Fish intelligence, sentience and ethics

Nile Tilapia Prefer Water Hyacinth as Structural Enrichment Regardless of Stocking Density

In this study, we investigated whether Nile tilapia (Oreochromis niloticus), a commonly farmed species worldwide, prefer artificial water hyacinth - easy-to-build and inexpensive - as a structural enrichment by investigating if different common farm stocking densities affect such response. We tested juveniles under three stocking densities (12, 16, or 20 fish per aquarium) in both the absence (control groups) and presence (artificial hyacinth treatments) of the structural enrichment for 6 weeks. We filmed fish every week, both when the hyacinth was spread and when it was concentrated in one aquarium section. We then analyzed their preference responses based on the number of fish recorded in each section. Nile tilapia juveniles preferred artificial hyacinth as a structural enrichment, a strong response that may override an initial preference for another area. Although all tested stocking densities showed a preference for the artificial hyacinth, the intensity of this response was stronger at the highest density. These findings indicate that artificial hyacinth is a highly preferred structural enrichment for Nile tilapia juveniles and should be implemented under farming conditions, particularly at higher stocking densities.

An adaptable, user-friendly score sheet to monitor welfare in experimental fish

Fish are increasingly used as experimental animals across research fields. Currently, around a quarter of all experimental animals used are fish. Less than 20% of these are standard model species. Welfare assessments for experimental fish are in their infancy compared with those for rodents. This can be attributed to the diversity of species used, the relative recency of fish as the go-to model for research, and challenges to assess welfare in non-vocal underwater species. The lack of guidelines and tools presents a challenge for researchers (particularly, for newcomers), for ethics committees and for implementing refinement measures. Here, we present an adaptable, user-friendly score sheet for fish based on MS Excel. The parameters are based on a literature review, have been validated by expert interviews and evaluated by a fish pathologist. The tool allows scoring of individual fish as well as groups, calculates summary scores and visualizes trends. We provide the underlying literature, give use examples and provide instructions on the adaptation and use of the score sheet. We hope that this tool will empower researchers to include welfare assessment in their routines, foster discussions on fish welfare parameters among scientists, facilitate interactions with ethics committees and, most importantly, enable the refinement of fish experiments.

Chains of Commerce: A Comprehensive Review of Animal Welfare Impacts in the International Wildlife Trade

The commercial wildlife trade involves billions of animals each year, consumed for various purposes, including food, fashion, entertainment, traditional medicine, and pets. The experiences of the animals involved vary widely, with negative welfare states being commonplace. To highlight the broad scope of animal welfare impacts across the commercial wildlife trade, we present ten case studies featuring a range of species traded globally for different purposes: (1) Ball pythons captured and farmed to serve as pets; (2) Zebrafish captive bred to serve as pets; (3) African Grey Parrots taken from the wild for the pet industry; (4) Sharks de-finned for traditional medicine; (5) Pangolins hunted for traditional medicine; (6) Crickets farmed for food and feed; (7) Frogs wild-caught for the frog-leg trade; (8) Crocodilians killed for their skins; (9) Lions farmed and killed for tourism; and (10) Elephants held captive for tourism. The case studies demonstrate that wild animals commercially traded can suffer from negative welfare states ranging from chronic stress and depression to frustration and extreme hunger. The individuals involved range from hundreds to billions, and their suffering can last a lifetime. Given the welfare issues identified and the growing recognition and scientific evidence for animal sentience, we propose reducing and redirecting consumer demand for these consumptive wildlife practices that negatively impact animals.

Habitat loss and discontinuity as drivers of habitat fragmentation: The role of contamination and connectivity of habitats

Habitat discontinuity of aquatic environments is a serious problem that might hamper the different activities performed by organisms. When combined with contamination, the consequences for the population's dynamics might be exacerbated, particularly regarding foraging activity. Therefore, the aim of this study was to evaluate the combined effects of habitat discontinuity and contamination on the foraging behavior by zebrafish (Danio rerio) and on their ability to explore heterogeneous landscapes. The organisms were exposed to three different scenarios of contamination (0, 0.5 and 25 μg L-1 of Cu) and habitat discontinuity (zero, low and high), using the Heterogeneous Multi-Habitat Assay System (HeMHAS). Generalized Bayesian linear models were used to analyze the data and evidence ratios (ER) were used to test the hypotheses. As results, both high levels of contamination and habitat discontinuity had significant effects on the probability of organisms to reach food (ER = 111.8 and > 1,000, respectively), the time taken to reach food (ER = 532.22 and > 1000, respectively) and the time spent in each compartment (ER = 614.4 and > 1000 for contamination and the number of connections available, respectively). As conclusion, the habitat fragmentation as a consequence of contamination and discontinuity affected the probability of fish to reach food and the time spent to reach it. This could lead to additional energy budget with serious consequences for population dynamics. Also, the HeMHAS demonstrated its suitability to assess the role of the contamination and habitat connectivity stressors in the spatial distribution and habitat selection response.

Life beyond a jar: Effects of tank size and furnishings on the behaviour and welfare of Siamese fighting fish (Betta splendens)

Globally, Siamese fighting fish (Betta splendens) continue to be sold and kept in small, barren jars or tanks, with little concern for their welfare. This study aimed to examine the impact of housing size and furnishings (i.e. live plants, refuges) on the behaviour of Siamese fighting fish, to understand optimal tank conditions. Thirteen male Siamese fighting fish were rotated between five different housing conditions: 'jar' (1.5 L); 'small' (3.3 L); 'medium' (5.6 L); 'large' (19.3 L); and 'large-barren' (19.3 L). All tanks had gravel and furnishings, except the large-barren tank which was devoid of these. Overall, tank size influenced behaviour. Fish were significantly more active and spent significantly less time resting and performing 'abnormal' behaviours (hovering and stereotypic swimming), in the large tank compared to the smaller tanks. Tank furnishings also influenced behaviour. Fishes in the large-barren tank performed more 'abnormal' behaviours (hovering, stereotypic swimming, interaction with the walls), compared to the large tank which had furnishings. These results suggest that the small, barren jars and tanks that Siamese fighting fish are often housed in are detrimental to their welfare, and larger, furnished tanks are more optimal. Behavioural variations were observed between the fish in this study, highlighting individual fish personality. We recommend a minimum tank size of 5.6 L for the display and sale of Siamese fighting fish, and tanks larger than this for keeping Siamese fighting fish at home. All tanks should contain gravel, live plants and refuges.

The ability of teleost fishes to recognize individual faces suggests an early evolutionary origin in vertebrates

The face is the most important area on the human body for visually differentiating between individuals. When encountering another person, humans initially gaze at and perceive the face holistically, utilizing first-order relational information and specific neural systems. Information such as identity and emotional state are then obtained from the face by distinguishing between small inter-individual differences, i.e., second-order relational information. Similar patterns and mechanisms underlying individual face recognition have been documented in primates, other social mammals, birds, and more recently in some fishes. Like humans, fish are capable of rapidly (<0.5 s) and accurately recognizing multiple familiar conspecifics by individual-specific variation in the face. Fish can also recognize faces from various distances and angles, providing evidence for mental representation of faces in this large and diverse vertebrate group. One species, the cleaner fish, has even demonstrated mirror self-recognition (MSR) via self-face recognition, strengthening the claim that non-human animals are capable of having mental images and concepts of faces. Here, we review the evidence for individual face recognition in fishes and speculate that face identification neural networks are both similar and widespread across vertebrates. Furthermore, we hypothesize that first-and second-order face recognition in vertebrates originated in bony fishes in the Paleozoic era ~450 Mya, when social systems first evolved, increasing the importance of individual recognition.

