This project studies contaminant levels in lake trout from Kusawa Lake and Lake Laberge in the Yukon to determine if these populations remain healthy in terms of contaminant loads, whether these important resources remain safe and healthy food choices for northerners and to see if contaminant levels are changing over time.

Why is this important?

Mercury in lake trout has prompted Yukon Health to advise that women of childbearing age and children under 12 should limit their consumption of large Yukon lake trout according to the following guidelines:

  • Fish shorter than 40 cm (about 2 lbs): unlimited consumption.
  • Fish measuring between 40 and 60 cm (about 2 to 6 lbs): limit to three to four meals/week.
  • Fish longer than 60 cm (>6 lbs): limit to one or two meals/week.

What are we doing?

This project monitors lake trout from Kusawa Lake and Lake Laberge every year, in collaboration with the Ta’an Kwach’an and Champagne and Aishihik First Nations. Twenty trout are sampled from each lake each year. PBDEs, mercury and other metals (e.g. arsenic and lead) are measured in trout muscle and PFASs are measured in liver. Every second year we measure POPs in trout muscle.

What do we know?

  • Mercury in fish is a concern in many places in the world, including the Arctic. Most mercury in Yukon lakes and rivers comes from natural sources such as volcanoes, erosion and forest fires.
  • The Yukon also receives mercury and other contaminants from pollution from the south that gets blown to the Arctic by wind. Fish may absorb these contaminants and pass them on to the humans who eat them.
  • Older, longer fish have more mercury, which is why health advice is based on the length of the fish.
  • Predatory fish have higher levels of mercury than those lower on the food chain. To minimize mercury consumption, eat lower on the food chain. Fish that are low in mercury include whitefish, salmon and grayling.
  • Levels of pesticides and flame retardants (PBDEs) in fish are below levels of concern.

How our research is helping the world

Data from this monitoring program were part of the evidence that led the United Nations Environmental Program to create the Minimata Convention. This is a global agreement that will limit mercury emissions to the environment and ultimately reduce the mercury in Arctic caribou. The convention came into force on August 16, 2017, and as of March 22, 2018, 90 countries have ratified thereby agreeing to reduce their mercury emissions. We are making a difference!

Where is this study being done?

Lake trout samples for this study are collected from Kusawa Lake, Yukon.

What has been done?

  • Samples have been collected from this lake in 1993, 1999 and then every year since 2001. The most recent collection was the summer of 2017 in collaboration with the Champagne and Aishihik First Nations.
  • Muscle and liver are being analyzed for a range of contaminants.

What we know so far

Mercury

  • levels are higher in bigger, older lake trout:
  • fluctuate from year to year but are not changing over the long-term:
  • These changes may be caused by changes in temperature, rain and snow, as well as how much mercury pollution is put into the air in other parts of the world.

Pesticides

  • have declined since we started measuring them in 1993:
  • Some pesticides have been banned from widespread use.
  • Descriptions of each compound are available in the Compounds tab.

PBDEs

  • We are not sure why levels were particularly high in 2007.
  • In general, levels have gone down since we started measuring them in 1993:

We are continuing to monitor contaminants in lake trout from Kusawa Lake to keep track of contaminant levels, and to try to better understand how and why contaminants accumulate in fish the way they do.

Where is this study being done?

Lake trout samples for this study are collected from Lake Labarge, Yukon.

What has been done?

  • Samples have been collected from this lake in 1993, 1996, 1998 and then every year since 2000. The most recent collection was the summer of 2017 in collaboration with the Ta’an Kwach’an Council.
  • Muscle and liver are being analyzed for a range of contaminants.

What we know so far

Mercury

  • levels are higher in bigger, older lake trout:
  • fluctuate from year to year but are not changing over the long-term:
  • These changes may be caused by changes in temperature, rain and snow, as well as how much mercury pollution is put into the air in other parts of the world.

Pesticides

  • have declined since we started measuring them in 1993:
  • Some pesticides have been banned from widespread use.
  • Descriptions of each compound are available in the Compounds tab.

PBDEs

  • We are not sure why levels were particularly high in 2006.
  • In general, levels have gone down since we started measuring them in 1993:

We are continuing to monitor contaminants in lake trout from Lake Laberge to keep track of contaminant levels, and to try to better understand how and why contaminants accumulate in fish the way they do

PCBs – polychlorinated biphenyls. This group of man-made chemicals was once widely used in industry as heat exchange fluids, in electric transformers and capacitors and as additives in paint, carbonless copy paper, and plastics. They were banned in the 1970s.

DDT – Dichlorodiphenyltrichloroethane. A man-made insecticide; used world-wide; banned in most countries by the early 1990s.

Chlordane – A man-made insecticide used extensively to control termites and on a range of agricultural crops; banned under the Stockholm Convention.

HCH – Hexachlorohexane; a man-made insecticide; one form (lindane) was used as a broad-spectrum insecticide for seed and soil treatment, foliar applications, tree and wood treatment and against ectoparasites in both veterinary and human applications; banned under the Stockholm Convention.

CHB – Chlorinated Bornanes (specifically toxaphene); a man-made insecticide; used on cotton and food crops; banned under the Stockholm Convention.

CBz – Chlorobenzene; a group of man-made chemicals used in industrial processes, as a fungicide and a flame retardant; banned under the Stockholm Convention.