Swai Fish: What It Is, Is It Safe & Better Fish to Buy

Dr. Josh Axe · Free quiz

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Swai is a freshwater catfish native to the Mekong, Chao Phraya and Maeklong river basins of Southeast Asia, and in the United States it usually shows up as a thin, boneless white fillet in the freezer case.17 A 2014 Purdue study listed it among the 10 most popular seafoods in the U.S.,5 and its mild taste and skinless, boneless fillets help explain why it sells so widely.8

A frozen white fillet doesn't tell you much about the fish it came from. By the time swai reaches your kitchen it has been skinned, boned and frozen, and it has often been treated with a phosphate that helps it hold water.879 The two questions worth asking about any fish are what kind it is and where and how it was raised. For swai, the answers are a catfish with no scales and a farm pond in Vietnam, which is why this guide points you to wild fish with fins and scales.

Did you know?

• The "striped" in striped catfish describes the young: they carry a black stripe along the side and a second one below it, while large adults turn a uniform gray.1

• Swai can breathe air. FishBase classes it as a facultative air-breather, a fish that can take in air at the surface as well as breathe through its gills.1

• In the wild, swai is a migratory Mekong River fish that can reach 130 centimeters (more than 4 feet) and 44 kilograms (about 97 pounds), and its wild population is listed as Endangered on the IUCN Red List.1

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What is swai fish?

Wild swai live in large rivers, and the species has been introduced into other river basins for fish farming.1 It belongs to the family Pangasiidae in the catfish order, Siluriformes. Catfishes have bodies that are either naked or covered with bony plates, with up to four pairs of barbels, the whiskers around the mouth, and swai fits the pattern, with smooth skin and no scales.41

Basa is a close relative, Pangasius bocourti, a separate species that FDA lists under its own market name.11 The names blur in practice: swai is also marketed as pangasius, basa and tra.13

You won't see the word "catfish" on a swai label. Since 2002, U.S. law has treated a fish sold as catfish as misbranded unless it belongs to one family, Ictaluridae, which leaves swai to its own market names.1411

Why I don't recommend swai fish

My standard for seafood is wild, ocean-caught fish with both fins and scales, as I lay it out in The Biblio Diet.15 It echoes Leviticus, which names river fish along with the fish of the sea: "These shall ye eat of all that are in the waters: whatsoever hath fins and scales in the waters, in the seas, and in the rivers, them shall ye eat" (Leviticus 11:9).17 Swai has no scales, so it falls outside that standard, and catfish is on the avoid side of my food lists.415 For more on eating this way, see the biblical diet.

Where swai comes from and how it's farmed

I advise avoiding farmed fish,18 and the swai sold in the U.S. is a farmed import, most of it from Vietnam: from 2014 to 2018, 91.2% of U.S. imports of catfish-family fish came from there.2 Vietnam's Mekong Delta produced 1.2 million tons of striped catfish in 2013, and a 2025 study put output above a million tons a year.1219 Our guide to fish you should never eat puts unverified imported farmed fish on its skip list.

Farmed swai eat mostly plant-based feed, such as rice bran and soy, along with fish by-products,9 and a farmed fish's fat reflects what it was fed.5 In a study of frozen fillets on the Italian market, polyunsaturated fats made up just 12.5% to 18.8% of the fatty acids, and 44% to 59% of that was linoleic acid, an omega-6 fat.20

Bacterial disease is a constant threat on these farms, and with vaccines not widely used, farmers rely on antimicrobial drugs to fight it.12 In a survey of 45 small-scale fish farmers in the upper Mekong Delta, 9 of the 13 striped catfish farmers (69%) used antibiotics; across the survey, most farmers treated for about 3 days, and some used antibiotics as prevention when their fish showed no sign of disease.21

Here's how a drug used on a pond can end up in a fillet, and what stops it at the U.S. border.

