Mercury in Fish Investigation

Photo: Azimuth-Consulting

Update: Mercury in Fish Investigation in Williston and Dinosaur Reservoirs

Our Peace Region Board approved a comprehensive study to collect tissue samples from fish in the Williston and Dinosaur Reservoirs and tributaries, in order to measure mercury concentrations. The mercury data collection project started in spring 2016 and will take up to three years to complete. The results of this study, which will be combined with and compared to information collected previously, will provide updated information on mercury levels in several fish species in the reservoirs and their tributaries. A preliminary report (May 2017) and an overview of preliminary findings are available.

The goal is to improve our understanding of mercury in fish in all parts of the reservoir system, and to provide this information to agencies responsible for advising the public on fish consumption so that they have enough information to consider in developing any potential revised mercury public advisory.

This is one of many fish and wildlife projects the FWCP is funding in its Peace Region in 2017 – 18. Learn more about Peace Region projects.

First Nation Involvement

This investigation into fish mercury concentrations included many opportunities for direct involvement of First Nations in the collection of fish samples. Citizens from six First Nations took part in a training session and learned how to collect fish samples; many participated in collecting fish in areas targeted for sampling; others acted as community coordinators and collected samples during community fishing activities; and some gathered information about fish consumption. First Nation-led businesses were directly involved or had the opportunity to be involved in the collection of fish samples and worked with the consultants leading this work on behalf of the FWCP.

FWCP Involvement

 The Fish & Wildlife Compensation Program (FWCP) recognizes that mercury concentrations in fish caught in Williston and Dinosaur reservoir basins are a priority concern for local First Nations and stakeholders. Our Action Plan for Reservoirs (2014) identifies mercury as a high-priority issue and defines objectives, and specific actions to address mercury in our Peace Region. One of those actions is to collaborate with First Nations and liaise with appropriate agencies in implementing a study to investigate mercury concentrations in fish for Williston-Dinosaur basins.

Our Peace Region board selected Azimuth Consulting Group Partnership (Azimuth) to conduct a multi-year investigation to study mercury from key fish species in Williston and Dinosaur Basins. The goal is to improve our understanding of mercury in fish in all parts of the reservoir system, and to provide this information to agencies responsible for advising the public on fish consumption so that they have enough information to consider in developing any potential revised mercury public advisory.

FWCP Role

Our role is to facilitate dialogue among partners, including engagement with First Nations, and oversee the scientific collection of relevant data. We do not have a mandate to specifically address human health issues related to fish consumption but we are committed to working with others in the region to fill information gaps and support a process to provide information to agencies responsible for human health.

Mercury in the Environment

Mercury (Hg) is an element of the Earth that is present in low concentrations everywhere in the environment – including in air, water, sediment, soil and in the tissue of all plants and animals. Some of this inorganic mercury is naturally transformed into a potentially more harmful form of mercury called methylmercury.

This transformation process occurs within the cells of bacteria, at the base of the food web, mostly in soil and in sediment of lakes and rivers. Under normal conditions, the natural rate of methylmercury creation is low. However, when a reservoir is formed, bacteria break down and decompose the flooded organic soil very rapidly, creating more methylmercury than under normal conditions until the flooded soil is fully broken down and the mercury in the soil runs out.

Once methylmercury has been created by bacteria, it is now part of the food web. Over time in new reservoirs, animals accumulate methylmercury at a greater rate than it can be eliminated from the body, so concentrations increase as animals get older and larger. Animals absorb mercury almost exclusively from their food, with ever increasing concentrations moving up the food chain. Because fish are at the end of a long chain of animals that eat other animals; from small and large invertebrates; and from small fish to large and carnivorous fish, methylmercury is always higher in fish than other animals. Furthermore, the concentration of methylmercury is always highest in large and old fish, especially those species at the top of the food chain such as Lake Trout, Bull Trout, Northern Pike and Walleye.

Mercury and methylmercury are present in other animals we consume, such as chicken, beef, deer, and moose – but in much lower amounts than fish, because these animals only eat plants, which are always low in mercury. Since the amount of mercury varies by fish species, size and age, it is important to measure mercury levels in fish from across the spectrum of species, sizes and ages.

Once the mercury present in the rotting, flooded organic soil runs out, mercury concentrations in fish slowly decline. Thus, fish mercury concentrations return to a new baseline level between 20 and 30 years after reservoir creation.

Mercury concentrations in fish are reported in units of ‘parts per million’ (ppm). In British Columbia, typical fish mercury concentrations range from less than 0.10 up to 1.0 ppm. By comparison, the mercury concentration in tinned tuna or store-bought halibut ranges from 0.15 to >0.30 ppm. Wild salmon normally have very low concentrations (<0.10 ppm), while other less commonly consumed species like marlin or swordfish can be higher (1 – 2 ppm). It is also important to realize that on their own, concentration data are not that meaningful. It is the “dose” that is important, which is a combination of fish mercury concentration and how often and how much fish are consumed over time by an individual.

Williston and Dinosaur Basins. The goal is to improve our understanding of mercury in fish in all parts of the reservoir system, and to provide this information to agencies responsible for advising the public on fish consumption so that they have enough information to consider in developing any potential revised mercury public advisory.


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