Investigating the influence of predictable and unpredictable feed delivery schedules upon the behaviour and welfare of Atlantic salmon parr (Salmo salar) using social network analysis and fin damage

Early-life environmental enrichment promotes positive animal welfare for juvenile Atlantic salmon (Salmo salar) in aquaculture research

Early life experiences have long-lasting effects on behaviour and physiology, influencing development of adaptive natural behaviours. Enriching farmed environments encourages expression of natural behaviours in captive fish, promoting positive animal welfare, important for conducting valid and reproducible research and informing better management practices. Using juvenile Atlantic Salmon (Salmo salar), we tested whether provision of environmental enrichment in early life improves welfare. Welfare indicators were measured comparing enriched to non-enriched tanks. Morphological (fin damage and body condition), physiological (plasma cortisol) and behavioural traits (activity, group cohesion, and neophobia) were recorded. Molecular expression of brain mRNA transcripts related to stress response, neuroplasticity and serotonergic system was analysed. Environmental enrichment did not affect morphological welfare indicators, activity, or cortisol. Enriched fish were more cohesive than non-enriched fish, less neophobic, with higher serotonergic turnover, suggesting enrichment mitigates against stress, promoting positive emotional states. Genes related to neuronal development and activity (bdnf and ndf1), cellular stress (hsp90 and hsp70), and serotonin synthesis (tph2) increased in enriched fish following stress, enhancing cognitive function. Our findings suggest early life environmental enrichment is advantageous for positive animal welfare by improving emotional states in captive environments, ensuring animals are free of negative experiences and able to access positive ones.

The effects of the predictability of acclimatory temperature on the growth and thermal tolerance of juvenile Spinibarbus sinensis

Heated effluent injection, cold hypolimnetic water inputs from dams, and extreme weather events can lead to unpredictable temperature fluctuations in natural waters, impacting fish performance and fitness. We hypothesized that fish exposed to such unpredictable fluctuations would exhibit weaker growth and enhanced thermal tolerance compared to predictable conditions. Qingbo (Spinibarbus sinensis) was selected as the experimental subject in this study. The qingbo were divided into a constant temperature group (C, 22 ± 0.5 °C), a predictable temperature fluctuation group (PF, 22 ± 4 °C, first warming, then cooling within a day) and an unpredictable temperature fluctuation group (UF, 22 ± 4 °C, the order of warming or cooling is random). After 40 days of temperature acclimation, the growth, metabolic rate, spontaneous activity, thermal tolerance, plasma cortisol concentration and liver hsp70 level of the fish were measured. Unexpectedly, neither the PF nor the UF group showed decreased growth compared to the C group. This could be attributed to the fact that temperature variation did not lead to a substantial increase in basic energy expenditure. Furthermore, feeding rates increased due to temperature fluctuations, although the difference was not significant. Both the PF and UF groups exhibited increased upper thermal tolerance, but only the UF group exhibited improved lower thermal tolerance and higher liver hsp70 levels compared to the C group. The qingbo that experienced unpredictable temperature fluctuations had the best thermal tolerance among the 3 groups, which might have occurred because they had the highest level of hsp70 expression. This may safeguard fish against the potential lethal consequences of extreme temperatures in the future. These findings suggested that qingbo exhibited excellent adaptability to both predictable and unpredictable temperature fluctuations, which may be associated with frequent temperature fluctuations in its natural habitat.

Feeding predictability as a cognitive enrichment protects brain function and physiological status in rainbow trout: a multidisciplinary approach to assess fish welfare