Bridging the divide in organismal physiology: a case for the integration of behaviour as a physiological process

The role of behaviour in animal physiology is much debated, with researchers divided between the traditional view that separates physiology and behaviour, and a progressive perspective that sees behaviour as a physiological effector. We advocate for the latter, and in this Commentary, we argue that behaviour is inherently a physiological process. To do so, we outline the physiological basis for behaviour and draw parallels with recognised physiological processes. We also emphasise the importance of precise language that is shared across biological disciplines, as clear communication is foundational in integrating behaviour into physiology. Our goal with this Commentary is to set the stage for a debate and persuade readers of the merits of including behaviour within the domain of animal physiology. We argue that recognising behaviour as a physiological process is crucial for advancing a unified understanding of physiology, especially in the context of anthropogenic impacts.

Behavioural Monitoring Underlines Habituation to Repeated Stressor Stimuli in Farmed Gilthead Sea Bream (Sparus aurata) Reared at a High Stocking Density

A confinement stress test with 75% tank space reduction and behavioural monitoring through tri-axial accelerometers externally attached to the operculum was designed. This procedure was validated by demonstrating the less pronounced stress response in gilthead sea bream than in European sea bass (950-1200 g). Our study aimed to assess habituation to high stocking densities with such procedure in gilthead sea bream. Animals (420-450 g) were reared (June-August) in a flow-through system at two stocking densities (CTRL: 10-15 kg/m3; HD: 18-24 kg/m3), with natural photoperiod and temperature (21-29 °C), and oxygen levels at 5.2-4.2 (CTRL) and 4.2-3.2 ppm (HD). At the end, blood and muscle were sampled for haematology and transcriptomic analyses, and external tissue damage was assessed by image-based scoring. Four days later, fish underwent a 45 min confinement stress test over two consecutive days. HD fish showed reduced feed intake, growth rates and haematopoietic activity. Muscle transcriptome changes indicated a shift from systemic to local growth regulation and a primed muscle regeneration over protein accretion in HD animals with slight external injuries. After stress testing, HD fish exhibited a decreased recovery time in activity and respiration rates, which was shorter after a second stressor exposure, confirming habituation to high densities.

Fish welfare in farms: potential, knowledge gaps and other insights from the fair-fish database

An adequate understanding of fish behaviors and their interaction with farm-specific environments is pivotal for enhancing fish welfare in aquaculture. The fair-fish database aims to provide a consistent overview of the welfare of farmed fish. This platform consolidates ethological knowledge into profiles of farmed aquatic species. Its WelfareCheck profiles are organized around welfare indicators, with each criterion receiving classifications (no findings, unclear, low, medium, and high) regarding the likelihood and potential for individuals of a given species to experience good welfare in aquaculture systems, along with the associated certainty level. These criteria include home range, depth range, migration patterns, reproduction, aggregation patterns, aggressive behavior, substrate needs, stress responses, malformations, and slaughtering protocols. We investigated which of these 10 criteria are most relevant to the overall welfare of a species, considering the likelihood, potential, and certainty of good welfare in aquaculture. To achieve this, we reviewed and recorded the high classifications across each criterion and dimension from all published WelfareCheck profiles. To further investigate knowledge gaps across the criteria, we also recorded classifications marked as unclear and no findings. These were then compared across the criteria to assess the frequency of such classifications. While no significant differences were found between the criteria regarding the likelihood that the surveyed species meet their basic welfare needs, criteria related to reproduction, slaughter practices, and substrate needs demonstrated a high potential for better welfare outcomes. Moreover, reproduction and migration patterns exhibited high certainty in the available literature. Based on these findings, we conclude that improving the reproduction of farmed aquatic species, considering their natural needs and behavior, could be an effective and reliable approach to improving welfare. However, we also found a low certainty of information on aggression and an absence or conflicting data on home range, aggregation patterns, stress, and malformations. This highlights an urgent need for research in these areas, which are fundamental for developing more accurate assessments and recommendations for farmed aquatic species.

Minding some animals but not others: Strategic attributions of mental capacities and moral worth to animals used for food in pescatarians, vegetarians, and omnivores

While moral concern for animals has become increasingly important for both consumer food choice and food policy makers, previous research demonstrated that meat eaters attribute lower moral status and mental capacities to animals raised for meat compared to non-food animals. The current research investigated whether this strategic flexibility in moral concern and mind perceptions also occurs when considering aquatic food animals and animals used for dairy and egg products, and the degree to which these concerns and perceptions are evident in pescatarians and vegetarians. We compared perceptions (mind attributions and moral concern) of land food animals versus aquatic food animals, and of animals in the meat versus dairy and egg industry between omnivores (n = 122), pescatarians (n = 118), vegetarians (n = 138), vegans (n = 120), and flexitarians (n = 60). Pescatarians scored lower than other dietary groups on moral concern and mind attribution for aquatic animals relative to farmed land animals. Unlike the other dietary groups, pescatarians and vegetarians scored lower on moral concern and mind attribution for dairy than beef cows and for layer chickens than broiler chickens. These findings demonstrate that pescatarians and vegetarians were flexible in their moral thinking about different types of food animals in ways that suited their consumption habits, even when the same animal was evaluated (e.g., dairy vs beef cows). This research highlights the psychological barriers that might prevent people from reducing animal product consumption and may need to be addressed in interventions to encourage transitioning towards more plant-based diets.

Surveying the welfare of farmed fish species on a global scale through the fair-fish database

Fish welfare is a critical issue that needs to be addressed by the rapidly growing aquaculture industry. Scientific knowledge regarding the natural behaviors of species and the conditions in which they are kept in farms is essential for improving their welfare in aquaculture. To provide a consistent overview of the welfare of farmed fish, the organization fair-fish has created the online platform fair-fish database, which gathers ethological knowledge categorized into profiles of farmed aquatic species. The WelfareChecks on this platform are profiles based on criteria that are rated based on the likelihood and potential of the species to experience a high level of welfare in aquaculture systems, together with the certainty about the findings. A score (WelfareScore) is calculated from these ratings, serving as a reference to identify knowledge gaps, assess welfare, and suggest ways to improve it. Here, we performed an in-depth analysis of the species with WelfareChecks already published in the fair-fish database based on their respective WelfareScores. In general, although just a small percentage of farmed aquatic species (~5%) have at least a 20% chance of experiencing a good level of welfare under minimal aquaculture conditions, 60% of them have at least some potential to achieve good welfare under high-standard conditions, with more than a third of the species (~37%) having at least a 20% potential. Despite that, several species exhibit a very high frequency of low chances and potential for experiencing good welfare levels under aquaculture conditions, besides a low degree of certainty based on literature reviews. Furthermore, many others show a very frequent occurrence of unclear or nonexistent knowledge in their profiles. The current welfare state is therefore poor for the majority of farmed aquatic species; yet, there is considerable potential for improvement. However, many species are very unlikely to achieve good welfare, even under high-standard conditions. Importantly, large knowledge gaps remain for an accurate assessment of the welfare of several farmed species.

Limited effects of culling on the behavior of invasive lionfish (Pterois miles) in the Mediterranean

Invasive species pose serious threats to ecosystems. To reduce ecological and economic consequences of invasions, efforts are made to control invaders and evaluating the effects of such efforts is paramount. Lionfishes (Pterois volitans and Pterois miles) are native to the Indo-Pacific Ocean and pose a major threat to local ecosystems in the invaded Atlantic and Mediterranean. Culling via spearfishing is a widespread measure to limit lionfish population size in invaded ranges. However, like most hunted fishes, lionfish alter their behavior after repeated culling, potentially decreasing the effectiveness of future culls. Previous studies on lionfish in the Caribbean have shown that lionfish are less bold after repeated culling. However, the impact of culling on lionfish in their newest invasive range, the Mediterranean, remains enigmatic. To determine the behavioral changes in response to culling in this second area of invasion, we tested for effects of culling on the behavior of lionfish in Cyprus, a region heavily impacted by the lionfish invasion in the Mediterranean. We compared the response of lionfish to an approaching free diver holding a metal pole (imitating a spear fisher) between protected areas where spearfishing is restricted and areas where culls are frequently conducted. We also assessed whether activity, hiding pattern, and site fidelity differed between these culled and unculled sites. Overall, we found limited effects of culling on the traits measured, indicating surprising resistance to culling-induced behavioral changes in Mediterranean lionfish. Future studies should monitor invasive lionfish population densities and the effects of culling in more detail to tailor management plans and reduce the negative effects of these fish in specific invaded ranges.

