![Brain morphology, habitat complexity and spatial learning abilities are related in intertidal gobies [42-45]. (a) Schematic representation of the brains of Krefft’s frillgoby Bathygobius krefftii which dwells in rockpools (top) and Hoese’s sandgoby Istigobius hoese which lives on sandy intertidal areas (bottom), showing the location of the telencephalon and optic tectum (modified from [45]). (b) Simplified diagram of the T-maze used in spatial learning tasks. (c) Comparison of relative brain lobe volumes (mean ± SE) between two goby species from different habitats. (d) Mean (± SE) proportion of fish that reached learning criterion in a T-maze task for rock pool and sand-dwelling species. (e) Proportion (± SE) of rock pool and sand-dwelling fish using plant landmarks and turn direction for orientation during probe trials.](https://www.researchgate.net/publication/315875059/figure/fig2/AS:482470526230528@1492041345749/Brain-morphology-habitat-complexity-and-spatial-learning-abilities-are-related-in_Q320.jpg)
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Contemporary topics in fish cognition and behaviour
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... and B > C, then A > C), something humans develop around the age of seven (Marino, 2017). Fish respond to pain emotionally in a manner similar to other vertebrates and symptoms can be alleviated with analgesics (Vila Pouca & Brown, 2017). Fish are used as standard models to understand the evolution of spatial learning, memory, and social cognition (Vila Pouca & Brown, 2017). ...
... Fish respond to pain emotionally in a manner similar to other vertebrates and symptoms can be alleviated with analgesics (Vila Pouca & Brown, 2017). Fish are used as standard models to understand the evolution of spatial learning, memory, and social cognition (Vila Pouca & Brown, 2017). Pigs, cows, chicken, and fish all show individual variation in personality traits (Marino, 2017;Marino & Allen, 2017;Marino & Colvin, 2016;Vila Pouca & Brown, 2017). ...
... Fish are used as standard models to understand the evolution of spatial learning, memory, and social cognition (Vila Pouca & Brown, 2017). Pigs, cows, chicken, and fish all show individual variation in personality traits (Marino, 2017;Marino & Allen, 2017;Marino & Colvin, 2016;Vila Pouca & Brown, 2017). ...
The global rise of animal-based consumption in the human diet is increasingly regarded as unsustainable, compromising the welfare of humans, animals and the environment. Nevertheless, calls for change from vegetarian and vegan (i.e., veg*n) minorities are often resisted by members of the omnivorous majority. In this dissertation, I examined the role of omnivores’ perceptions toward veg*ns within the context of promoting (more) plant-based diets through three experimental studies and one theoretical study. Each study is informed by sociopsychological theorizing relevant to social identity and the following topics are covered: (1) the role of social identity and perceived inconsistency in omnivores’ perception of a fellow meat-eater versus a vegetarian promoting a meat reduction message, (2) the role of moral minority stereotypes (moral, moralistic, eccentric, unsociable) in predicting the social attractiveness of veg*ns, (3) vegan advocacy and the relationship between the meat paradox (i.e., people care about animals, but also eat them) and the vegan paradox (i.e., vegans’ reputation as being morally committed, but also as arrogantly overcommitted) in promoting veganism, and (4) how perceptions of vegans depend on their dietary motivation (animal ethics vs. health) and their advocacy status (advocacy present or not). In the general introduction, the studies are embedded within relevant literature and the societal relevance of the dissertation is highlighted. The concluding chapter discusses main findings, limitations, future research and theoretical and practical implications.
... European consumers expect that the production of fish in aquaculture in Europe respects sustainability, complies with consumer protection standards and that animal welfare is safeguarded during production and the time of slaughtering [2,4,5]. In addition, cognitive and mental capacities of fish were subject of various scientific studies and review articles published recently [6][7][8][9][10][11][12]. However, vertebrate organisms, commonly called "fish" account for more than 60% of the known vertebrate species and are adapted to various aquatic habitats. ...
... These studies, however showed that several teleost fish species respond to stressful situations and painful stimuli by behavioural and physiological reactions [7,9,13,14]. Furthermore, in several finfish species observational and social learning was documented (cited from [6]), as well as longterm memories and the development of complex traditions [7,10]. These cognitive and learning capacities of fish are used as indicators for consciousness and pain perception [6,7,10,13,15] and are regarded as important for the ethical treatment of fish [7,16]. ...
... Furthermore, in several finfish species observational and social learning was documented (cited from [6]), as well as longterm memories and the development of complex traditions [7,10]. These cognitive and learning capacities of fish are used as indicators for consciousness and pain perception [6,7,10,13,15] and are regarded as important for the ethical treatment of fish [7,16]. ...
Background:
Rainbow trout, Oncorhynchus mykiss, is an important fish in European freshwater aquaculture. This industry sector is dominated by small family-owned enterprises located in rural areas. A large percentage of rainbow trout produced by these small enterprises is marketed directly and killed on demand and not processed in commercial processing plants. EU and national regulations stipulate that fish shall be stunned prior to killing and slaughter. The overall objective of this study was to monitor how stunning interventions were integrated into the production chains of German conventional trout aquaculture in order to safeguard animal welfare during stunning and killing. For this, the stunning and slaughtering processes were monitored on 18 rainbow trout farms in various German federal states. During the on-farm research, (i) the stunning success, (ii) injuries related to the stunning procedure, (iii) duration between stunning and killing, and (iv) visible responses at the time of slaughtering were assessed as welfare indicators. In addition, haematological and biochemical blood parameters were measured as indicators for physiological stress. Due to the fact that stunning interventions should induce a loss of consciousness in fish, in a laboratory study, it was examined whether the absence of the brainstem/ behavioural responses, opercular movements (OM) or eye-rolling reflex (vestibulo-ocular reflex, VOR) was correlated with the stage of insensibility.
Results:
The majority of rainbow trout farms applied manual percussion (38%) or electrical stunning (48%), while on 14% of the farms, the fish were stunned by electrical stunning which was immediately followed by manual percussion. After percussive stunning, about 92.3% of the rainbow trout displayed no OM or VOR as brainstem/ behavioural indicators of consciousness. This percentage varied on farms which applied electrical stunning. While on the majority of farms, 95 to 100% of the fish were unconscious according to the observation of brainstem/ behavioural indicators, the stunning intervention was less effective on farms where rainbow trout were stunned at current densities below 0.1 A dm2 or for a few seconds only. The laboratory study confirmed that the absence of brainstem/ behavioural indicators correlated with the absence of visually evoked responses (VER) of the brain to light stimuli as a neuronal indicator of insensibility. Therefore, the brainstem/ behavioural signs can be used to interpret the stage of insensibility in rainbow trout. A stage of insensibility could safely be induced by exposing portion-sized rainbow trout to an electric current density above 0.1 A dm2. This was not influenced by the orientation of the electric field.
Conclusions:
In conventional aquaculture, rainbow trout can effectively be stunned by manual percussion or electrical stunning. Consciousness can be monitored by the absence of opercular movements or the eye-rolling reflex, which are lost approximately at the same time as neurological responses like VER. For safeguarding animal welfare during stunning and killing of rainbow trout in conventional production processes, the stunning process requires careful attention and the operating personnel need to be trained in using the stunning devices and recognising indicators of consciousness.
... However, the higher cognitive demand involved in inspecting unfamiliar schooling partners likely delays initiation of the M-cell, causing a longer latency but an equally high motor output response. Thus, familiarity may be a key proximate mechanism underlying social behaviour in gregarious species 57 . ...
... Introduction of unfamiliar newcomers to social groups may burden cognitive processes associated with attention and drive uncertainty in the accuracy of socially acquired information, which can hinder or delay the decision-making of individuals 9,82,84 . Social fishes, like C. viridis, provide valuable comparative insights into vertebrate social behaviour, given the many analogous processes guiding social cognition, brain organisation and function, and group decisionmaking among fish, birds, and mammals 57,82 . Hence, this study highlights the importance of familiarity and its role in collective cognition within the context of anti-predator behaviour for both individuals and groups. ...
Using social groups (i.e. schools) of the tropical damselfish Chromis viridis, we test how familiarity through repeated social interactions influences fast-start responses, the primary defensive behaviour in a range of taxa, including fish, sharks, and larval amphibians. We focus on reactivity through response latency and kinematic performance (i.e. agility and propulsion) following a simulated predator attack, while distinguishing between first and subsequent responders (direct response to stimulation versus response triggered by integrated direct and social stimulation, respectively). In familiar schools, first and subsequent responders exhibit shorter latency than unfamiliar individuals, demonstrating that familiarity increases reactivity to direct and, potentially, social stimulation. Further, familiarity modulates kinematic performance in subsequent responders, demonstrated by increased agility and propulsion. These findings demonstrate that the benefits of social recognition and memory may enhance individual fitness through greater survival of predator attacks.
... It has been traditionally believed that species with larger brain size display greater cognitive abilities (reviewed in Jerison 2012), although current knowledge does not support the generality of this relationship (Healy & Rowe, 2013;Herculano-Houzel 2017;Perry et al., 2017). For instance, the literature on fish includes a long list of unexpected skills in small species, in spite of their small brain size among vertebrates (reviewed in Bshary and Brown 2014;Pouca and Brown 2017). A large comparative study with the cylinder task (and a second task not yet adopted in fish, the A-not-B task) investigated the relationship between brain size and IC in mammals and birds, finding a positive correlation between a species' inhibitory performance and its absolute brain size (MacLean et al. 2014). ...
