Skip to main content
Oregon.gov Homepage

Statewide fish advisory for mercury in bass FAQs

What is a fish advisory? Requirement or recommendation?

This is an advisory and not a rule or law. Fish consumption advisories are issued when fish tissue data that have been collected and analyzed verify that the level of a particular contaminant—in this case, mercury—is above Oregon’s target analyte screening value. This means that this contaminant is high enough to be of concern to human health if fish contaminated with mercury are not consumed in moderation. For reference, the screening values used by OHA when determining if the concentration of mercury found in fish tissue is a health risk are 0.2 mg/kg for at-risk populations (infants, children, and pregnant or breastfeeding women), and 0.6 mg/kg for the general public. Average total concentrations found in fish tissue ranged from 0.08 to 0.86 across the state.

It is the responsibility of the OHA, when data is available, to evaluate contaminant concentrations in fish tissue, to calculate the number of meals per month that can safely be consumed, and to provide that information to the public by issuing an advisory. Advisory recommendations are not mandatory, and OHA does not have the authority to require the public consume only those levels calculated. We provide the best information currently available that people need to reduce their exposure to a given contaminant, and rely on the public to use the information to inform the decisions they make when consuming fish listed in an advisory. If people choose to eat more than the recommended meal amounts listed, that is their individual choice.

Who tested the fish and when were they tested?

The Oregon Department of Environmental Quality (DEQ), the U.S. Environmental Protection Agency (EPA) and the National Parks Service (NPS) supplied data sets on mercury concentrations in fish tissue. Most of the data utilized for this advisory was originally collected for DEQ’s Toxics Monitoring Program [DEQ, 2015) and EPA’s National Rivers and Streams Assessment program (Merrick, 2015). Sampling events took place between 2008 and 2014.

Why did it take so long for a statewide advisory to be issued?

Fish sampling for contaminants is very costly and time consuming. There is also a great demand for fish sampling, some of it more urgent than others. It is not unusual for the data results to take several months and even years to get to the Oregon Health Authority (OHA). Once OHA receives the data, scientists must evaluate the human health effects, determine the recommended meal allowances for separate populations, and then inform stakeholders who live and fish in Oregon of the results. As mentioned above, much of the data used for bass was compiled through partner agency programs for the purpose of determining the health of Oregon’s rivers, streams and fish populations. To determine if a statewide advisory for a particular species of fish is warranted, OHA must have enough data to analyze for health impacts and the species of fish must be widespread across the state.

Where does the mercury come from?

Mercury comes from both natural and man-made sources. Man-made sources include current and past agricultural, commercial and industrial practices. Natural sources include volcanoes and geologic deposits. Mercury is also transported globally through air pollution from coal-fired power plants in the U.S and abroad. This atmospheric mercury is deposited in lakes, rivers and stream.

Can I reduce my exposure by just eating the fillet/muscle of the fish and nothing else?

No. Unlike other chemicals like PCBs that are fat soluble, meaning they build up mostly in the fat of the fish and not so much in the fillet, mercury is a metal that builds up mostly in the fillet or muscle of the fish. The level of mercury depends on the life expectancy of the fish (the longer it lives, the more time it has to build up mercury) and how predatory the fish is. Highly predatory fish eat many other fish contaminated with mercury. The more they eat, the higher the level of mercury they build up over time. Bass is a predatory fish that can live a long time in the same environment.

What about the people who have been eating bass from across Oregon? Is their health in danger?

Currently, the OHA has mercury advisories in place for 16 water bodies in Oregon, 15 of which have resident bass species with some of the highest mercury concentrations. Most of these advisories have been in place for some time and many people have followed the recommended meal allowances. People who may be concerned because they’ve eaten a lot of bass over the years can call OHA for more information (971-673-0400) or speak to their health care provider.

Who is most likely to be harmed by eating fish contaminated with mercury?

Unborn fetuses, nursing babies and small children are most vulnerable to the health effects from mercury in fish. It is particularly important that pregnant and nursing women as well as those of childbearing age (18-45) follow the meal recommendations in all current advisories.

Why a “statewide” advisory when there are advisories in place for bass already?

A statewide advisory for mercury in bass is necessary for two reasons:

  1. Current data has verified that bass contain enough mercury to be of concern if not eaten in moderation, which is the reason for the meal recommendations in the advisory.
  2. Many water bodies in Oregon have never been monitored for fish tissue concentrations of mercury. The presence of specific advisories on some water bodies but not others can give the impression that any water body without an advisory has mercury-free fish when, in fact, there are limited or non-existent data for those water bodies.

