Disease management has become a critical priority for the aquaculture industry, especially with the intensification of farming for shrimp, salmon, trout, tilapia, catfish and other finfish. Many diseases are caused not by bacteria but by viruses, parasites, fungi or multifactorial conditions that weaken immunity. Despite this, antibiotics are often used inappropriately, which poses two major risks: reduced effectiveness of antibiotics against human disease due to rising antimicrobial resistance and environmental contamination that promotes resistance in wild ecosystems.
During the first ten months of 2025, the European Rapid Alert System for Food and Feed (RASFF) recorded 26 notifications related to drug-residue detections, primarily antimicrobial, in seafood, involving either prohibited substances or levels exceeding the maximum residue limit (MRL). This follows a 50% increase in such notifications in 2024 compared with 2023, highlighting a continued and growing concern regarding drug residues in aquaculture products.
European regulations
The European Union (EU) has implemented regulations to reduce these risks, restricting the use of certain substances in livestock and aquaculture. Regulations 37/2010 and 470/2018 prohibit the use of two antibiotics – chloramphenicol and nitrofurans – which are reserved exclusively for human medicine. Additionally, Regulation 2019/1871 bans triphenylmethane dyes (malachite green, crystal violet) due to their carcinogenic effects in humans.
Other antibiotics may be used in farming, but only under strict conditions – via veterinary prescription following a proper diagnosis, specifying a treatment plan and mandatory withdrawal period. This withdrawal period ensures that, by the time of harvest, drug residues in animal tissues fall below the MRL.
For substances without an established MRL, which include nitrofuran metabolites, chloramphenicol, and malachite green, the EU enforces reference points for action (RPAs) under Regulation 2019/1871. These RPAs represent the lowest validated concentration detectable by laboratory analysis. If residues are found at or above these levels, the product is deemed non-compliant with EU legislation.[1] The RPAs under Regulation 2019/1871 include:
| Substance | RPA (µg/kg) | Other provisions |
|---|---|---|
| Chloramphenicol | 0.15 | |
| Malachite green | 0.5 | 0.5 µg/kg from the sum of malachite and leucomalachite green |
| Nitrofuran metabolites | 0.5 | 0.5 µg/kg for each metabolite (furaltadone (AMOZ), furazolidone (AOZ), nitrofurantoin (AHD), nitrofurazone (SEM), 3,5-dinitrosalicylic acid hydrazide (DNSH) |
Producers must be vigilant in monitoring and controlling these residues to avoid regulatory breaches and ensure continued market access.
Which drugs to monitor
A 2020 study found that among the 15 leading aquaculture-producing nations, the most commonly used antibiotic families are quinolones, tetracyclines, amphenicols and sulfonamides. Notably, China, India, Indonesia and Vietnam together represent a significant share of global antimicrobial consumption in aquaculture.[2]
According to the RASFF, notifications since 2022 have flagged frequent detections relating to a number of antibiotic classes, including:
- Triphenylmethane dyes – malachite green, leuco-malachite green, crystal violet (gentian violet), leuco-crystal violet
- Nitrofuran metabolites – AMOZ, AOZ, AHD, SEM
- Amphenicols – chloramphenicol, florfenicol, florfenicol amine, thiamphenicol
- Fluoroquinolones and quinolones – enrofloxacin, ciprofloxacin
- Sulfonamides – sulfamethoxazole
- Tetracyclines – tetracycline, chlortetracycline, oxytetracycline, doxycycline
Producers should prioritize monitoring and controlling these substances to ensure compliance with international food safety standards.
It should be noted, however, that some of these substances may originate from non-antibiotic sources. For example, SEM occurs naturally in some foods and materials, such as shellfish, seaweed, eggs and milk products, as well as disinfecting agents and sodium bicarbonate. Because SEM is an ambiguous marker in crustaceans, EU Regulation 2023/411 specifies that only elevated levels of other nitrofuran metabolites (AMOZ, AOZ and AHD) clearly indicate illegal use of nitrofurazone.
Similarly, crystal violet, often detected in seafood, may stem from cross-contamination via everyday items like ballpoint pens, paper towels and gloves, which must be strictly excluded from food handling environments.
SGS solutions
Our accredited laboratories use advanced LC-MSMS techniques to test for antibiotic and other drug residues in seafood, ensuring full compliance with EU and US regulations. These analyses can be conducted either in Europe or prior to shipment from major producing regions in Asia and Latin America, helping producers avoid import refusals and delays at EU ports.
Leveraging our global network of laboratories and food safety experts, we provide scientific expertise, validated analytical methods and regulatory interpretation support. Our services are designed to help seafood businesses navigate complex residue requirements and ensure their products meet international standards with confidence.
For further information, please contact:
Jennifer Buckley
Senior Global Marketing Manager, Health & Nutrition
t: +1 973 461 1498
About SGS
SGS is the world’s leading Testing, Inspection and Certification company. We operate a network of over 2,500 laboratories and business facilities across 115 countries, supported by a team of 99,500 dedicated professionals. With over 145 years of service excellence, we combine the precision and accuracy that define Swiss companies to help organizations achieve the highest standards of quality, compliance and sustainability.
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