10.4 Status of mercury in fish

Last Updated: 
January 8, 2018

 

This indicator tracks mercury levels in fish sampled in Northwest Territories (NWT) streams and lakes.

Smoking fish in camp, NWT
Smoking fish in camp, NWT.

Contaminants such as mercury and others like PCBs, DDT, PBDEs, and organohalogens are being monitored in predatory fish in the NWT. Predatory fish (lake trout, pickerel, burbot, and northern pike), are specially sampled because they have a greater potential for bioaccumulation of contaminants.

Fish muscles and livers are sampled from burbot at the Rampart Rapids, Great Slave Lake and several smaller lakes in the NWT. Fish from lakes have been tested in the Deh Cho (Trout Lake, Cli Lake, Deep Lake, and Fish Lake) the Sahtu (Lac Ste. Therese and Kelly Lake) and the Akaitcho (Stark Lake and Nonacho Lake).

Data and information are from Northern Contaminants Program Synopsis Reports with specific data from a study by Dr. Marlene Evans (Environment Canada), pers. comm., and from Public Health Advisories issued by Health and Social Services, GNWT. The Northern Contaminants Program monitors long range contaminants in fish across northern Canada. This includes Yukon, NWT, Nunatsiavut, Nunavik, and Nunavut. Text drafted for this report by Indigenous and Northern Affairs Canada, and edited by the GNWT.

Definitions

Mercury: a liquid silvery-coloured metal.

PCBs: Polychlorinated biphenyls. Toxic organic compounds used as coolant in transformers and electric motors.

DDT: dichlorodiphenyltrichloroethane. A pesticide. Banned in many countries.

PBDEs: Polybrominated diphenyl ethers. Organobromine compounds currently used as flame retardants, on for example furniture.

Organohalogens: Organic compounds (e.g. plastic polymers), containing halogen atoms. Includes organochlorides.

Bioaccumulation/Biomagnification: accumulation of substances in an organism.

NWT focus

Aboriginal people in the NWT consume traditional country foods such as fish as a mainstay of their diet (see USE OF RENEWABLE RESOURCES focal point). Generally, fish is a good source of nutrition and high in protein, Vitamin B and omega-3 fatty acids. The health benefits of eating fish outweigh the potential risks.

Mercury is a contaminant that can be found in fish. Levels of mercury differ from lake to lake and can be due to human activities or to natural causes. 

Current view: status and trend

Increases of mercury in fish have led to Public Health Advisories in the NWT. Mercury is rising in predatory fish due to long range contaminants from other countries such as China. Climate change is also a contributor as the longer summer seasons allow for changes in the bioaccumulation of mercury in fish. Older and larger fish tend to have increased mercury due to the biomagnification over time. Over the last 35 years temperatures have increased in the Mackenzie Basin approximately 1°C  per decade. (See CLIMATE AND WEATHER focal point).

Trends are showing that levels of mercury and other contaminants are increasing at a greater rate in smaller lakes than the larger water bodies such as Great Slave Lake and Great Bear Lake.

Mercury in lake trout and burbot in Great Slave Lake's East Arm (Taiga Shield) is showing an increase since early 2000.
Mercury in lake trout and burbot in Great Slave Lake's East Arm (Taiga Shield) is showing an increase since early 2000. Dr. Marlene Evans, Environment Canada, pers. comm.

A significant increase in mercury in fish from smaller lakes was detected in Stark Lake (62.46ºN; -110.33ºW), and Nonacho Lake (61.98ºN; -109.46ºW). Both lakes are in Taiga Shield south of the East Arm of Great Slave Lake.
A significant increase in mercury in fish from smaller lakes was detected in Stark Lake (62.46ºN; -110.33ºW), and Nonacho Lake (61.98ºN; -109.46ºW). Both lakes are in Taiga Shield south of the East Arm of Great Slave Lake. Data compiled by Dr. Marlene Evans, Environment Canada.

Looking forward

The NWT will continue to monitor contaminants to ensure northerners are well informed as to their consumption of fish. 

This data is also used to influence international policies on contaminants such as United Nations Economic Commission for Europe Convention on Long-Range Transboundary Air Pollution, Protocols on POPs and heavy metals and the global United Nations Environment Programme and the Stockholm Convention on POPs. 

It is important to continue monitoring temporal trends of contaminants in fish to understand why changes are occurring. International policy on mercury use could influence this trend and the Northern Contaminants Program is compiling all of its mercury data over the last 18 years to support international policy discussions. Challenges of logistics in the North continue to add to the costs to monitor many lakes and funding is limited.

The Chief Public Health Officer has recommended limiting or avoiding consumption of fish from specific lakes in the NWT due to elevated levels of mercury. Please visit the Health and Social Services website for the most up-to-date consumption advice.

For more information

Contact us

Found an error or have a question? Contact the team at NWTSOER@gov.nt.ca.