Makivik Magazine Issue 91

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Nunavik Research
Fact Sheet 24
The Nepihjee River Arctic Charr
The Nepihjee River Arctic charr population, introduced in 1999
to this river system directly northwest of Kuujjuaq, has had variable
success over the past decade. According to monitoring reports
compiled by the Nunavik Research Centre staff, a maximum of
approximately 1000 individual charr went to sea in 2005. However,
in the following years, monitoring the population became difficult
due to extremely high and extremely low water flows in the river.
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Measuring a charr.
in oxygen signatures of each annual
growth ring within an otolith, we can
estimate the average temperature
experienced by a fish in each year.
We can then look at the relationship
between temperature changes and
growth within each year and over a
fish’s lifetime.
In short, by looking
at the changes in
oxygen signatures of
each annual growth
ring within an otolith,
we can estimate the
average temperature
experienced by a fish
in each year.
What is the PIT-tagging for?
Some charr are more likely to
be affected by changes in temperature
due to their size, diet or condition. Tagging charr will allow
us to measure the growth of each individual fish from the time it
was tagged until it is recaptured. This information can be used to
study the differences in growth patterns among individuals. With
enough recaptures, we can also get a more accurate estimate of
the Nepihjee Arctic charr population size.
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Efforts to monitor the population have recently been redoubled.
In addition, researchers and technicians from the Nunavik Research
Centre, in collaboration with the University of Waterloo, initiated
a project during the summer of 2009 to investigate the effects of
temperature on the growth of Arctic charr in the Nepihjee River
system. Using the fish-way site built previously by the Nayumivik
Landholding Corporation, the core monitoring program to count
the number and size of migrants was continued—but with a twist.
Twenty Arctic charr from the run were harvested for temperaturegrowth
analyses, and another 250 charr were measured and tagged
with Passive Integrated Transponder (PIT) tags.
How can temperature effects on growth be measured?
Arctic charr otoliths (the small “ear stones” found in fish) are
a very valuable tool because they continue to grow throughout a
fish’s life. As a result, annual growth rings are formed, much like the
rings in a tree. The width of these rings is related to how much a fish
grew during that year. Each growth ring also reflects the chemical
signatures of the fish’s surroundings during the time that it formed.
One particularly interesting element included in the otolith is oxygen.
The types of oxygen molecules in the otolith are directly related
to the temperature of the water a fish was living in at the time that
part of the otolith was formed. In short, by looking at the changes
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A fishway trap that was installed in August 2009.
Can Arctic charr adapt?
Warming temperatures threaten cold-water adapted species
such as Arctic charr, particularly in polar regions where climate
change impacts are likely to be accelerated. It is a great challenge
to forecast the fate of Arctic charr, especially in unique areas such
as the Nepihjee where the population is so young. Obtaining
essential information such as population size, individual lengths,
and the relationship between growth and temperature, is critical
in terms of maintaining a sustainable fishery within an uncertain
climate.