by Phelly Vasilaki, Irida, Pantelis Katharios, Aquatic Biologicals, and Kiranpreet Kaur, from AQC
Mediterranean aquaculture, particularly seabass and seabream farming, plays a major role in global seafood production, with Greece and Turkey leading the industry. The sector continues to expand, contributing significantly to global aquaculture. In 2024, combined production from Greece and Turkey reached 564700 tonnes, marking a 3.9 percent increase from 2023.
Organic Production Gains Momentum
Organic production is a holistic approach to farm management and food production that integrates the best environmental practices, promotes biodiversity, and preserves natural resources. Organic farming of seabream and seabass is gaining traction in Mediterranean aquaculture due to its focus on sustainability, fish welfare, and consumer demand for environmentally responsible seafood.
Organic practices emphasise the use of high-quality, certified organic feeds, which exclude synthetic additives, ensuring traceability and responsible sourcing. Studies have shown that organic seabream and seabass exhibit better growth performance compared to conventionally farmed fish, with healthier conditions and minimal signs of stress or disease.
However, organic diets often result in lower omega-3 fatty acid levels due to their reliance on plant-based ingredients and fish oil from trimmings that are low in EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) percent, which can affect the nutritional profile of the fish. While both organic and conventional systems have minor environmental effects, organic farming aligns more closely with sustainability goals by reducing reliance on wild fish for feed and promoting ecological balance. This approach not only meets growing consumer preferences for sustainable seafood but also supports long-term environmental health and market differentiation for producers.
Supporting Sustainable Goals
Similar to conventional farming, feed plays a crucial role in organic farming. In organic farming, only natural and sustainably produced ingredients are used. MSC-certified Antarctic krill fulfils all those criteria and hence is suitable for organic farming. Antarctic krill (Euphausia superba) is found in the Southern Ocean. Its harvesting is strictly regulated with an annual precautionary quota limited to 1 percent of the total estimated biomass in a unique area, Area 48.
These strict regulations of Antarctic krill harvesting have led to a stable biomass over the years, from 60.3 million tonnes measured in 2000 to 62.6 million in 2018/19, according to the findings of the Commission for the Conservation of Antarctic Marine Living Resources. Furthermore, the implementation of an eco-harvesting system ensures exceptionally low bycatch levels (only 0.1 percent–0.3 percent), with independent observers present on all fishing vessels. The krill fishery has long been acknowledged as one of the most sustainable globally.
Krill meal is a natural ingredient obtained from whole Antarctic krill. It is rich in nutrients including proteins (similar amino acid profile to high-quality fish meal), water-soluble nitrogenous components (free amino acids, peptides, nucleotides, and trimethylamine N-oxide), feed attractants, astaxanthin, marine omega-3 fatty acids (eicosapentaenoic acid and docosahexaenoic acid), and phospholipids. Its balanced nutritional profile, together with feed attractants, explains the growth-enhancing effects of krill meal, making it an ideal feed additive.
Field Trial in Organic Seabass
Based on this, the company, in collaboration with research partners, conducted a trial to test the inclusion of 12 percent krill meal in diets for European seabass juveniles weighing 4.5g, in comparison to a commercial organic feed with high levels of fish meal certified for organic production. The feeds were iso-caloric and iso-nitrogenous, and fish were fed on their respective diets for 12 weeks. The trial was conducted at sea cages of the experimental facilities of Galaxidi Marine Farm.
After the feeding period, no significant differences were observed between the groups for growth performance, indicating that 12 percent krill meal was successful in maintaining the key biological indices (feed conversion ratio, weight and mortality) in the field when compared to high levels (57 percent) of organic fish meal diets. Interestingly, an outbreak of vibriosis, caused by Vibrio harveyi, occurred during the feeding period, which led to high mortality in both groups. This was mainly due to the organic farming practices, as none of the fish were treated with antibiotics.
