Unlocking algae's potential for healthier aquaculture

Ana Teresa Gonçalves is a senior scientist at SPAROS and RIASEARCH, and the leader of the Animal Nutrition Working Group at GreenCoLab, all partners in the LOCALITY project. She is an expert in functional fish feed ingredients, focusing on how innovative feed solutions can enhance fish welfare, resilience, and overall health throughout aquaculture production.

Ana Teresa helps the research team identify and develop algae-derived functional ingredients that target key challenges in aquaculture, from immune support to mucosal health. In her words, she aims to turn complex biological and environmental challenges into actionable strategies that improve fish well-being, reduce reliance on pharmaceuticals, and promote sustainable aquaculture practices.

Kristine Jung: As an expert in functional fish feed ingredients, what are the advantages and what are the challenges of using functional feeds in aquaculture?

Ana Teresa Gonçalves: When it comes to using functional feeds in aquaculture, the primary advantage is their ability to enhance fish resilience. By including functional ingredients, these feeds give fish an extra boost, helping them cope with stressors or pathogens encountered during their life cycle. This allows fish to be more robust and better equipped to handle challenging situations.

The main challenge, however, lies in the cost and availability of these functional ingredients. They are often not specific, require significant resources to produce, and are not as readily available as conventional feed ingredients. More, many are derived from terrestrial animal applications and are directly adapted to aquaculture in a generalized manner.

KJ: How and why could algae help traditional fish feed? 

ATG: Algae help traditional fish feeds by acting as functional ingredients that enhance — not replace — the base diet. Traditional feeds provide the essential nutrients fish need throughout their life cycle. “When these algae or algae extracts are added, they bring extra benefits since they were selected for targeting specific functions such as immune boosting, improved mucosal health or defensive properties, helping fish handle stress, pathogens, and other challenges throughout the production cycle.” In the case of LOCALITY, we're working with Atlantic salmon, and the basic diet is always constructed with all the nutrients that the fish needs to live normally. On top of that we add on the algae for coping with particular challenges. 

KJ: What are the challenges fish face in aquaculture where algae can be a beneficial additive, and how does the research team identify the specific algae for these applications?

ATG: Fish in aquaculture face challenges such as stress from confinement, fluctuating environmental conditions, and episodes where they must cope with opportunistic microorganisms or parasitic infections (especially ectoparasites). Algae can be a valuable additive by boosting fish immune systems, maintaining their internal balance, and specifically improving mucosal systems to accelerate healing of skin, gill, and gut injuries.

Our research team identifies beneficial algae by starting with species already produced by the partners, particularly those known for bioactive properties in other applications like cosmetics and human nutraceuticals. While we don't start from completely unknown species, our research involves extensive trials that go from in vitro, ex vivo until in vivo, to determine if the whole algae biomass or specific fractions are most effective, and if processing is needed to enhance bioactivity.  We also prioritise commercially viable species to ensure potential for large-scale application.

KJ: Can algae-derived fish feed currently be produced on an industrial scale?

ATG: Yes, the industrial-scale production of functional algae-derived fish feed is already achievable for certain algae species. This is helped by the fact that functional ingredients are incorporated at lower dosages compared to conventional feed components, reducing the overall biomass required. The necessary quantities also vary depending on the specific life stage of the fish being fed, with earlier stages such as juveniles requiring less due to their stronger responsiveness. While not all algae systems are fully adapted for industrial scale yet, rapid progress is being made in this field, with widespread industrial application expected very soon.

KJ: Can you explain the production steps of algae?

ATG: In the LOCALITY project, algae are first produced by partners and sent to the biorefineries, where they're processed down (by breaking, hydrolysis or other processes) and separated into different fractions. These fractions functional properties are screened in our ex-vivo platform that uses fish intestine explants, employing nutrigenomics, to pinpoint those with the highest bioactivity for improving fish health. The most promising fractions are then produced in larger quantities, dried, and incorporated into fish feed during an industrial-like feed production process, where they're mixed with other ingredients and pelleted. Finally, these feeds are used in controlled in-vivo trials with fish, and their responses are analysed using advanced techniques such as transcriptomics coupled with physiological analysis to confirm the health benefits.

KJ: What methods are used to evaluate the response?

ATG: Our fellow researchers keep track on the first fish’s response throughout trials by observing animal behaviour related to feeding. After the feeding period, we conduct sampling focused on mucosal systems (skin, gills, and gut). This involves analysing microbiome modulation to see how algae affect the associated microbial communities and whether these changes are positive. Additionally, they evaluate immune stimulation and the regeneration process of these tissues using molecular biology techniques to understand the overall impact on these processes that are key for the resistance and performance of the first barriers in fish.

KJ: What outcomes are you aiming for?

ATG: We're aiming for two main outcomes. Firstly, we want to ensure the fish's microbiota remains balanced even when they're stressed, as a healthy microbiome is crucial for their overall well-being and resilience. Secondly, we're focused on improving skin health, particularly concerning ectoparasites like sea lice. While we are aware of the difficulties in controlling sea lice and therefore, we certainly don't expect to eliminate it, we aim for algae to help fish recover faster from infestations and mitigate their negative effects, thereby boosting fish welfare and complementing existing aquaculture strategies, and with it to reduce even more the need for pharmacological interventions.

KJ: Have you already found some promising results and what are the next steps in your research?

ATG: We've found promising results, particularly in improving wound healing in fish, especially in their skin and gut. Our initial screenings show strong positive effects on triggering the early stages of wound repair and providing an immune boost. This is crucial for accelerating fish recovery from stressors like ectoparasites, significantly improving their welfare and reducing the chance of secondary infections after treatments.

Based on these findings, we've selected four prototype algae ingredients. Our next steps involve testing these in more realistic environments, moving beyond the lab. We'll conduct field trials with fish exposed to parasites and other typical challenges to observe the algae's actual protective effects. The goal is to conduct full-scale trials in real fish farm conditions to demonstrate their impact in an industrial setting.

KJ: What are your expectations for innovative algae-derived products and their future impact on the fish industry, particularly regarding their potential to reduce the need for pharmaceutical and medical feeds?

ATG: We expect innovative algae-derived products to significantly impact the fish industry, primarily by positively modulating the fish's microbiota in the skin, gut and gills. This rapid and beneficial shift in microbial composition of the first defensive barriers is crucial for improving overall fish health and performance, leading to better resilience against stressors.

Ultimately, the goal is that algae derived functional ingredients can be developed and applied in targeted situations in aquaculture to be integrated in a strategy for reducing the reliance on pharmaceutical and medical feeds. By using algae to prevent or support fish during challenges like stress, sea lice, or bacterial issues, and even more relevant on the aftermath of the treatments, we aim to ensure fish welfare and sustainable aquaculture without the need for further interventions, medicated or not. This aligns with broader European strategies for high-quality, trustworthy fish production and it is our golden goal to contribute towards that.

KJ: Does the fish taste different in the end?

ATG: When fish are raised with strategies that improve their health, like functional feeds, it enhances their overall quality — and that includes taste.

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