Inhibitory control (IC) plays a central role in behaviour control allowing an individual to resist external lures and internal predispositions. While IC has been consistently investigated in humans, other mammals, and birds, research has only recently begun to explore IC in other vertebrates. This review examines current literature on teleost fish, focusing on both methodological and conceptual aspects. I describe the main paradigms adopted to study IC in fish, identifying well-established tasks that fit various research applications and highlighting their advantages and limitations. In the conceptual analysis, I identify two well-developed lines of research with fish examining IC. The first line focuses on a comparative approach aimed to describe IC at the level of species and to understand the evolution of interspecific differences in relation to ecological specialisation, brain size, and factors affecting cognitive performance. Findings suggest several similarities between fish and previously studied vertebrates. The second line of research focuses on intraspecific variability of IC. Available results indicate substantial variation in fish IC related to sex, personality, genetic, age, and phenotypic plasticity, aligning with what is observed with other vertebrates. Overall, this review suggests that although data on teleosts are still scarce compared to mammals, the contribution of this group to IC research is already substantial and can further increase in various disciplines including comparative psychology, cognitive ecology, and neurosciences, and even in applied fields such as psychiatry research.
... A better-informed understanding of the cognitive abilities of other species-and how, in several aspects, they can be comparable to our own (e.g., Zentall, 2023)-can affect positively the way we treat other species. Fish are a good example of a taxon that, despite intensive exploration by humans, has been historically underestimated in their cognitive abilities and pain perception (e.g., Brown, 2015;Vila Pouca & Brown, 2017). The wider the dissemination of our findings, the more likely that improvements in animal welfare are to come about. ...
... Much of the now classic work in animal cognition has focused on birds and mammals, with other taxa being relatively underrepresented [5,8,20,28]. This is now rapidly changing as the literature on the cognitive abilities of nonavian and nonmammalian systems is steadily growing, especially for aquatic organisms (for recent reviews, see [29][30][31][32][33][34]). What this brings with it, however, is an increased need to resolve the above issue of making cognitive research 'comparable'. ...
Cognitive abilities vary within and among species, and several hypotheses have been proposed to explain this variation. Two of the most prominent hypotheses regarding the evolution of cognition link increased social and habitat complexity with advanced cognitive abilities. Several studies have tested predictions derived from these two hypotheses, but these were rarely conducted under natural conditions with wild animals. However, this is of particular importance if we aim to link cognitive abilities with fitness-relevant factors to better understand the evolution of cognition. The biggest hurdle to assessing cognition in the wild is to find a suitable setup that is easy to use under field conditions. Here, we set out to evaluate an extremely simple test of cognitive ability for use with a broad range of aquatic animals in their natural habitat. We did so by developing a detour test paradigm in which fish had to detour a clear obstacle to reach a food reward. By altering the difficulty of the task, we confirmed that this setup is a valid test of cognitive abilities in wild groups of a Lake Tanganyika cichlid, Neolamprologus pulcher. Subsequently, we probed specific predictions from the two major hypotheses regarding cognitive evolution using the most difficult test configuration. Specifically, we tested the variation in cognitive abilities among groups of different sizes occupying habitats of varying complexity. We find mixed support for both hypotheses, but we hope that our work inspires future investigations on the evolution of cognition in Lake Tanganyika cichlids.
... How fishes acquire, process, store and act on environmental cues has received an increasing amount of research during the recent decades [1][2][3][4][5][6]. As fishes represent the ancestral state of all vertebrates, investigating how and why cognitive abilities differ across fish species may offer insights into the evolutionary history of cognitive abilities in all vertebrates. ...
Over recent decades, substantial research has focused on fish cognitive evolution to increase our understanding of the evolution of the enormous diversity of cognitive abilities that exists in fishes. One important but understudied aspect of cognitive evolution is sexual dimorphism in cognitive abilities. Sex-specific variation in brain region morphology has been proposed to be an important mechanism in this context. However, it is also common to find sex-specific variation in behavior and cognition without associated differences in brain morphology among the sexes. The telencephalon is the major cognitive center in the vertebrate brain and variation in telencephalon size has been associated with variation in cognition. Here, we utilize recently developed guppy artificial selection lines with ca. 10% differences in relative telencephalon size to investigate whether similar responses to selection of the size of this region may affect cognitive abilities differently in males and females. To that end, we compared two ecologically relevant aspects of cognition, detour learning and binary spatial discrimination. We tested the significance of the interaction between telencephalon size and sex, and we found no sex-specific effects of evolutionary increases in telencephalon size in the cognitive abilities tested. This study indicates that no clear cognitive sex-specific effects occur in response to rapid selection of telencephalon size. We suggest that future research on sexual dimorphism in cognitive abilities in fish could use various cognitive tests and examine telencephalic sub-regions to gain a more comprehensive understanding of their evolution.
... The fish species is proven to have cognitive ability where the fish is able to learn and form memory (Brown, 2020;Salena et al., 2021). Several studies even reported numerical cognition in fish Vila Pouca and Brown, 2017). However, only few social stress studies using fish models have included cognitive functions as a parameter. ...
Stress is an important aspect of our everyday life and exposure to it is an unavoidable occurrence. In humans, this can come in the form of social stress or physical stress from an injury. Studies in animal models have helped researchers to understand the body’s adaptive response to stress in human. Notably, the use of behavioural tests in animal models plays a pivotal role in understanding the neural, endocrine and behavioural changes induced by social stress. Under socially stressed conditions, behavioural parameters are often measured physiological and molecular parameters as changes in behaviour are direct responses to stress and are easily assessed by behavioural tests. Throughout the past few decades, the rodent model has been used as a well-established animal model for stress and behavioural changes. Recently, more attention has been drawn towards using fish as an animal model. Common fish models such as zebrafish, medaka, and African cichlids have the advantage of a higher rate of reproduction, easier handling techniques, sociability and most importantly, share evolutionary conserved genetic make-up, neural circuitry, neuropeptide molecular structure and function with mammalian species. In fact, some fish species exhibit a clear diurnal or seasonal rhythmicity in their stress response, similar to humans, as opposed to rodents. Various social stress models have been established in fish including but not limited to chronic social defeat stress, social stress avoidance, and social stress-related decision-making. The huge variety of behavioural patterns in teleost also aids in the study of more behavioural phenotypes than the mammalian species. In this review, we focus on the use of fish models as alternative models to study the effects of stress on different types of behaviours. Finally, fish behavioural tests against the typical mammalian model-based behavioural test are compared and discussed for their viability.
... For many, an aquarium may be a home for fish or a work of art, but for a researcher, an aquarium can serve as a self-contained laboratory. Increasingly, behavioural experiments are using aquarium fish as models to answer diverse questions over a range of fields including neuroscience (Steward et al., 2014;Orger and de Oilavieja, 2017;Roberts et al., 2022), medicine (Shenoy et al., 2022), sensory ecology (Marshall et al., 2018;Newport and Schuster, 2020), cognition (Pouca and Brown, 2017), biomechanics (Liao, 2007), and bio-inspired robotics (Hu et al., 2006). In many cases, the behavioural metrics of interest relate to spatiotemporal patterns of movement measured under different experimental conditions. ...
Developments in automated animal tracking software are increasing the efficiency of data collection and improving the standardization of behavioural measurements. There are now several open-source tools for tracking laboratory animals, but often these are only accurate under limited conditions (e.g. uniform lighting and background, uncluttered scenes, unobstructed focal animal). Tracking fish presents a particular challenge for these tools because movement at the water's surface introduces significant noise. Partial occlusion of the focal animal can also be troublesome, particularly when tracking the whole organism. We conducted a behavioural experiment that required us to track the trajectory of a fish as it swam through a field of obstacles. In addition to measuring the body's trajectory, we also needed to record the position of the obstacles, and to identify when the fish passed through the "virtual gates" between adjacent obstacles and/or the aquarium wall. We automated data collection by employing a range of computer vision and computational geometry algorithms (e.g. object detection and tracking, optical flow, parallel plane homology mapping, Voronoi tessellation). Our workflow is divided into several discrete steps, and provides a set of modular software building blocks that can be adapted to analyse other experimental designs. A detailed tutorial is provided, together with all the data and code required to reproduce our results.
... In spite of their huge ecological, neuroanatomical and behavioural diversity, historically fish have been underrepresented in the cognitive and psychological literatures for decades (Bitterman, 2006;Newport, 2021;Shettleworth, 2009), with primates, corvids, pigeons, rodents and more recently dogs being favoured models (though see Bitterman, 1975;Chase & Hill, 1999;Gerlai, 2014;Pouca & Brown, 2017;Salena et al., 2021). Increasing the availability of userfriendly, open-source, experimental platforms that allow for automated testing and data acquisition in fish may help to mitigate this bias (Brock et al., 2017;Gatto et al., 2021). ...
