Introduction
The increasing replacement of fish meal and fish oil with plant-based ingredients in aquaculture, together with the effects of climate change, has led to a higher risk of mycotoxin contamination in aquaculture’s feeds.
Mycotoxins are secondary metabolites produced by filamentous fungi, primarily from the genera Aspergillus, Fusarium, and Penicillium. Among the most relevant in aquaculture are aflatoxins (AF), fumonisins (FB), ochratoxin A (OTA), and trichothecenes such as deoxynivalenol (DON) and zearalenone (ZEN). These toxins may be present in plant raw materials and, consequently, be incorporated into feed used in fish farms.
As a result of exposure, these toxins can reduce growth performance and feed efficiency, and may cause severe damage to organs, particularly the liver (e.g., necrosis and tumor formation). They also induce immunosuppression, increasing vulnerability to disease and significantly raising mortality rates in farms.
Although the effects of mycotoxins on the growth and health of aquatic species have been widely described, recent research has increasingly focused on their impact on fillet quality, muscle condition, and the safety of edible tissues—key aspects for both consumers and the processing industry. Furthermore, the bioaccumulation capacity of mycotoxins such as ochratoxin A (OTA) and aflatoxin B1 (AFB1) in edible tissues may pose a critical risk to food safety and public health (Oliveira et al., 2020).
Effects of mycotoxins on the quality and condition of edible fish tissues
In general terms, dietary exposure to mycotoxins can directly and indirectly affect the muscle quality of aquaculture species, even in the absence of obvious clinical signs or growth reductions (Anater et al., 2016).
Oxidative stress and muscle stability
One of the main mechanisms of mycotoxin toxicity is the induction of oxidative stress, a key process contributing to fillet quality deterioration.
Experimental studies in gilthead seabream (Sparus aurata) have shown that exposure to mycotoxins such as enniatin B (ENNB) increases lipid peroxidation in muscle, as measured by malondialdehyde (MDA) levels (Anacleto et al., 2025).
In these trials, MDA levels reached approximately 2.2 mg/kg of muscle, compared to 1.6 mg/kg in unexposed fish, indicating impaired lipid stability in the fillet.
Lipid oxidation directly affects (Anater et al., 2016):
- The shelf life of the fish.
- The flavor and odor of the fillet.
- Susceptibility to rancidity.
Protein and texture alterations
Beyond lipid damage, mycotoxins can also alter protein metabolism.
In studies on gilthead seabream exposed to fumonisin B1 (FB1) and enniatin B (ENNB), unexpectedly low levels of protein oxidation markers were detected (1–3.2 nmol protein carbonyls/mg protein compared to 5.7 nmol/mg in controls), possibly reflecting a compensatory antioxidant response (Anacleto et al., 2025).
Nevertheless, chronic long-term exposure has been associated with structural alterations in muscle fibers, reduced fiber diameter, and changes in fillet texture and firmness—parameters that are critical for commercial acceptance.
Nutritional value
Mycotoxin exposure may also affect the nutritional profile of muscle tissue. Reported effects include (Oliveira et al., 2020):
- Reduced levels of saturated (SFA), monounsaturated (MUFA), and polyunsaturated fatty acids (PUFA).
- Altered concentrations of essential minerals such as potassium (K), magnesium (Mg), zinc (Zn), and iron (Fe).
Although subtle in some cases, these changes may compromise the nutritional value of fish and reduce the health benefits associated with its regular consumption.
Transfer of mycotoxins to edible tissues
From a food safety perspective, a major concern is the transfer of mycotoxins from feed to edible animal tissues, which may ultimately reach the consumer.
Differential bioaccumulation by tissue
Mycotoxin bioaccumulation is not equally distributed across animal tissues (Bashorun et al., 2023). The liver generally exhibits the highest concentrations due to its central role in metabolism and detoxification. However, muscle tissue, although typically less affected, is not exempt from accumulation—particularly under prolonged exposure to low doses.
In the case of aflatoxin B1, concentrations around 4.25 ± 0.85 ppb have been documented in the muscle of European sea bass (Dicentrarchus labrax) following chronic exposure (Ziarati et al., 2024). Although these levels remain below regulatory limits established for human food in certain regions (e.g., 20 ppb according to the U.S. Food and Drug Administration), their detection confirms that fillets may serve as a route of mycotoxin entry into the human food chain.
Factors influencing mycotoxin transfer to edible tissues
The transfer of mycotoxins to edible tissues depends on various factors (Anater et al., 2016):
- Type of mycotoxin (liposolubility, stability).
- Dose and duration of exposure.
- Animal species and physiological status.
- Feed composition and mitigation strategies employed.
It is important to highlight that chronic exposure to low concentrations, which is common under real production conditions, represents a greater risk than acute exposures, as it may go unnoticed while allowing progressive accumulation in tissues (Oliveira et al., 2020).
Conclusion
Mycotoxins represent an increasingly significant challenge in aquaculture due to the growing inclusion of plant-based ingredients in feed. Their impact extends beyond animal health and growth performance, as they can also alter muscle quality and transfer to edible tissues.
They may induce oxidative stress, structural alterations, and nutritional modifications in fillets—even in the absence of clinical signs.
Therefore, seafood quality assessment should not rely solely on growth performance and proximate composition but should also consider oxidative stability, lipid profile, and potential toxic residues.
Effective prevention and control strategies—including monitoring programs, proper storage practices, and targeted mitigation solutions—are essential to ensure sustainable aquaculture production, product quality, and consumer safety.
