservoir that are more problematic than others; can we link the movement rates and success to hydropower operations at the dam; and how do Atlantic salmon smolts and kelts (post-spawned, overwintered salmon) approach the dam?