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Will guide tired salmon back to sea
Author: Juliet Landrø

Will guide tired salmon back to sea

Researchers are about to uncover the secret life of kelts in the river. These winter-survivors are important for securing the salmon population, and now researchers seek to help them pass obstacles in the river come spring. 

– We know very little about what influences the swimming patterns of kelts, but we know that this is a very important life stage for salmon, says Kelt2SEA project manager Ana Silva at the research centre HydroCen and the Norwegian institute of Nature research.

Researchers have already succeeded in making guiding solutions for salmon smolt. However, providing cost-effective downstream solutions for salmonid kelts is still one of the major remaining challenges when it comes to safe two-ways passage of migrating fish, particularly past hydropower installations in large river systems.

–The ultimate goal is to get the salmon safely past turbines and dams so they can reach the sea and survive for a new spawning season, says Silva.

Will study how kelts react to hydrodynamics and flow discharge fluctuations in the river

Atlantic salmon kelts are adult salmon that have spawned in the river and stayed in the river over winter. These individuals start their downstream migration back to the sea for foraging to survive and return as repeat spawners the following year. 

Kelts cease feeding at the beginning of their migration to spawn in the river, which together with the spawning rigors, can cause them to lose almost half their original body weight. A fast return to the sea is then vital for their survival. Nonetheless, the majority of kelts choose to stay in the river over the winter instead of migrating immediately after spawning. The researchers do not know exactly why some salmon choose to spend the winter in the river. Maybe spawning took such a toll that they needed a bit of a break before heading back to the sea?

NINA-forsker Ana Silva leder prosjektet for HydroCen.

When spring finally comes, they start their downstream migration to the sea. During migration, if they have to spend energy overcoming man-made obstacles, the chances are high that they die before reaching the oceans food supply.

– If we can better understand the swimming behaviour of the kelts, then we can develop some solutions to help them past dams and other obstacles in the river, says Silva. 
She works as a researcher at the Norwegian Institute for Nature research (NINA) and is one of the world's leading experts on fish behaviour.

In her project Kelt2Sea,  there is an interdisciplinary team of researchers and experts from several countries and disciplines, from engineers to biologists and ecologists.

Laboratory experiments with live fish

At the moment, the researchers are preparing experiments that are to be done in the laboratories of the power company Vattenfall in Sweden. In the "Laxeleratorn" flume they will measure the fish's response to different velocities and acceleration that commonly exist in the vicinity of a hydropower plant station. 

I laboratoriet til Vattenfall i Sverige skal forskerne bruke forsøkskanalen "Laxeleratorn" for å sjekke hvordan fisken reagerer på ulike hindringer og forhold i vannet. Foto: David Aldven/Vattenfall.

– First, we will try to understand the behavior of the fish under various water conditions, says Olivia Simmons, who is a researcher in the project.
– Then we will study the kelts’ behaviour in the vicinity of different racks and bypass entrances, she says.

Olivia Simmons skal utvikle en modell for å vise fiskenssvømmemønster.

Simmons is originally from Canada and recently completed her PhD at Bournemouth University, UK. She has come to Norway, and the Norwegian Institute of Natural Sciences, to do this work in the Kelt2Sea project in HydroCen.

Will develop a model for power producers and management

The aim is that results from this research can be used by power producers and authorities, both in Norway and internationally, to ensure better two-way fish migration.

–By expanding the knowledge on kelt behaviour to hydraulic properties of the flow, we will better understand the swimming choices that have been observed in previous projects such as SafePass, says Silva.

 – Among other things, we will develop predictive models for kelts, that will then help us create new solutions to facilitate downstream migration of kelts, says Silva.
Previous research shows that the longer kelts swim around in the reservoirs, the more energy they use. For every day they are prevented from reaching the sea, it can lose as much as 4-5% of their remaining energy reserves.

The video shows how a salmon swims for several days before it finds its way out of the river. Illustration Henrik Baktoft/DTU Aqua.

– So, if we can help their migration, it will have a big impact on the salmon survival, says Silva.


Ana Silva, project leader, NINA

Olivia Simmons, NINA

David Aldven, Vattenfall

Partnere i prosjektet er:

NINA, Vattenfall, Karlstad University 



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