Fish are the most species-rich vertebrate group, displaying vast ecological, anatomical and behavioural diversity, and therefore are of major interest for the study of behaviour and its evolution. However, with respect to other vertebrates, fish are relatively underrepresented in psychological and cognitive research. A greater availability of easily accessible, flexible, open-source experimental platforms that facilitate the automation of task control and data acquisition may help to reduce this bias and improve the scalability and refinement of behavioural experiments in a range of different fish species. Here we present GoFish, a fully automated platform for behavioural experiments in aquatic species. GoFish includes real-time video tracking of subjects, presentation of stimuli in a computer screen, an automatic feeder device, and closed-loop control of task contingencies and data acquisition. The design and software components of the platform are freely available, while the hardware is open-source and relatively inexpensive. The control software, Bonsai, is designed to facilitate rapid development of task workflows and is supported by a growing community of users. As an illustration and test of its use, we present the results of two experiments on discrimination learning, reversal, and choice in goldfish (Carassius auratus). GoFish facilitates the automation of high-throughput protocols and the acquisition of rich behavioural data. Our platform has the potential to become a widely used tool that facilitates complex behavioural experiments in aquatic species.
... Fish will avoid areas where they have experienced pain demonstrating cognitive engagement including learning and memory, and an emotional response (e.g. fear) to the negative stimuli (Vila Pouca and Brown, 2017;Sneddon, 2020). The painful event may be so consuming that they cease to exhibit normal fear or antipredator responses (Sneddon, 2020). ...
Wild animal welfare may be compromised in many different ways during hunting, trapping, fishing and whaling activities. Some key hunting methods and their welfare implications for both target and non-target animals are discussed highlighting the issues that impact on animal welfare, including the equipment used in hunting, the skill of the hunter and the duration of the hunt. The impacts on fish welfare of catch and release recreational fishing, subsistence fishing, bycatch in artisanal fisheries and killing methods are also presented. The hunting of whales and other cetaceans is considered, focused on Japanese dolphin drive hunts and the commercial hunting of large whales and how these activities impact cetacean welfare.
Open Access: https://www.taylorfrancis.com/books/oa-edit/10.4324/9781003182351/routledge-handbook-animal-welfare-andrew-knight-clive-phillips-paula-sparks
... Spatial cognition is one of the best studied cognitive abilities in bony fish (Vila Pouca and Brown 2017) and is also well studied in elasmobranchs. Many of the experiments mentioned above have spatial elements to them. ...
450 million years of evolution have given chondrichthyans (sharks, rays and allies) ample time to adapt perfectly to their respective everyday life challenges and cognitive abilities have played an important part in that process. The diversity of niches that sharks and rays occupy corresponds to matching diversity in brains and behaviour, but we have only scratched the surface in terms of investigating cognition in this important group of animals. The handful of species that have been cognitively assessed in some detail over the last decade have provided enough data to safely conclude that sharks and rays are cognitively on par with most other vertebrates, including mammals and birds. Experiments in the lab as well as in the wild pose their own unique challenges, mainly due to the handling and maintenance of these animals as well as controlling environmental conditions and elimination of confounding factors. Nonetheless, significant advancements have been obtained in the fields of spatial and social cognition, discrimination learning, memory retention as well as several others. Most studies have focused on behaviour and the underlying neural substrates involved in cognitive information processing are still largely unknown. Our understanding of shark cognition has multiple practical benefits for welfare and conservation management but there are obvious gaps in our knowledge. Like most marine animals, sharks and rays face multiple threats. The effects of climate change, pollution and resulting ecosystem changes on the cognitive abilities of sharks and stingrays remain poorly investigated and we can only speculate what the likely impacts might be based on research on bony fishes. Lastly, sharks still suffer from their bad reputation as mindless killers and are heavily targeted by commercial fishing operations for their fins. This public relations issue clouds people's expectations of shark intelligence and is a serious impediment to their conservation. In the light of the fascinating results presented here, it seems obvious that the general perception of sharks and rays as well as their status as sentient, cognitive animals, needs to be urgently revisited.
... While less is known about cognition in fishes than in mammals, the field is growing. Fish are capable of all the main kinds of learning identified in mammals [78][79][80][81][82][83], with individual differences in learning capacity [74,[84][85][86][87] and possible relationships with personality. Looking at the relationship between the shy-bold continuum and learning, research has shown, for example, that shy brook trout were better at learning to navigate a maze than were bold brook trout [88], that bold sea trout were better at learning to avoid parasites [89], and that bold zebrafish and guppies showed better inhibition in a tube task [90]. ...
Welfare is an individual attribute. In general, providing captive nonhuman animals with conditions conducive to good welfare is an idea more easily applied when dealing with few individuals. However, this becomes much harder—if not impossible—under farming conditions that may imply high numbers of animals living in large group sizes. Although this is a problem inherent to intensive animal farming, it is possibly best exemplified in fish farming, for these practices often rely on extremely high numbers. In this paper we review evidence supporting the notion that fishes are individuals and fish welfare should thus also be considered at the individual level, examine the current state of welfare assessment in the aquaculture industry, evaluate these practices in light of individualized terrestrial animal welfare assessment methods, and make recommendations regarding research that could lead to a better understanding of how to provide each individual fish with good welfare in captivity.
... This first review section focussed on teleost fish. Interest on sex differences in this group has mostly arisen in the last decade but has rapidly become key in the field (Pouca and Brown, 2017). Interestingly, several studies in fish have been specifically designed to detect sex differences in EFs, a trend that is not observed in other vertebrate groups. ...
Cognitive sex differences have been reported in several vertebrate species, mostly in spatial abilities. Here, I review evidence of sex differences in a family of general cognitive functions that control behaviour and cognition, i.e., executive functions such as cognitive flexibility and inhibitory control. Most of this evidence derives from studies in teleost fish. However, analysis of literature from other fields (e.g., biomedicine, genetic, ecology) concerning mammals and birds reveals that more than 40% of species investigated exhibit sex differences in executive functions. Among species, the direction and magnitude of these sex differences vary greatly, even within the same family, suggesting sex-specific selection due to species' reproductive systems and reproductive roles of males and females. Evidence also suggests that sex differences in executive functions might provide males and females highly differentiated cognitive phenotypes. To understand the evolution of cognitive sex differences in vertebrates, future research should consider executive functions.
... A second approach, 'physiological', attempts to measure pain and stress as negative indicators of a fish's welfare state (Daskalova, 2019). A third approach uses behavioural analyses to infer learning, preference and choice and to support arguments for fish cognition and emotions (Vila Pouca & Brown, 2017). In a fourth approach, a fish's welfare is considered good if it is able to lead a natural life and express the behaviours that it would in the wild (Huntingford & Kadri, 2009 (Goolish, Okutake & Lesure, 1999) and environmental enrichment (Lee, Paull & Tyler, 2019a) Easily understood Difficult to differentiate between underlying and immediate causes (Ellis et al., 2012a) Growth Body length, mass, body condition Evaluate effects of social isolation (Forsatkar, Safari & Boiti, 2017), stocking density (Rabbane, Rahman & Hossain, 2016), and the use of body condition scoring to assess health and welfare (Clark et al., 2018) Straightforward to measure Depends upon many factors, including temperature, photoperiod, strain, diet, life stage (MacIntyre et al., 2008); optimal growth for zebrafish has yet to be established (Siccardi et al., 2009) Health Fish appearance (skin, fin, eye and gill integrity and colour) and behaviour (feeding, air-gasping, balance, activity) (Segner et al., 2012); regular health surveillance (Harper & Lawrence, 2012); body condition (Wilson et al., 2013) Evaluate husbandry stress on mycobacterial infections (Ramsay et al., 2009) and compare success of pathogen detection during health inspections (Marancik et al., 2019) Assessing is pragmatic; incidence of disease relatively easy to recognise and measure ...
Globally, millions of zebrafish (Danio rerio) are used for scientific laboratory experiments for which researchers have a duty of care, with legal obligations to consider their welfare. Considering the growing use of the zebrafish as a vertebrate model for addressing a diverse range of scientific questions, optimising their laboratory conditions is of major importance for both welfare and improving scientific research. However, most guidelines for the care and breeding of zebrafish for research are concerned primarily with maximising production and minimising costs and pay little attention to the effects on welfare of the environments in which the fish are maintained, or how those conditions affect their scientific research. Here we review the physical and social conditions in which laboratory zebrafish are kept, identifying and drawing attention to factors likely to affect their welfare and experimental science. We also identify a fundamental lack knowledge of how zebrafish interact with many biotic and abiotic features in their natural environment to support ways to optimise zebrafish health and well-being in the laboratory, and in turn the quality of scientific data produced. We advocate that the conditions under which zebrafish are maintained need to become a more integral part of research and that we understand more fully how they influence experimental outcome and in turn interpretations of the data generated.
... The ability of animals to optimize fitness gain by adjusting their movement in response to complexities depends on both innate and learned skills that enable animals to perceive, respond, learn, and remember the structure and dynamics of such factors in their environment. Studies of animal cognition have yielded numerous insights into the mechanisms affecting spatial learning and memory in various taxa [227,270] and fish in particular [30,40,78,142,146,158,215,298,303]. These insights divulged the role of ontogenetic and cognitive processes in shaping movement patterns and their fitness consequences, stressing the critical role of learning from experience during early life. ...
