Organic aquaculture emerges as a key response to the growing demand for sustainable aquatic products, prioritizing animal welfare, environmental conservation, and product quality. However, its development faces challenges, especially in fish nutrition, where the aim is to minimize dependence on fish meal and fish oil.
A recent study published by researchers from Fondazione COISPA ETS, Aristotle University of Thessaloniki, Istituto Zooprofilattico Sperimentale delle Venezie (IZSVe), IRIDA S.A, and Univ Montpellier evaluated an innovative, cost-effective, and environmentally friendly feed for gilthead seabream (Sparus aurata), a key Mediterranean species whose organic production is booming.
According to the results published in the Journal of the World Aquaculture Society, this feed replaces 51% of fish meal with a mixture of plant and animal protein sources, including fermented soy meal, pea, krill, squid, and yeast. The objective was to determine its impact on growth performance, health, and overall welfare of the gilthead seabream using a multi-parametric approach.
Comparing Diets
To evaluate the new feed, a feeding trial was conducted over 135 days at the Fondazione COISPA ETS facilities (Italy). Young gilthead seabream (approx. 1.5 years old) were used. After an acclimation period and individual tagging (PIT-tags), they were randomly distributed into four tanks.
Two tanks received a standard commercial organic feed (control diet), while the other two received the innovative organic feed. Both feeds were produced by the Greek company IRIDA SA and complied with organic regulations. The innovative diet was formulated to replace 51% of the fish meal with alternative ingredients such as fermented soy, pea protein, krill meal, squid meal, and yeast (Saccharomyces cerevisiae), plus a supplement (Synergen™). The detailed composition and the amino acid and fatty acid profiles were analyzed for both diets.
During the experiment, key parameters were monitored at three time points (T0 – before the start, T1 – day 72/73, T2 – day 134/135):
- Growth: Individual weight, Specific Growth Rate (SGR), Feed Conversion Ratio (FCR), and Protein Efficiency Ratio (PER).
- Health and Welfare: Blood samples were taken to analyze hematological indicators (hematocrit, hemoglobin, red blood cell count) and biochemical indicators (cortisol, glucose, lactate, total proteins, protein fractions such as albumin, alpha, beta, and gamma globulins, and immunoglobulin M – IgM). The expression of the heat shock protein 70 (Hsp70) gene in various organs was also measured at the end of the study (T2).
- Behavior: Acoustic accelerometers were implanted in a subgroup of fish (10 per diet) to continuously record their swimming activity, an indicator of energy expenditure. The impact of the implant on mortality and growth was evaluated.
Data were statistically analyzed to compare the effects of diet and sampling time, and multivariate analysis (Principal Component Analysis – PCA) and Multi-Criteria Decision Analysis (MCDA) were used to obtain a global view of welfare.
How Did the Innovative Feed Affect the Gilthead Seabream?
The study revealed promising findings for the innovative diet:
Growth and Survival Without Significant Differences
- Mortality: The mortality rate was low and similar in both groups (approximately 7%), with no significant differences between diets.
- Growth: No significant differences were observed in final weight, SGR, FCR, or PER between fish fed the control diet and the innovative one. Both groups showed healthy growth over the 135 days.
- Tagging Impact: The accelerometer implantation did not negatively affect survival (no mortality in tagged fish) or growth parameters (final weight, SGR, FCR, PER). This suggests the technology is viable for monitoring fish under these conditions.
Blood Indicators: Minimal Alterations and Possible Immune Boost
- Stress and General Health: Most hematological and biochemical indicators related to stress (cortisol, glucose, hematocrit, hemoglobin, RBCC) and general welfare showed no significant differences between diets, although they did vary with sampling time. Values remained within the normal ranges reported for gilthead seabream. Hsp70 expression also did not differ between diets at the end of the study.
- Lactate: The only stress indicator showing a significant interaction was lactate, with levels being higher in the innovative diet group at T2 compared to T1, and also higher than the control group at both times (T1 and T2). Although increased lactate can indicate stress, this was not corroborated by other indicators.
