Mercury in Kokanee Salmon

While there are many benefits of eating fish, it’s important to be conscious of the mercury in the fish you consume. Here’s a look at mercury levels in kokanee salmon, how they absorb mercury, and what limitations you should have on your kokanee consumption.

Health Benefits of Eating Fish

The majority of Americans consume some form of seafood on a weekly basis. Fish has been found to contain many essential nutrients such as omega-3 fatty acids and vitamin D. These nutrients are important for eye health and may help reduce risk for developing age-related macular degeneration (AMD).

However, many people are concerned about the high levels of mercury found in some types of fish. Mercury is a toxic heavy metal that can negatively affect the nervous system if consumed at high levels.

If you eat a lot of high-mercury seafood over time, your risk for health problems increases. High levels could harm an unborn baby’s developing nervous system or cause brain damage, or affect memory and learning ability in children or adults. The FDA recommends that pregnant women avoid eating shark, swordfish, king mackerel and tilefish because these types of fish often contain high amounts of mercury, but what about kokanee salmon? Salmon is generally considered safe, but that doesn’t mean that its completely free of mercury. So, how does it compare to other fish, and how safe is it actually?

Health Risks of Mercury in Fish

The type of mercury that’s found in fish is methylmercury, which is actually a neurotoxin. If you consume too much of it, it can certainly have an effect on your health. According to the EPA, possible symptoms include muscle weakness, impaired hearing, speech, or walking, a feeling of pins and needles in your mouth, feet, and hands, losing your peripheral vision, and generally losing coordination of movement.

Babies and unborn children are at an increased risk from mercury exposure and can suffer from a host of development problems, especially with the brain and nervous system. Remember, its a neurotoxin. These issues could lead to problems in later life with memory, language, attention, fine motor skills, and a host of other problems. For these reasons, pregnant women, women who may become pregnant, and children usually have more warnings and are at higher risk for the adverse affects of methylmercury than men and women who cannot become pregnant.

Factors that Increase the Likelihood of Mercury in Kokanee

• Pollution in the water
• Diet of the fish
• Size of the fish
• Freshwater or saltwater

Pollution

Obviously, the more mercury there is in the water, the more a fish will consume, absorb, and hold on to. I went searching the web for any instances where there were warnings not to eat kokanee. I found some warnings that were lake based, not species based, for some lakes in Oregon from back in the 1940s. These were based on pollution, and most of the warnings from that era were for rivers, but there were some for lakes that had a kokanee population. These warnings didn’t include any data about mercury levels or testing in kokanee, but were rather just general blanket statements about pollution in these bodies of water, and with warnings to avoid them.

Diet

There is more mercury in fish that eat fish. Once mercury is consumed, it stays in the body. A fish that eats other fish, and absorbs the mercury that the other fish ate, means that these predatory fish will be higher in mercury, which explains why sharks have one of the highest mercury levels of any marine life. Chinook and some other salmon eat other fish, but kokanee don’t eat other fish. Kokanee are at the bottom of the food chain. They only eat zooplankton and other really small things like that. While they might strike at other fish out of aggression, they aren’t eating any other fish.

Size of the Fish

Size of the fish is an indicator of both the age of the fish, and how much the fish has been eating. An older fish has been consuming longer, and will have absorbed more mercury. Additionally, if the fish is fatter, especially if it eats other fish, then its more likely to have eaten more mercury. Long story short, the bigger the fish, the more likely it is to be toxic. This is especially true for lake trout in the freshwater world.

Freshwater vs Salt Water Salmon:

There is generally a higher concentration of methylmercury in fresh water as opposed to salt water. However, the mercury in salt water is more likely to be consumed by fish. The mercury in fresh water sticks to decomposing organic material and is then broken down easier. The mercury in salt water sticks to the salt, and doesn’t break down as easily, and is more likely to be consumed and absorbed by fish. Because of that, you would expect to find higher levels of mercury in sockeye salmon as opposed to kokanee salmon, which are the landlocked freshwater sockeye salmon. There haven’t been any direct comparisons by biologists, but I’d love to see one. That said, shark and swordfish have about 60x more mercury than salmon. Halibut has about 15x more.

The Difference Between Wild and Farmed Salmon

Wild salmon have less fat, and have less Omega-6, but more Omega-3s than farmed salmon. I didn’t find any discussion about mercury in wild vs farmed salmon, but it stands to reason that a wild salmon is less likely to be in a high pollution area. Less pollution, less mercury. Kokanee are obviously a wild fish. I haven’t heard of any instance of farmed kokanee. Perhaps some farmed sockeye, but not kokanee.

How Much Salmon Can You Eat?

Different organizations and groups have different recommendations and guidance as far as salmon consumption. We’ve taken the most common responses and put them all together.

Women:

• 36oz
• 2 servings per week
• 10 servings per month

Children

• 18oz
• 10 servings per month

Men

• 5 servings per week,
• 20 servings per month

Montana produced the only series of recommendations specifically about kokanee salmon consumption. The state of Montana didn’t recommend any limitation for men or older women, but did recommend limiting consumption for children and pregnant women to 2 servings per week, or 10 servings per month.

Conclusion

Long story short, if you want to eat fish and you’re worried about mercury, kokanee salmon should be a fish you target. They’re a lower risk fish that live in deep water, and don’t eat other fish that can contain mercury. That diet, paired with their relatively short lifespan, means they have little opportunity to absorb mercury. And if that wasn’t enough, on top of it all, kokanee salmon are just delicious.