Movement ecology is increasingly relying on experimental approaches and hypothesis testing to reveal how, when, where, why, and which animals move. Movement of megafauna is inherently interesting but many of the fundamental questions of movement ecology can be efficiently tested in study systems with high degrees of control. Lakes can be seen as microcosms for studying ecological processes and the use of high-resolution positioning systems to triangulate exact coordinates of fish, along with sensors that relay information about depth, temperature, acceleration, predation, and more, can be used to answer some of movement ecology’s most pressing questions. We describe how key questions in animal movement have been approached and how experiments can be designed to gather information about movement processes to answer questions about the physiological, genetic, and environmental drivers of movement using lakes. We submit that whole lake telemetry studies have a key role to play not only in movement ecology but more broadly in biology as key scientific arenas for knowledge advancement. New hardware for tracking aquatic animals and statistical tools for understanding the processes underlying detection data will continue to advance the potential for revealing the paradigms that govern movement and biological phenomena not just within lakes but in other realms spanning lands and oceans.
... The literature provides a great number of studies on the effects of a variety of intrinsic and extrinsic factors on the cognitive abilities of fish and other ectotherms (e.g., Braithwaite, 2006;Brown et al., 2008;Shettleworth, 2010). These studies include effects on various processes, including spatial learning (Laland et al., 2003), which is one of the contemporary topics and basal research areas in fish cognition and behaviour (Pouca & Brown, 2017). It has been revealed that spatial learning in fish depends on sex in blennid fishes (Costa et al., 2011) and in guppy (Lucon-Xiccato & Bisazza, 2017), habitat type in gobies (e.g., White & Brown, 2014) or personality type in weakly electric fish (Kareklas et al., 2017) and in brook trout (White et al., 2017). ...
Temperature has a wide range of effects on the biology and ecology of ectotherms, including fish. However, the literature provides only a few studies assessing its effect on their cognitive abilities. We tested the effect of temperature on the spatial learning rate of zebrafish by comparing the daily rate of change in the number of fish choosing
the correct arm first and behavioural performance (i.e., distance travelled, time needed to locate the daily food reward and swimming speed) in two temperatures (21 and 31°C) in 7 successive sessions. The daily rate of change in behavioural performance was expressed as the percentage difference between the value in a given session and the value in the previous session. Two experiments were performed in a T-maze with single feeders in the arms, one empty and the other with a food reward. In each of the experiments, we used 10 naive fish, which were placed in the T-maze individually once a day. The fish were fed between sessions to avoid increasing differences in hunger levels and, in turn, increasing the differences in motivation to find the
food between the temperature treatments. The results revealed that the learning rate was greater at the higher temperature, which was apparent in a greater percentage reduction in the time and distance travelled needed to locate the daily food reward between successive sessions at the higher temperature than at the lower temperature.
The results show there was a significant effect of temperature on the daily rate of change in the number of fish choosing the correct arm, distance travelled and time needed to locate the daily food reward, which may be attributed to the positive effect of temperature on learning rate, and may indicate the importance of temperature for
the cognitive testing of zebrafish.
... Nowadays, fish have been gathering the attention of researchers to understand how the previously thought simple brain can produce complex cognitive behaviours (e.g., Braithwaite, 2006;Bshary, 2011;O'Connell & Hofmann, 2011;Vila Pouca & Brown, 2017). In this scenario, P. scalare is a significant model species, mainly regarding quantity discrimination, considered to be a highly demanding cognitive ability (Agrillo & Bisazza, 2018). ...
Some common practices in aquaculture, ornamental trade and fish facilities may disturb the behavioural repertoire of fish and its natural adaptive value, reducing welfare and impairing fish production. Hence, it is necessary to understand fish behaviour, as well as the factors affecting it, to improve the quality of fish's life under artificial environment. Here, we reviewed the behaviour of the angelfish Pterophyllum scalare, an Amazonian cichlid used worldwide both as an ornamental fish and as a fish model in scientific research. We characterized social, reproductive and feeding behaviour, as well as the amazing cognitive ability of the angelfish. In addition, we reviewed the effects of environmental enrichment and suggested some important variables that need to be considered for rearing P. scalare. In this review, we show for the first time a synthesis on behaviour and a best practice overview to improve the welfare of angelfish as a target species. Nonetheless, most topics reviewed fit a broader set of fish species, particularly ornamental ones. This synthesis can therefore open a path for further behavioural research applied to the welfare of angelfish and bring insights to other fish species.
... The nature of pain is biologically quite complex to address but controversy about the conscious experience of the emotional component of pain in animals is fading [54,69,70], with mounting evidence of an emotional component of pain in all vertebrates [71]. The lack of a gold standard for evaluating the affective states of pain in non-verbal mammals has led to the exploration of bodily behavior or physiological markers to convey information about internal states [72]. ...
Automated recognition of human facial expressions of pain and emotions is to a certain degree a solved problem, using approaches based on computer vision and machine learning. However, the application of such methods to horses has proven difficult. Major barriers are the lack of sufficiently large, annotated databases for horses and difficulties in obtaining correct classifications of pain because horses are non-verbal. This review describes our work to overcome these barriers, using two different approaches. One involves the use of a manual, but relatively objective, classification system for facial activity (Facial Action Coding System), where data are analyzed for pain expressions after coding using machine learning principles. We have devised tools that can aid manual labeling by identifying the faces and facial keypoints of horses. This approach provides promising results in the automated recognition of facial action units from images. The second approach, recurrent neural network end-to-end learning, requires less extraction of features and representations from the video but instead depends on large volumes of video data with ground truth. Our preliminary results suggest clearly that dynamics are important for pain recognition and show that combinations of recurrent neural networks can classify experimental pain in a small number of horses better than human raters.
... This statement roughly aligns with the position taken at law, as only some jurisdictions recognize fish, crustacea, cephalopods and fetuses as animals (Table 3). However, there is growing evidence in support of fish sentience [241][242][243], and consequently increasing international support for their recognition and protection under animal welfare statutes [244]. Furthermore, fetuses whose age is beyond half the gestation period have also been acknowledged as having sentient abilities and awarded protection under the delegated legislation for animal research, the Australian Code for the Care and Use of Animals for Scientific Purposes [245]. ...
Animal welfare is not included in the Australian Constitution, rendering it a residual power of the states and territories. Commentators have suggested that inconsistencies exist between the state and territory statutes, and that a uniform approach would be beneficial. However, there has been no comprehensive assessment of the nature or extent of these purported inconsistencies. This review addresses this gap by providing a state-by-state comparison of animal protection statutes based on key provisions. Utilizing systematic review methodology, every current Australian statute with an enforceable protection provision relating to animal welfare was identified. A total of 436 statutes were examined, with 42 statutes being included in the detailed analysis. The comparison showed that animal protection laws are generally consistent between each Australian jurisdiction and were found to have similar shortcomings, notably including lack of a consistent definition of ‘animal’ and reliance on forms of legal punishment to promote animal welfare which have questionable effectiveness. It is argued that there is a need for attention to definitions of key terms and future consideration of alternative forms of penalties, but that a uniform federal approach may not be necessary to address these shortcomings.
... The use of fishes as models for studies of social cognition is becoming increasingly popular (Brown & Laland, 2003;Bshary, Gingins, & Vail, 2014;Vila Pouca & Brown, 2017). In this study, we examined differences in discrimination abilities (familiarity recognition and group-size assessment capability) between cooperative and noncooperative Lamprologine cichlids from Lake Tanganyika. ...
Cooperation is a highly complex social interaction that often requires coordination and communication between two individuals. Reciprocity is one explanation for how cooperation evolves and is maintained; help now will eventually be repaid in kind. For reciprocity to work, individuals must be able to differentiate between those who helped previously versus those who cheated. However, there is little empirical evidence that cooperative species have an enhanced recognition capacity compared to noncooperative species. Here we conducted a comparative study to address this question using three cooperatively breeding cichlids and three of their close relatives that are not cooperative breeders, all from Lake Tanganyika. In a first experiment, we offered fish a choice between spending time with a familiar versus an unfamiliar conspecific and found that while cooperative cichlids spent more time with familiar individuals, the noncooperative cichlids spent more time with unfamiliar individuals. In a second experiment, we provided a choice between affiliating with one versus three individuals (all unfamiliar) and found that 2/3 cooperative and 3/3 noncooperative cichlids strongly preferred to affiliate with larger groups. Our results suggest that both cooperative and noncooperative cichlids have evolved the ability to recognise familiar individuals and have affiliative preferences; however, the nature of these preferences differ.
... However, progress in developing methodologies for assessing zebrafish cognitive performance seems much slower than progress in molecular tools. We know that teleost fish possess various complex cognitive functions similar to those of many mammalian and avian species (Vila Pouca and Brown, 2017); however, most of these complex cognitive abilities have not yet been demonstrated in zebrafish. For example, archerfish can discriminate images as complex as human faces (Newport et al., 2016). ...
