What Fish Are Lowest in Contamination? A Comprehensive Guide

October 7, 2025 •

3 min read

Studies confirm that almost all people have at least trace amounts of methylmercury in their bodies, with the primary source being seafood consumption. Knowing what fish are lowest in contamination is essential for mitigating your intake of environmental pollutants while still reaping the immense nutritional benefits of seafood.

Quick Summary

This guide provides an overview of fish with the lowest levels of contaminants like mercury and PCBs, focusing on safer, smaller species and providing actionable tips for reducing exposure.

Key Points

Prioritize smaller fish: Smaller, shorter-lived species like sardines, anchovies, and pollock are significantly lower in mercury and other contaminants.
Choose wisely with tuna: Canned light (skipjack) tuna is a much lower mercury option than canned or fresh albacore tuna.
Source salmon carefully: Opt for wild-caught Alaskan salmon, including canned varieties, for high omega-3s and low contaminant levels.
Select U.S. farmed options: For tilapia and catfish, choosing U.S.-farmed fish helps avoid potentially poor environmental practices associated with some imported alternatives.
Prepare to reduce PCBs: Removing the skin and fat from fish, then baking or broiling it, can help reduce the intake of fat-soluble contaminants like PCBs.
Diversify your diet: Consuming a variety of low-contamination fish, rather than just one type, helps minimize your exposure to any single toxin.

Understanding Fish Contamination

Concerns about contaminants in seafood, especially heavy metals and other chemicals, have led many to question the safety of fish consumption. These contaminants, which enter waterways from industrial and natural sources, can accumulate in the tissues of aquatic organisms. While a healthy diet with fish offers numerous benefits, from heart health to brain function, it is wise to make informed choices.

The Science of Bioaccumulation

Contaminants like methylmercury and polychlorinated biphenyls (PCBs) build up in aquatic life through a process called bioaccumulation. Mercury is absorbed by lower organisms and accumulates as it moves up the food chain, a process known as biomagnification. Consequently, larger, longer-lived predatory fish tend to have higher levels of contaminants, while smaller fish, lower on the food chain, accumulate fewer toxins.

What Fish Are Lowest in Contamination? The Best Choices

To minimize contamination risk while enjoying the benefits of fish, focus on smaller species and those responsibly managed. The FDA and EPA offer guidance on safe seafood choices.

Low-Mercury and Low-PCB Fish

Some of the best choices for fish with the lowest levels of contamination include:

Sardines (Wild-Caught): Small, low-mercury, rich in omega-3s, vitamin D, and calcium.
Anchovies: Tiny, very low in mercury and high in omega-3s.
Salmon (Wild-Caught Alaskan, Canned): Consistently low in mercury and often from sustainable sources.
Tilapia (U.S. Farmed): A good, low-mercury option when sourced from U.S. recirculating tanks.
Catfish (U.S. Farmed): Safer than imported versions.
Pollock: A versatile white fish with low contamination.
Atlantic Mackerel: A low-mercury source of omega-3 fats.
Shrimp (U.S. Wild-Caught or Farmed): Generally very low in mercury; U.S. sources are preferred over imported farmed shrimp.
Scallops: Very low in mercury.
Canned Light Tuna (Skipjack): Choosing skipjack over albacore significantly reduces mercury exposure.

Comparison of Contamination Levels

Based on FDA data, this table shows mean mercury levels in various seafood, illustrating the difference between low and high contamination risks.


Seafood Type	Mean Mercury Concentration (ppm)	Typical Size / Contamination Risk
Scallop	0.003	Small, low-trophic level, very low risk
Shrimp	0.009	Small, low-trophic level, very low risk
Sardine	0.013	Small, fast-reproducing, very low risk
Salmon (Canned)	0.014	Various sizes, wild Alaskan is low-mercury, very low risk
Tilapia	0.013	Small to medium, farmed conditions vary, low risk (U.S. farmed)
Canned Light Tuna	0.126	Small skipjack species, low to moderate risk
Albacore Tuna	0.350	Larger species, higher on food chain, moderate to high risk
King Mackerel	0.730	Large predatory species, very high risk
Swordfish	0.995	Large predatory species, very high risk
Tilefish (Gulf of Mexico)	1.123	High-trophic level, long-lived, very high risk

What Fish Are Highest in Contamination? The Ones to Limit

Limit or avoid species known for high mercury and contaminant levels, including:

King Mackerel
Marlin
Orange Roughy
Shark
Swordfish
Tilefish (especially from the Gulf of Mexico)
Bigeye Tuna

The Easiest Way to Remember: The "Small and Fast" Rule

To quickly identify low-contamination fish, remember that smaller and faster-reproducing fish are lower on the food chain and accumulate fewer pollutants than large, long-lived predators like swordfish and shark.

How to Further Reduce Contamination Risk

In addition to choosing low-contamination species, consider these steps:

Eat a variety of fish to avoid overexposure to any single contaminant.
Prepare fish properly by removing skin and trimming fat to reduce intake of fat-soluble chemicals like PCBs; baking or broiling can help further.
Check local advisories for locally-caught fish.
Be mindful of sensitive groups like pregnant women and young children who are more vulnerable to contaminants.
Choose sustainably sourced seafood using guides like Monterey Bay Aquarium's Seafood Watch, which often overlap with low-contamination criteria.

Conclusion

By making informed choices based on size, species, and sourcing, you can safely enjoy the nutritional benefits of seafood while minimizing contaminant exposure. Prioritizing smaller, lower-trophic level fish and limiting large predators, along with proper preparation and checking advisories, allows for healthier and safer fish consumption. Rely on resources from the FDA and USDA for guidance on making smart seafood decisions. The key is variety and choosing low-contamination options.

Visit the FDA's Advice about Eating Fish page for more information

Frequently Asked Questions

Among the most common seafood options, small fish like sardines, anchovies, and canned salmon typically have the lowest mercury levels. Shellfish such as shrimp and scallops also contain very little mercury.

No, mercury levels differ significantly between tuna species. Canned light tuna (typically skipjack) has much lower mercury content than canned white (albacore) or fresh/frozen bigeye tuna.

Contaminants like mercury accumulate through the food chain in a process called biomagnification. Large, predatory fish at the top of the food chain, such as shark and swordfish, accumulate higher levels over their longer lifespans than smaller, shorter-lived fish.

No, cooking does not remove methylmercury, which is stored in the muscle tissue. However, removing the skin and fat and then baking or broiling can help reduce exposure to other fat-soluble contaminants like PCBs.

Yes, but pregnant women should be selective. They are advised to eat 8–12 ounces per week of low-mercury fish like salmon, shrimp, and tilapia while avoiding high-mercury options like shark and king mackerel.

It depends on the species and farming methods. Some U.S. farmed fish, like tilapia and catfish raised in monitored recirculating tanks, can be safer than their imported or wild counterparts. However, certain farmed fish, like salmon raised in crowded open-net pens, can have other environmental concerns.

The 'small and fast' rule is a helpful guideline. Smaller, faster-reproducing fish are typically lower on the food chain and accumulate fewer toxins than larger, longer-lived predators.