Is Steelhead High in Mercury? Understanding the Contaminant Risk

November 27, 2025 •

4 min read

According to the U.S. Food and Drug Administration (FDA), freshwater trout, including steelhead, contains some of the lowest levels of mercury among commercially available seafood. This places steelhead in the 'Best Choices' category for consumption, even for sensitive populations like pregnant women and young children.

Quick Summary

Steelhead trout generally has low mercury levels, making it a safe seafood choice. Mercury accumulation varies based on factors like the fish's diet, age, and whether it is wild-caught or farmed. Sourcing from reputable farms or monitored wild populations can further minimize potential exposure.

Key Points

Low Mercury Content: Steelhead trout, a type of rainbow trout, is listed as a 'Best Choice' for low mercury levels by health authorities.
Sourcing Matters: Farmed steelhead typically have lower mercury than wild ones due to controlled environments and regulated diets.
Predators have Higher Mercury: Larger, longer-lived predatory fish accumulate more mercury through bioaccumulation, unlike steelhead.
High in Nutrients: Steelhead is an excellent source of lean protein, omega-3 fatty acids, and essential vitamins like B12 and D.
Safe for Sensitive Groups: Because of its low mercury level, steelhead is a safe choice for pregnant women and young children in recommended amounts.
Variety is Key: Eating a variety of fish, not just one type, helps minimize overall exposure to potential contaminants.

Understanding Mercury in Fish: The Bioaccumulation Process

Mercury is a naturally occurring element that, through human activity, enters water bodies. In aquatic ecosystems, bacteria convert elemental mercury into methylmercury, a highly toxic form. This methylmercury is then absorbed by plankton and algae, which are eaten by small fish. As larger fish consume smaller fish, the concentration of methylmercury bioaccumulates and biomagnifies up the food chain, meaning the largest, oldest predatory fish tend to have the highest mercury levels.

Because steelhead are a migratory form of rainbow trout that are not top-tier ocean predators, their mercury levels remain relatively low, similar to salmon. Larger, longer-lived predators such as shark, swordfish, and some types of tuna are at the top of the food chain and therefore accumulate significantly higher concentrations of mercury.

Factors Influencing Mercury Levels in Steelhead

Several factors can influence the amount of mercury found in an individual steelhead trout, which is why average data is used for generalized advice but may not reflect every individual fish.

Environment: A steelhead's mercury level is impacted by the water quality of its environment. Fish caught in lakes or reservoirs can sometimes have higher chemical levels than those from rivers and coastal waters. A study analyzing mercury in steelhead and sculpin found higher concentrations in some smaller watersheds, underscoring the importance of local water quality.
Farmed vs. Wild: Farmed steelhead, often raised in controlled recirculating aquaculture systems (RAS), typically have lower mercury levels than their wild counterparts. This is because their diet is regulated and the water quality is constantly monitored and filtered to minimize contaminants. Wild steelhead's diet is more varied and includes a wider range of potentially mercury-containing organisms.
Diet: The type of prey a fish consumes significantly impacts its mercury content. Wild steelhead feed on smaller fish, crustaceans, and insects, inheriting the mercury from their prey. Some advanced farmed fish feed contains fish meal from responsibly managed, low-mercury fisheries, which helps keep their levels in check.
Age and Size: As with any fish, older and larger steelhead may have higher mercury concentrations due to a longer period of bioaccumulation. Eating smaller, legal-sized fish is a suggested method for reducing exposure.

Nutritional Benefits of Steelhead Trout

Beyond its low mercury profile, steelhead offers a range of health benefits, making it an excellent addition to a balanced diet.

Rich in Omega-3s: Steelhead is a fantastic source of omega-3 fatty acids, including EPA and DHA, which support brain and heart health. Some farmed steelhead can contain a significant amount per serving.
Excellent Protein Source: With around 21 grams of protein per 100-gram serving, steelhead is a lean and nutrient-dense protein source.
Packed with Vitamins and Minerals: This fish provides vital nutrients like Vitamin D, Vitamin B12, selenium, and phosphorus.
Versatility: Its delicate flavor and flaky texture make it versatile for various cooking methods, from baking and grilling to pan-frying.

