Flounder sustainability depends entirely on which species you’re buying and where it was caught. Some flounder fisheries are among the healthiest and best-managed in the world, while others are overfished or caught using methods that damage the ocean floor. The good news is that making a sustainable choice is straightforward once you know what to look for.
Pacific Flounder Is the Safest Bet
Flounder and sole caught in Alaska, the U.S. Pacific coast, and British Columbia consistently earn the highest sustainability ratings. Monterey Bay Aquarium’s Seafood Watch program puts Alaska flounder and sole on its “Super Green” list, meaning they’re both environmentally responsible and nutritious. Arrowtooth flounder, one of the most abundant flatfish in the North Pacific, has a healthy population with no overfishing occurring. About 94 percent of arrowtooth flounder by volume comes from fisheries rated as a good alternative, and the rest qualifies as a best choice.
California flounder, Kamchatka flounder, and southern flounder from Texas also get green ratings. If you’re shopping without overthinking it, “Pacific-caught” or “Alaska” on the label is your simplest shortcut to a sustainable option.
Atlantic Flounder Is More Complicated
The Atlantic side of the story is messier. Seafood Watch recommends avoiding witch flounder and yellowtail flounder caught in the U.S. Atlantic, along with certain sources of summer flounder (also called fluke) and blackback flounder. These stocks have faced decades of fishing pressure, and some remain at low population levels.
Yellowtail flounder illustrates the problem well. NOAA manages three separate stocks along the U.S. Atlantic coast, and all three have required conservative catch limits. The Georges Bank stock, shared with Canada, operates under a “limiter” approach that caps catches at just 200 metric tons when the population is between 1,000 and roughly 8,000 metric tons of estimated biomass. If the population drops below 1,000 metric tons, allowable catch scales down toward zero. These are tight restrictions that signal a stock under pressure.
Summer flounder is in somewhat better shape and actively managed with annual catch limits. For 2025, NOAA set the acceptable biological catch at about 19.3 million pounds, split between commercial and recreational fishing. That quota is based on recent stock assessments and distributed among Atlantic states from Maine to North Carolina. Summer flounder populations have recovered significantly since their lows in the 1990s, but sustainability ratings still vary depending on the specific fishery and gear used.
The Trawling Problem
Even when a flounder population is healthy, the way it’s caught matters. Most flounder is harvested by bottom trawling, where heavy nets are dragged across the seafloor. This method kills between 5 and 26 percent of bottom-dwelling invertebrates with each pass, depending on the gear type and habitat. Otter trawls, the most common type used for flatfish, cause the least damage among trawl types, but beam trawls and dredges are significantly more destructive.
Bycatch is the other concern. Bottom otter trawls discard roughly 31 percent of what they catch, and beam trawls discard around 46 percent. These discards include juvenile fish, non-target species, and other marine life that doesn’t survive being hauled up and thrown back. However, not all trawl fisheries are equal. The flatfish trawl fishery in Alaska’s Bering Sea has reduced its bycatch rate to just 6 to 8 percent of total catch, showing that well-managed trawl operations can dramatically cut waste.
California flounder caught in Mexico gets a red rating not because of the flounder population itself, but because the fishing methods there risk catching sea turtles, marine mammals, seabirds, and rays.
What European Flounder Looks Like
In Europe, flounder sustainability varies by region. Baltic flounder in the northern and central Baltic Sea currently faces fishing pressure below sustainable limits, which is a positive sign. However, in heavily trawled European waters like the Adriatic Sea, over 82 percent of the seabed is trawled at least once every three years, a threshold at which the most sensitive bottom-dwelling species face local extinction. European flatfish fisheries are a patchwork: some are well-managed, others are not, and labeling at the retail level rarely gives you enough detail to tell the difference.
How to Choose Sustainable Flounder
The simplest framework breaks down by geography and certification:
- Best choices: Flounder and sole from Alaska, the U.S. Pacific, or British Columbia. Southern flounder from Texas. Any flounder carrying Marine Stewardship Council (MSC) certification.
- Good alternatives: Summer flounder (fluke) from well-managed U.S. Atlantic fisheries, particularly those using hook-and-line or lower-impact gear.
- Avoid: Witch flounder and yellowtail flounder from the U.S. Atlantic. California flounder from Mexico. Any Atlantic flounder where you can’t identify the source.
If you see “flounder” on a menu or at a fish counter with no further detail, it’s worth asking where it’s from. The difference between a best choice and an avoid rating often comes down to a few hundred miles of coastline.
Flounder Is Also a Low-Mercury Option
On the health side, flounder is one of the cleanest fish you can eat. Flatfish (including flounder, plaice, and sole) average just 0.06 parts per million of mercury, well below the threshold for concern. The EPA and FDA both classify flatfish as a “best choice” for mercury, meaning you can safely eat two to three servings per week. That’s lower than general whitefish (0.09 ppm) and far below higher-mercury species like tuna or swordfish. For pregnant women and young children, flounder is one of the safest seafood options available.