Due to their unique characteristics, the zebrafish plays a key role in the comprehension of neurobiology of cognition and its pathologies, such as neurodegenerative diseases. More and more molecular tools for this aim are being developed, but our knowledge about the cognitive abilities of zebrafish remains extremely scarce compared to other teleost fish. We aimed to investigate the complex cognitive abilities of zebrafish using a tracking-based automated conditioning chamber that allowed precise experimental control, avoided potential cueing provided by the observer (Clever Hans phenomenon), and was shown to considerably improve learning in other teleosts. A computer presented two visual stimuli in two sectors of the chamber, and zebrafish had to enter the correct sector to obtain a food reward. Zebrafish quickly learned to use the conditioning device and easily performed up to 80 trials per day. In Experiment 1, zebrafish efficiently discriminated between two differently coloured sides, reaching a 75% accuracy in only 10 training sessions. Surprisingly, zebrafish failed to choose the correct chamber when the stimuli were two shapes, a small circle and a small triangle, even when, in Experiment 2, training on shape discrimination was prolonged for up to 30 sessions. In Experiment 3, we tested the hypothesis that simultaneously learning to use the conditioning chamber and learning discrimination imposes a too-high cognitive load. However, zebrafish that first successfully learned how the conditioning chamber functioned (in the colour discrimination) subsequently failed in the shape discrimination. Conversely, zebrafish that firstly failed the shape discrimination subsequently learned colour discrimination. In Experiment 4, zebrafish showed some evidence of learning when the stimuli were two large shapes, suggesting that zebrafish did not discriminate between the shapes of the previous experiments because they were not salient enough. Altogether, results suggest constraints in the discrimination learning abilities of zebrafish, which should be taken into account when developing cognitive tasks for this species.
... Fish behavioral habits in response to their surrounding are either positively (taxis) and negative (phobias) (Fitri 2012;Gutowsky et al. 2017;Pouca and Brown 2017;Benitez et al. 2018;Suriyampola et al. 2018). This research revealed six patterns of behavior of A. bicolor elver against different trap designs, which include: (i). ...
Fitri ADP, Boesono H, Kurohman F, Jayanto BB, Dewi DE, Sabdono A. 2019. Short Communication: Behavioral study on Anguilla bicolor using a modified trap design at laboratory scale. Biodiversitas 20: 2159-2165. The information on the behavioral juvenile eels Anguilla bicolor is urgently needed as basic design of selective and sustainable traps. The objectives of this study were to find out and analyze the behavioral pattern and characteristics of A. bicolor elvers in the modified and non-modified eel traps. The test organism, A. bicolor juvenile eels with 150-170 mm in length, were obtained from Segara Anakan waters, Cilcacap. The 2 trap designs, which were modifications of the 450 mm long PVC eel trap, with and without the addition of bait hole, were used in this study. All experiments were carried out in the laboratory of Fish Behavior, Diponegoro University, Semarang, Indonesia. The eel characters and response time were recorded using a handy camera that placed on top of the aquariums. The results indicated six types of A. bicolor behavior in response to the modification of eel traps. Moreover, the trap design with an additional hole on the wall, with or without bait, was proven to have no significant effect on the response time. While trap without column and bait possessed the fastest response time at which elver penetrated to the trap (p-value ≤ 0.05). Furthermore, these results indicated that A. bicolor elver gained entrance into the trap, in an attempt to take shelter.
... Fish pain in general is reviewed elsewhere (ie. Chatigny, 2018;EFSA, 2009;Pouca & Brown, 2017;Sneddon, 2009). The salmon showed immediate strong aversive behaviors like bursts, colliding in tank walls, headshake and increased swimming speed at these temperatures (reported in details in Nilsson et al., 2019 and at ensured oxygen conditions). ...
Thermal delousing is a new method for removing sea lice from farmed Atlantic salmon (Salmo salar L). We investigated thermally-related tissue injuries in Atlantic salmon in a pilot laboratory trial to describe the acute effect of high water temperatures (34–38 °C). Acute tissue injuries in gills, eyes, brain and possible also nasal cavity and thymus were seen in salmon exposed to water temperatures of 34 - 38 °C in 72 to 140 s. This implies that exposing salmon to such water temperatures is a welfare risk, not only due to the direct tissue injuries that may also be dependent on exposure time, but also due to risk of thermal pain and aversion, including flight reactions. Key words: Fish, Delousing, Thermal pain, Tissue damage, Welfare
... En milieu naturel, seulement 25% des couples arrivent à amener des jeunes jusqu'à l'indépendance. Lorsqu'un seul parent est présent, cette probabilité chute drastiquement et sans parent les jeunes survivent environ 6 minutes seulement (Smith-Grayton and Keenleyside 1978;Clutton-Brock 1991;Alonzo et al. 2001 (Helfman and Schultz 1984;Bshary et al. 2002Bshary et al. , 2014Brown and Laland 2003;Reader et al. 2003;Burghardt 2005;Stanley et al. 2008;Pike and Laland 2010;Brown et al. 2011;Laland et al. 2011;Agrillo et al. 2016;Satoh et al. 2016;Vila Pouca and Brown 2017;Miller 2017;Kohda et al. 2018 La convergence comportementale entre les partenaires est une question qui n'était pas encore apparue dans les études sur la personnalité animale alors qu'elle fait l'objet de nombreuses études et de débats en psychologie humaine (Anderson et al. 2003;Humbad et al. 2010Humbad et al. , 2013Gonzaga et al. 2010;Ask et al. 2013 (Taborsky et al. 2009;Galipaud et al. 2013Galipaud et al. , 2015b. Par exemple, l'homogamie pour des traits comportementaux peut résulter d'une convergence comportementale entre les partenaires après l'appariement (Burley 1983 ...
Au cours de leur vie, les animaux doivent sans cesse prendre des décisions qui impactent leur survie et leur succès reproducteur. L’objectif de cette thèse était d’étudier le rôle de deux sources de variabilité dans la prise de décision — la personnalité et l’état émotionnel — en contexte sexuel chez un poisson monogame, le cichlidé zébré. Nos travaux sur la personnalité ont mis en évidence son importance sur la compatibilité comportementale et le succès reproducteur des partenaires. De plus, les individus les plus réactifs se sont ajustés à leur partenaire et ont augmenté leur succès reproducteur. Ceci supporte l’hypothèse d’une plus grande flexibilité de ces individus qui compenseraient ainsi leur faible compétitivité. Les différents profils de personnalité peuvent ainsi être considérés comme des stratégies alternatives. Le maintien de la variabilité interindividuelle pourrait ainsi s’expliquer par le succès équivalent de ces stratégies.Les émotions sont, elles, une cause de variabilité intra-individuelle souvent négligée qui pourrait pourtant représenter une information interne utilisée par l’individu pour prendre ses décisions. En transposant le test cognitif du biais de jugement aux poissons, nous avons pu observer un lien étroit entre leur état émotionnel et la présence/absence du partenaire. Ces résultats suggèrent un rôle des émotions dans les processus d’appariement et interrogent sur leur utilisation dans les prises de décision. Les individus se basent-ils sur leurs émotions pour choisir un partenaire ? Est-ce adaptatif ? À travers l’étude de ces sources de variabilité comportementale, nous avons observé que, loin d’être distribuée aléatoirement, la variabilité était liée à des stratégies décisionnelles et pouvait influencer le succès reproducteur des individus. Il serait donc crucial de la prendre en compte pour appréhender l’évolution des processus décisionnels.
... Despite the increasing interest in the study of fish cognition (Bshary & Brown, 2014;Pouca & Brown, 2017), few cases of species-specific cognitive abilities have been reported for this taxon so far. ...
Animal species are expected to evolve specialised cognitive abilities to solve the tasks that are critical for their fitness. The literature contains several examples of specialised cognitive abilities, but few regard fish. The guppy, Poecilia reticulata, is a freshwater fish in which females choose their mates based on colouration, and orange‐coloured fruits are important diet enrichments for both sexes. For these reasons, we expect that this species has evolved enhanced learning abilities in colour discrimination compared to other types of discrimination. The comparison between studies in which guppies were tested for colour discrimination and studies in which guppies were tested for shape discrimination seems to support this hypothesis, but direct testing is still lacking. We experimentally compared the learning performance of guppies trained in a red–yellow colour discrimination learning task and that of guppies trained in a shape discrimination learning task using the same, automated conditioning procedure. Guppies trained in the colour discrimination showed greater learning performance, which provides support to the hypothesis that guppies possess enhanced colour discrimination abilities. Moreover, we found that male guppies performed better than females in both shape and colour discrimination learning.
This handbook lays out the science behind how animals think, remember, create, calculate, and remember. It provides concise overviews on major areas of study such as animal communication and language, memory and recall, social cognition, social learning and teaching, numerical and quantitative abilities, as well as innovation and problem solving. The chapters also explore more nuanced topics in greater detail, showing how the research was conducted and how it can be used for further study. The authors range from academics working in renowned university departments to those from research institutions and practitioners in zoos. The volume encompasses a wide variety of species, ensuring the breadth of the field is explored.