- Immune Response: Significantly higher levels of total proteins, alpha 1 globulin, beta 1 globulin, and Immunoglobulin M (IgM) were observed in the plasma of fish fed the innovative diet compared to the control diet. Total proteins are crucial for physiological functions and immunity, and alpha, beta, and IgM globulins are important components of the humoral and acute-phase immune response in fish. These results suggest a potential immunostimulant effect of the innovative diet, possibly related to ingredients like yeast or krill.
Swimming Activity: Subtle Differences
- Accelerometers showed that, overall, swimming activity was lower at night than during the day for both groups.
- A statistically significant difference in activity between diets was detected, although it was subtle and mainly localized towards the end of the daytime period.
- Frequency analysis showed that fish on the control diet tended to display slightly higher activity values, suggesting greater use of anaerobic metabolism compared to the innovative group, which remained mainly in an aerobic range. However, this difference was not reflected in lactate levels or growth.
Integrated Analysis: Innovative Feed Favors Overall Welfare
To integrate the information from the 22 measured parameters, a multivariate analysis (PCA and MCDA) was performed.
- The PCA showed a significant separation between the diet groups based mainly on the first component, which was influenced by variables such as total proteins, various globulin fractions (beta 2, alpha 1, beta 1, gamma), prealbumin, glucose, and lactate. This indicates a differential overall impact of the diets on the physiological profile of the fish.
- The MCDA, designed to objectively compare the general welfare status considering the 9 most influential PCA parameters, concluded that the innovative diet resulted in a better overall health and welfare status for the gilthead seabream, regardless of whether different weights were assigned to each variable or they were considered equally important.
Conclusions and Implications for Organic Aquaculture
This study demonstrates that the innovative feed, with 51% replacement of fish meal by sustainable alternative sources, is a viable and promising option for feeding gilthead seabream (Sparus aurata) in organic aquaculture systems.
Key Points:
- No adverse effects: The innovative diet did not compromise the survival or growth performance of gilthead seabream compared to a commercial organic feed.
- Welfare maintained: Blood stress and health indicators showed minimal alterations, suggesting that overall welfare was not negatively affected.
- Potential immunostimulant: A possible enhancement of the innate immune response (higher levels of total proteins, alpha 1, beta 1, and IgM) was observed in fish fed the innovative diet, which is positive in aquaculture.
- Better overall status: The integrated multiparametric analysis indicated that the innovative diet promoted better overall health and welfare.
These results are encouraging for the development of more sustainable and cost-effective feeds in organic aquaculture, reducing pressure on wild fish stocks used for fish meal and fish oil. However, the authors note the need for further long-term research to fully understand the mechanisms behind the observed immunological changes and to assess other aspects such as the environmental impact of the feed in open systems.
In summary, this innovative feed represents a step forward towards more sustainable and efficient organic gilthead seabream aquaculture, maintaining fish health and welfare.
Contact
Lola Toomey
Fondazione COISPA ETS
via dei Trulli 18-20, 70126 Bari, Italy.
Email: toomey@fondazionecoispa.org
Reference (open access)
Toomey, L., Alfonso, S., Mente, E., Bitetto, I., Fiocchi, E., Manfrin, A., Vasilaki, P., Zupa, W., Bégout, L., Spedicato, M. T., Lembo, G., & Carbonara, P. (2025). Toward the use of innovative environmentally sustainable feed in organic aquaculture: Impact on growth performance, health, and welfare of gilthead seabream (Sparus aurata). Journal of the World Aquaculture Society, 56(2), e70021. https://doi.org/10.1111/jwas.70021
Editor at the digital magazine AquaHoy. He holds a degree in Aquaculture Biology from the National University of Santa (UNS) and a Master’s degree in Science and Innovation Management from the Polytechnic University of Valencia, with postgraduate diplomas in Business Innovation and Innovation Management. He possesses extensive experience in the aquaculture and fisheries sector, having led the Fisheries Innovation Unit of the National Program for Innovation in Fisheries and Aquaculture (PNIPA). He has served as a senior consultant in technology watch, an innovation project formulator and advisor, and a lecturer at UNS. He is a member of the Peruvian College of Biologists and was recognized by the World Aquaculture Society (WAS) in 2016 for his contribution to aquaculture.
