Tilapia (Oreochromis niloticus) aquaculture is an undeniable pillar of global food security, valued for the species’ high adaptability and accelerated growth. However, the drive for profitability often necessitates the use of intensive systems with high stocking densities. While this strategy maximizes physical space usage, a recent study published in Scientific Reports (2025) warns of its hidden costs: chronic cellular stress and a significant deterioration in the nutritional quality of the fillet.
Research led by Gabriel Roldi and Samuel Robath, in collaboration with scientists from São Paulo State University (UNESP), the State University of Maringá (UEM), and other Brazilian institutions, reveals how stocking density modulates not only production performance but also the lipid profile and molecular composition of juvenile GIFT strain tilapia.
Key study findings
- Efficiency vs. Yield: High density improves the Apparent Feed Conversion Ratio (AFCR) but reduces the percentage of usable fillet.
- Stress Markers: Fish in crowded conditions accumulate phosphatidylcholines (PC), indicating a rigidification of cell membranes as a defense mechanism.
- Nutritional Value: Low density favors a higher concentration of polyunsaturated fatty acids (PUFAs), elevating the final product’s quality.
- Texture and Firmness: The meat of tilapia cultured at high densities showed greater hardness regarding deformation.
- Metabolic Reprogramming: Density-induced stress alters lipid metabolism, modifying how the fish manages and stores energy.
The density dilemma: Growth or quality?
The team evaluated two controlled scenarios: a high density (HD) of 14 fish per tank versus a low density (LD) of 7 fish, keeping water quality parameters constant.
The results revealed a production paradox. Specimens in high density presented a notably better feed conversion (1.29 in HD vs. 1.61 in LD). Although this suggests efficiency at first glance, the researchers explain it as a “metabolic modulation” induced by moderate stress: the fish prioritizes homeostasis and vital maintenance over muscle growth.
In contrast, fish in low density (LD) recorded higher intake and, crucially, a higher fillet yield (28.16% vs. 25.95% in HD). This confirms that, without the stress of overcrowding, nutrients are effectively allocated to muscle production rather than being expended on competition or physiological stress responses.
Commercial impact: Texture and color
For the processing industry, physical characteristics are determinant. The study found that fillets from the high-density group were harder to deform, suggesting an altered muscle structure—possibly more elastic but with equal resistance to compression.
Regarding color, low-density fish exhibited a more yellowish hue (higher b* value). The authors link this to a superior fat content in the fillet (1.18% in LD vs. 1.10% in HD), the result of reduced competition for food and a greater lipid reserve capacity.
Deep science: Phospholipid remodeling
The most innovative aspect of the study is its lipidomic analysis. Lipids, more than simple energy reserves, act as vital biological signals and structural components. Density stress triggers restructuring at the membrane level:
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- High Density (Stress): Accumulation of phosphatidylcholines (PC). This generates more rigid and stable membranes—an adaptive response to protect cellular integrity against chronic stress, at the sacrifice of fluidity.
- Low Density (Welfare): Higher turnover of phospholipids, with high levels of lysophosphatidylcholines (LPC) and lysophosphatidylethanolamine (LPE). These compounds facilitate membrane fluidity and cell signaling, indicating a dynamic metabolic state conducive to growth.
Which fillet is more nutritious?
From a consumer perspective, stocking density is crucial. The low-density group presented significantly higher concentrations of polyunsaturated fatty acids (PUFAs), including omega-3 and omega-6 series.
This suggests that animal welfare favors the retention of lipids essential for human health. Conversely, high density appears to induce energy expenditure or lipid oxidation that limits the deposition of these beneficial nutrients.
Implications for the aquaculture industry
The study, supported by the UNESP Aquaculture Center (CAUNESP) and the Goiano Federal Institute, concludes that density is a critical factor of quality, not just volume. Although high density is attractive for space utilization, it carries hidden trade-offs:
- Lower yield of marketable fillet.
- Alterations in texture and coloration.
- Loss of nutritional quality (fewer PUFAs).
- Chronic stress is evidenced at the cellular level.
The authors suggest that reducing density promotes better performance in terms of useful biomass and final quality. Although the study was limited to juveniles over 20 days, it opens the debate on the need to balance productivity with animal welfare to obtain a superior product.
Contact
Samuel Robath
Provincial Directorate of Science and Technology, Higher Education and Technical-Vocational Training of Niassa
Maputo, Mozambique
Email: samuelrobath44@gmail.com
Reference (open access)
Roldi, G., Robath, S., Porto, C., Pilau, E., Giaquinto, P., Neto, J. F., Lala, B., Mari, G. C., Santos, C. T., Anastácio, G. N., Cangianelli, G. H., Ferreira, A. L., Ouros, C. C., Chavesk, G. H., Souza, M. L., & Caroline, S. (2025). Stocking density modulates tilapia (Oreochromis niloticus) performance and fillet quality through phospholipid remodeling. Scientific Reports, 15(1), 41944. https://doi.org/10.1038/s41598-025-25814-7
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.