Estimating global numbers of fishes caught from the wild annually from 2000 to 2019

Finfishes are caught from the wild for food, feed (often in the form of fishmeal and oil) and bait. According to the Food and Agriculture Organisation of the United Nations (FAO), between 74 and 83 million tonnes (averaging 77 million tonnes) were caught annually in 2000-2019. Although fishes are now widely recognised as sentient beings, capture is still quantified as biomass rather than number of individuals (in contrast to wild-caught marine mammals and crocodiles; and farmed mammals and birds). Here, we estimate global numbers of wild-caught finfishes using FAO capture production (landing) tonnages (2000-2019 data) and estimates of mean individual weight at capture, based on internet-sourced capture and market weights. We estimate that between 1,100 and 2,200 billion (1.1-2.2 × 1012), or 1.1-2.2 trillion, wild finfishes were caught annually, on average, during 2000-2019. Anchoveta (Engraulis ringens) comprised 28%, by estimate midpoint. Estimated numbers in 2019, totalling 980-1,900 billion, were lower due to reduced anchoveta landings, but still represented 87.5% of vertebrate numbers killed for food or feed, as obtained or estimated from FAO data. These figures exclude unrecorded capture such as illegal fishing, discards and ghost fishing. Estimated finfish numbers used for reduction to fishmeal and oil represented 56% of the total 2010 estimate (1,000-1,900 billion), by midpoint. It is recommended that the FAO reports fish capture numbers. The welfare of wild-caught fishes, which is generally very poor during and after capture, should be addressed as part of sustainable utilisation of aquatic resources.

Stocking density affects immune and stress-related gene expression of Butter catfish (Ompok bimaculatus) fry in biofloc landscapes

Scientific research into fish wellness is critical, and the concerns about crowding-related stress due to increased stocking density are inevitable. Taking this into consideration, the study defines the physiological signature of Ompok bimaculatus (Butter catfish) in a biofloc system when subjected to varying levels of stocking density. Fish (mean weight = 1.21 g ± 0.08, n = 600) were randomly stocked in 40-L glass aquaria at stocking densities of 0.5 g/L (T1), 1 g/L (T2), 1.5 g/L (T3), and 2 g/L (T4) and fed a 35% protein diet. After the 90-day trial, the physio-biochemical, molecular, and tissue-level changes were assessed. An integrated biomarker response (IBR) analysis for the key stress indicators aided us in better understanding them. There was a significant difference in blood count between T1 and T4 (total erythrocyte count, hemoglobin, and packed cell volume). T1 had higher levels of globulin and total plasma protein, but T2 had higher levels of albumin. Only in T1 did the respiratory burst and lysozyme activity appear to be higher (p < 0.05). Increased stocking densities had a significant impact on the liver function enzymes, GOT and GPT (p < 0.05). In comparison to lower densities (T1 & T2), higher stocking density (T3 & T4) was found to raise glucose and cortisol levels (p < 0.05). Antioxidant enzymes such as catalase, glutathione-S-transferase, and malondialdehyde were found to be more pronounced in lower density tissues (T1). Furthermore, the IBR plots show that lower densities have better health than higher densities. At higher stocking densities, mRNA expression of HSP70, IL-1, and IL-20 increased (p < 0.05) in kidney and liver tissues. The Nrf-2 and Tlr-9 genes were also upregulated. Also, when stocking density was increased, tissue-level histo-architectural changes were more pronounced than when stocking density was kept low. The findings of this study show that the welfare of Butter catfish cultured at high density in biofloc systems suffers from severe stress, and therefore draw more attention to the development of a species-specific standard rearing methodology in the pursuit of a profitable aqua-farming enterprise.

Feeling morally troubled about meat, dairy, egg, and fish consumption: Dissonance reduction strategies among different dietary groups

A largescale shift towards plant-based diets is considered a critical requirement for tackling ethical, environmental, and global health issues associated with animal food production and consumption. Although previous research has identified psychological strategies that enable meat-eaters to justify and continue meat consumption and feel less morally conflicted about it, research on the psychological strategies that enable consumers to continue dairy, egg, and fish consumption is scarce. We conducted an online survey study using an adjusted version of the Meat-Eating Justification Scale to investigate the use of psychological strategies to cope with cognitive dissonance related to meat, dairy, egg, and fish consumption in omnivores (n = 186), pescatarians (n = 106), vegetarians (n = 143), vegans (n = 203), and flexitarians (n = 63). Results indicated greater use of meat-related dissonance reduction strategies among omnivores as compared to other dietary groups, greater use of fish-related dissonance reduction strategies among fish consumers (omnivores, flexitarians and pescatarians) compared to vegetarians and vegans, and greater use of dairy and egg-related dissonance reduction strategies among dairy and egg consumers (omnivores, flexitarians, pescatarians, and vegetarians) as compared to vegans. This pattern was particularly clear for justifications used to defend animal product consumption, denial of animal suffering, and use of dichotomization when considering meat and fish consumption. These findings highlight the importance of extending the research on dissonance reduction strategies beyond meat consumption and studying the consumption of a range of animal products. This can help in identifying the psychological barriers to adopting a plant-based diet and informing interventions for behaviour change.

Qualitative Behavioural Assessment as a welfare indicator for farmed Atlantic salmon (Salmo salar) in response to a stressful challenge

Animal welfare assessments have struggled to investigate the emotional states of animals while focusing solely on available empirical evidence. Qualitative Behavioural Assessment (QBA) may provide insights into an animal's subjective experiences without compromising scientific rigor. Rather than assessing explicit, physical behaviours (i.e., what animals are doing, such as swimming or feeding), QBA describes and quantifies the overall expressive manner in which animals execute those behaviours (i.e., how relaxed or agitated they appear). While QBA has been successfully applied to scientific welfare assessments in a variety of species, its application within aquaculture remains largely unexplored. This study aimed to assess QBA's effectiveness in capturing changes in the emotional behaviour of Atlantic salmon following exposure to a stressful challenge. Nine tanks of juvenile Atlantic salmon were video-recorded every morning for 15 min over a 7-day period, in the middle of which a stressful challenge (intrusive sampling) was conducted on the salmon. The resultant 1-min, 63 video clips were then semi-randomised to avoid predictability and treatment bias for QBA scorers. Twelve salmon-industry professionals generated a list of 16 qualitative descriptors (e.g., relaxed, agitated, stressed) after viewing unrelated video-recordings depicting varying expressive characteristics of salmon in different contexts. A different group of 5 observers, with varied experience of salmon farming, subsequently scored the 16 descriptors for each clip using a Visual Analogue Scale (VAS). Principal Components Analysis (correlation matrix, no rotation) was used to identify perceived patterns of expressive characteristics across the video-clips, which revealed 4 dimensions explaining 74.5% of the variation between clips. PC1, ranging from 'relaxed/content/positive active' to 'unsettled/stressed/spooked/skittish' explained the highest percentage of variation (37%). QBA scores for video-clips on PC1, PC2, and PC4 achieved good inter- and intra-observer reliability. Linear Mixed Effects Models, controlled for observer variation in PC1 scores, showed a significant difference between PC1 scores before and after sampling (p = 0.03), with salmon being perceived as more stressed afterwards. PC1 scores also correlated positively with darting behaviours (r = 0.42, p < 0.001). These results are the first to report QBA's sensitivity to changes in expressive characteristics of salmon following a putatively stressful challenge, demonstrating QBA's potential as a welfare indicator within aquaculture.

