November 15, 2022

Juvenile Chinook Habitat Research Using Strontium

The Yukon First Nation Salmon Stewardship Alliance partnered on research to study juvenile Chinook salmon habitat.

Juvenile chinook. Photo: Elizabeth MacDonald

The Yukon First Nation Salmon Stewardship Alliance partnered on research studying juvenile Chinook salmon habitat use in the Yukon River with Natasha Ayoub. This project will take several years, but will improve our understanding of where Chinook juveniles are spending their summers and winters in freshwater.

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What is strontium, and how can it be used?

Strontium is a natural element found in bedrock. Strontium dissolves into water as water travels over and through the land. Water flows into creeks, lakes, and rivers where strontium ratios/levels are distinct from one tributary to another. As fish grow, they absorb the naturally occurring strontium from the water and this element gets incorporated into their bones. Otoliths, or ear bones, are of interest to scientists because these bones grow annuli (or new rings) each year.

The growth of these rings is like the growth rings of a tree. Using a laser you can analyse the strontium ratios from each ring, which can be compared to a baseline of strontium in different water samples. Matching the strontium ratios in the fish otoliths to the ratios in the baseline of the water samples help to find out where each fish was at different times in its life.

Research Goals

  • Learn where juvenile Chinook are rearing and over wintering within the Yukon River drainage.
  • Timing of when juveniles move between habitats.
  • Create a map and dataset of Chinook locations within the Yukon River drainage.
  • Create a strontium baseline that can be used by future researchers studying fish.

Yukon River Strontium Baseline

A baseline was first initiated by Sean Brennan to study Chinook habitat use patterns in freshwater across the entire Yukon River. Our goal is to increase our understanding of how habitat is used by juvenile Chinook salmon in the Yukon River so that important habitats are identified and can be considered for protection. For the baseline data to be representative of juvenile habitat, we needed to expand it by collecting more water samples, which are then shipped out to a laboratory for analysis. The laboratory can then determine the strontium ratios (as a ratio of two isotopes), or two forms of strontium with different chemical properties for a specific location.

Computer models can be used to estimate the strontium ratios between collection sites. Once enough water samples are collected, a map can be developed to indicate naturally occurring elements and help us understand baseline conditions for the sample sites. A drainage as large as the Yukon River will require many water samples.

Otolith encased in resin. Photo: Natasha Ayoub

2022 Research

Otolith and Water Collections

In 2022, 76 water samples were collected by YFNSSA, Natasha Ayoub, Tr’ondëk Hwëch’in and the Wildlife Conservation Society. These water samples, and previous water samples will be used to form the baseline map. These samples will be analysed in late winter and will inform future water sample collection sites that will be needed to complete the strontium baseline map.

In total 102 otoliths were donated to the project in 2022 from Yukon First Nation citizens, Whitehorse Rapids Fish Hatchery, Alaska Department of Fish and Game and a joint Chinook carcass project from Will Twardek and Kwanlin Dün First Nations (KDFN). Will Twardek and KDFN also donated 109 otoliths that were collected from previous carcass surveys in 2018, 2019 and 2021.

Otoliths will be analysed and compared to the strontium baseline created from the water samples. This should provide valuable information on where juvenile Chinook are rearing in the spring, summer, fall, and where they are overwintering before heading out to the ocean. The otolith rings will provide the timeline for these movements, including when the Chinook reaches the ocean.

Water sample bottle at acollection location. Photo:Marina Milligan

Traditional Knowledge

Including Traditional Knowledge (TK) into this project is a must. TK covers a much longer time series than scientific data. It is important to capture all areas that were used by Chinook historically.

As Chinook numbers decrease, we know that their freshwater habitat needs have also shrunk. If we only look at the last 30 years, we are unlikely to understand their full habitat range prior to their decline. This is particularly important when considering areas to protect and conserve.

YFNSSA is working with Yukon First Nations to find the most appropriate way to incorporate this knowledge.

Juvenile chinook. Photo: Elizabeth MacDonald

Mapping Products

We have created a series of maps for the entire Yukon River drainage in Canada and showing bedrock type (differing strontium ratios) and locations of adult and juvenile Chinook habitat. An overview map (below), as well as map subsets corresponding with each Yukon First Nation’s Traditional Territory were produced for a total of 15 maps. These maps provide the first comprehensive mapping of juvenile Chinook locations. YFNSSA wants to continue compiling data to fill gaps in our knowledge, including the addition of TK locations.

Thank You

Kwanlin Dün First Nation, Teslin Tlingit Council, Tr’ondëk Hwëch’in, Yukon First Nation citizens, Al von Finster, Alaska Department of Fish and Game, Whitehorse Rapids Fish Hatchery, Wildlife Conservation Society, Will Twardek – Ecofish Research, Canadian Mountain Network, Fisheries and Oceans Canada – Aboriginal Aquatic Resource and Oceans Management, Fisheries and Oceans Canada – Indigenous Habitat Participation Program, Mitacs, Yukon Fish and Wildlife Management Board – Enhancement Trust.


Natasha Ayoub, PhD student, Fisheries Biology, University of Waterloo

Natasha is a conservation biologist who is passionate about salmon and habitat conservation. Natasha is a Yukoner who believes that weaving together Indigenous knowledge and western science is a key way to see the big picture. She hopes that projects such as this will provide valuable information to support future land use planning, habitat restoration activities and conservation and protection of critical habitats in the Yukon.

Marina Milligan, Fisheries Biologist, YFNSSA/CYFN

I am an ecologist interested in the connections between all living things. I love advocating for salmon because of their deep ecological and cultural significance to our waters and lands. My contributions to this project include providing logistical support, collecting samples, reviewing literature, and managing data.

Elizabeth MacDonald, Manager of Fisheries, YFNSSA/CYFN

I live in Whitehorse with my family and enjoy the outdoors (including fishing), flying my drone and being engaged with people on salmon. Salmon are my passion. I am the lead on the Traditional Knowledge collection and financial agreements for YFNSSA/CYFN.

University of Waterloo

University of Waterloo is located in Waterloo, Ontario and has been operating since 1957. It was rated as #1 in most innovative and experiential learning by Maclean’s in 2022. The water samples and the otoliths will all be analyzed at the University of Waterloo laboratories.

Yukon First Nation Salmon Stewardship Alliance/Council of Yukon First Nations (YFNSSA)

YFNSSA started in 2021 and is located at the Council of Yukon First Nations. YFNSSA supports Yukon First Nations investigations of salmon, other aquatic resources such as freshwater fish and their habitats, and healthy ecosystems at a watershed level through a funding agreement with Fisheries and Oceans Canada (DFO) and its Aboriginal Aquatic Resource and Oceans Management (AAROM). YFNSSA is committed to ensuring that Yukon First Nations knowledge, skills, values, and experience guide research investigations and fisheries policy in the Yukon.