A presente pesquisa teve como objetivo avaliar a preferência do peixe Guppy (Poecilia reticulata) por diferentes aspectos de seu ambiente em aquários, comparando o comportamento em um aquário simulando o ambiente natural e outro com enriquecimento ambiental. O experimento foi realizado no Laboratório de Ranicultura do Instituto Federal de Educação, Ciência e Tecnologia do Espírito Santo - campus de Alegre e utilizou 36 exemplares jovens da espécie P. reticulata, obtidos de um criadouro particular. Foram utilizados três aquários divididos em cinco regiões espaciais, e neles, foram colocados fêmeas e machos do Guppy em proporção de 3:1 (fêmeas:machos) e densidade de estocagem de 0,061 peixes por litro de água. Foram realizados cinco testes de preferência para avaliar a resposta do Guppy em relação a diferentes aspectos do ambiente: preferência por lados (direito e esquerdo) e níveis de profundidade (superfície, intermediário e fundo); e teste de preferência por recinto (abrigo, vegetação e coloração). Os resultados mostraram que a espécie P. reticulata não apresentou uma preferência específica pelos lados do aquário, mas visitou com maior frequência o lado direito. Em relação aos níveis de profundidade, os peixes preferiram a superfície do aquário. Quanto aos abrigos, o tronco e o tijolo foram os preferidos, proporcionando melhores desempenhos e refúgio. A vegetação Pistia stratiotes (Alface d'água) foi a mais frequentada pelos peixes em comparação com outras vegetações utilizadas. Além disso, os Guppys mostraram preferência pela coloração azul, que pode ter comprimento de onda de luz visível em níveis confortantes para a espécie, favorecendo a expressão de comportamentos naturais. Em resumo, os resultados indicam que os Guppys são animais ativos, mostrando interesse principalmente pela superfície do aquário em busca de alimentos. Eles também demonstraram preferência por abrigos naturais, como troncos e tijolos, e foram atraídos pela vegetação Pistia stratiotes. A coloração azul parece ser reconfortante para a espécie, influenciando positivamente seu comportamento. Esses achados são relevantes para o campo da agroecologia e bem-estar animal, pois fornecem informações sobre como enriquecer o ambiente dos Guppys em aquários, promovendo seu bem-estar e comportamentos naturais. Além disso, o estudo destaca a importância do uso de cores específicas no ambiente para favorecer o bem-estar de animais aquáticos. A compreensão desses aspectos pode contribuir para o manejo adequado desses peixes em cativeiro, garantindo sua saúde e qualidade de vida.
Although studies on fish cognition are increasing, consideration of how methodological details influence the ability to detect and measure performance is lagging. Here, in two separate experiments the authors compared latency to leave the start position, latency to make a decision, levels of participation and success rates (whether fish entered the rewarded chamber as first choice) across different physical designs. Experiments compared fish performance across (a) two sizes of T‐mazes, large and standard, and a plus‐maze, and (b) open choice arenas with either two or four doors. Fish in T‐mazes with longer arms took longer to leave the start chamber and were less likely to participate in a trial than fish in T‐mazes with shorter arms. The number of options, or complexity, in a maze significantly impacted success but did not necessarily impact behavioural measures, and did not impact the number of fish that reached a chamber. Fish in the plus‐maze had similar latencies to leave the start box and time to reach any chamber as fish in the same‐sized T‐maze but exhibited lower overall success. Similarly, in an open choice arena, increasing the number of options – doors to potential reward chambers − resulted in lower probability of success. There was an influence of reward position in the choice arena, with rewarded chambers closest to the sides of the arena resulting in lower latencies to enter and higher probability of decision success. Together the results allow the authors to offer practical suggestions towards optimal maze design for studies of fish cognition.
Fishes are complex animals, with emotions, individual personalities and intelligence. Humans have wide-ranging impacts on the lives and welfare of fishes, but until recently we have given very little thought to the suffering we cause. This is beginning to change as the gap between public understanding and the science on fish intelligence closes. Governments are increasingly recognising sentience in fishes, and other marine animals like octopuses and lobsters, and are reviewing animal welfare legislation to better include them. However, with trillions of fishes killed each for food, addressing welfare in fisheries and aquaculture is complex, and fisheries in particular have largely been left in the ‘too hard basket’. It doesn’t have to be this way. There are solutions—we can keep feeding our growing populations whilst also ensuring fishes are treated with respect and compassion. It’s a journey we need to start as soon as possible
The study of birds in the natural environment largely falls to two disciplines: ecology and ethology. At this time of substantial decline of bird species and numbers, it is argued that ecology cannot do without ethology, especially cognitive ethology, if real progress of saving species is to be made. The paper is concerned with problems of methodology, partly to do with lack of familiarity with behaviour and characteristics of the species (the anonymity problem) on one hand and partly to do with an underestimation of the effects of ‘an ecology of fear’. It will raise the question of sampling bias, express concern about the use of technological gadgets that may produce large data sets but often too little of value. It is not just an argument of quantitative versus qualitative data but of distortions, oversights, and insights that are not used. Studying cognition and emotional intelligence are as important hallmarks of animals ability to cope in the current wildlife crisis as are knowing about migration routes. Moreover, there is little doubt that systematic discussions in ethology rarely prepare one on how to respond to unexpected or incidental behaviour and to discuss the future of ethological fieldwork and cognitive studies. Examples of rare behaviour will also be provided to show how they can be pivotal in good science when momentary surprises in witnessing unusual behaviour can lead to new insight, and then to experiments and data. The paper will suggest, however, that new insights may only be possible when a robust methodology used in field research reflects a positive, non-invasive approach. The paper proposes that social interactions between conspecifics can become one of the drivers of cognition and social bonding that provides critical support for avian survival.
This article builds upon Amerindian epistemologies and develops a perspectival ethnography of industrial Northwestern European skilled modes of engaging with wild fish. It explores Amerindian perspectivism as an ethnographic methodology grounded on animic premises: subject or object status are relative and relational, experience is intersubjective; the body is permeable, and its perspectives can be exchanged through tools and mimetic processes. Thus subjectivity is collectively constituted and the fundamental means of knowing, leading to the acknowledgement of subjectivity in others. Documenting a perspectival exchange guided by Shetland fishers trawling for monkfish, the article focuses on some possible dynamics and affective affordances involved in gutting processes. Gutting is physically and emotionally taxing labour that involves brief but intimate encounters with responsive beings that may offer effective resistance, affecting fishers or damaging their own value as catch. It entails the possibility of developing an intimate knowledge of fish anatomy, ecology, and behaviour, as well as potentially awareness of fish suffering and fishiness , an empathic quality. The research reveals how Shetland fishers maintain animic modes of learning and being in their understandings of the body and fish. The ethnography presents first‐hand insights into ‘relations of trust’, which, although widely reported, continue to be dismissed as implausible. These relations and their dynamics are further attested through Shetlands háfwords and other language practices that establish synecdochical relations between fishers and fish, restricting violence and making it endurable. These insights problematize violence, illustrating the social skills of fishing and the political dynamics of predation, suggesting paths towards addressing cruelty.
The astonishing diversity of brain sizes observed across the animal kingdom is typically explained in the context of trade‐offs: the benefits of a larger brain, such as enhanced cognitive ability, are balanced against potential costs, such as increased energetic demands. Several hypotheses have been formulated in this framework, placing different emphasis on ecological, behavioural, or physiological aspects of trade‐offs in brain size evolution. Within this body of work, there exists considerable taxonomic bias towards studies of birds and mammals, leaving some uncertainty about the generality of the respective arguments. Here, we test three of the most prominent such hypotheses, the ‘expensive tissue’, ‘social brain’ and ‘cognitive buffer’ hypotheses, in a large dataset of fishes, derived from a publicly available resource (FishBase). In accordance with predictions from the ‘expensive tissue’ and the ‘social brain’ hypothesis, larger brains co‐occur with reduced fecundity and increased sociality in at least some Classes of fish. Contrary to expectations, however, lifespan is reduced in large‐brained fishes, and there is a tendency for species that perform parental care to have smaller brains. As such, it appears that some potential costs (reduced fecundity) and benefits (increased sociality) of large brains are near universal to vertebrates, whereas others have more lineage‐specific effects. We discuss our findings in the context of fundamental differences between the classically studied birds and mammals and the fishes we analyse here, namely divergent patterns of growth, parenting and neurogenesis. As such, our work highlights the need for a taxonomically diverse approach to any fundamental question in evolutionary biology. Traits associated with brain size across fishes.
The average mammal or bird has a roughly ten times larger brain relative to body size than the average ectotherm vertebrate. It has been surprisingly challenging to determine how this translates into increased cognitive performance. In particular, it is unclear whether the brain size differences translate into qualitative differences in specific cognitive abilities. Here, we provide a first exploratory study to examine the possibility that the larger brains of endotherms support a different organisation of information processing, rather than specific differences in cognitive processes. In mammals, individual performance across domain‐general cognitive tasks is positively correlated, resulting in the psychometric factor g. The value of g is positively correlated with brain size. We tested wild‐caught female cleaner fish Labroides dimidiatus, known for its highly sophisticated social behaviour, in four ecologically nonrelevant cognitive tasks that have been used to varying degrees to assess g in mammals. Cleaner fish solved three of these four tasks, flexibility (reversal learning), self‐control (detour around an obstacle) and numerical competence (simultaneous two‐choice task), while also providing enough interindividual variation to test for g. They did not perform above chance levels in the fourth task, which tested for object permanence. For the three retained tasks, individual performance did not load positively on one principal component. Furthermore, all pairwise correlation coefficients were close to zero. These negative results contradict a frequent criticism of g studies, which proposes that g is a default result of how brains are designed. Rather, the results provide a first indication that endotherm and ectotherm vertebrates may process cognitive tasks in fundamentally different ways due to differences in brain organisation. Our relatively low number of experiments compared to mammalian studies enhances this hypothesis, as the probability of finding a g factor by chance would have been higher. It is known that endotherm vertebrates have on average a ten times larger brain relative to body size compared with ectotherm vertebrates. It remains largely unknown what advantages the larger brains convey. Our preliminary study may provide a partial answer: it appears that cleaner fish cognitive abilities are organised in a rather modular way (Figure), and that their brain may hence lack centralised units that cause correlated individual performance across cognitive domains, yielding the general intelligence factor ‘g’ in mammals. Figure: No evidence for g in a fish. Principal component analysis (PCA) of the three cognitive tasks. Dimension 1 (explaining 38.54% of the variance in performance) and dimension 2 (explaining 32.78% of the variance) are represented. The results for each task are represented as vectors.
