What is the cleanest type of fish? A comprehensive guide to safe and sustainable seafood

November 30, 2025 •

3 min read

According to the U.S. Food and Drug Administration (FDA), many types of fish are safe to eat as part of a healthy diet, particularly those low in mercury. The perception of what is the cleanest type of fish depends on several factors, including mercury levels, contaminants, and sustainable harvesting practices.

Quick Summary

This guide details how to identify the cleanest fish, considering mercury levels, sustainability, and potential contaminants. It compares wild-caught versus farmed fish and provides a list of recommended options and species to limit.

Key Points

Sardines are Very Clean: Small, low on the food chain, and rich in omega-3s with minimal mercury.
Choose Wild Alaskan Salmon: Sourced from sustainably managed fisheries and lower in contaminants than some farmed varieties.
Pollock is a Low-Mercury Choice: Wild Alaskan pollock is a lean, sustainable white fish with very low mercury levels.
Avoid High-Mercury Predators: Larger, predatory fish like shark, swordfish, and king mackerel accumulate the most mercury.
Consider Responsible Aquaculture: Domestically farmed trout and bivalves from well-managed farms can be excellent clean and sustainable options.
Check for Sustainability Certifications: Organizations like the MSC and ASC certify fish from sustainable sources, ensuring a more responsible choice.

Defining “Clean”: Beyond Just Water Purity

For consumers, the concept of a “clean” fish is multifaceted. It's not just about the purity of the water it came from, but a balance of low contaminant levels, a rich nutritional profile, and responsible harvesting methods. Understanding these factors is key to making informed and healthy seafood choices.

1. Mercury Levels: The Impact of the Food Chain

Mercury is a neurotoxin that can accumulate in fish, particularly larger, predatory species that have longer lifespans. The FDA and EPA provide specific guidance on safe consumption, especially for vulnerable populations like pregnant women and young children.

2. Sustainable Harvesting: Protecting the Planet

Overfishing and destructive fishing practices can harm marine ecosystems, depleting fish populations and damaging habitats. Poorly managed fish farms can also contribute to environmental problems. For the cleanest and most ethical choice, look for fish from well-managed, sustainable fisheries or responsible aquaculture operations. Certifications from organizations like the Marine Stewardship Council (MSC) for wild-caught fish or the Aquaculture Stewardship Council (ASC) for farmed fish can guide your decisions.

3. Contaminant Exposure: Wild vs. Farmed

Beyond mercury, fish can be exposed to other environmental contaminants like polychlorinated biphenyls (PCBs) and dioxins. While wild fish are exposed to naturally occurring pollutants, some concerns exist about antibiotic and pesticide use in specific farming operations. The source and fishing method are key to minimizing exposure.

Comparison: Wild-Caught vs. Farmed Fish

The debate between wild-caught and farmed fish often focuses on which is truly "cleaner." The answer is not black and white and depends heavily on the specific source.


Feature	Wild-Caught Fish	Farmed Fish
Mercury Levels	Generally lower for smaller fish, but varies by species and location.	Can be consistently low due to controlled feeding.
Contaminants (PCBs, etc.)	Exposure depends on water cleanliness; less control over pollutants.	Potential for exposure to antibiotics/chemicals in poorly managed operations; feed/water quality crucial.
Nutritional Profile	Often leaner with richer flavor due to natural diet.	Can have higher fat content; diets may be supplemented for omega-3s.
Sustainability	Risk of overfishing/bycatch; need for responsible harvesting.	Can alleviate pressure on wild stocks but raise concerns if not managed responsibly.

The Cleanest Fish to Consider for Your Diet

Based on low mercury levels, sustainable practices, and overall health benefits, several fish consistently rank high for a "clean" profile:

Sardines and Anchovies: Small, low on the food chain, minimal mercury. Rich in omega-3s and sustainable.
Wild-Caught Alaskan Salmon: From sustainably managed Alaskan fisheries, high in omega-3s.
Wild Alaskan Pollock: Low-fat, low-mercury white fish from well-managed, sustainable fisheries.
Farm-Raised U.S. Rainbow Trout: Low-mercury, sustainable when farmed domestically in recirculating tanks.
Mussels and Oysters: Filter-feeders from regulated aquaculture are clean, sustainable, and mineral-rich.

Fish to Limit or Avoid

For the cleanest diet, be mindful of fish with higher mercury levels or questionable harvesting.

King Mackerel: High mercury levels.
Swordfish: Accumulates significant mercury; consume sparingly.
Shark: Apex predator with very high mercury levels.
Orange Roughy: Long lifespan leads to mercury accumulation; vulnerable to overfishing.

Making an Informed Decision

Choosing the cleanest fish involves considering its source, how it was raised or caught, and its place in the food chain. Prioritizing smaller species, looking for sustainability certifications, and being aware of FDA/EPA recommendations can lead to safer, healthier, and more environmentally friendly seafood choices. The Monterey Bay Aquarium's Seafood Watch program is a valuable resource for guiding your choices.(https://www.scripps.org/news_items/2913-what-is-the-healthiest-fish-to-eat)

Conclusion

While no fish is entirely free of potential contaminants, the cleanest type of fish is typically a small, sustainably sourced species low on the food chain, such as sardines or wild Alaskan pollock. By prioritizing species known for low mercury levels and opting for fish from well-managed wild fisheries or responsible aquaculture, consumers can make healthy, clean, and environmentally conscious seafood choices. Always consider both the source and species to determine the best option for you and your family.

Frequently Asked Questions

Small, forage fish such as sardines, anchovies, and Atlantic mackerel generally have the lowest mercury levels. Shellfish like shrimp and scallops are also very low in mercury.

Not necessarily. While some wild-caught fish are cleaner, the cleanliness of both wild and farmed fish depends on their source. Well-managed aquaculture, especially in closed recirculating systems, can be cleaner than wild fish from polluted waters.

For sandwiches or salads, canned light tuna (typically skipjack) is a better low-mercury option than albacore or bigeye tuna. Other low-mercury alternatives include salmon, trout, or canned sardines.

Look for sustainability certifications on the packaging, such as the Marine Stewardship Council (MSC) for wild-caught fish or the Aquaculture Stewardship Council (ASC) for farmed fish. These labels indicate that the fish meets specific environmental standards.

Yes, tilapia is generally considered a clean and safe fish with low mercury levels, according to the FDA. It is often farm-raised, so it's best to choose tilapia from responsibly managed farms.

Pregnant women and young children should avoid fish with the highest mercury levels, including shark, swordfish, king mackerel, and marlin. The FDA provides detailed guidance on safe fish choices for these groups.

Not inherently. The cleanliness depends on the specific species, its diet, and the water quality of its environment. Both freshwater and saltwater fish can be excellent choices if they come from clean, well-regulated sources.