There's real progress on the farms too. In interviews with 44 striped catfish farmers across six provinces, a 2025 study found a trend toward using fewer antimicrobials, with many farmers working to avoid them, especially near harvest.19

Is swai fish safe to eat? What U.S. inspection has found

Swai sold in the U.S. today is inspected by USDA rather than FDA. Under a rule published December 2, 2015, USDA's Food Safety and Inspection Service (FSIS) took over inspection of all fish in the catfish order, Siluriformes, swai included; it began testing in May 2016, and since August 2, 2017, every imported shipment has been reinspected before it can enter the country, with random samples pulled for species and residue testing.23222425 FSIS checks imports for more than 100 compounds, including drugs, metals and pesticides.2 During the changeover it found residue violations in shipments from Vietnam, notified Vietnam's food-safety authority and stepped up sampling,25 and in 2019 USDA made Vietnam eligible to export, with the border reinspection still in place.2

The record before USDA took over was weaker. In government inspection data from the European Union, the United States, Canada and Japan for 2000 to 2009, Asian catfish, or fish sold as catfish, was among the farmed seafood most often in violation for veterinary drugs, and Vietnam had more violations than any other exporting country.6

USDA's review of its first five years of testing, fiscal years 2016 through 2020, covers 10,116 samples, including its tests for banned dyes.22 The dyes, malachite green and crystal violet, have been used in fish farming for their antimicrobial properties, and the U.S. bans them in feed and fish farming because of their potential to cause cancer, gene mutations and birth defects.22

Imported fish of the catfish order, Siluriformes, the group that includes swai. Source: USDA FSIS five-year review, Table 7.22

Other residues were rare across all the catfish-family fish FSIS tested. It found 2 veterinary-drug violations in 4,058 samples, enrofloxacin in an imported product in 2016 and lasalocid in a domestic farmed fish in 2020, and 2 violations for nitrofuran antibiotics, banned in U.S. food animals since 1991, in 2,658 samples, both in imported fish in 2016 and 2017.22 Pesticide residues exceeded an EPA tolerance, or turned up where no tolerance exists, in 8 of 1,964 imported samples (0.41%).22

Lead turned up in 8 of 1,843 imported samples, and every lead detection, 17 to 88 parts per billion (ppb), fell below the 100 ppb limit the EU and Australia set for most meats; one imported sample, at 61.8 ppb of cadmium, was above the 50 ppb level used in the EU, Australia and New Zealand.22 Salmonella turned up on 0.32% of imported samples, a low rate FSIS says may reflect imported fish usually arriving frozen.22

Independent testing points the same way. When researchers tested 27 seafood samples from Arizona and California stores for 47 antibiotics, the 2 farmed swai samples from Vietnam had none above the detection limits.13

Better results at the border don't change what swai lacks: scales and omega-3 fat. The fish in the better-choices section have both.

Does swai fish have mercury?

In that U.S. analysis of 77 fish species, total mercury ran from 1 ppb in channel catfish to 1,425 ppb in king mackerel, and swai measured 2 ppb.3 In Italy, frozen fillets showed low mercury, pesticide and PCB residues,20 and frozen fillets sent to Poland, Germany and Ukraine carried heavy metal residues far below the official limits.26

Other batches sold abroad tested higher. In a market survey of imported fillets traded in Sicily, pangasius averaged 0.41 milligrams per kilogram (mg/kg), against 0.11 mg/kg in cod.27 In 80 frozen samples sold in Spain, mercury ranged from 0.10 to 0.69 mg/kg and averaged 0.22.8 And in 10 Vietnamese fillets from supermarkets in Rio de Janeiro, 5 were above the 0.5 mg/kg limit that FAO and WHO recommend for nonpredatory fish, and one, at 1.31 mg/kg, was above FDA's 1.0 part per million action level.9 A separate Brazilian test of 20 fillets found no detectable arsenic, chromium or lead; cadmium averaged 0.0547 mg/kg, with some samples over the limit.28

FDA's own table of mercury in commercial fish has no entry for swai, and USDA's five-year testing report doesn't list mercury among the metals it tested.2922 For comparison, sardines average 0.013 parts per million in FDA testing and fresh or frozen salmon 0.022.29 For the signs and sources of too much mercury, see mercury poisoning.