Cognitive enrichment is a promising but understudied type of environmental enrichment that aims to stimulate the cognitive abilities of animals by providing them with more opportunities to interact with (namely, to predict events than can occur) and to control their environment. In a previous study, we highlighted that farmed rainbow trout can predict daily feedings after two weeks of conditioning, the highest conditioned response being elicited by the combination of both temporal and signalled predictability. In the present study, we tested the feeding predictability that elicited the highest conditioned response in rainbow trout (both temporal and signalled by bubbles, BUBBLE + TIME treatment) as a cognitive enrichment strategy to improve their welfare. We thus analysed the long-term effects of this feeding predictability condition as compared with an unpredictable feeding condition (RANDOM treatment) on the welfare of rainbow trout, including the markers in the modulation of brain function, through a multidisciplinary approach. To reveal the brain regulatory pathways and networks involved in the long-term effects of feeding predictability, we measured gene markers of cerebral activity and plasticity, neurotransmitter pathways and physiological status of fish (oxidative stress, inflammatory status, cell type and stress status). After almost three months under these predictability conditions of feeding, we found clear evidence of improved welfare in fish from BUBBLE + TIME treatment. Feeding predictability allowed for a food anticipatory activity and resulted in fewer aggressive behaviours, burst of accelerations, and jumps before mealtime. BUBBLE + TIME fish were also less active between meals, which is in line with the observed decreased expression of transcripts related to the dopaminergic system. BUBBLE + TIME fish tented to present fewer eroded dorsal fin and infections to the pathogen Flavobacterium psychrophilum. Decreased expression of most of the studied mRNA involved in oxidative stress and immune responses confirm these tendencies else suggesting a strong role of feeding predictability on fish health status and that RANDOM fish may have undergone chronic stress. Fish emotional reactivity while isolated in a novel-tank as measured by fear behaviour and plasma cortisol levels were similar between the two treatments, as well as fish weight and size. To conclude, signalled combined with temporal predictability of feeding appears to be a promising approach of cognitive enrichment to protect brain function via the physiological status of farmed rainbow trout in the long term.

Looking beyond the Shoal: Fish Welfare as an Individual Attribute

Simple Summary

The fish farming industry is characterized by settings where large numbers of fishes are raised together at high stocking densities, effectively obliterating the individual. Given that animal welfare is an individual attribute that refers to how an animal experiences her world, it follows that ensuring good welfare for the different individuals is difficult in fish farms. In this paper we review evidence supporting the notion that fishes are individuals and fish welfare should thus also be considered at the individual level, examine the ways that animal welfare is assessed in fish farms, evaluate these practices in light of individualized terrestrial animal welfare assessment methods, and make recommendations regarding research that could lead to a better understanding of how to provide each individual fish with good welfare in captivity.

Abstract

Welfare is an individual attribute. In general, providing captive nonhuman animals with conditions conducive to good welfare is an idea more easily applied when dealing with few individuals. However, this becomes much harder—if not impossible—under farming conditions that may imply high numbers of animals living in large group sizes. Although this is a problem inherent to intensive animal farming, it is possibly best exemplified in fish farming, for these practices often rely on extremely high numbers. In this paper we review evidence supporting the notion that fishes are individuals and fish welfare should thus also be considered at the individual level, examine the current state of welfare assessment in the aquaculture industry, evaluate these practices in light of individualized terrestrial animal welfare assessment methods, and make recommendations regarding research that could lead to a better understanding of how to provide each individual fish with good welfare in captivity.

Positive effects of bubbles as a feeding predictor on behaviour of farmed rainbow trout

Occupational enrichment emerges as a promising strategy for improving the welfare of farmed animals. This form of enrichment aims to stimulate cognitive abilities of animals by providing them with more opportunities to interact with and control their environment. Predictability of salient daily events, and in particular predictability of feeding, is currently one of the most studied occupational enrichment strategies and can take several forms. In fish, while temporal predictability of feeding has been widely investigated, signalled predictability (based on a signal, such as light or sound) has received little attention. Depending on the type of predictability used and the ecology of the species, the effects on fish welfare often differ. The present study aimed to determine which feeding predictability would be most appropriate for rainbow trout, the main continental farmed fish in Europe, and what the consequences might be for their welfare. We tested four feeding predictability conditions: temporal (based on time of day), signalled (based on bubble diffusion), temporal + signalled (based on time and bubble diffusion), and unpredictable (random feeding times). Behavioural and zootechnical outcomes recorded were swimming activity, aggressive behaviours, burst of accelerations, and jumps, emotional reactivity, and growth. Our results showed that rainbow trout can predict daily feedings relying on time and/or bubbles as predictors as early as two weeks of conditioning, as evidenced by their increased swimming activity before feeding or during feed omission tests, which allowed to reinforce their conditioned response. Temporal predictability alone resulted in an increase in pre-feeding aggressive behaviours, burst of accelerations, and jumps, suggesting that the use of time as the sole predictor of feedings in husbandry practices may be detrimental to fish welfare. Signalled predictability with bubbles alone resulted in fewer pre-feeding agonistic behaviours, burst of accelerations, and jumps than in the temporal predictability condition. The combination of temporal and signalled predictability elicited the highest conditioned response and the level of pre-feeding aggression behaviours, burst of accelerations and jumps tended to be lower than for temporal predictability alone. Interestingly, fish swimming activity during bubble diffusion also revealed that bubbles were highly attractive regardless of the condition. Rainbow trout growth and emotional reactivity were not affected by the predictability condition. We conclude, therefore, that the use of bubbles as a feeding predictor could represent an interesting approach to improve rainbow trout welfare in farms, by acting as both an occupational and physical enrichment.