Comparison Table: Steelhead vs. Other Fish Mercury Levels


Fish Species	Mercury Level Category (FDA)	Average Mercury Concentration (ppm)	Notes
Steelhead/Rainbow Trout	Best Choices	0.071 (for freshwater trout)	Generally very low mercury; wild levels depend on local water quality.
Farmed Salmon	Best Choices	0.022 (fresh/frozen)	Low mercury, comparable to farmed steelhead.
Light Canned Tuna	Best Choices	0.126	Lower than albacore but still higher than trout and salmon.
Albacore Tuna	Good Choices	0.350	Contains more mercury than canned light tuna.
Swordfish	Choices to Avoid	0.995	A large predatory fish with very high mercury levels.
King Mackerel	Choices to Avoid	0.730	A large predator with elevated mercury levels.
Shark	Choices to Avoid	0.979	A top predator with among the highest mercury concentrations.

Minimizing Mercury Exposure from Seafood

For those who enjoy seafood, following guidelines from health authorities like the FDA and Environmental Protection Agency (EPA) helps balance nutritional benefits and minimize mercury risk. The core recommendation is to choose a variety of fish and prioritize those known to be low in mercury.

Here are some practical steps to minimize mercury exposure:

Choose Low-Mercury Fish: Regularly consume fish from the FDA's 'Best Choices' list, which includes steelhead, salmon, cod, and canned light tuna.
Vary Your Seafood Intake: Don’t rely on just one type of seafood. Eating a variety of fish helps distribute potential exposure to contaminants.
Prefer Farmed over Wild in Some Cases: For species that are prone to higher contaminants in the wild, choosing farmed options can sometimes be a safer bet due to controlled diets and cleaner environments. Reputable farmed steelhead is a good example.
Check Local Advisories: If you are consuming locally caught wild fish, always check for specific advisories for your region or particular water body, as local contamination can increase risk.
Preparation Method: Some cooking techniques can help. Removing the skin and fat before cooking and using methods like grilling or baking can help remove some fat-soluble contaminants.
Consume Smaller Fish: When possible, opt for smaller, younger fish of legal size, as they will have had less time to accumulate mercury.

Conclusion: A Healthy Seafood Choice with Low Mercury

In summary, steelhead trout is not high in mercury and is considered a safe and healthy seafood option by major health organizations. Its position lower on the food chain, especially for farmed varieties, results in significantly lower mercury levels compared to large predatory fish like swordfish or shark. By choosing steelhead from reputable sources and incorporating it into a varied diet, consumers can enjoy its impressive nutritional benefits, including omega-3 fatty acids, with minimal concern for mercury contamination. Following general seafood safety advice and being mindful of sourcing can help you make informed choices for a healthy and balanced diet.

Frequently Asked Questions

Both steelhead and most types of salmon are considered low-mercury fish. Their safety profiles are comparable, with both offering excellent nutritional benefits and being included on 'Best Choices' lists by health organizations.

Farmed steelhead generally has lower mercury levels than its wild-caught counterpart. This is because farmed fish are raised in controlled environments with monitored, low-contaminant feed, unlike wild fish whose diet is determined by nature.

Due to its low mercury content, steelhead can be consumed regularly as part of a healthy diet. Health organizations often classify it as suitable for frequent consumption, even for sensitive populations.

The primary factor is its position on the food chain and its lifespan. Larger, longer-lived predatory fish accumulate more mercury through biomagnification, while smaller fish like steelhead have significantly lower levels.

No, cooking fish does not remove mercury. Mercury is bound to the fish's flesh, not its fat, so preparation methods like grilling or baking will not reduce the mercury content.

Steelhead and rainbow trout are the same species, Oncorhynchus mykiss. Steelhead are the anadromous (sea-run) form that migrate to the ocean, while rainbow trout stay in freshwater.

The Dietary Guidelines for Americans recommend at least 8 ounces of seafood per week for adults, with sensitive groups like pregnant women advised to consume 8 to 12 ounces of low-mercury fish like steelhead.