Fish sentience denial: Muddying the waters

Listen to Us: Perceptions of Animal Voice and Agency

In many contexts, the interests of nonhuman animals (hereafter "animals") are often overlooked or considered to be a lower priority than those of humans. While strong arguments exist for taking animal moral claims seriously, these largely go unheard due to dominant anthropocentric attitudes and beliefs. This study aimed to explore how animal interests might be best represented in the human world. We conducted interviews to investigate people's perceptions of what it means to speak for other animals and who can reliably represent animal interests. Using Grounded Theory analytical methods, we identified one major theme: "Animal voice", and its subthemes: "Animals do/do not have a voice", "Human language constructs realities and paradigms", and "Let animals speak". Our findings illustrate how human language constructs contribute to shaping the realities of animals by contextually defining them as voiceless. This has serious implications for animals, society, and the environment. Drawing parallels with the relevant literature, our results reflect calls for the social and political recognition of animal voice as fundamental to animal representation. We recommend future research to focus on developing ethical and compassionate approaches to understanding animal subjective experiences to empower and amplify animal voices.

From egg to slaughter: monitoring the welfare of Nile tilapia, Oreochromis niloticus, throughout their entire life cycle in aquaculture

The primary aim of this study was to comprehensively evaluate the welfare of Nile tilapia (Oreochromis niloticus) throughout their entire life cycle within aquaculture, spanning from reproduction to slaughter. The methodology was structured to identify welfare indicators closely aligned with the principles of animal freedoms defined by the Farm Animal Council, encompassing environmental, health, nutritional, behavioral, and psychological freedom. Notably, psychological freedom was inherently considered within the behavioral and physical analyses of the animals. To accomplish this, an integrative systematic literature review was conducted to define precise indicators and their corresponding reference values for each stage of tilapia cultivation. These reference values were subsequently categorized using a scoring system that assessed the deviation of each indicator from established ideal (score 1), tolerable (score 2), and critical (score 3) ranges for the welfare of the target species. Subsequently, a laboratory experiment was executed to validate the pre-selected health indicators, specifically tailored for the early life stages of tilapia. This test facilitated an assessment of the applicability of these indicators under operational conditions. Building on the insights gained from this experimentation, partial welfare indices (PWIs) were computed for each assessed freedom, culminating in the derivation of a general welfare index (GWI). Mathematical equations were employed to calculate these indices, offering a quantitative and standardized measure of welfare. This approach equips tilapia farmers and processors with the tools necessary for the continuous monitoring and enhancement of their production systems and stimulate the adoption of more sustainable and ethical practices within the tilapia farming.

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.

When should we ascribe sentience to animals? A commentary on "Hermit crabs, shells and sentience" (Elwood 2022)

In a new review article, experiments on hermit crab behaviour are discussed in the context of possible animal sentience. Sentience can be defined as the ability to experience feelings such as pleasure or pain but there are also broader definitions that include elements of awareness. Here I suggest that of the different levels of awareness described as components of sentience, only the higher levels (assessment and executive awareness) seem distinct from the basic non-sentient cognitive tasks of gathering, processing and storing information, which are demonstrated by most animals. Studies that attempt to differentiate between basic cognitive functions and higher levels of awareness are rare for most animal taxa, including hermit crabs. Therefore, while results such as those obtained from studies of hermit crab behaviour are compatible with sentience they cannot yet be distinguished from simpler explanations based on basic cognitive functions, which we should prefer for the time-being. Nevertheless, hermit crabs are promising model systems for investigating awareness in animals.

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.

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.

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.

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.

Timing of isolation from an enriched environment determines the level of aggressive behavior and sexual maturity in Siamese fighting fish (Betta splendens)

Background

Teleost fish are known to respond to environmental manipulation, which makes them an ideal model animal for testing relationships between the environment and behavior. The Siamese fighting fish, Betta splendens, is a solitary, highly territorial fish that displays fierce stereotyped aggressive behavior toward conspecifics or members of other species. Adult fish, especially males, are generally housed in isolation in captivity. Here we report evidence that an enriched rearing environment can decrease the level of aggression in bettas and enable adults to be housed in groups.

Results

B. splendens individuals were hatched in our laboratory and raised in groups in an enriched environment. At the juvenile or subadult stage, some individuals were relocated to a poor environment and kept in isolation. To evaluate aggression, a mirror-image test was conducted at the juvenile, subadult, and adult stages for each fish, and body parameters as well as plasma concentrations of 11-ketotestosterone, estradiol, and cortisol were evaluated. Male and female adult bettas raised in a group showed lower levels of aggression than other adult fish. The magnitude of threatening behavior was greater in adult bettas isolated as subadults, whereas the magnitude of fighting behavior was grater in adult bettas isolated as juveniles. The influence of rearing conditions on behavior was greater in females than in males. Plasma cortisol concentrations of adult bettas isolated as subadults after the mirror-image test were higher than those in other experimental groups. Adult males isolated as subadults had significantly higher plasma concentrations of 11-ketotestosterone than males raised in a group and isolated as juveniles. Females isolated as subadults had a higher gonadosomatic index than females raised in a group and females isolated as juveniles.