Swai fish nutrition

Label data for plain swai fillets with one ingredient, swai: USDA FoodData Central, Branded Foods record 2425878. USDA has no laboratory-analyzed record for swai, pangasius or basa.30

Many fillets are sold with more than swai inside. In a sample of 46 plain swai fillet labels in USDA's branded database, 26 listed a phosphate, usually sodium tripolyphosphate "to retain moisture," and 11 listed added water.7 Water dilutes the protein: untreated farmed pangasius from Vietnam measured 17.2% to 18.7% protein in a German analysis,31 while frozen fillets on the Italian market measured 12.6% to 15.6% protein and 80% to 85% water.20 Of 10 Vietnamese fillets sold in Brazil, which held 12.5 to 14.5 grams of protein per 100 grams, 3 carried more polyphosphate than the 1 gram per 100 grams Codex Alimentarius sets for the final product.9 The phosphate brings sodium with it: the Italian fillets carried 222 to 594 mg of sodium per 100 grams, which the researchers attributed partly to sodium tripolyphosphate, against 27 mg on the one-ingredient label.2030 On any frozen white fish, read the ingredient list and choose fillets that list only the fish.

The bigger gap is omega-3 fat. Purdue researchers measured EPA and DHA in fillets of 76 fish species bought from seafood sellers in six U.S. regions, 293 samples in all, each a blend of three fish. Swai had the least of any species, 17 mg per 100 grams, while salmon species ran from 717 to 1,533 mg, Atlantic cod 253 and Alaska pollock 236.5 These are the omega-3 fatty acids fish is prized for, and the FDA and EPA count them among the key nutrients fish provide during pregnancy and early childhood.32

Swai is also light on selenium: untreated farmed pangasius carried 0.12 to 0.18 mg per kilogram, or 12 to 18 micrograms per 100 grams,31 against 29.8 micrograms in sockeye salmon and 52.7 in canned sardines in USDA data.3334

Is swai fish healthy?

The closest look at swai as food comes from a feeding study in mice. Over 12 weeks, groups of 10 male mice on a high-fat diet with cod as the protein gained less body fat than mice given chicken, while mice given pangasius landed in between, and the pangasius group handled blood sugar less well than the cod group.35 The researchers tied the difference to the omega-3s bound up in cod, which raised EPA- and DHA-derived compounds in the mice's tissues more than pangasius or chicken did.35

The nutrient data point the same way. Alaska pollock gives you 17.2 grams of protein and 235 milligrams of EPA and DHA per 100 grams for 76 calories, the same lean profile as swai with many times the omega-3s.36 Sole, flounder, cod and haddock are mild white fillets with fins and scales as well, and they're in the comparison table below.

How often is swai sold as another fish?

Often enough to watch for. In 2016, the ocean advocacy group Oceana reviewed more than 200 studies covering more than 25,000 seafood samples from 55 countries and found that Asian catfish, hake and escolar were the three fish most commonly substituted. In 141 cases, pangasius had been sold as 18 different higher-value fish, mostly perch, grouper and sole.16 The same review notes that the most recent large pan-European study found pangasius replacing only 3% of 3,900 samples.16

Packaged swai tends to be what the package says. In a DNA test of 111 frozen fish fillets from Southern California grocery stores, all 8 packages labeled swai were swai, and 95.5% of all the fillets were labeled correctly.37 The bigger risk is swai sold under another fish's name.

Two habits protect you. Store packages of these fillets must name the country of origin and whether the fish was farmed or wild, so read that line,37 and at a fish counter or restaurant, ask for the species and the country.

Better fish to buy instead of swai

As I've written, wild-caught fish delivers complete protein along with ready-made EPA and DHA,18 and the fish below do that while meeting the fins-and-scales standard. Aim to eat plenty of fish: the Dietary Guidelines for Americans call for at least 8 ounces of seafood a week, and 8 to 12 ounces during pregnancy and breastfeeding.32

Omega-3s and selenium: USDA FoodData Central SR Legacy records, raw, per 100 grams (sardines canned in oil, drained, with bone).394041343342364344 Mercury: FDA's table of mercury in commercial fish, using fresh or frozen salmon for the salmon row; FDA's Atlantic mackerel figure comes from a 1978 National Marine Fisheries Service report.29 Fins and scales: the Orthodox Union's kosher fish list.38 *Swai values come from Purdue's U.S. store testing, since USDA has no laboratory record for swai. Purdue's store-bought fillets, used in the chart above, measured somewhat different values for the same fish (Atlantic cod 253 mg, Alaska pollock 236 mg per 100 g).53

Build your week around the oily fish at the top of the table, and keep pollock, sole or flounder, cod or haddock for recipes that call for a mild fillet. Any of them can stand in for swai in a recipe; for ideas, see these baked fish recipes, and for more choices, the best fish to eat and omega-3 foods.