Recordings in an integrating central neuron reveal the mode of action of isoeugenol

Although isoeugenol is one of the most widely used anesthetics in fish, its actual mode of action and thus its applicability for particular interventions is poorly understood. Here we determined effects of isoeugenol on various aspects of sensory and neural function, taking advantage of intracellular in vivo recordings in a uniquely suited identified neuron, the Mauthner neuron in the brain of goldfish. We show that isoeugenol strongly affects hearing and vision, but sensitivity and time course of action differed largely in these two senses. The action potential, chemical and electric synaptic transmission at the central neuron were not affected at low but efficient anesthesia. Effects seen at high concentration thereby do not support current views of how isoeugenol might act on central neurons. We show that isoeugenol is highly useful to anesthetize fish for handling, but that in more severe treatment its application needs to be carefully adapted to task.

Improving welfare assessment in aquaculture

While global aquaculture is rapidly expanding, there remains little attention given to the assessment of animal welfare within aquacultural systems. It is crucial that animal welfare concerns are central in the development and implementation of aquaculture as if they are not prioritized early on, it becomes much more difficult to adapt in future. To this end, it is important to ensure the availability of high-quality welfare assessment schemes to evaluate the welfare of animals in aquaculture and promote and maintain high welfare standards. This paper will first discuss some of the current certification and assessment frameworks, highlighting the primary limitations that need to be addressed, before going on to describe the recommendations for a best-practice welfare assessment process for aquaculture; with the hope that these considerations can be taken on board and used to help improve welfare assessment for aquaculture and, ultimately, to ensure animals used in aquaculture have a higher level of welfare. Any aquacultural system should be assessed according to a suitable framework in order to be considered adequate for the welfare of the animals it contains, and thus to maintain social license to operate.

Exploiting animal personality to reduce chronic stress in captive fish populations

Chronic stress is a major source of welfare problems in many captive populations, including fishes. While we have long known that chronic stress effects arise from maladaptive expression of acute stress response pathways, predicting where and when problems will arise is difficult. Here we highlight how insights from animal personality research could be useful in this regard. Since behavior is the first line of organismal defense when challenged by a stressor, assays of shy-bold type personality variation can provide information about individual stress response that is expected to predict susceptibility to chronic stress. Moreover, recent demonstrations that among-individual differences in stress-related physiology and behaviors are underpinned by genetic factors means that selection on behavioral biomarkers could offer a route to genetic improvement of welfare outcomes in captive fish stocks. Here we review the evidence in support of this proposition, identify remaining empirical gaps in our understanding, and set out appropriate criteria to guide development of biomarkers. The article is largely prospective: fundamental research into fish personality shows how behavioral biomarkers could be used to achieve welfare gains in captive fish populations. However, translating potential to actual gains will require an interdisciplinary approach that integrates the expertise and viewpoints of researchers working across animal behavior, genetics, and welfare science.

Wild Fish Welfare in UK Commercial Sea Fisheries: Qualitative Analysis of Stakeholder Views

An estimated 1.5-2.7 billion wild fish are caught by UK commercial sea fishing fleets annually. Most are subjected to severe stressors during capture; stunning is rare and gutting alive is common practice. Fish are recognised in UK law as sentient beings, but commercially caught wild fish are excluded from welfare protections. Animal welfare impacts in wild capture sea fisheries are therefore on a massive scale, with major potential for legislative and market-based reforms. Interviews were conducted with 18 experts working within the fishing and seafood industry, fisheries management, scientific research and animal/fish advocacy organisations. The findings reveal a significant welfare gap between societally acceptable ways to treat sentient animals and the reality of capture fisheries. The participants pointed to harms caused to fish throughout different stages of the capture process caused by combinations of variables from fishing gear and methods to biological, environmental and other factors, noting that all require mitigation. Interviews revealed that the nature of harms may be exacerbated by conservative attitudes towards brutal practices in the industry, driven by profit and efficiency and free from legal restraint. To address the welfare gap, stakeholders favour engagement with the industry to improve understanding of harms and to identify mutually beneficial and shared objectives through alleviating stressors to fish in the capture process. This empirical research is focused on UK wild capture sea fisheries. However, given the dearth of welfare legislation globally, it has significance for fishing nations and the many billions of wild sea fish captured each year around the world.

Environmental enrichment improves the growth rate, behavioral and physiological response of juveniles of Clarias gariepinus under laboratory conditions

Environmental enrichment (EE) improves the growth rate and welfare of some cultured fishes. However, most cultured fish species are raised in non-enriched housing conditions. Clarias gariepinus is an important commercial fish species, but little is known about the effect of EE on their welfare. This study examined the effect of different EE on the survival rate (SR), growth [mean weight gain (MWG), specific growth rate (SGR) and feed conversion ratio (FCR)], behavioral (feed response, aggressive acts and shoaling time) and physiological responses (blood glucose) of C. gariepinus. One hundred and twenty juveniles of C. gariepinus (31.65 ± 0.69 g) were randomly allocated at 10 fish/tank and subjected to either Plant Enriched (PE), Substratum Enriched (SE), Plant and Substratum Enriched (PSE) and Non-Enriched (NE) tanks in triplicates for 56-days. Behavioral acts were observed for 10 min twice daily, and glucose level in blood samples was evaluated. Data were checked for normality using the Shapiro-Wilk test before being analyzed with the Kruskal-Wallis test. SR and MWG were significantly higher in Clarias gariepinus exposed to SE, with no significant differences among PE, PSE and NE treatments. There was no significant difference between the SGR of PSE and NE. FCR was similar between treatments. The highest condition factor (k) was recorded in SE tanks. Duration of feed response was shorter in SE, but there was no significant difference between the feed response of C. gariepinus exposed to PE and PSE. C. gariepinus exposed to PE, SE and PSE displayed a similar frequency of aggressive acts. African catfish reared in NE (barren) tanks had the least duration of shoaling period. The experiment consistently found the highest and least glucose values in PSE and SE. In conclusion, environmentally enriched housing tanks with SE resulted in the best MWG with a reduced level of aggression in C. gariepinus under laboratory conditions. Thus, EE might be applicable to boost fish productivity on a commercial scale.

Assessing tests of animal consciousness

Which animals have conscious experiences? Many different, diverse and unrelated behaviors and cognitive capacities have been proposed as tests of the presence of consciousness in an animal. It is unclear which of these tests, if any, are valid. To remedy this problem, I develop a list consisting of eight desiderata which can be used to assess putative tests of animal consciousness. These desiderata are based either on detailed analogies between consciousness-linked human behavior and non-human behavior, on theories of consciousness or on methods from human consciousness science. If a test or set of tests satisfies more of these desiderata, passing it provides stronger evidence of consciousness. Moreover, one can design future tests of animal consciousness with the intention of satisfying these desiderata to ensure their evidential strength.

A “Good Life” for Dairy Cattle: Developing and Piloting a Framework for Assessing Positive Welfare Opportunities Based on Scientific Evidence and Farmer Expertise

Simple Summary

There is increasing appetite to understand how we can provide quality of life to farm animals. A framework to evaluate positive welfare opportunities for dairy cattle was developed using a participatory approach where farmer’s recommendations were integrated into a scientific framework and piloted on farm by vets. When provided with the opportunity to collaborate, farmers and scientists broadly agree on what constitutes “a good life” for dairy cattle and worked together to develop an assessment framework. Farmers did not agree equally on the value of each positive welfare opportunity. However, farmers supported positive welfare assessment as a means of recognition and reward for higher animal welfare, within existing farm assurance schemes, and to justify national and global marketing claims of higher animal welfare.

Abstract

On-farm welfare assessment tends to focus on minimising negative welfare, but providing positive welfare is important in order to give animals a good life. This study developed a positive welfare framework for dairy cows based on the existing scientific literature which has focused on developing positive welfare indicators, and trialled a participatory approach with farmers; refining the framework based on their recommendations, followed by a vet pilot phase on farm. The results revealed that farmers and scientists agree on what constitutes “a good life” for dairy cattle. Farmers value positive welfare because they value their cows’ quality of life, and want to be proud of their work, improve their own wellbeing as well as receive business benefits. For each good life resource, the proportion of farmers going above and beyond legislation ranged from 27 to 84%. Furthermore, barriers to achieving positive welfare opportunities, including monetary and time costs, were not apparently insurmountable if implementation costs were remunerated (by the government). However, the intrinsic value in providing such opportunities also incentivises farmers. Overall, most farmers appeared to support positive welfare assessment, with the largest proportion (50%) supporting its use within existing farm assurance schemes, or to justify national and global marketing claims. Collaborating with farmers to co-create policy is crucial to showcase and quantify the UK’s high welfare standards, and to maximise engagement, relevance and uptake of animal welfare policy, to ensure continuous improvement and leadership in the quality of lives for farm animals.

