Great news: juvenile salmon moving through habitats reconnected after 100 years
It’s an exciting time for Raincoast’s juvenile salmon work in the Fraser River estuary. Our Steveston jetty breaches are enabling them to migrate in a way they once did.
Success! Since the removal of sections of the Steveston jetty in February, we have been sampling our new jetty ‘breaches’ and have consistently caught juvenile salmon moving through them! This is a huge success and was realized just weeks after their construction. The breaches were placed in the Steveston Jetty to create pathways for juvenile salmon to move from the river and into the estuary delta and marsh during their outmigration which begins every March. The three, 50-meter wide breaches are a small step toward restoring an estuary where the natural movement of salmon, freshwater and sediment is being encouraged. These processes have been restricted by a variety of structures built since the early 1900s, including the 8km long Steveston jetty.
When we created the breaches in February, our strategy was to remove sections of the jetty and then let the flow of the river create natural channels onto Sturgeon Bank over time. To sample, we work in marsh channels on the back side of the jetty, find a place to set our nets and try to withstand the current created by the water flow moving through the breach. Using fyke nets, which consist of two wings connected to a square frame with a small opening at the back, fish are directed through the opening and are unable to swim out. Our luck at both the east and west breaches means the marsh directs the water flow into a narrow channel and our net has successfully interrupted any fish moving through.
In just 45 minutes on March 26th at the east breach, we caught dozens of juvenile Chinook and chum salmon moving through the breach and into the safety of the marsh. This seems like a much better alternative for tiny salmon than being blown out to Georgia Strait.
On day two at the west breach, we again captured juvenile salmon moving through. We set the net when the tide had fallen. Despite this, the strong current still made it tough to keep the net in place. But in two hours on our first sampling round, we captured 85 juvenile salmon – 55 chum and 30 Chinook. We were back sampling the breaches on May 10th and we found similar results. We again set up at our east breach, where a small channel has begun to form, and as the tide fell we captured 176 juvenile chum and 31 juvenile Chinook! We couldn’t believe our eyes as we kept retrieving them, thwarting their efforts to scurry away from my net.
From our previous years research, we know that May is the peak of the outmigration for juvenile chum in the Lower Fraser and also the peak for juvenile Chinook from the Harrison River. These little fry are barely 4 to 5 centimeters long. In March, some are still buttoning up from having a yolk sac protruding from their belly, their source of nutrition for the first weeks of life. These juvenile salmon likely need to spend at least a few tidal cycles in the marsh before they are ready for the saltier water that lie at the end of the jetty. As such, these breaches may play a critical role in supporting their transition.
The Steveston jetty is only one of the many barriers which exist today in the Fraser estuary, altering the movement of salmon, freshwater and fine sediments. While we are hoping to continue our progress by restoring connectivity through other barriers such as the North Arm jetty and Iona causeway, the opposite is proposed for the southern portion of the Fraser estuary at Roberts Bank. Roberts Bank is home to a highly productive eelgrass beds but habitats there are fragmented by the presence of the Deltaport and BC Ferries causeways.1
The Port of Vancouver is proposing to expand the Deltaport terminal. The project is in the final stages of its environmental assessment. At a time when the focus should rightfully be on restoration of Fraser estuary habitats and the Chinook that rely on them, this proposal takes the estuary in the opposite direction. It would create further barriers and further alter migration pathways for juvenile salmon.
We will continue to sample at our jetty breach sites every two weeks until July when the outmigration finally ends. The last juvenile Chinook to arrive in the estuary are from the South Thompson watershed. As the spring freshet is underway, the river level will rise and the current will increase, the exact conditions needed to carve the migration channels onto Sturgeon Bank. Of course, this will also make the sites increasingly difficult to sample. Always a fun challenge. Wish us luck!
- This map of the Lower Fraser river was published at The Narwhal. ↩
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