Swai fish safety: who should be careful

The same European study found no other reason for concern with frozen pangasius fillets, and its heavy metal results were far below official limits.26 Bacteria that resist antibiotics are a separate point: in a Swiss study of 44 imported raw seafood samples, strains resistant to several antibiotics turned up in 17% of the pangasius samples.46 FDA's steps for seafood cover both: cook fish to an internal temperature of 145°F, or until the flesh separates easily with a fork, and keep raw seafood and its juices away from food that's ready to eat.45 It also helps to know the signs of food poisoning.

During pregnancy and breastfeeding, FDA and EPA advise 2 to 3 servings of fish a week from their Best Choices list, and 2 servings a week for children, because fish supplies DHA, EPA, iodine and choline for a child's development.32 FDA's chart doesn't name swai, and the catfish it lists as a Best Choice has no scales either, so fill those servings with fins-and-scales Best Choices such as salmon, sardines, anchovies, pollock or sole.32

The bottom line

Swai fish: frequently asked questions

References

1. Froese R, Pauly D, editors. Pangasianodon hypophthalmus, Striped catfish. FishBase. Accessed October 18, 2026.
2. Food Safety and Inspection Service, USDA. Eligibility of the Socialist Republic of Vietnam To Export Siluriformes Fish and Fish Products to the United States. Final rule. Federal Register. 2019;84:59682 (November 5, 2019).
3. Cladis DP, Kleiner AC, Santerre CR. Mercury content in commercially available finfish in the United States. J Food Prot. 2014;77(8):1361-1366. doi:10.4315/0362-028X.JFP-14-097. PMID:25198598
4. Froese R, Pauly D, editors. Order Siluriformes (catfishes): order summary. FishBase. Accessed October 18, 2026.
5. Cladis DP, Kleiner AC, Freiser HH, Santerre CR. Fatty acid profiles of commercially available finfish fillets in the United States. Lipids. 2014;49(10):1005-1018. doi:10.1007/s11745-014-3932-5. PMID:25108414
6. Love DC, Rodman S, Neff RA, Nachman KE. Veterinary drug residues in seafood inspected by the European Union, United States, Canada, and Japan from 2000 to 2009. Environ Sci Technol. 2011;45(17):7232-7240. doi:10.1021/es201608q. PMID:21797221
7. U.S. Department of Agriculture, Agricultural Research Service. FoodData Central, Branded Foods: search "swai" (96 records; the first 50 unique records, 46 of them plain fillets, read October 18, 2026; phosphate and added-water counts tallied by DrAxe.com).
8. Rodríguez M, Gutiérrez ÁJ, Rodríguez N, et al. Assessment of mercury content in Panga (Pangasius hypophthalmus). Chemosphere. 2018;196:53-57. doi:10.1016/j.chemosphere.2017.12.137. PMID:29291514
9. Guimarães CF, Mársico ET, Monteiro ML, et al. The chemical quality of frozen Vietnamese Pangasius hypophthalmus fillets. Food Sci Nutr. 2016;4(3):398-408. doi:10.1002/fsn3.302. PMID:27247770
10. Axe J. The Anti-Inflammatory Reset: The 30-Day Healing Protocol. DrAxe.com protocol. 2026 (written; "The foods that cool inflammation," p. 22: wild salmon and sardines, 4 to 6 oz, three times a week).
11. U.S. Food and Drug Administration. The Seafood List: acceptable market names for Pangasius species (Pangasianodon hypophthalmus: "Swai or Sutchi or Striped Pangasius or Tra"; Pangasius bocourti: "Basa"). Accessed October 18, 2026.
12. Phu TM, Phuong NT, Scippo ML, Dalsgaard A. Quality of antimicrobial products used in striped catfish (Pangasianodon hypophthalmus) aquaculture in Vietnam. PLoS One. 2015;10(4):e0124267. doi:10.1371/journal.pone.0124267. PMID:25897517
13. Done HY, Halden RU. Reconnaissance of 47 antibiotics and associated microbial risks in seafood sold in the United States. J Hazard Mater. 2015;282:10-17. doi:10.1016/j.jhazmat.2014.08.075. PMID:25449970