To help prevent this misconception, and to reduce the public’s exposure to mercury on water bodies with no advisories, OHA is issuing a statewide advisory for mercury in bass. This advisory will provide protection for bass fishers on all water bodies, including those water bodies that have not been monitored.

Why is this statewide advisory just for bass and not for other resident fish?

Reason 1: Unlike other predatory fish species such as yellow perch, brown bullhead and northern pike minnow, bass are found across the state in many popular fishing waters (both lakes and rivers) and are eaten by fishers on a regular basis. Large and small-mouth bass live a long time in one place, which equates to a longer-term exposure to contaminants present in the water, including mercury. The longer they live, the more mercury they accumulate. Bass are also considered top predators, eating other mercury contaminated fish within the ecosystem, which is why they tend to be higher in mercury content than other less predatory fish.

Reason 2: Much of the data OHA received from DEQ, EPA the NPS was for bass. The statewide data received was adequate enough to verify that the mercury content in bass could be harmful to health if not eaten in moderation. Unlike many species, bass are also abundant across the state and tend to be easier to catch. Since collection events are sporadic and time consuming, field staff are limited to the species of fish they can catch at any given time.

In an advisory, what is the difference between resident and migratory fish?

Resident fish such as bass, crappie, walleye, carp, catfish, yellow perch, brown bullhead and sturgeon spend their entire lives in one place. Migratory fish like salmon and steelhead spend their lives traveling to and from the ocean. Trout, when possible, move in and out of lakes via river systems, and up and down the length of a river into other tributaries. This migratory movement helps to reduce their exposure to contaminants in a single environment and, therefore, the amount of toxins and metals that may build up in tissue, unlike resident fish. Salmon, steelhead and trout are not considered predatory fish. This also reduces the build-up of mercury in their tissue.

How much migratory fish can I eat?

Fish are a nutritious food source and OHA recommends eating a variety of fish as part of a healthy diet, especially fish with less accumulated contaminants such as migratory (traveling) fish that do not live the bulk of their lives in one place. This advisory does not affect the amount of migratory fish a person can eat. Therefore, there is no limit established for migratory fish as part of this advisory.

What do I do if the meal recommendation for an individual advisory is different from those in the statewide advisory?

Current advisories and differences in meal recommendations for resident fish or bass (less or more) from OHA’s fish consumption website supersede the six- and two-meal consumption recommendations in the statewide advisory. This is because there is adequate data on these individual water bodies to allow OHA to establish separate meal allowances. If no advisory is in place for a specific water body, the public should adhere to the six- and two-meal recommendations for migratory fish or bass in the statewide advisory.

Am I “required” to follow the meal consumption limits in the advisory?

This is an advisory and not a rule or law. Fish consumption advisories are issued when fish tissue data that have been collected and analyzed verify that the level of mercury (or any other contaminant) is high enough to be of concern to human health, if not consumed in moderation. It is the responsibility of the OHA, when data is available, to evaluate contaminant concentrations in fish tissue, to calculate the number of meals per month that can be safely consumed, and to provide that information to the public by issuing an advisory. Advisory recommendations are not mandatory, and OHA does not have the authority to require the public consume only those levels calculated. We provide the information people need as a way to reduce their exposure to a given contaminant, and rely on the public to use the information to inform the decisions they make when consuming fish listed in an advisory. If people choose to eat more than the recommended meal amounts listed, that is their choice based on the best information OHA currently has available.

This is all too confusing. Why not just give up eating fish altogether?

By issuing advisories, health officials hope to increase the public’s awareness of fish species they should avoid or limit consumption of, and those they can keep eating. While it’s important for people to know about contaminants in fish, it is equally important to keep fish on the table. Health officials continue to encourage people, including pregnant women, to eat a variety of fish as part of a healthy diet. Migratory fish such as salmon and steelhead and non-predatory fish such as many species of trout are an essential source of protein, omega-3 fatty acids and other nutrients, and are low in contaminants. OHA tries to make advisories as simple as possible while continuing to determine what is best for the public’s health.

Why just Oregon?

Other states like Washington and Idaho have statewide advisories in place for bass. OHA used both Washington’s and Idaho’s methods in their calculations of total mercury, compared the average number for each (average of all data and average by water body), and used the more conservative of the two numbers to calculate the recommended number of meals per month for Oregon’s statewide advisory. The recommended meal allowances for Oregon are similar to those established in Washington and Idaho.

Your browser is out-of-date! It has known security flaws and may not display all features of this and other websites. Learn how

×