From Sushi to Tuna Sandwiches — Here’s the Line

Of the twenty three distinct populations of wild tuna, 61% are at a healthy level of abundance.

This action guide for tuna rounds out our three-part series on sustainable seafood. (See part one for sustainable salmon and part two for sustainable shrimp.)

Sushi is the second most popular way to eat tuna. (Canned tuna is the most popular.)

We all need protein in our diet. Tuna can be a sustainable source, in moderation. The good news about all seafood, including tuna, is that we have superbly sustainable choices that can feed billions of people now and far into the future. The bad news is that “over 50 percent of the most popular kinds of tuna caught globally” fail to meet the sustainability standards set by the Monterey Bay Aquarium’s Seafood Watch. If we can teach ourselves to choose wisely, we can eat sustainably for a lifetime.

Tuna is the common name for several species of oceanic fish, including albacore ( Thunnus alalunga), bigeye ( Thunnus obesus), bluefin ( Thunnus thynnus, T. orientalis, and T. maccoyii), skipjack ( Katsuwonus pelamis), and yellowfin ( Thunnus albacares). An easy rule: avoid eating the bluefin tuna species.

Avoid all bluefin tuna species because the populations are depleted, experiencing overfishing, or both.

Avoid all farmed bluefin because it’s sourced from wild populations.

Avoid “kuro maguro” or “hon maguro” sushi because it’s bluefin.

- Sustainable tuna guide, Monterey Bay Aquarium Seafood Watch

Almost all (99.9%) tuna is wild caught, so to choose sustainable tuna among the non-bluefin species, look for the MSC label. The Marine Stewardship Council certifies the sustainability of wild fish populations and the methods used to catch them.

Help! I know bluefin tuna are in trouble. What about the other kinds?

The International Union for Conservation of Nature (IUCN) assesses the extinction risk of species on the following scale:

• Extinct (no individuals remaining alive on Earth)
• Extinct in the Wild
• Critically Endangered
• Endangered
• Vulnerable
• Near Threatened
• Least Concern

In 2021, IUCN reassessed the seven most commercially fished tuna species and determined that

• Southern bluefin tuna (Thunnus maccoyii) improved from Critically Endangered to Endangered.
• Pacific bluefin tuna (Thunnus orientalis) improved from Vulnerable to Near Threatened, with the note: “This species remains severely depleted at less than 5% of its original biomass.”
• Atlantic bluefin tuna (Thunnus thynnus) improved from Endangered to Least Concern, with the note: “While the larger, eastern population of Atlantic bluefin tuna, which originates in the Mediterranean, has increased by at least 22% over the last four decades, the species’ smaller native western Atlantic population, which spawns in the Gulf of Mexico, has declined by more than half in the same period.”
• Bigeye tuna (Thunnus obesus) remains Vulnerable.
• Albacore (Thunnus alalunga) and yellowfin tunas (Thunnus albacares) both improved from Near Threatened to Least Concern.
• Skipjack tuna (Katsuwonus pelamis) remains Least Concern.

Help! What’s the deal with dolphins and tuna?

Yellowfin tuna swim with dolphins in parts of the eastern tropical Pacific Ocean, making it difficult to catch yellowfin in these places without catching dolphins, too. The National Oceanic and Atmospheric Administration explain in a FAQ that:

• “Porpoise fishing” is a technique for catching yellowfin. It involves looking for dolphins, which are easy to see because they come to the surface to breathe, using speedboats to herd the dolphins into a tight group, and then setting “purse seine” nets around them. If all goes well, the fishermen keep the yellowfin and let the dolphins go.
• The United States has rules to certify whether canned tuna is dolphin-safe or not. Not all tuna sold in the United States has to be dolphin-safe.
• The Inter-American Tropical Tuna Commission observed that the fishery killed about 132,000 dolphins in 1986 but only 819 in 2018.

Help! What about mercury in tuna?

A Healthline article explains, “Tuna contains more mercury than other popular seafood items, including salmon, oysters, lobster, scallops and tilapia. This is because tuna feed on smaller fish which are already contaminated with varying amounts of mercury. Since mercury is not easily excreted, it builds up in the tissues of tuna over time.” In 2023, Consumer Reports tested for mercury in canned tuna and found that skipjack (“light tuna”) usually had lower levels than albacore tuna. That didn’t surprise them, “since albacore is larger and lives longer than the tunas that make up the light tuna or skipjack tunas.”

If you’d like to eat more fish and less mercury, studies suggest that your best bet is to eat salmon or shrimp instead of any kind of tuna.

Help! How can I tell which kind of tuna is on the menu when I’m eating sushi or seafood?

For a helpful overview, check out “A foodie’s guide to tuna” published by the Marine Stewardship Council. Here are a few tips from that guide:

• Skipjack is often labeled ‘Chunk Light.’ Common in cans, but usually not served raw as sushi.
• Albacore is known as both ‘white tuna’ and ‘chicken of the sea.’ Its sushi name is binnaga maguro. In Portugal and Spain it’s called Bonito del Norte.
• Yellowfin is commonly served raw as sushi (kihada maguro). One of two tuna species called Ahi.
• Bigeye is also commonly served raw as sushi (mebachi maguro), and cooked as a tuna steak. Like Yellowfin, this tuna species is also called Ahi.
• Bluefin has been removed from most restaurant menus but might be served as high-end sushi (hon maguro or minami maguro).

What’s Still Ahead on the Pathway…

Last year, we explored the pathway to sustainable movement, energy, and goods. Now, we’re exploring the pathway to sustainable food to transition from the standard American diet to a healthier-for-our-planet plant-centered diet and transition from industrial to regenerative agriculture. Stay with us on the journey as we blaze a trail to a superbly sustainable future, one practical step at a time.

References and Further Reading

• Status of the World Fisheries for Tuna. March 2024, International Seafood Sustainability Foundation
• Sustainable tuna guide, Monterey Bay Aquarium Seafood Watch
• An overview of the global tuna market, Food and Agriculture Organization of the United Nations
• Wild Tuna Vs. Farmed, ATUNA
• What are The IUCN Red List Categories and Criteria?, International Union for Conservation of Nature and Natural Resources (IUCN)
• Tuna species recovering despite growing pressures on marine life — IUCN Red List, IUCN
• Frequent Questions: Dolphin-Safe, National Oceanic and Atmospheric Administration
• Mercury in Tuna: Is This Fish Safe to Eat?, Healthline
• How Worried Should You Be About Mercury in Your Tuna?, Consumer Reports
• Fish Species, Mercury data, and FDA/EPA Fish Advice Category, United States Food and Drug Administration
• A foodie’s guide to tuna, Marine Stewardship Council

Originally published at https://sustainablepractice.substack.com.