Percorrer por autor "Arechavala-Lopez, Pablo"
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- Effects of environmental enrichment on the welfare of gilthead seabream broodstockPublication . Oliveira, Ana Rita; Cabrera-Álvarez, María J.; Soares, Florbela; Candeias-Mendes, Ana; Arechavala-Lopez, Pablo; Saraiva, JoãoThe intensification of aquaculture practices in the last decade has led to the reduction in welfare of farmed fish. Recently, one of the tools that has been considered important to guarantee or improve the welfare of captive fish is the application of environmental enrichment (EE). The physiological state and behaviour of fish can be used as indicators of the welfare of the animal, as well as of the positive impact of the EE in their well-being. In this study, behavioural and physiological indicators were measured to assess the effects of structural environmental enrichment on the welfare of gilthead seabream broodstock. Over the course of 5 months, 60 adult seabreams were distributed in six 3000 L cylindrical tanks. Three of the tanks were enriched with nine hanging organic ropes on 1 m2 floating structures, while the other three tanks had no enrichment. Fish were filmed regularly before, during, and after feeding, cleaning, and sampling procedures. Operational welfare indicators (OWIs) recently developed for farmed seabream were used and adapted to build an ethogram for the broodstock behaviour analysis. According to our results, fish reared in enriched tanks hardly schooled and presented a more independent swimming activity compared to fish from non-enriched tanks. Moreover, structural enrichment seemed to increase the spatial use of the bottom of the tank, and promoted seabream natural behaviour (hierarchical competitions, foraging, etc.). In addition, fish in enriched tanks presented a higher growth rate, and further studies will determine if such enrichment structures also affect reproductive potential of seabream broodstocks as well as epigenetic effects on offspring.
- From signals to states: biologger-based classification of seabass welfare states in sea-cagesPublication . Hoyo-Alvarez, Esther; Cabrera-Álvarez, María José; Vanrell-Valls, Margalida; Palstra, Arjan P.; Arechavala-Lopez, PabloBackground Aquaculture has grown significantly in recent years, increasing the need for advanced monitoring techniques to ensure fish welfare and optimise management practices. Understanding how fish respond to environmental and anthropogenic factors is key for improving welfare standards, and biologgers capable of measuring heart rate (HR) and external acceleration (ACC) provide valuable insights into physiological and behavioural dynamics. Results In this study, HR and ACC were recorded from adult European seabass implanted with biologgers and monitored in sea-cages for two 14-day periods in March and July. Feeding and routine cage maintenance occurred from Monday to Friday, whereas no aquaculture-related human activity took place during weekends. A Random Forest (RF) model was developed using labelled data from controlled stress-challenge experiments to classify four welfare states: resting, regular activity, reactive response, and proactive response. Standardized ACC was identified as the main predictor for proactive responses, whereas standardized HR contributed most strongly to resting and reactive states. Application of the model to sea-cage data revealed clear diel patterns: regular activity and resting predominated at night and early morning, while proactive responses increased from midday onwards and were closely related to feeding routines. Significant differences also emerged between weekdays and weekends, with stress-related states more frequent during weekdays and resting and regular activity dominating weekends, reflecting the influence of routine operations and human activity in the farming facilities. Seasonal patterns further revealed higher HR levels and a greater prevalence of proactive responses in July, likely driven by elevated water temperatures, increased anthropogenic pressure and enhanced behavioural alertness under summer conditions. Conclusions Overall, the integration of biologgers with machine learning classification provides a robust framework for identifying welfare states in seabass reared in sea-cages, demonstrating how physiological, behavioural, and environmental data can be combined to inform management decisions, optimise operational protocols, and ultimately enhance welfare-oriented aquaculture practices.
- 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 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.