14. 21 U.S.C. 343(t), Misbranded food: catfish (added by the Farm Security and Rural Investment Act of 2002, Pub. L. 107-171, §10806, May 13, 2002). Legal Information Institute, Cornell Law School.
15. Axe J, Rubin J. The Biblio Diet. Hachette Book Group; 2025. ISBN 9781546008439 (written; "Hooked on Fish," ebook p. 84: "Choose wild, ocean-caught fish. Make sure it has fins and scales"; the food lists, catfish on the avoid side; unclean foods as "not a sin issue").
16. Warner K, Mustain P, Lowell B, Geren S, Talmage S. Deceptive Dishes: Seafood Swaps Found Worldwide. Oceana. September 2016.
17. The Holy Bible, King James Version. Leviticus 11:9. Project Gutenberg eBook #10. Verse quoted from this text.
18. Axe J, Cole W. Heal Your Cells. Avery; 2026. ISBN 9798217181353 (written; "Avoid farmed fish and processed meats," p. 67; "Wild-caught fish deliver complete proteins alongside direct sources of EPA and DHA," p. 131).
19. Tran VLT, Barnes AC, Samsing F, Vu UN, Wiley K. Striped catfish (Pangasianodon hypophthalmus) farmers' perspectives on challenges and health management practices in the Mekong Delta, Vietnam: a qualitative study. Prev Vet Med. 2025;239:106527. doi:10.1016/j.prevetmed.2025.106527. PMID:40198944
20. Orban E, Nevigato T, Di Lena G, et al. New trends in the seafood market. Sutchi catfish (Pangasius hypophthalmus) fillets from Vietnam: nutritional quality and safety aspects. Food Chem. 2008;110(2):383-389. doi:10.1016/j.foodchem.2008.02.014. PMID:26049230
21. Ström GH, Björklund H, Barnes AC, et al. Antibiotic use by small-scale farmers for freshwater aquaculture in the upper Mekong Delta, Vietnam. J Aquat Anim Health. 2019;31(3):290-298. doi:10.1002/aah.10084. PMID:31407408
22. Berutti T, Duverna R, Saini G. Data Summary of Siluriformes Fish Testing: A Five-Year Review, FY 2016-2020. Food Safety and Inspection Service, USDA. March 29, 2022.
23. Food Safety and Inspection Service, USDA. Mandatory Inspection of Fish of the Order Siluriformes and Products Derived From Such Fish. Final rule. Federal Register. 2015;80(231):75590 (December 2, 2015).
24. Food Safety and Inspection Service, USDA. Import Reinspection of Fish of the Order Siluriformes. Federal Register. 2017;82:30721 (July 3, 2017).
25. Food Safety and Inspection Service, USDA. Eligibility of the Socialist Republic of Vietnam To Export Siluriformes Fish and Fish Products to the United States. Proposed rule. Federal Register. 2018;83:47528 (September 19, 2018).
26. Kulawik P, Migdał W, Gambuś F, et al. Microbiological and chemical safety concerns regarding frozen fillets obtained from Pangasius sutchi and Nile tilapia exported to European countries. J Sci Food Agric. 2016;96(4):1373-1379. doi:10.1002/jsfa.7233. PMID:25907121
27. Ferrantelli V, Giangrosso G, Cicero A, et al. Evaluation of mercury levels in pangasius and cod fillets traded in Sicily (Italy). Food Addit Contam Part A Chem Anal Control Expo Risk Assess. 2012;29(7):1046-1051. doi:10.1080/19440049.2012.675595. PMID:22575000
28. Molognoni L, Vitali L, Ploêncio LA, Santos JN, Daguer H. Determining the arsenic, cadmium, lead, copper and chromium contents by atomic absorption spectrometry in Pangasius fillets from Vietnam. J Sci Food Agric. 2016;96(9):3109-3113. doi:10.1002/jsfa.7486. PMID:26439310
29. U.S. Food and Drug Administration. Mercury Levels in Commercial Fish and Shellfish (1990-2012). Accessed October 18, 2026.
30. U.S. Department of Agriculture, Agricultural Research Service. Swai fillets (label data, raw; ingredient: swai). FoodData Central, Branded Foods, FDC ID 2425878. Published December 22, 2022.
31. Manthey-Karl M, Lehmann I, Ostermeyer U, Schröder U. Natural chemical composition of commercial fish species: characterisation of pangasius, wild and farmed turbot and barramundi. Foods. 2016;5(3):58. doi:10.3390/foods5030058. PMID:28231154