Conclusions

These results indicate that bettas can be kept in a group under enriched environments and that the timing of isolation influences the aggression and sexual maturity of bettas. Female and male bettas responded differently to environmental manipulation. Judging from their level of sexual maturity, bettas isolated as subadults show proper development.

Potential Pain in Fish and Decapods: Similar Experimental Approaches and Similar Results

I review studies that examined the possibility of pain experience in fish and note how they provided guidance on general methods that could be applied to other animals such as decapod crustaceans. The fish studies initially reported the occurrence of prolonged rocking movements in trout and rubbing of their lips if they were injected with acetic acid. Subsequent studies examined the role of morphine in reducing these activities and examined shifts in attention when responding to noxious stimuli. Various studies take up these themes in decapods. The results reported for the two taxonomic groups are remarkably similar and indicate that responses of both go beyond those expected of mere nociceptive reflex. Thus, the idea of pain cannot be dismissed by the argument that fish and decapods respond only by reflex. The responses of both clearly involve central processing, and pain experience, although not proven for either, is a distinct possibility. These studies have been the subjects of highly critical opinion pieces and these are examined and rebutted. The conclusion is that both fish and decapods should be awarded consideration for their welfare.

Sudden exposure to warm water causes instant behavioural responses indicative of nociception or pain in Atlantic salmon

Thermal treatment has become the most used delousing method in salmonid aquaculture. However, concerns have been raised about it being painful for the fish. We studied the behavioural response of Atlantic salmon acclimated to 8 °C when transferred to temperatures in the range 0-38 °C. Exposure time was 5 min or until they reached the endpoint of losing equilibrium and laying on their side, a sign of imminent death. At temperatures below 28 °C, none of the fish reached endpoint within the 5-min maximum. At 28 °C four of five fish reached endpoint, and fish reached endpoint more rapidly as temperature increased further. Fish transferred to temperatures above 28 °C had higher swimming speed immediately after transfer and maintained a high swimming speed until just before loss of equilibrium. Their behaviour was from the start characterised by collisions into tank walls and head shaking. Just before loss of equilibrium they started breaking the surface of the water, swimming in a circle pattern and in some instances displayed a side-wise bending of their body. In other words, salmon transferred to temperatures above 28 °C showed instant behavioural responses indicative of nociception or pain.

Discrimination between nociceptive reflexes and more complex responses consistent with pain in crustaceans

Animals have quick-acting nociceptive reflexes that protect them from tissue damage. Some taxa have also evolved the capacity for pain. Pain appears to be linked to long-term changes in motivation brought about by the aversive nature of the experience. Pain presumably enhances long-term protection through behaviour modification based, in part, on memory. However, crustaceans have long been viewed as responding purely by reflex and thus not experiencing pain. This paper considers behavioural and physiological criteria that distinguish nociception from potential pain in this taxon. These include trade-offs with other motivational systems and prolonged motivational change. Complex, prolonged grooming or rubbing demonstrate the perception of the specific site of stimulus application. Recent evidence of fitness-enhancing, anxiety-like states is also consistent with the idea of pain. Physiological changes in response to noxious stimuli mediate some of the behavioural change. Rapid avoidance learning and prolonged memory indicate central processing rather than mere reflexes. Thus, available data go beyond the idea of just nociception. However, the impossibility of total proof of pain described in ways appropriate for our own species means that pain in crustaceans is still disputed. Pain in animals should be defined in ways that do not depend on human pain experience. This article is part of the Theo Murphy meeting issue 'Evolution of mechanisms and behaviour important for pain'.

Recordings in an integrating central neuron provide a quick way for identifying appropriate anaesthetic use in fish

In animal husbandry, livestock industry and research facilities, anaesthetic agents are frequently used to moderate stressful intervention. For mammals and birds, procedures have been established to fine-tune anaesthesia according to the intervention. In ectothermic vertebrates, however, and despite changes in legislation and growing evidence on their cognitive abilities, the presently available information is insufficient to make similarly informed decisions. Here we suggest a straightforward way for rapidly filling this gap. By recording from a command neuron in the brain of fish whose crucial role requires it to integrate and process information from all sensory systems and to relay it to motor output pathways, the specific effects of candidate anaesthesia on central processing of sensory information can directly and efficiently be probed. Our approach allows a rapid and reliable way of deciding if and at which concentration a given anaesthetic affects the central nervous system and sensory processing. We employ our method to four anaesthetics commonly used in fish and demonstrate that our method quickly and with small numbers of animals provides the critical data for informed decisions on anaesthetic use.