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- Structural enrichment promotes natural behaviour and welfare of captive gilthead seabream broodstockPublication . Oliveira, Ana Rita; Cabrera-Álvarez, María José; Soares, Florbela; Diáz-Gil, Carlos; Candeias-Mendes, Ana; Saraiva, João; Arechavala-Lopez, PabloThe intensification of aquaculture practices in the last decade can compromise the welfare of farmed fish. However, one strategy to be considered to improve the welfare of captive fish is the implementation of structural enrichment in the rearing environment. The behavioural and physiological effects of suspended ropes inside rearing tanks were experimentally assessed on gilthead seabream (Sparus aurata) breeders, evaluating the potential use of such structures in production units. Over the course of six months, 60 adult gilthead seabreams, were reared in cylindrical tanks with and without structural enrichment. Fish were video recorded regularly before, during and after feeding. Biometry and blood samples for biochemical analyses of plasma (cortisol, glucose and lactate) were taken throughout the experiment. Suspended ropes modified the horizontal distribution of fish after feeding, influencing the swimming activity and social interactions throughout the experimental period. In addition, structural enrichment promoted foraging and anticipatory behaviour of gilthead seabream. No effects of structural enrichment were detected on gilthead seabream condition or growth, although there was an apparent positive yet fading effect of enrichment on plasma cortisol and glucose. In general, structural enrichment had diverse positive effects on the behaviour diversity and natural repertoire of captive gilthead seabream, and therefore, on fish welfare. This type of structural environmental enrichment can be easily incorporated into land-based flow-through and recirculating aquaculture systems, both for experimentation and commercial purposes.
- Stunning and slaughter methods in gilthead seabream: animal welfare and muscle qualityPublication . Cabrera-Álvarez, María José; Soares, Sónia Marina António; Nuñez Velazquez, Samira; Anibal, Jaime; Esteves, Eduardo; Costa, Rita; Guerreiro, Pedro Miguel; Pousão-Ferreira, Pedro; Arechavala-López, Pablo; Saraiva, JoãoEuropean Union directives and international guidelines emphasise the need for humane slaughter practices, with particular attention to the proper stunning of fish prior to slaughter. This study investigates the impact of various combinations of stunning and slaughter methods on the welfare of gilthead seabream (Sparus aurata), a widely farmed species in the Mediterranean and Black Sea regions. Specifically, the study explores electrical stunning, anaesthesia, and no stunning, followed by slaughter using either ice-slurry or the ikejime (hand-held spike tool) technique. Fish were monitored for visual signs of consciousness, heart rate, internal temperature, plasma stress and osmotic parameters, and muscle quality parameters. The findings revealed that electrical stunning, although inducing brief unconsciousness, did not sustain it long enough to be effectively combined with ice-slurry, resulting in stress responses and muscle quality parameters comparable to those observed in unstunned fish. In contrast, anaesthesia effectively reduced stress and improved meat quality. The ikejime technique, despite its labour-intensive nature, demonstrated significant advantages, including reduced physiological stress and superior muscle quality outcomes. These results suggest that the viability of electrical stunning as a humane option for industry implementation has important limitations, while ikejime, with further refinement and automation, could offer a humane and effective solution to optimise both animal welfare and meat quality in industrial settings.
- Stunning challenges: operational indicators flag failures, but neurological validation is needed to confirm stunning effectiveness in seabass and seabreamPublication . Gräns, Albin; Cabrera-Álvarez, María José; Oliveira, Gonçalo; Saraiva, João; Arechavala-Lopez, Pablo; Bortoletti, Martina; Schwerte, Thorsten; Brijs, JeroenHumane slaughter in aquaculture depends on accurate assessments of insensibility, yet commonly used operational indicators remain poorly validated against neurological benchmarks. This study compared operational indicators such as the loss or recovery of equilibrium, ’eye-roll’ reflex, and ventilation reflex with visually evoked responses (VERs) in European seabass (Dicentrarchus labrax) and gilthead seabream (Sparus aurata) subjected to anaesthetic immersion or in-water electrical stunning. Operational indicators consistently preceded or lagged behind VERs, risking misjudgment of fish sensibility. Notable species differences emerged, with seabass losing and recovering indicators faster than seabream, whose indicator sequences varied depending on stunning method. Among all indicators, the ventilation reflex aligned most closely with VERs in both species, suggesting it may be the most reliable operational proxy. Despite the increasing use of electrical stunning in commercial settings, rapid recovery times (within seconds to minutes) observed in most fish raise serious welfare concerns. These findings underscore the urgent need to improve and validate electrical stunning methods for seabass and seabream before they can be considered humane and are widely implemented. Until neurological tools are feasible for commercial use, thorough species- and method-specific validation of operational indicators remains essential for safeguarding fish welfare.