The behavioural responses of fish to a stressful situation must be considered an adverse reaction caused by the perception of pain. Consequently, the handling prior to stunning and the immediacy of loss consciousness following stunning are the aspects to take into account during the slaughtering process. The most common commercial stunning method in seabream and seabass is based on hypothermia, but other methods such as electrical stunning, carbon dioxide narcosis or anaesthetic with clove oil, are discussed in relation to the time to reach the unconsciousness stage and some welfare indicators. Although seawater plus ice slurry is currently accepted in some guidelines of fish welfare well practices at slaughter, it cannot be considered completely adequate due to the deferred speed at which cause loss of consciousness. New methods of incorporating some kind of anaesthetic in the stunning tank could be a solution to minimize the impact on the welfare of seabass and seabream at slaughtering.

Aquaculture advancement depends on alternative raw materials to reduce reliance on fishmeal (FM) and fish oil (FO) from extractive fisheries. Strategies like restricted feeding reduce costs and improve sustainability by minimizing feed waste and enhancing water quality, while selective breeding boosts growth and adapts fish to innovative diets. However, these measures may affect quality and shelf life. Gilthead seabream selected for high growth or non-selected were fed in 500 L tanks for 300 days until apparent satiety (AS) or with food restrictions (85AS or 65AS) using a control diet with low FM and FO balanced with vegetable ingredients, and an alternative diet (ALT) where FM was substantially replaced with insect, poultry by-product, feather, and porcine blood meals, while FO was completely replaced by microalgae, poultry, and salmon by-product oils. The ALT diet improved EPA + DHA levels, n-3/n-6 ratio, and fillet hardness. The selected fish outperformed the non-selected ones in growth and were more resilient to ALT diet and feeding restrictions. The 85AS feeding strategy optimized fillet quality by preventing lipid accumulation and muscle adaptations, as observed with the other feeding strategies. Combining sustainable feed formulations, genetic selection, and moderate feed restriction enables a viable, long-term strategy for high-quality, environmentally responsible seabream farming.

The impact of changes in dietary lipids and protein sources on texture was evaluated on farmed blackspot seabream (Pagellus bogaraveo) throughout 14 days of ice storage and compared with wild fish. A commercial diet formulated with a high proportion of lipids, and two diets formulated with an important reduction of lipid levels by 60% and adding either plant protein sources (LL diet) or fishmeal (LL + diet) were supplied during growth until commercial size was attained. In the wild fish, the raw fillet hardness was significantly higher than in farmed fish during the entire ice‐storage period. In the farmed fish, an increase of muscle lipid accumulation and change of fiber density were responsible for the variations in texture in the raw fillet. The highest reduction was found in fish fed with diets LL+ and LL. The texture parameters studied on the cooked fillets showed no significant differences, neither attributable to the diets nor to the ice‐storage period.

Gilthead seabream (Sparus aurata) is a prominent aquaculture species in Europe; however, the repercussions of growth-oriented selective breeding on reproductive performance under industrial conditions have not been adequately characterised. The present study evaluated the influence of divergent Best Liner Unbiased Prediction (BLUP)-based selection for low growth (LG) (n = 49; mean weigh ± SD = 842 ± 189 g) and high growth (HG) (n = 50; mean weight ± SD = 1127 ± 407 g) on spawning quality throughout the commercial mass-spawning season. A number of significant differences were detected between the genetic lines. The LG broodstock produced substantially higher oocyte yields and numbers of fertilised eggs (26% and 25% increases, respectively), indicating greater quantitative reproductive output. In contrast, the HG line exhibited marginally higher fertilisation, egg viability, and hatching rates, indicative of enhanced early developmental efficiency. Despite these contrasting patterns, both lines exhibited similar numbers of viable eggs, larvae, and comparable larval survival. These findings demonstrate that selection for growth impacts reproductive traits through different pathways: The selection of HG results in an enhancement of developmental performance, while the selection of LG leads to an optimisation of egg production. Across the spawning period, oocyte yield was identified as the primary driver of overall spawn quality. The findings of this study offer pertinent insights into the optimisation of broodstock management and the enhancement of sustainability and efficiency in gilthead seabream aquaculture.

An alternative fish feed (ALT) replacing 50% of the fishmeal with poultry byproduct meal and insect meal and total fish oil with microalgae, poultry, and salmon byproducts oils was tested for 300 days on 900 gilthead seabream (Sparus aurata) with an initial body weight of 17.1 ± 1.8 g (mean ± SD) of unselected (REF) and selected (HG) genotypes. Using in situ, histochemistry, and immunohistochemistry techniques, we assessed the immune response by characterizing IgT and IgM immunoglobulins, CD3ε⁺ T lymphocytes, and eosinophilic granular cells (EGCs) along the digestive system. IgT mRNA⁺ cells were concentrated in the second part of the digestive tract, while IgM⁺ predominated in the first and occasionally showed intraepithelial localization. CD3ε⁺ and EGCs were most prominent in the midgut. The diet affected IgT and IgM mRNA⁺ cells mainly in the initial part of the digestive tract. For CD3ε⁺, the diet only affected the initial and final parts, while the ALT diet increased EGC abundance across the middle compartments. Genetic selection had minimal effect on IgT⁺ and CD3ε⁺ cells, affecting only the first compartments. The REF group showed higher IgM⁺ cell abundance in specific regions, while EGCs differed between genotypes, favoring anterior accumulation in HG and ileocecal abundance in the REF group.