The Salmon and the Beaver: Resilience Amidst the Struggle of Drought

By Marjorie Lieuwen, Conservation Science Coordinator, Northern BC

November 1, 2023

When the month of September rolls around we at the Buck Creek Hatchery and Nature Centre in Houston start to feel the excitement and anticipation of the arrival of coho salmon spawners. The coho have undertaken a vast journey up the Skeena River, Bulkley River, and through Hagilwet Canyon until finally they reach the fork in the stream where the Bulkley River branches into the Morice River (Widzin Kwah) and Upper Bulkley River (UBR, Neexdzii Kwah).

We are eager to see how many coho will come up the UBR, which skirts around the town of Houston before continuing past Topley to Bulkley Lake. Some of these coho may have hatched and grown into fry at our hatchery! Having reached their home waters where they were either born or released, the coho have now reached the end of their life’s journey and will lay their eggs in redds, which are rock nests in the gravel of the river bed.

Our goal is to monitor the return of the UBR coho spawners and capture a small number of them in order to collect a target of 10,000 eggs for our hatchery. This year we anticipated that the coho would have a challenging migration up the UBR as the river levels were very low from the drought. We knew of some beaver dams blocking chinook spawners in August, and with very little rain since then the number of beaver dams had likely increased. With the concerns about the low returns of salmon spawners to the UBR, we want to ensure they have the best chance to reach their spawning grounds in time. We also want to see them spread out throughout the river so that redds are not too concentrated. Careful management of beaver dams is one tool in our belt to help achieve this goal. We secured funding from the Pacific Salmon Foundation Drought Response Fund, called on our network of amazing volunteers, reached out to our landowner contacts to secure access to the river and began journeying with the coho up the UBR!

One of the largest impassable beaver dams we encountered this year. Note how shallow the water is below the beaver dam, leaving fish vulnerable to predators as they have no way through the dam.

It became clear quite early on that the beavers had been hard at work, as we found the first dam within 1 km of the Morice/UBR confluence and about 100 coho stuck below it. We have an interesting relationship with beavers. They are amazing river engineers.

We found one dam created from a huge tree the beavers felled into the water, and then built around it with branches stripped from that tree and other trees. We marvel at how they move big rocks and logs.

Without beaver dams the water levels in the river would have been even lower in this drought year. Beaver ponds slowly release water and create perfect rearing pools for juvenile coho salmon. However, when the dam completely spans the river it becomes an impassable barrier to coho spawners migrating upstream.

This year we found 15 such beaver dams within the first 30 km of the UBR. When the fall rains come they bring the river level up so it typically flows around the side of the dam and salmon can swim by. But in the last few years the rains have been coming later, and while coho will wait for a while, eventually they start trying to push through.

Between September 27 and October 5 we found 2 dead pre-spawn females and 4 dead males that had become stranded or stuck from trying to get past a beaver dam. We didn’t get a major rainfall event until October 16. But through our beaver dam management activities we were able to successfully assist at least 300 coho spawners past the beaver dams. While some of them stopped to spawn along the way, about 100 made it at least 30 km up the river to an area of valuable spawning habitat.

A dead coho found on the sticks of a beaver dam. While we were there another coho attempted the same thing and we were able to pick him up and put him on the other side. 
A beaver dam after we have created an opening for fish passage. 

You’re probably wondering, what does managing a beaver dam look like? Some people ask “Why don’t you just get rid of the whole dam and then you won’t have to deal with it anymore?”

But this is actually counterproductive. Besides the harassment to the beavers, the juvenile salmon rearing in the beaver pond would be flushed out in the ensuing rush of water, or become stranded and die on the rocks as the river level rapidly drops. Instead, an effective compromise is to create an opening in the dam about 1 meter wide, removing the major sticks and rocks but leaving the base of the dam intact so we don’t drain too much from the beaver pond. The flow of water and some encouragement from our kicking feet creates a plunge pool at the bottom, giving the fish enough momentum to swim up and through the opening.

The fish respond quickly to the change in water flow and typically within an hour are starting to jump through. The beavers make quick work of repairing this, typically overnight, and so we may have to return a few days in a row until we’re satisfied the fish have made it through, and then find the next dam the fish are stuck at.

To find the beaver dams we used a combination of prior knowledge, drone flights and many hours of river walking. I want to make special mention of Marcy, Regina, Joanne, Tasheena, Laurie, Sarah and Cindy who hiked, bushwhacked, waded, and clambered up and down riverbanks with me to get to the beaver dams.

It was so rewarding to come back to one dam after notching another 1 km upstream, and hear a cacophony of splashing and whooshing, and count 250 coho spawners swim through the dam in the course of an hour.

A coho salmon enthusiastically swimming up through a notch in the beaver dam to get further upstream to spawn.
 Long-time volunteer Regina Meints with a beautiful coho male caught at the outflow of Buck Creek.  

Of course the other thing on our minds while all this is going on is to capture some of the coho for broodstock for our hatchery. In this regard the beaver dams are helpful to us as we find where the salmon are held up, catch some and then open the dam for the rest to keep moving upstream. We caught most of our broodstock in one day!

We transported them to our holding tanks to wait for the females to be ready for egg take. We tried on two later days to find females that were “farther along.” On one day we caught 16 females and 18 males, and the second day 17 females and 9 males. Of these we kept 2 males and 1 female, and we were so encouraged to see that proportion of females, a very promising sign for the future of UBR coho.

On that second day we pursed a seine net downstream of the Buck Creek confluence and came up with nothing. A second try upstream of the confluence yielded a net bursting with fish and we thought of Jesus and his disciples in John 21:6, “Cast the net on the right side {of Buck Creek}”. And in the end we were blessed with 10,600 coho eggs which are now incubating in the egg room of our hatchery. 

We marvel at the wonder of God’s creation in the remarkable life story of the salmon and are thankful to be a part of stewarding this piece of creation. 

Thank you to all the amazing volunteers who came to help us catch fish, notch beaver dams, perform egg takes, count eggs & fertilize them. Thank you to the landowners and business owners all along the Upper Bulkley River who generously grant us access to the river from their property. We were also supported by Department of Fisheries and Oceans staff and the Pacific Salmon Foundation. Thank you for helping us care for the salmon in so many ways!

Marjorie Lieuwen serves as Conservation Science Coordinator at A Rocha’s Buck Creek Canfor Hatchery and Nature Centre in Houston BC. 

Dripping hands after a full day of broodstock capture
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