Empirical support for sequential imprinting during downstream migration in Atlantic salmon (Salmo salar) smolts

The precise homing of Atlantic salmon to their natal river and spawning grounds is the foundation for locally adapted genetically differentiated populations across rivers or across river sections. A sequential imprinting hypothesis states that salmon smolts may imprint on environmental clues along the outward migration route and then use this in reverse order to direct the spawning migration later in life. In this study, we provide empirical support for this hypothesis. PIT-tagged wild Atlantic salmon using a 2 km hydropower tunnel as downstream migrating smolts had a 18% (1SW) and 23% (2SW) lower probability of successfully migrating through the parallel river stretch as adult spawners compared to spawners that migrated through the same river stretch as smolts. These findings highlight how a fine-scale riverine migration route may be imprinted in wild Atlantic salmon smolts. From an applied perspective, these results stress the importance of not depriving smolts from parts of their migration route to ensure successful return of adults to their natal spawning grounds.

Brain morphology correlates of learning and cognitive flexibility in a fish species (Poecilia reticulata)

Determining how variation in brain morphology affects cognitive abilities is important to understand inter-individual variation in cognition and, ultimately, cognitive evolution. Yet, despite many decades of research in this area, there is surprisingly little experimental data available from assays that quantify cognitive abilities and brain morphology in the same individuals. Here, we tested female guppies (Poecilia reticulata) in two tasks, colour discrimination and reversal learning, to evaluate their learning abilities and cognitive flexibility. We then estimated the size of five brain regions (telencephalon, optic tectum, hypothalamus, cerebellum and dorsal medulla), in addition to relative brain size. We found that optic tectum relative size, in relation to the rest of the brain, correlated positively with discrimination learning performance, while relative telencephalon size correlated positively with reversal learning performance. The other brain measures were not associated with performance in either task. By evaluating how fast learning occurs and how fast an animal adjusts its learning rules to changing conditions, we find support for that different brain regions have distinct functional correlations at the individual level. Importantly, telencephalon size emerges as an important neural correlate of higher executive functions such as cognitive flexibility. This is rare evidence supporting the theory that more neural tissue in key brain regions confers cognitive benefits.

Accurate Fish Detection under Marine Background Noise Based on the Retinex Enhancement Algorithm and CNN

Underwater detection equipment with fish detection technology has broad application prospects in marine fishery resources exploration and conservation. In this paper, we establish a multi-scale retinex enhancement algorithm and a multi-scale feature-based fish detection model to improve underwater detection accuracy and ensure real-time performance. During image preprocessing, the enhancement algorithm combines the bionic structure of the fish retina and classical retinex theory to filter out underwater environmental noise. The detection model focuses on improving the detection performance on small-size targets using a deep learning method based on a convolutional neural network. We compare our method to current mainstream detection models (Faster R-CNN, RetinaNet, YOLO, SSDetc.), and the proposed model achieves better performance, with a mean Average Precision (mAP) of 78.31% and a mean Miss Rate (mMR) of 54.11% in the open fish image data set. The test results for the data from the field experiment prove the feasibility and stability of our model.

Spatial Learning of Individual Cichlid Fish and Its Effect on Group Decision Making

Learning and memory abilities and their roles in group decision-making have important ecological relevance in routine activities such as foraging and anti-predator behaviors in fish species. The aims of the present study were to explore individual spatial learning abilities of juvenile cichlids (Chindongo demasoni) in a foraging context, and to explore the influence of heterogeneity of memory information among group members on group performance in a six-arm radiation maze. In the context of an association between landmarks and food, learning ability was evaluated by the speed and accuracy of reaching the arm with food during seven days of reinforcement, and memory retention was tested at intervals of 2, 5, 8 and 11 days of detraining. Then, the speed and accuracy of an eight-member group with different proportions of memory-trained fish were measured. Both speed and accuracy of individual fish improved significantly and linearly in the first five days of training and leveled off between five and seven days, with values 60% shorter (in speed) and 50% higher (in accuracy) compared to those of the first day. Neither speed nor accuracy showed any decrease after 11 days of detraining, suggesting memory retention of the spatial task. When measured in a group, the speed and accuracy of the majority of the group (more than half) in reaching the arm with food changed linearly with an increasing ratio of trained members. This shows that cichlids can acquire associative learning information through a training process, and group behavior of cichlids seems not likely be determined by a minority of group members under a foraging context.

A Kettle of Fish: A Review of the Scientific Literature for Evidence of Fish Sentience

Fish are traded, caught, farmed, and killed in their trillions every year around the world, yet their welfare is often neglected and their sentience regularly disregarded. In this review, we have sought to (1) catalogue the extent to which fish sentience has featured over the past 31 years in the scientific literature and (2) discuss the importance of fish sentience in relation to their commercial uses. We searched the journal database Science Direct using 42 keywords that describe traits or elements of sentience to find articles that were referring to or exploring fish sentience. Our review returned 470 results for fish sentience in 142 different species and subspecies of fish, and featured 19 different sentience keywords. The top four keywords were; 'stress' (psychological) (n = 216, 45.9% of total results), 'anxiety' (n = 144, 30.6%), 'fear' (n = 46, 9.7%), and 'pain' (n = 27, 5.7%). Our findings highlight an abundance of evidence for fish sentience in the published scientific literature. We conclude that legislation governing the treatment of fish and attitudes towards their welfare require scrutiny so that their welfare can be safeguarded across the globe.

Animal sentience

'Sentience' sometimes refers to the capacity for any type of subjective experience, and sometimes to the capacity to have subjective experiences with a positive or negative valence, such as pain or pleasure. We review recent controversies regarding sentience in fish and invertebrates and consider the deep methodological challenge posed by these cases. We then present two ways of responding to the challenge. In a policy-making context, precautionary thinking can help us treat animals appropriately despite continuing uncertainty about their sentience. In a scientific context, we can draw inspiration from the science of human consciousness to disentangle conscious and unconscious perception (especially vision) in animals. Developing better ways to disentangle conscious and unconscious affect is a key priority for future research.

Fish slaughter practices in Brazilian aquaculture and their consequences for animal welfare

Slaughter is considered an important fish welfare issue. For a slaughter method to be considered humane, effective stunning that lasts until death as well as the reduction of pain and fear throughout all procedures are essential. Our objective was to investigate current techniques for slaughtering fish in Brazil. A digital questionnaire with six multiple-choice and three open questions was distributed to companies registered as fish slaughterhouses and to fish farms in 2019, addressing fish species, quantities processed and slaughter procedures adopted. From 62 facilities in 15 Brazilian states that answered the survey, nine slaughterhouses and 30 fish farms slaughtered fish, totalling 452 tonnes per day. All reported pre-slaughter stunning, and live chilling to be the most commonly cited method (82.0%), followed by electronarcosis (18.0%). Slaughtering techniques included exsanguination (38.5%) and decapitation (2.5%). For the remaining companies, no slaughter method was declared, suggesting death by asphyxiation or by further processing (59.0%). Twenty-nine companies adopted pre-slaughter fasting, lasting from 10 to 48 h. All sites worked with tilapia (100%) and 24 (82.7%) reported that they worked exclusively with this species. Other species reported were: pacu (25.6%), tambacu (17.9%), tambaqui and carp (15.3%), jundiá (12.8%), pintado and pirarucu (7.7%), matrinxã and pangassius (5.1%). Asphyxia and live chilling are not considered humane, as animals remain conscious and, thus, suffer. Results show that most establishments do not perform humane slaughter. This scenario highlights the urgent need for development and enforcement of humane fish slaughter techniques, with routine supervision and normative requirements.