32. U.S. Food and Drug Administration, U.S. Environmental Protection Agency. Advice about Eating Fish. Revised October 2021; content current as of March 5, 2024.
33. U.S. Department of Agriculture, Agricultural Research Service. Fish, salmon, sockeye, raw. FoodData Central, SR Legacy, FDC ID 173691. Published April 1, 2019. Values read from the FDC portal data, October 18, 2026.
34. U.S. Department of Agriculture, Agricultural Research Service. Fish, sardine, Atlantic, canned in oil, drained solids with bone. FoodData Central, SR Legacy, FDC ID 175139. Published April 1, 2019. Values read from the FDC portal data, October 18, 2026.
35. Fjære E, Myrmel LS, Dybing K, et al. The anti-obesogenic effect of lean fish species is influenced by the fatty acid composition in fish fillets. Nutrients. 2020;12(10):3038. doi:10.3390/nu12103038. PMID:33022997
36. U.S. Department of Agriculture, Agricultural Research Service. Fish, pollock, Alaska, raw. FoodData Central, SR Legacy, FDC ID 173725. Published April 1, 2019. Values read from the FDC portal data, October 18, 2026.
37. Peterson AM, McBride GE, Jhita SK, Hellberg RS. An investigation into country of origin labeling, species authentication and short weighting of commercially sold frozen fish fillets. Heliyon. 2021;7(4):e06713. doi:10.1016/j.heliyon.2021.e06713. PMID:33898833
38. Atz JW. Kosher and Non-Kosher Fish. Orthodox Union Kosher Guide (1991), reprinted by Kashrut.com with permission of the Orthodox Union; list updated July 19, 2017 (kosher fish are fish with fins and scales; non-kosher catfishes include "Basa (Pangasius bocourti), Swai, Tra (Pangasius hypophthalmus)").
39. U.S. Department of Agriculture, Agricultural Research Service. Fish, mackerel, Atlantic, raw. FoodData Central, SR Legacy, FDC ID 175119. Published April 1, 2019. Values read from the FDC portal data, October 18, 2026.
40. U.S. Department of Agriculture, Agricultural Research Service. Fish, herring, Atlantic, raw. FoodData Central, SR Legacy, FDC ID 175116. Published April 1, 2019. Values read from the FDC portal data, October 18, 2026.
41. U.S. Department of Agriculture, Agricultural Research Service. Fish, anchovy, european, raw. FoodData Central, SR Legacy, FDC ID 174182. Published April 1, 2019. Values read from the FDC portal data, October 18, 2026.
42. U.S. Department of Agriculture, Agricultural Research Service. Fish, flatfish (flounder and sole species), raw. FoodData Central, SR Legacy, FDC ID 174196. Published April 1, 2019. Values read from the FDC portal data, October 18, 2026.
43. U.S. Department of Agriculture, Agricultural Research Service. Fish, cod, Atlantic, raw. FoodData Central, SR Legacy, FDC ID 171955. Published April 1, 2019. Values read from the FDC portal data, October 18, 2026.
44. U.S. Department of Agriculture, Agricultural Research Service. Fish, haddock, raw. FoodData Central, SR Legacy, FDC ID 171964. Published April 1, 2019. Values read from the FDC portal data, October 18, 2026.
45. U.S. Food and Drug Administration. Selecting and Serving Fresh and Frozen Seafood Safely. Content current as of March 5, 2024.
46. Boss R, Overesch G, Baumgartner A. Antimicrobial resistance of Escherichia coli, enterococci, Pseudomonas aeruginosa, and Staphylococcus aureus from raw fish and seafood imported into Switzerland. J Food Prot. 2016;79(7):1240-1246. doi:10.4315/0362-028X.JFP-15-463. PMID:27357045

Dr. Josh Axe, DC, DNM, CNS

Doctor of Natural Medicine · Founder, DrAxe.com

Dr. Axe is a certified doctor of natural medicine, clinical nutritionist, and multiple New York Times bestselling author. He has spent 20+ years in clinical practice helping people heal at the root cause and founded one of the most-visited natural-health platforms in the world.

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