BioMar provides experimental and farm-scale evidence on improving European seabass survival under bacterial pressure

For a European seabass producer, the value of a nutritional strategy depends on whether its benefits can be demonstrated under farm conditions.

A study presented at Aquaculture Europe 2026 (AE2026) by Gabriela Carril Leiva and colleagues from BioMar Group addresses this question through two complementary assessments: a controlled bacterial challenge and monitoring at a commercial farm under demanding commercial conditions.

The first experiment used 21-gram juveniles, fed for seven weeks before an immersion challenge with Photobacterium damselae subsp. piscicida at 22 °C.

The researchers compared a control diet with one incorporating a functional blend of additives and microingredients.

In this trial, the researchers reported an RPS of approximately 32% for the group receiving the functional diet, alongside a favourable statistical association compared with the control.

The field assessment took the comparison to a commercial grow-out farm. The trial involved million seabass distributed across seven sea cages (three receiving the control diet and four receiving the functional diet), with fish weighing approximately 185 grams initially.

Monitoring took place from August to November, a window identified by the authors as presenting a high risk of bacterial outbreaks.

Under the conditions of this commercial assessment, the researchers observed mortality that was 47% lower in relative terms in the cages receiving the evaluated diet compared with the control cages.

This specific result may help inform the planning of functional feeding strategies intended to support fish robustness and maintain performance during demanding production periods.

As Gabriela Carril explains misPeces, functional diets should not be regarded as a reactive response to an already established health problem; functional diets can help producers prepare for periods of greater health risk, helping to strengthen fish resilience when they need it most.

They are not a standalone solution, but can add value when used in a planned way and combined with sound management of fish health and the farming environment.

Their greatest potential is realised when they are used ahead of the risk window, during periods when more demanding production conditions have historically been expected.