What Is It Like to Be a Bass? Red Herrings, Fish Pain and the Study of Animal Sentience

Debates around fishes' ability to feel pain concern sentience: do reactions to tissue damage indicate evaluative consciousness (conscious affect), or mere nociception? Thanks to Braithwaite's discovery of trout nociceptors, and concerns that current practices could compromise welfare in countless fish, this issue's importance is beyond dispute. However, nociceptors are merely necessary, not sufficient, for true pain, and many measures held to indicate sentience have the same problem. The question of whether fish feel pain - or indeed anything at all - therefore stimulates sometimes polarized debate. Here, we try to bridge the divide. After reviewing key consciousness concepts, we identify "red herring" measures that should not be used to infer sentience because also present in non-sentient organisms, notably those lacking nervous systems, like plants and protozoa (P); spines disconnected from brains (S); decerebrate mammals and birds (D); and humans in unaware states (U). These "S.P.U.D. subjects" can show approach/withdrawal; react with apparent emotion; change their reactivity with food deprivation or analgesia; discriminate between stimuli; display Pavlovian learning, including some forms of trace conditioning; and even learn simple instrumental responses. Consequently, none of these responses are good indicators of sentience. Potentially more valid are aspects of working memory, operant conditioning, the self-report of state, and forms of higher order cognition. We suggest new experiments on humans to test these hypotheses, as well as modifications to tests for "mental time travel" and self-awareness (e.g., mirror self-recognition) that could allow these to now probe sentience (since currently they reflect perceptual rather than evaluative, affective aspects of consciousness). Because "bullet-proof" neurological and behavioral indicators of sentience are thus still lacking, agnosticism about fish sentience remains widespread. To end, we address how to balance such doubts with welfare protection, discussing concerns raised by key skeptics in this debate. Overall, we celebrate the rigorous evidential standards required by those unconvinced that fish are sentient; laud the compassion and ethical rigor shown by those advocating for welfare protections; and seek to show how precautionary principles still support protecting fish from physical harm.

Social isolation impairs feed intake, growth and behavioural patterns of catfish under culture conditions

Globally, the culture of fishes is important for food production. There is a growing interest in understanding and improving the welfare of cultured fish from both ethical and production perspectives. Social isolation is a common practice in catfish farming. This study assessed how social interactions affect the feeding behaviour, growth performance, and behavioural pattern of Clarias gariepinus under different social conditions. Juveniles of African catfish with a mean weight of 23.6 ± 1.09 g were stocked in 20L-aquaria (1.7 m × 1.2 m × 1.0 m) and fed twice daily in isolated (one fish/tank; N = 6 replicates) and non-isolated (six fish/tank; N = 6 replicates) conditions for a 36-day experimental period. Feed intake and growth response were monitored, while behavioural patterns were observed twice per week using focal sampling techniques for a total of 40 minutes per day. Wilcoxon two-sample tests and GLMs were used to analyse the data. Social context significantly (P < 0.001) affected the feed intake, feeding duration, and other observed behavioural patterns. However, the time of feeding (P > 0.001) did not affect the feed intake or the duration of feeding. Fish cultured in non-isolated conditions consumed more pellets (63 ± 2.36). The duration of feeding was longer in isolated conditions (431 s) while the latency to feed increased significantly (P < 0.001) from the first and fifth day of the experiment for the non-isolated and isolated, respectively. Behaviourally, isolated groups were inactive (W_s = 446.34, z = 5.397; P < 0.01) and displayed fewer aggressive acts (W_s = 0.95, z = 1.19; P < 0.01), while non-isolated groups were more active (W_s = 564.39, z = -5.397; P < 0.01) and displayed more escape attempts (W_s = 11.56, z =  -5.47; P < 0.01). Non-isolated groups had higher (W_s = 23.41, z = 1.06; P < 0.01) number of scars and bruises. Furthermore, non-isolated fish had a higher specific growth rate (2.36 ± 0.12), feed conversion ratio (1.27 ± 0.01) and a better condition factor (1.01 ± 0.08). Conclusively, these findings are relevant to African catfish welfare as social isolation changes the behavioural attributes, feeding pattern and growth rate of C. gariepinus. However, social context should be monitored since it resulted in more scars and bruises, which might affect the acceptability and welfare of this aquatic fish species.

The Geometric World of Fishes: A Synthesis on Spatial Reorientation in Teleosts

Fishes navigate through underwater environments with remarkable spatial precision and memory. Freshwater and seawater species make use of several orientation strategies for adaptative behavior that is on par with terrestrial organisms, and research on cognitive mapping and landmark use in fish have shown that relational and associative spatial learning guide goal-directed navigation not only in terrestrial but also in aquatic habitats. In the past thirty years, researchers explored spatial cognition in fishes in relation to the use of environmental geometry, perhaps because of the scientific value to compare them with land-dwelling animals. Geometric navigation involves the encoding of macrostructural characteristics of space, which are based on the Euclidean concepts of "points", "surfaces", and "boundaries". The current review aims to inspect the extant literature on navigation by geometry in fishes, emphasizing both the recruitment of visual/extra-visual strategies and the nature of the behavioral task on orientation performance.

Estimating Discard Mortality in Commercial Fisheries without Fish Dying: A 3R Challenge

Simple Summary

Due to the implementation of a landing obligation in fisheries in the European Union (EU), with an exemption for species with “high survival”, discard survival studies (henceforth DSSs) have become one of the most politically prioritized fisheries research areas in European fisheries. In contrast to most fisheries science research areas, DSSs are embedded by the EUs animal research welfare directive. This is a challenge, and there has not been any focus on how to implement animal welfare (AW) regulations experimentally in DSSs. This paper focuses on AW regulations in relation to conducting DSSs, but the outreach is much broader. We investigate experimental procedures by bringing in relevant examples, using the output results, and relating this information to relevant AW guidelines and regulations by focusing on implementing 3R principles.

Abstract

Globally, it is estimated that around 10% of the fish that are caught are discarded. This is considered to be a wasteful human marine activity since these fish are often dead or dying. To reduce the high discard rates of commercial fisheries, the European Union (E.U.) has enacted a landing obligation that includes the ability to exempt “species for which scientific evidence demonstrates high survival rates”. Therefore, discard survival studies (henceforth DSSs) have become one of the most politically prioritized fisheries research areas in European fisheries. International expert groups have produced guidance reports to promote best practices and to harmonize the methodologies. Nevertheless, there has not been any focus on how to implement animal welfare (AW) regulations experimentally. Discard survival studies are “frontrunners” in fisheries science research areas that are embedded by animal research welfare requirements and are expected to be more restrictive in the future because of an increased public focus on fish welfare. This paper focuses on AW regulations in relation to conducting DSSs, but the outreach is much broader. We investigate experimental procedures by bringing in relevant examples, using output results, and relating this information to relevant AW guidelines and regulations by focusing on implementing 3R principles.

“I am Wolf, I Rule!” - Attributing Intentions to Animals in Human-Wildlife Interactions

Human interactions with potentially problematic wildlife spawn intense and polarized sentiments. This study investigates one contributing factor: People perceive wildlife as having intentions toward them, and consequently, they feel targeted by the animals' behavior. Thematic analysis of semi-structured interviews with 20 German-speaking participants on three model wildlife – wolves, corvids, and spiders – yielded 12 different kinds of intentions attributed to the animals. The form of these intentions can be analyzed in terms of whether the attribution has a metaphoric or literal meaning; whether it is potentially correct, and whether it occurs at an individual or species level. In terms of these criteria, attributions made to wolves, corvids, and spiders take different forms, that appear to correspond to differential degrees of direct experience with the respective animals. For example, attributions to wolves tend to be made at a species-level, and thus are of a rather abstract quality, corresponding to the rather elusive nature of wolf presence. Simultaneously, attributions to the three model wildlife exhibit thematic similarities: With regard to their content, the 12 kinds of intentions can be integrated into four motives referring to the animals' alleged deeper incentives: rebellion, menace, relationality, and unintentionality. These motives are ascribed to wolves, corvids and spiders in comparable ways, evidencing similarities in participants' mental representations of ecologically dissimilar cases of human-wildlife interactions. The discussion of the qualitative findings traces how the species-specific and the overarching dynamics, as well as people's biographies factor into their views of animal intentionality in a way that causes ascriptions to be polarized across people, yet similar across wildlife. Evidently, the inclination to feel personally targeted by animal agents' intentional behavior is a universal feature in human-wildlife conflicts, that is co-determined by wildlife ecology and human psychology.