The welfare state of a fish strongly affects its physiology and behavior. Poor welfare conditions result in reduced growth rates and in a higher susceptibility to infections and disease and therefore, fish welfare is critical for a sustainable fish farming industry. Furthermore, recent scientific research has set evidence about fish sentience and cognition abilities that have been the base of the still increasing public awareness about fish well-being, which in turn has resulted in the development of stricter regulations when working with fish. In spite of its importance, quantifying fish welfare is not an easy task. It is currently considered that a precise evaluation of fish welfare requires a multiparametric approach based on the determination of both environmental and fish-based variables, the latter including an array of anatomical, physiological, and behavioral observations. Stress hormones and metabolites are among the most relevant physiological welfare-related variables, due to the close relationship between stress and welfare: stressful conditions or events are one of the most important determinants of poor welfare, particularly when the stressors are severe and/or sustained. Therefore determining the stress status of a fish constitutes an important part of its welfare assessment. However, the evaluation of the stress state might be also challenging, since fish, as other vertebrates, respond to stress by initiating a rather complex neuroendocrine response. This response comprises the activation of stress brain centers and the subsequent hormonal cascade leading to the release of stress hormones from the anterior kidney into circulation. In this chapter, the relevance and the methodology for quantification of different hormones and metabolites of the neuroendocrine stress response in fish, and their potential use in fish welfare assessment, is explained and discussed.
Day length in conjunction with seasonal cycles affects many aspects of animal biology. We have studied photoperiod-dependent alterations of complex behaviour in the teleost, medaka (Oryzias latipes), a photoperiodic breeder, in a learning paradigm whereby fish have to activate a sensor to obtain a food reward. Medaka were tested under a long (14:10 LD) and short (10:14 LD) photoperiod in 3 different groups: mixed-sex, all-males and all-females. Under long photoperiod, medaka mixed-sex groups learned rapidly with a stable response. Unexpectedly, males-only groups showed a strong learning deficit, whereas females-only groups performed efficiently. In mixed-sex groups, female individuals drove group learning whereas males apparently prioritized mating over feeding behaviour resulting in strongly reduced learning performance. Under short photoperiod, where medaka do not mate, male performance improved to a level similar to that of females. Thus, photoperiod has sex-specific effects on the learning performance of a seasonal vertebrate.
Humans interact with fishes in many contexts including aquaculture, scientific study and companion animals. In all of these contexts, fish welfare can be compromised through anthropogenic means. Concern for fish welfare has grown considerably in recent years, with many states and territories now protecting fish through animal welfare regulations. We are not only morally obliged to ensure good welfare of animals in our care, but increasingly required to do so by law. A greater understanding of fish behaviour can lead to the development of welfare indicators. Here we suggest that laterality has wide-spread consequences for fish behaviour and a better understanding of how laterality shapes and interacts with fish behaviour may provide opportunities to enhance fish welfare. Moreover, assessment of laterality through behavioural assays may well be a useful welfare indicator in its own right given the close apparent link between laterality, personality and stress reactivity. Here we review the current research investigating laterality in fishes and highlight instances which may have important consequences for fish welfare.
Scientists have built a significant body of research that shows that fishes display all the features
commonly associated with intelligence in mammals, and that they experience stress, fear and pain. These
findings have significant ramifications for animal welfare legislation, an area from which fishes have been
traditionally excluded. Our most detrimental interaction with fishes is through commercial fisheries and
aquaculture, an industry that feeds billions of humans and employs millions more. We have invented a
vast array of fishing methods that extract fishes from almost every region on the planet in an equally vast
range of violent and painful ways. Fisheries managers regularly fail to prevent overfishing to ensure
healthy populations of target species, have not adequately addressed the impacts on other marine
species and the broader environment, nor prevented human rights abuses on board fishing vessels. Fish
welfare has not been a consideration. Farmed fishes are under our control for their entire lives, and while
there are welfare guidelines available, where these are applied, the goal is primarily to maximise
production and reduce losses, rather than ensure good welfare. These industries are important to many of
us; however, we need to change these systems to address both welfare and sustainability. For fisheries
this means a reduction in the number of fishes killed, by addressing overfishing and wasteful capture
methods, and reducing the length of time fishes suffer during capture. For aquaculture this means
keeping fishes in more natural environments at lower densities, reducing transport and handling impacts,
and choosing species that cope better with farming. Both sectors need to develop humane slaughtering
practices. Fish behaviour and welfare experts will benefit from working with the people and systems that
are driving more ethical and sustainable practices in fisheries and farming, to help initiate improvements
that will benefit individual fishes and the broader marine environment, as well as the lives of those
working in the industry. We must ensure that where we do need to farm and capture fishes it is done
humanely, fairly and without unnecessary waste of trillions of lives. A simple way forward would be to
reduce our reliance on fish as a primary source of protein, particularly in wealthy countries where
alternatives abound.
The present study aims at identifying the lowest number of fish (European seabass) that could be used for monitoring and/or experimental purposes in small-scale fish facilities by quantifying the effect that the number of individuals has on the Shannon entropy (SE) of the trajectory followed by the shoal’s centroid. Two different experiments were performed: (i) one starting with 50 fish and decreasing to 25, 13, and 1 fish, and (ii) a second experiment starting with one fish, adding one new fish per day during 5 days, ending up with five fish in the tank. The fish were recorded for 1h daily, during which time a stochastic event (a hit in the tank) was introduced. The SE values were calculated from the images corresponding to three arbitrary basal (shoaling) periods of 3.5 min prior to the event, and to the 3.5 min period immediately after the event (schooling response). Taking both experiments together, the coefficient of variation (CV) of the SE among measurements was largest for one fish systems (CV 37.12 and 17.94% for the daily average basal and response SE, respectively) and decreased concomitantly with the number of fish (CV 8.6–10% for the basal SE of 2 to 5 fish systems and 5.86, 2.69, and 2.31% for the basal SE of 13, 25, and 50 fish, respectively). The SE of the systems kept a power relationship with the number of fish (basal: R²= 0.93 and response: R²= 0.92). Thus, 5–13 individuals should be the lowest number for a compromise between acceptable variability (<10%) in the data and reduction in the number of fish. We believe this to be the first scientific work made to estimate the minimum number of individuals to be used in subsequent experimental (including behavioral) studies using shoaling fish species that reaches a compromise between the reduction in number demanded by animal welfare guidelines and a low variability in the fish system’s response.
In mammals, the so-called “seat of the cognitive map” is located in place cells within the hippocampus. Recent work suggests that the shape of place cell fields might be defined by the animals’ natural movement; in rats the fields appear to be laterally compressed (meaning that the spatial map of the animal is more highly resolved in the horizontal dimensions than in the vertical), whereas the place cell fields of bats are statistically spherical (which should result in a spatial map that is equally resolved in all three dimensions). It follows that navigational error should be equal in the horizontal and vertical dimensions in animals that travel freely through volumes, whereas in surface-bound animals would demonstrate greater vertical error. Here, we describe behavioural experiments on pelagic fish in which we investigated the way that fish encode three-dimensional space and we make inferences about the underlying processing. Our work suggests that fish, like mammals, have a higher order representation of space that assembles incoming sensory information into a neural unit that can be used to determine position and heading in three-dimensions. Further, our results are consistent with this representation being encoded isotropically, as would be expected for animals that move freely through volumes. Definitive evidence for spherical place fields in fish will not only reveal the neural correlates of space to be a deep seated vertebrate trait, but will also help address the questions of the degree to which environment spatial ecology has shaped cognitive processes and their underlying neural mechanisms.
Humans and other animals use previous experiences to make behavioural decisions, balancing the probabilities of receiving rewards or punishments with alternative actions. The dopaminergic system plays a key role in this assessment: for instance, a decrease in dopamine transmission, which is signalled by the failure of an expected reward, may elicit a distinct behavioural response. Here, we tested the effect of exogenously administered dopaminergic compounds on a cooperative vertebrate’s decision-making process, in a natural setting. We show, in the Indo-Pacific bluestreak cleaner wrasse Labroides dimidiatus, that blocking dopamine receptors in the wild induces cleaners to initiate more interactions with and to provide greater amounts of physical contact to their client fish partners. This costly form of tactile stimulation using their fins is typically used to prolong interactions and to reconcile with clients after cheating. Interestingly, client jolt rate, a correlate of cheating by cleaners, remained unaffected. Thus, in low effective dopaminergic transmission conditions cleaners may renegotiate the occurrence and duration of the interaction with a costly offer. Our results provide first evidence for a prominent role of the dopaminergic system in decision-making in the context of cooperation in fish.
Whether fishes are sentient beings remains an unresolved and controversial question. Among characteristics thought to reflect a low level of sentience in fishes is an inability to show stress-induced hyperthermia (SIH), a transient rise in body temperature shown in response to a variety of stressors. This is a real fever response, so is often referred to as 'emotional fever'. It has been suggested that the capacity for emotional fever evolved only in amniotes (mammals, birds and reptiles), in association with the evolution of consciousness in these groups. According to this view, lack of emotional fever in fishes reflects a lack of consciousness. We report here on a study in which six zebrafish groups with access to a temperature gradient were either left as undisturbed controls or subjected to a short period of confinement. The results were striking: compared to controls, stressed zebrafish spent significantly more time at higher temperatures, achieving an estimated rise in body temperature of about 2-4°C. Thus, zebrafish clearly have the capacity to show emotional fever. While the link between emotion and consciousness is still debated, this finding removes a key argument for lack of consciousness in fishes.