Welfare Indicators in Tilapia: An Epidemiological Approach

Interest and concern about rearing methods and their impact on animal welfare have increased. Production evaluation is population-based, and animal welfare analysis should be similar. In fish, the most common welfare indicators are gill state, fin damage, and body condition. The objective of this study was to evaluate the feeding rate effect on the welfare indicators of Oreochromis niloticus using an epidemiological approach. Five growth stages (from 1.2 to 360 g) were studied using four feeding rates as treatments: underfeeding (80%), recommended feeding (100%), and two levels of overfeeding (120% and 140%). The evaluated welfare indicators include the presence of lesions in different body areas and fins, the decrease in body condition index, and their impact on biomass production. Incidence and relative risk were determined for each indicator. Statistically significant associations were found in the indicators of mortality, weight, body condition (K), and presence of evident damage in the caudal and anal fin in all stages. The results showed that the feed rate directly affects the welfare indicators and production. Mortality, weight reduction, K reduction, and caudal and anal fin damage incidence showed to be relevant indicators in all O. niloticus growing stages. As a result of this study, the epidemiological approach seems to be a valuable tool for production. A risk traffic light method is a proposal that could have great potential, with the suggested limits for WI's concerning the individuals present in the culture pond, allowing progressive evaluation and decision-making to correct risky situations.

Rainbow trout discriminate 2-D photographs of conspecifics from distracting stimuli using an innovative operant conditioning device

Cognitive abilities were studied in rainbow trout, the first continental fish production in Europe. Increasing public concern for the welfare of farmed-fish species highlighted the need for better knowledge of the cognitive status of fish. We trained and tested 15 rainbow trout with an operant conditioning device composed of self-feeders positioned in front of visual stimuli displayed on a screen. The device was coupled with a two-alternative forced-choice (2-AFC) paradigm to test whether rainbow trout can discriminate 2-D photographs of conspecifics (S+) from different visual stimuli (S-). The S- were applied in four stages, the last three stages representing increasing discrimination difficulty: (1) blue shapes; (2) black shape (star); (3) photograph of an object (among a pool of 60); (4) photograph of another fish species (among a pool of 60). Nine fish (out of 15) correctly managed to activate the conditioning device after 30-150 trials. The rainbow trout were able to discriminate images of conspecifics from an abstract shape (five individuals out of five) or objects (four out of five) but not from other fish species. Their ability to learn the category "fish shape" rather than distinguishing between conspecifics and heterospecifics is discussed. The successful visual discrimination task using this complex operant conditioning device is particularly remarkable and novel for this farmed-fish species, and could be exploited to develop cognitive enrichments in future farming systems. This device can also be added to the existing repertoire of testing devices suitable for investigating cognitive abilities in fish.

The Effect of an Irregular Feeding Schedule on Equine Behavior

We used eight horses 1 to 12 years old to investigate the influence of irregular feeding times on the behavior. The animals were housed in individual boxes, fed with hay ad libitum and barley-oat mixture at three set times; 05:00 (earlier feeding) on Thursdays, 07:00 (delayed feeding) on Saturdays and 06:00 (regular feeding) on other weekdays. Direct observations took place in 10 continuous weeks; they started 1 h prior to feeding and lasted for 2 h. Long-term behaviors (i.e. hay and concentrate consumption, resting) were recorded every 5 min, short-term behaviors (i.e. kicking, pawing the ground, comfort behavior, taking a look toward the door) were recorded continuously. Compared to the regular feeding time, horses spent less time consuming hay, more time resting and less often took a look toward the door during the earlier feeding, whereas during the delayed feeding horses more often performed pawing the ground, kicking, comfort behavior, and took a look toward the door (p < .05). Our results indicate that deviations from the regular feeding schedule affected the behavior of horses and compromised their temporal predictability.