Managing Vibriosis Without Antibiotics
Vibriosis is one of the most serious diseases in marine aquaculture, causing high mortality, poor fish welfare, and significant economic losses. Among its causative agents, Vibrio harveyi is particularly harmful, as it disrupts gut health by altering the microbial balance and triggering inflammation. This leads to damage of the gut lining and villi, resulting in ulcers, sores, and impaired nutrient absorption, which negatively impacts fish growth, immunity, and overall health.
If left untreated, the infection can rapidly escalate, leading to widespread mortality and increased production costs. Effective management through probiotics, functional feeds, and farm biosecurity measures is essential to prevent outbreaks and ensure sustainable aquaculture practices.
Krill meal is widely recognised for its anti-inflammatory properties and its ability to promote gut health in various fish species, including gilthead seabream and Atlantic salmon. Given these documented benefits, this study assessed whether krill meal could similarly support intestinal health under organic farming conditions, where fish are more vulnerable to disease due to the absence of conventional treatments such as antibiotics or vaccines.
Histological analysis of infected fish, fed on commercial feed with high levels of fish meal certified for organic production, revealed severe enteritis, significant structural damage to intestinal villi, and inflammatory infiltration of the intestinal mucosa, indicating a severely compromised gut. However, fish fed on the experimental diet with 12 percent krill meal showed a remarkable improvement in intestinal structure, with normal villi folding and restored tissue architecture. This clear contrast suggests that krill meal played a crucial role in reducing inflammation, promoting tissue regeneration, and accelerating recovery from Vibrio harveyi-induced vibriosis. These findings further reinforce krill meal’s potential as a functional feed ingredient in aquaculture, particularly in organic production systems, where disease management options are limited.
Figure 2 b: After one month of 10% KM supplementation Necrotic area and fibrotic area of the lamina propria with mature spores, loss of the normal structure of the villi
Krill Meal Helps Fight Parasites
Coincidentally, another trial further demonstrated the gut health benefits of krill meal, specifically against Enteromyxum leei, a highly pathogenic myxosporidian parasite that severely affects the intestinal structure and function of fish, leading to poor nutrient absorption, chronic enteritis, and high mortality in gilthead seabream.
This parasite induces severe inflammation, atrophy of intestinal villi, and disruption of the gut barrier, ultimately compromising digestion and overall fish health. However, in this trial, seabream infected with E. leei and fed a diet containing 10 percent krill meal and a phytogenic additive against endoparasites exhibited significant gut tissue restoration within just one month of feeding post-infection.
Histological analysis revealed that fish in the krill meal-fed group had intact villi, reduced inflammatory cell infiltration, and a well-preserved intestinal architecture, in stark contrast to infected fish on standard diets, which continued to show signs of severe gut damage. These findings provide further evidence of krill meal’s powerful anti-inflammatory and gut-restorative effects, reinforcing its potential as a functional feed ingredient for improving intestinal health and resilience in aquaculture species facing severe enteric infections.
Functional Feeds for Resilient Fish
These two independent trials provide strong evidence that krill meal inclusion plays a crucial role in the restoration of intestinal tissues damaged by infections, whether caused by bacterial pathogens like Vibrio harveyi or parasitic infections like Enteromyxum leei. The observed improvements in gut health and faster recovery in infected fish can be largely attributed to the bioactive compounds present in krill meal, particularly omega-3 fatty acids (EPA and DHA) and astaxanthin.
These long-chain polyunsaturated fatty acids are well known for their anti-inflammatory properties, which help reduce excessive immune responses that contribute to intestinal tissue damage. Additionally, EPA and DHA play a key role in cell membrane integrity and tissue regeneration, allowing for faster healing and the restoration of gut structure. Astaxanthin, a powerful marine-derived antioxidant, further supports this process by reducing oxidative stress, which often exacerbates inflammation in infected tissues.
Together, these nutrients create an optimal environment for gut repair, improved nutrient absorption, and overall fish health, demonstrating krill meal’s potential as a functional feed ingredient to enhance disease resilience and recovery in aquaculture species. Integrating krill meal as a functional ingredient into aquaculture feeds ensures a healthier, more resilient fish stock, ultimately leading to a more sustainable and productive aquaculture industry.
Published in the May 2025 issue of International Aquafeed & Fish Farming Technology