Further evidence for the capacity of mirror self-recognition in cleaner fish and the significance of ecologically relevant marks

An animal that tries to remove a mark from its body that is only visible when looking into a mirror displays the capacity for mirror self-recognition (MSR), which has been interpreted as evidence for self-awareness. Conservative interpretations of existing data conclude that convincing evidence for MSR is currently restricted to great apes. Here, we address proposed shortcomings of a previous study on MSR in the cleaner wrasse Labroides dimidiatus, by varying preexposure to mirrors and by marking individuals with different colors. We found that (1) 14/14 new individuals scraped their throat when a brown mark had been provisioned, but only in the presence of a mirror; (2) blue and green color marks did not elicit scraping; (3) intentionally injecting the mark deeper beneath the skin reliably elicited spontaneous scraping in the absence of a mirror; (4) mirror-naive individuals injected with a brown mark scraped their throat with lower probability and/or lower frequency compared to mirror-experienced individuals; (5) in contrast to the mirror images, seeing another fish with the same marking did not induce throat scraping; and (6) moving the mirror to another location did not elicit renewed aggression in mirror-experienced individuals. Taken together, these results increase our confidence that cleaner fish indeed pass the mark test, although only if it is presented in ecologically relevant contexts. Therefore, we reiterate the conclusion of the previous study that either self-awareness in animals or the validity of the mirror test needs to be revised.

When animal tries to remove a mark from its body that is only visible when looking into a mirror (the "mark test"), it displays the capacity for mirror self-recognition, often interpreted as evidence for self-awareness. This follow-up to a previous PLOS Biology study increases confidence that cleaner fish indeed pass the mark test, but only if it is presented in ecologically relevant contexts.

Research Before Policy: Identifying Gaps in Salmonid Welfare Research That Require Further Study to Inform Evidence-Based Aquaculture Guidelines in Canada

Aquaculture is a growing industry worldwide and Canadian finfish culture is dominated by marine salmonid farming. In part due to increasing public and stakeholder concerns around fish welfare protection, the first-ever Canadian Code of Practice for the Care and Handling of Farmed Salmonids was recently completed, following the National Farm Animal Care Council's (NFACC) rigorous Code development process. During this process, both the Scientific (responsible for reviewing existing literature and producing a peer-reviewed report that informs the Code) and Code Development (a diverse group of stakeholders including aquaculture producers, fish transporters, aquaculture veterinarians, animal welfare advocates, food retailers, government, and researchers) Committees identified research gaps in tandem, as they worked through the literature on salmonid physiology, health, husbandry, and welfare. When those lists are combined with the results of a public "top-of-mind" survey conducted by NFACC, they reveal several overlapping areas of scientific, stakeholder, and public concern where scientific evidence is currently lacking: (1) biodensity; (2) health monitoring and management, with a focus on sea lice infection prevention and management; (3) feed quality and management, particularly whether feed restriction or deprivation has consequences for welfare; (4) enclosure design, especially focused on environmental enrichment provision and lighting design; and (5) slaughter and euthanasia. For each of these five research areas, we provide a brief overview of current research on the topic and outline the specific research gaps present. The final section of this review identifies future research avenues that will help address these research gaps, including using existing paradigms developed by terrestrial animal welfare researchers, developing novel methods for assessing fish welfare, and the validation of new salmonid welfare indices. We conclude that there is no dearth of relevant research to be done in the realm of farmed salmonid welfare that can support crucial evidence-based fish welfare policy development.

Curiosity in zebrafish (Danio rerio)? Behavioral responses to 30 novel objects

Curiosity-the motivation to seek out information-has been studied widely across the animal kingdom. To investigate curiosity in zebrafish we presented 30 novel objects to groups of zebrafish housed in semi-naturalistic tanks (6 tanks; 10 fish/tank; 10-min presentations). During the first 100 s and final 100 s of each object's 10-min presentation period, we recorded each group's: (i) latency to approach the object, (ii) attraction to the object, (iii) social dynamics: agonistic behavior and group cohesion and coordination, and (iv) diving behavior, a stress response in zebrafish. Comparing these behaviors to a 100 s baseline period when no object was present, we tested for neophobia (avoidance of novelty), neophilia (overall attraction to novelty), sustained interest (prolonged attraction to at least some presentations), discriminant interest (certain objects eliciting more attention than others), habituation (loss of interest over time), and alterations to social and stress behaviors. Zebrafish groups readily approached all objects (1 s median latency), were neophilic throughout all object presentations, and showed systematic sustained interest only for some object presentations at the beginning of the study (object presentations 1-10). Over the course of the study, zebrafish also showed signs of habituation such that by the final ten object presentations (21-30), there were no signs of overall sustained interest. During the beginning of the study (object presentations 1-10), we also found evidence for specific object-driven interest, with object ID accounting for 11% of the variability in interest scores (p < 0.01), and object-driven interest corresponding to alterations in social behavior: decreased aggression (p < 0.02), increased group cohesion (p < 0.02), and increased group coordination (p < 0.05). By explicitly investigating curiosity in fish, this work reveals that under certain conditions, zebrafish voluntarily engage in cognitive stimulation opportunities. More work is needed to clarify what types of information zebrafish find most rewarding and how long-term exposure to such opportunities may affect fish welfare.

Aggressive interactions and consistency of dominance hierarchies of the native and nonnative cichlid fishes of the Balsas basin

Dominance hierarchies are generally established based on the levels of aggressiveness that animals present. Frequently, animals fight to establish a dominance hierarchy and obtain a disputed resource. The Mexican mojarra Cichlasoma istlanum is a native species of the Balsas river basin and coexists there with four nonnative cichlids: tilapia Oreochromis sp., convict cichlid Amatitlania nigrofasciata, spotcheek cichlid Thorichthys maculipinnis, and green terror Andinoacara rivulatus. These five cichlid species compete for spaces for reproduction, feeding, and shelter and frequently engage in aggressive interactions to obtain these resources. We quantified dominance indices to evaluate the hierarchical structure of dominance among these five cichlids and the duration of aggressive behaviors of the Mexican mojarra during experimental contests between the native species and each of the four nonnative species. The Mexican mojarra was consistently dominant over the other four cichlid species, performing a larger number of aggressive behaviors and investing more time in attacking than the nonnative cichlids, which resulted in a higher hierarchical position. Our results show that the native fish, Mexican mojarra, established dominance over all four nonnative cichlid fish of the Balsas basin. Thus, the establishment of nonnative cichlid species in the Balsas basin is likely associated with factors other than behavioral dominance.

MS-222 and Propofol Sedation during and after the Simulated Transport of Nile tilapia (Oreochromis niloticus)

The use of anesthetics has been suggested as a strategy to hamper live fish transport-induced stress. Still, there is insufficient data available on the use of alternative anesthetics to MS-222. This study investigated the use of propofol to mitigate stress in Nile tilapia (Oreochromis niloticus, 143.8 ± 20.9 g and 20.4 ± 0.9 cm) during a 6 h simulated transport. Individuals (n = 7) were divided into three groups: control, 40 mg L-1 MS-222, and 0.8 mg L-1 propofol. A naïve group non-transported was also considered. During the 6 h transport and 24 h after, the response to external stimuli, opercular movements, water quality parameters, behavior, blood hematology and other physiological values, the histopathology of the gills, the quality of the fillet, and oxidative-stress changes in gills, muscle, brain, and liver were evaluated. Propofol increased swimming activity of fish but decreased opercular movements and responses to external stimuli, indicating oscillations of the sedation depth. Water pH and glucose levels increased, while hematocrit (HCT) and lactate decreased in propofol groups at 6 h. At this time-point, MS-222 also induced a decrease in the HCT and lactate levels while increasing cortisol levels. Despite these effects, the stress-related behaviors lessened with anesthetics compared to the control group. After the recovery period, physiological responses normalized in animals from both anesthetic groups, but the control still had high cortisol levels. Overall, propofol is a good alternative for the transportation of this species, showing efficient sedation without compromising health or fillet quality. However, further pharmacodynamics and pharmacokinetics knowledge is required to support its use in aquaculture settings.