A Global Assessment of Welfare in Farmed Fishes: The FishEthoBase

Fish welfare is an essential issue that needs to be tackled by the aquaculture industry. In order to address it, studies have been limited to a small number of species and the information is generally scattered. In order to have a consistent overview of the welfare of farmed fishes, we present the FishEthoBase, an open-access database that ultimately aims to provide information on the welfare of all fish species currently farmed worldwide. Presently with 41 species, this database is directed to all stakeholders in the field and targets not only to bridge the gaps between them but also to provide scientific information to improve the welfare of fish. The current text explains the database and presents an analysis of the welfare scores of 41 species, suggesting that (i) the general welfare state of farmed fishes is poor, (ii) there is some potential for improvement and (iii) this potential is related to research on species’ needs, but (iv) there are many remaining knowledge gaps and (v) current fish farming technologies do not seem to fully address welfare issues. The existence of a framework, such as the FishEthoBase, is proposed as fundamental to the design of strategies that improve the welfare of farmed fish.

Maternal temperature exposure impairs emotional and cognitive responses and triggers dysregulation of neurodevelopment genes in fish

Fish are sensitive to temperature, but the intergenerational consequences of maternal exposure to high temperature on offspring behavioural plasticity and underlying mechanisms are unknown. Here we show that a thermal maternal stress induces impaired emotional and cognitive responses in offspring rainbow trout (Oncorhynchus mykiss). Thermal stress in mothers triggered the inhibition of locomotor fear-related responses upon exposure to a novel environment and decreased spatial learning abilities in progeny. Impaired behavioural phenotypes were associated with the dysregulation of several genes known to play major roles in neurodevelopment, including auts2 (autism susceptibility candidate 2), a key gene for neurodevelopment, more specifically neuronal migration and neurite extension, and critical for the acquisition of neurocognitive function. In addition, our analysis revealed the dysregulation of another neurodevelopment gene (dpysl5) as well as genes associated with human cognitive disorders (arv1, plp2). We observed major differences in maternal mRNA abundance in the eggs following maternal exposure to high temperature indicating that some of the observed intergenerational effects are mediated by maternally-inherited mRNAs accumulated in the egg. Together, our observations shed new light on the intergenerational determinism of fish behaviour and associated underlying mechanisms. They also stress the importance of maternal history on fish behavioural plasticity.

Social networks: a tool for assessing the impact of perturbations on wildlife behaviour and implications for pathogen transmission

Wildlife are increasingly subject to perturbations, which can impact pathogen transmission and lead to disease emergence. While a myriad of factors influence disease dynamics in wildlife, behaviour is emerging as a major influence. In this review, we examine how perturbations alter the behaviour of individuals and how, in turn, disease transmission may be impacted, with a focus on the use of network models as a powerful tool. There are emerging hypotheses as to how networks respond to different types of perturbations. The broad effects of perturbations make predicting potential outcomes and identifying mitigation opportunities for disease emergence critical; yet, the current paucity of data makes identification of underlying trends difficult. Social network analysis facilitates a mechanistic approach to how perturbation-induced behavioural changes result in shifts in pathogen transmission. However, the field is still developing, and future work should strive to address current deficits. There is particular need for empirical data to support modelling predictions and increased inclusion of pathogen monitoring in network studies.

Animal welfare: a social networks perspective

Social network theory provides a useful tool to study complex social relationships in animals. The possibility to look beyond dyadic interactions by considering whole networks of social relationships allows researchers the opportunity to study social groups in more natural ways. As such, network-based analyses provide an informative way to investigate the factors influencing the social environment of group-living animals, and so has direct application to animal welfare. For example, animal groups in captivity are frequently disrupted by separations, reintroductions and/or mixing with unfamiliar individuals and this can lead to social stress and associated aggression. Social network analysis ofanimal groups can help identify the underlying causes of these socially-derived animal welfare concerns. In this review we discuss how this approach can be applied, and how it could be used to identify potential interventions and solutions in the area of animal welfare.