Do Farm Raised Fish Have Mercury

Do Farm Raised Fish Have Mercury

Most people have shifted to aquaculture after the US Food and Drug Administration pointed out that most wild-caught fish have high mercury levels.

However, there have been rumors that aquaculture fish may have mercury too. And the most popular question we have in mind is; do farm raised fish have mercury?

The “harvest of fear” has spread, with most fish farmers stranded on how to improve their profitable fish businesses. This was after warning pregnant women, breastfeeding mothers, and children against consuming high mercury fish.

Surprisingly, according to US Food and Drug Administration, seafood consumption is now limited. You either take 8 ounces of seafood per week else; you face methylmercury poisoning. So unfortunate.

Do Farm Raised Fish Have Mercury?

clown fish in shallow focus photography

Why Do Fish Have Mercury

Due to the burning of fossil fuels in factories, mercury levels have increased in our atmosphere. The leading mercury-causing fuels are;

  • Coal
  • Natural gas
  • Oils

At last, when it rains, most of these mercury elements are swept by the runoff water. They end up in the rivers and later in the oceans, seas, and lakes.

Mercury is later ingested into the fish tissues through their gills or the digestive tracts. The worst is the predator fish that feed on small fish. Also, fish with a longer lifespan have higher levels of mercury.

school of assorted-color fish

How Mercury Affects Human Health

The most lethal element is methylmercury, which, when ingested into the fish tissues, later affects humans after feeding on its meat. Methylmercury is absorbed into the body six times easier than inorganic mercury.

The element is believed to turn into liquid at room temperature, therefore easily ingestible.

Later, methylmercury moves within body cells to form toxin barriers. It’s also notorious for crossing the brain membrane. Once it crosses, it reacts with the brain cells, later affecting the neurological processes.

Read: How long do betta fish live as a pet?

Well, Do Farm-Raised Fish Have Mercury?

Farm-raised fish have less exposure to mercury than wild-caught fish. That’s what we believed before modern studies revealed they, too, may contain mercury. While we thought farm-raised fish was the way to go, here are shocking factors;

1. Most Fish Farms are Set Around the Oceans

The United States boasts of the new technology and the future of aquaculture using federal waters. On the other hand, China is also rising with offshore aquaculture.

Fish are raised in submersible cages in deeper and less sheltered water a distance from the shore. They are exposed to natural living like the strong ocean currents and untreated water. With this method, reproduction and growth are fastened using special food.

Unfortunately, shores and their surrounding areas are the first stop for the runoff water from the land. For that reason, offshore raised fish are prone to mercury.

2. Most Farm Water is Taken from the Rivers

Rivers are the most mercury carriers to the oceans. Most factories direct their waste to the rivers, although it’s illegal. Unfortunately, water filtration may be expensive for most fish farmers. To avoid costs, they direct piped water to the fish ponds.

For that reason, most of farm-raised fish with piped water are prone to mercury.

Read: Bottom feeder fish price

close up photography of red fish

3. Rain Water Enters Fish Ponds

Due to industrial emissions, rainwater showed higher concentrations of mercury in California. According to research published in the Journal of Geographical Research-Atmospheres, inland rainwater had 44% higher mercury than coastal areas.

According to the paper’s lead author, elemental mercury remains a gas until it’s oxidized to a charged iconic form. The charged mercury is then captured by water droplets that fall on the ground.

See also: Do goldfish need to be fed everyday?

4. Fish Meal is Made from Fish Scrap

Most fish meal is made with fish scrapes after human food processing. While the food formula may be balanced and passed through several treatments, the fish from which it’s drawn may contain mercury.

When this meal is fed to the farm-raised fish, they ingest mercury in their tissues. This happens just as the predator fish eat the small fish containing lower levels of mercury.

5. Pesticides and Herbicides from Feeding Grains

Although mercury in the manufacturing of pesticides and herbicides is banned, some manufacturers still produce using it.

Most farm fish are fed with grains and soy from farms that may have been sprayed with these chemicals. Research points out that some of these grains are harvested with some pesticide’s traits, including mercury and other elements.

Once fed on fish, they ingest some mercury, although in small quantities.

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FAQs on Farm-Raised Fish and Mercury

Is Farm-raised Salmon High in Mercury?

According to the Washington State Department of Health, wild-caught and farm-raised salmon have low PCBs, mercury, and other contaminants. However, the controversy about eating farmed or wild salmon may be complex due to various factors. Take a look;

Disease – transfer of eggs from the wild stock to the farmed stock or vice versa may transfer diseases. Secondly, it’s advisable to avoid overstocking the fish to control diseases.

Omega 3 Protein – wild salmon rely on algae and plankton in the ocean. On the other hand, farmed salmon is fed on fishmeal, grains, and various plants. For that reason, farmed salmon may contain high levels of omega-3 fatty acids.

Although health professionals recommend omega-3 fatty acids for brain, heart, and nervous system health, mercury in fish can be a great concern.

How Much Mercury is in Farmed Fish?

Most farmed fish have low mercury levels. For instance, a farmed salmon contains an average of 0.05 micrograms of mercury per gram. Considering United States Dietary Guidelines for Americans is by far below the safe deemed intake levels.

Which Fish Has Least Mercury?

Although most seafood is contaminated with mercury elements, there are five common fish with lower mercury levels. Check the list;

– Catfish
– Salmon
– Pollock
– Shrimp
– Canned light tuna

What Fish Has High Mercury?

Nearly all predator fish have high mercury, although levels vary with the fish type. Here is a list of fish believed to have the highest mercury in parts per million (PPM).

– Shark
– Swordfish
– Orange roughy
– Bigeye Tuna

The only option left for taking seafood is following the health professionals’ guidelines. Unfortunately, farm-raised fish have mercury too. But their levels are lower compared to wild-caught fish. 

Read: Panda telescope goldfish for sale


Washington State Department of Health: Farmed Salmon vs. Wild Salmon

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