Tracking and Analysis of the Movement Behavior of European Seabass (Dicentrarchus labrax) in Aquaculture Systems

Monitoring and understanding fish behavior is crucial for achieving precision in everyday husbandry practices (i.e. for optimizing farm performance), and for improving fish welfare in aquaculture. Various intelligent monitoring and control methods, using mathematical models, acoustic methods and computer vision, have been recently developed for this reason. Here, a tracking algorithm based on computer vision that extracts short trajectories of individual European seabass in both recirculating aquaculture systems and sea cages was developed using videos from network cameras. Using this methodology, parameters such as instantaneous normalized speed, travel direction and preference for the tank surface by European seabass could be quantified. When testing the sensitivity of this algorithm for detecting fish swimming variations under different husbandry scenarios, we found that the algorithm could detect variations in all of the abovementioned parameters and could potentially be a useful tool for monitoring the behavioral state of European seabass.

A bolder One Health: expanding the moral circle to optimize health for all

One Health is a ground-breaking philosophy for improving health. It imaginatively challenges centuries-old assumptions about wellbeing and is now widely regarded as the 'best solution' for mitigating human health problems, including pandemic zoonotic diseases. One Health's success is imperative because without big changes to the status quo, great suffering and ill-health will follow. However, even in its more ambitious guises, One Health is not radical enough. For example, it has not embraced the emerging philosophical view that historical anthropocentrism is an unfounded ethical prejudice against other animals. This paper argues that One Health should be more imaginative and adventurous in its core philosophy and ultimately in its recommendations and activities. It must expand the circle of moral concern beyond a narrow focus on human interests to include nonhuman beings and the environment. On this bolder agenda, progressive ethical and practical thinking converge for the benefit of the planet and its diverse inhabitants-human and nonhuman.

Neuroecology beyond the brain: learning in Echinodermata

We propose an expansion of neuroecological comparisons to include the capabilities of brainless and non-neural organisms. We begin this enterprise by conducting a systematic search for studies on learning in echinoderms. Echinodermata are marine invertebrates comprising starfish, brittle stars, sea cucumbers, sea urchins, and sea lilies. Animals in this phylum lack any centralized brain and instead possess diffuse neural networks known as nerve nets. The learning abilities of these animals are of particular interest as, within the bilaterian clade, they are close evolutionary neighbors to chordates, a phylum whose members exhibit complex feats in learning and contain highly specialized brains. The learning capacities and limitations of echinoderms can inform the evolution of nervous systems and learning in Bilateria. We find evidence of both non-associative and associative learning (in the form of classical conditioning) in echinoderms, which was primarily focused on starfish. Additional evidence of learning is documented in brittle stars, sand dollars, and sea urchins. We then discuss the evolutionary significance of learning capabilities without a brain, the presence of embodied cognition across multiple groups, and compare the learning present in echinoderms with the impressive cognitive abilities documented in the oldest linage group within vertebrates (the major group within the phylum of chordates), fish.

The Neural Correlates of Access Consciousness and Phenomenal Consciousness Seem to Coincide and Would Correspond to a Memory Center, an Activation Center and Eight Parallel Convergence Centers

An increasing number of authors suggest that the neural correlates of consciousness (NCC) have no selective, executive, or metacognitive function. It is believed that attention unconsciously selects the contents that will become conscious. Consciousness would have only the fundamental function of transforming the selected contents into a format easily used by high-level processors, such as working memory, language, or autobiographical memory. According to Dehaene, the neural correlates (NC) of access consciousness (AC; cognitive consciousness) constitute a widespread network in the frontal, parietal, and temporal cortices. While Tononi localized the correlates of phenomenal consciousness (PC; subjective consciousness) to a posterior “hot zone” in the temporo-parietal cortex. A careful examination of the works of these two groups leads to the conclusion that the correlates of access and PC coincide. The two consciousnesses are therefore two faces of the same single consciousness with both its cognitive and subjective contents. A review of the literature of the pathology called “neglect” confirms that the common correlates include 10: a memory center, an activation center, and eight parallel centers. From study of the “imagery” it can be deduced that these eight parallel centers would operate as points of convergence in the third person linking the respective eight sensory-motor-emotional areas activated by external perceptions and the corresponding memories of these perceptions deposited in the memory center. The first four centers of convergence appear in the most evolved fish and gradually reach eight in humans.

Welfare in Nile Tilapia Production: Dorsal Fin Erection as a Visual Indicator for Insensibility

Simple Summary

Aquaculture has been the fastest-growing production segment in recent years, and as such, it is necessary to have clear guidelines on how fish are reared, stunned and slaughtered, always taking into account their welfare. By aiming for the stunning stage to be efficient, quick and practical before the fish are finally slaughtered in the fish farming process, we propose to verify and validate dorsal fin erection as a painless visual indicator of sensibility in Nile tilapia, ensuring that animals do not suffer during the stunning and slaughtering processes. Our results have validated the method as an effective indicator to assess the state of fish sensibility, and is simple to be carried out in large-scale production systems. The presence/absence of an erect dorsal fin alone does not totally ensure fish insensibility, and must be used together with other well-established visual sensibility indicators, for a better assessment of the state of fish sensibility, such as fish equilibrium, vestibulo-ocular reflex and opercular beats.

Abstract

In aquaculture, to ensure animal welfare in pre-slaughter and slaughter stages, it is fundamental that fish are insensible. A method for evaluating fish insensibility is based on visual sensibility indicators (VSI) assessment (i.e., self-initiated behavior, responses to stimuli and reflexes). However, many stimuli used to assess fish responses are painful. Therefore, this study verifies whether the presence/absence of a dorsal fin erection (DFE) response can be used as a painless VSI in Nile tilapia (Oreochromis niloticus). Three stunning protocols were applied to fish: benzocaine anesthesia (40 mg/L and 80 mg/L), ice water immersion (0–1, 2–3 and 5–6 °C) and CO₂ stunning. After these stunning methods were applied in fish, the time of loss and return of DFE was observed, along with the vestibulo-ocular reflex (VOR). All fish stunned using benzocaine and ice water immersion lose both VSIs, while 95% of fish stunned using CO₂ lose these VSIs. In all treatments, DFEs return quicker than VOR. Therefore, DFE can be used as a VSI in Nile tilapia, which is simple for producers to assess and does not require a painful stimulus. However, the DFE alone does not totally ensure fish insensibility and must be used together with other well-established VSIs at fish farms.

On and beyond artifacts in moral relations: accounting for power and violence in Coeckelbergh’s social relationism

The ubiquity of technology in our lives and its culmination in artificial intelligence raises questions about its role in our moral considerations. In this paper, we address a moral concern in relation to technological systems given their deep integration in our lives. Coeckelbergh develops a social-relational account, suggesting that it can point us toward a dynamic, historicised evaluation of moral concern. While agreeing with Coeckelbergh’s move away from grounding moral concern in the ontological properties of entities, we suggest that it problematically upholds moral relativism. We suggest that the role of power, as described by Arendt and Foucault, is significant in social relations and as curating moral possibilities. This produces a clearer picture of the relations at hand and opens up the possibility that relations may be deemed violent. Violence as such gives us some way of evaluating the morality of a social relation, moving away from Coeckelbergh’s seeming relativism while retaining his emphasis on social–historical moral precedent.