FAQs
At Clover Leaf, we pride ourselves on our extensive knowledge of seafood and our willingness to provide information. Here are a few frequently asked questions. Please select a category and click on a question below.
Questions - Mercury
- What is mercury?
- What are the Canadian Guidelines for mercury in fish?
- What type of fish are affected by mercury?
Answers
1) What is mercury?
Mercury is a naturally-occurring element which is found in soil and rocks and also exists in lakes, streams and oceans. In addition to natural sources, mercury is released into the environment by human activities such as pulp and paper processing, mining operations, and burning garbage and fossil fuels.
2) What are the Canadian Guidelines for mercury in fish?
Health Canada has established a guideline level of 0.5 parts per million (ppm) for mercury in most commercial fish. This guideline is enforced by the Canadian Food Inspection Agency (CFIA). It was first set in the 1970's and, based on a recent re-evaluation, is still considered appropriate to ensure that the health of Canadians is protected from the toxic effects of methyl mercury.
3) What type of fish are affected by mercury?
Most of the methyl mercury (MeHg) that humans consume in our diet comes from seafood. All fish and shellfish have varying levels of MeHg in their flesh. In general, the larger predatory species of fish are most likely to have higher levels of MeHg due to bioaccumulation over their lifespan. Small and mid-size fish farther down the food chain tend to have lower levels of MeHg. The vast majority of the fish and shellfish consumed in Canada have been shown to have low mercury levels, including canned tuna.
Canada’s Food Guide to Healthy Eating recommends that Canadians eat at least two servings (of 75 grams each) of fish each week. Children, pregnant and breastfeeding women and women who may become pregnant can particularly benefit from the nutrients offered by fish. However, because the developing fetus and young children are also most at risk from mercury exposure, it's important that pregnant and breastfeeding women, women who may become pregnant and parents of young children are aware of what types of fish are a good choice for frequent consumption and which should be eaten less often.
Which to Choose More Often?
Fish and shellfish that contain higher levels of omega-3 fatty acids and are also low in mercury include: anchovy, char, hake, herring (including sardines), Atlantic mackerel, mullet, Pollock (Boston bluefish), salmon, rainbow trout, Lake Whitefish, blue crab, shrimp, clams, mussels and oysters.
Many types of fish are also a significant source of vitamin D and contribute valuable mineral nutrients to the diet such as selenium, iodine, magnesium, iron and copper.
Which to Choose Less Often?
These include fresh/frozen tuna, shark, swordfish, marlin, orange roughy and escolar.
Canadians who like to consume these types of fish can continue to do so, but should limit their consumption to the amounts shown in the table below. Other types of fish should be chosen to make up the rest of their recommended weekly fish consumption.
General Population - 150 g per week
Specified Women * - 150 g per month
Children 5-11 years old - 125 g per month
Children 1-4 years old - 75 g per month
* Specified women are those who are or may become pregnant or are breastfeeding.
Note that this advice does NOT apply to canned tuna.
Canned Tuna
Canned tuna, especially canned light tuna, is one of the most popular types of fish for many Canadians. The fish used in canned tuna products are generally younger and smaller and have significantly less mercury than fresh or frozen tuna, so that most Canadians don't need to be concerned about consuming canned tuna.
However, for a very specific group of people who consume large amounts of canned albacore tuna, there is some potential for exposure to higher levels of mercury than is considered acceptable. Because of this, Health Canada has issued advice for children and some women on the consumption of canned albacore tuna. The advice does not apply to canned light tuna, nor does it apply to Canadians outside of the specified groups.
Canned Albacore (White) Tuna Advice (does not apply to canned light tuna)
Specified Women * - 300 grams a week (4 Food Guide servings)
Children 5-11 years old - 150 grams a week (2 Food Guide servings)
Children 1-4 years old - 75 grams a week (1 Food Guide serving)
* Specified women are those who are or may become pregnant or are breastfeeding.
Canned albacore tuna is also often called canned white tuna, but it is not the same as canned light tuna. Canned light tuna contains other species of tuna such as skipjack, yellowfin, and tongol, which are relatively low in mercury. Canned light tuna also tends to be lower in cost relative to albacore tuna.
