NEW SPECIES

Greater amberjack farming: long photoperiod and more space not always better

Canarias, Spain, 5 September 2025 | Study challenges belief that lower density is better for farming and welfare of greater amberjack

Medregal o pez limón (Seriola dumerili)

Greater amberjack (Seriola dumerili), prized for its fast growth and high market value, is seen as a key species for diversifying Mediterranean aquaculture. Yet developing sustainable farming methods remains a challenge, particularly when balancing productivity with fish welfare.

A study by the Centro Oceanográfico de Canarias, Centro Oceanográfico de Murcia and the University of Murcia, Spain, has examined how photoperiod and stocking density interact to affect the species under controlled conditions. The trial used fish averaging 9.5 kg in weight and 74.9 cm in length, and measured welfare indicators such as cortisol levels.

Results revealed complex – and at times counterintuitive – effects. Growth was not significantly influenced by either photoperiod or stocking density, meaning no clear “optimal” conditions emerged. Unexpectedly, fish exposed to longer daylight hours and lower stocking densities showed higher stress levels after 30 days.

The researchers also reported evidence of oxidative stress. Extended photoperiods increased oxidative damage in liver, brain and muscle tissue, while plasma bactericidal activity declined over the experiment. Although growth was unaffected, elevated cortisol in skin mucus, changes in antioxidant activity and greater lipid peroxidation pointed to acute stress responses.

The findings suggest that while photoperiod manipulation can be useful for controlling reproduction in aquaculture, excessive light exposure may compromise antioxidant defences and fish welfare.

The authors recommend maintaining stocking densities of up to 5 kg/m³ and avoiding prolonged photoperiods to minimise physiological stress. They stress the need for further research under commercial conditions to refine husbandry practices, ensuring that greater amberjack can be farmed efficiently without compromising welfare.

What appears to be a more “natural” environment – more light and more space – may in fact cause hidden stress, underlining the importance of tailoring aquaculture systems to species-specific needs.

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