Arguments against the fact that fish feel pain repeatedly appear even in the face of growing evidence that they do. The standards used to judge pain perception keep moving as the hurdles are repeatedly cleared by novel research findings. There is undoubtedly a vested commercial interest in proving that fish do not feel pain so the topic has a half-‐life well past its due date. Key reiterates previous perspectives on this topic characterised by a black or white view that is based on the proposed role of the human cortex in pain perception. I argue that this is incongruent with our understanding of evolutionary processes.
Mammals and birds can process ordinal numerical information which can be used, for instance, for recognising an object on the basis of its position in a sequence of similar objects. Recent studies have shown that teleost fish possess numerical abilities comparable to those of other vertebrates, but it is unknown if they can also learn ordinal numerical relations. Guppies (Poecilia reticulata) learned to recognise the 3rd feeder in a row of 8 identical ones even when inter-feeder distance and feeder positions were varied among trials to prevent the use of any spatial information. To assess whether guppies spontaneously use ordinal or spatial information when both are simultaneously available, fish were then trained with constant feeder positions and inter-feeder distance. In probe trials where these two sources of information were contrasted, the subjects selected the correct ordinal position significantly more often than the original spatial position, indicating that the former was preferentially encoded during training. Finally, a comparison between subjects trained on the 3rd and the 5th position revealed that guppies can also learn the latter discrimination, but the larger error rate observed in this case suggests that 5 is close to the upper limit of discrimination in guppies.
According to the social decision-making (SDM) network hypothesis, SDM is encoded in a network of forebrain and midbrain structures in a distributed and dynamic fashion, such that the expression of a given social behaviour is better reflected by the overall profile of activation across the different loci rather than by the activity of a single node. This proposal has the implicit assumption that SDM relies on integration across brain regions, rather than on regional specialization. Here we tested the occurrence of functional localization and of functional connectivity in the SDM network. For this purpose we used zebrafish to map different social behaviour states into patterns of neuronal activity, as indicated by the expression of the immediate early genes c-fos and egr-1, across the SDM network. The results did not support functional localization, as some loci had similar patterns of activity associated with different social behaviour states, and showed socially driven changes in functional connectivity. Thus, this study provides functional support to the SDM network hypothesis and suggests that the neural context in which a given node of the network is operating (i.e. the state of its interconnected areas) is central to its functional relevance.
It has been hypothesized that cerebral lateralization can significantly enhance cognition and that this was one of the primary selective forces shaping its wide-spread evolution amongst vertebrate taxa. Here we tested this hypothesis by examining the link between cerebral lateralization and numerical discrimination. Guppies, Poecilia reticulata, were sorted into left, right and non-lateralized groups using a standard mirror test and their numerical discrimination abilities tested in both natural shoal choice and abstract contexts. Our results show that strongly lateralized guppies have enhanced numerical abilities compared to non-lateralized guppies irrespective of context. These data provide further credence to the notion that cerebral lateralization can enhance cognitive efficiency.
Theory suggests that living in large social groups with dynamic social interactions often favors the evolution of enhanced cognitive abilities. Studies of how animals assess their own contest ability commonly focus on a single cognitive task, and little is known about the diversity or co-occurrence of cognitive abilities in social species. We examined how a highly social cichlid fish Julidochromis transcriptus uses four major cognitive abilities in contest situations; direct experience, winner/loser effects, social eavesdropping and transitive inference (TI). We conducted experiments in which fish assessed the social status of rivals after either direct physical contests or observed contests. Individuals used direct information from a previous physical encounter to re-establish dominance without additional contact, but winner/loser effects were not observed. Social eavesdropping alone was ruled out, but we found that transitive reasoning was used to infer social dominance of other individuals of unknown status. Our results suggest that in stable hierarchical social groups, estimations of contest ability, based on individual recognition pathways such as TI and direct experience, are more prevalent than social eavesdropping or winner/loser effects. We suggest that advanced cognitive abilities might be widespread among highly social fishes, but have previously gone undetected.
Discrimination of quantity (magnitude) was investigated in zebrafish (Danio rerio). Male zebrafish chose to approach the location previously occupied by the larger in number between 2 groups of female conspecifics (no longer visible at test) in sets of 1 versus 2 items, and 2 versus 3 items, but failed at 3 versus 4 items; similarly, when tested with larger numbers, zebrafish succeeded with 2 versus 4, 4 versus 6, and 4 versus 8 items, but failed with 6 versus 8 items. The results suggest that zebrafish rely on an approximate number system to discriminate memorized sets of conspecifics of different magnitudes, the degree of precision in recall being mainly dependent on the ratio between the sets to be discriminated. (PsycINFO Database Record
The ability to discriminate between different
quantities is widespread throughout the animal kingdom,
and the underlying mechanisms of quantity discrimination
are currently intensely discussed. In contrast, questions
elucidating the limits of quantity estimation received rather
little attention so far. Here, we examined fine-tuned
quantity estimation in the three-spined stickleback (Gasterosteus
aculeatus) in a natural context, i.e. during
shoaling decisions. Wild-caught focal fish were given the
spontaneous choice between two shoals which differed in
group size by 1 fish (0 vs. 1, 1 vs. 2, 2 vs. 3, 3 vs. 4, 4 vs. 5,
5 vs. 6 and 6 vs. 7), based on visual assessment. The results
show that sticklebacks generally prefer to shoal with the
larger group. They discriminated numerical contrasts up to
6 versus 7, equalling a numerical ratio of 0.86. Preference
patterns followed Weber’s law, i.e. decreased with
increasing numerical ratio. This pattern was found across
all numerical conditions as well as within the small number
range (ranging from 1 vs. 2 to 3 vs. 4). The results suggest
that wild-caught three-spined sticklebacks are spontaneously
able (i.e. without prior learning) to detect subtle
differences in shoal sizes. Further, they confirm findings of
previous studies highlighting the contribution of the analogue
magnitude system to quantity estimation in fishes.
There have been many investigations into consistent, individual differences in behavior (animal personalities), but rather less attention has been given to the possibility that individuals might differ consistently in their “cognitive style,” which refers to the way information is acquired, processed, stored, or acted on. Both personality and cognition have important fitness consequences, and it has been proposed that variation in cognition could be functionally related to variation in personality. Here, we test this hypothesis using three-spined sticklebacks (Gasterosteus aculeatus) as a model and adopt a classic T-maze with food reward experimental paradigm. We first confirmed that fish choose the correct arm of the maze significantly more than would be expected by chance and that this improves with trial number. We then explored predictors of individual differences in the speed (time to making a decision) and accuracy (whether the first decision is correct) in decision making. We find bolder behavioral types (who tend to be male) arrive at the correct decision sooner than their shyer conspecifics. However, boldness was not related to decision accuracy. Moreover, we did not find any significant difference in fish’s improvement in decision accuracy over successive trials according to boldness or sex. This suggests that although bolder fish may acquire information more quickly because they make decisions faster, they do not differ from shyer conspecifics in their decision-making accuracy. The absence of such a trade-off might offer a functional explanation for why, in stickleback fish and many other species, bolder individuals tend to initiate movement and shyer individuals to follow—bold leaders may result in faster group decisions without compromising accuracy.
The ecological cognition hypothesis poses that the brains and behaviours of individuals are largely shaped by the environments in which they live and the associated challenges they must overcome during their lives. Here we examine the effect of environmental complexity on relative brain size in 4 species of intertidal gobies from differing habitats. Two species were rock pool specialists that lived on spatially complex rocky shores, while the remainder lived on dynamic, but structurally simple, sandy shores. We found that rock pool-dwelling species had relatively larger brains and telencephalons in particular, while sand-dwelling species had a larger optic tectum and hypothalamus. In general, it appears that various fish species trade off neural investment in specific brain lobes depending on the environment in which they live. Our previous research suggests that rock pool species have greater spatial learning abilities, enabling them to navigate their spatially complex environment, which may account for their enlarged telencephalon, while sand-dwelling species likely have a reduced need for spatial learning, due to their spatially simple habitat, and a greater need for visual acuity. The dorsal medulla and cerebellum size was unaffected by the habitat in which the fish lived, but there were differences between species indicative of species-specific trade-offs in neural investment. © 2015 S. Karger AG, Basel.
Behavioural flexibility allows an animal to adapt its behaviour in response to changes in the environment. Research conducted in primates, rodents and domestic fowl suggests greater behavioural persistence and reduced behavioural flexibility in males. We investigated sex differences in behavioural flexibility in fish by comparing male and female guppies (Poecilia reticulata) in a reversal learning task. Fish were first trained on a colour discrimination, which was learned equally rapidly by males and females. However, once the reward contingency was reversed, females were better at inhibiting the previous response and reached criterion twice as fast as males. When reward reversing was repeated, males gradually reduced the number of errors, and the two sexes had a comparable performance after four reversals. We suggest that sex differences in behavioural flexibility in guppies can be explained in terms of the different roles that males and females play in reproduction.
It has been widely supported that individual animals express different strategies to cope with environmental challenge. In ectothermic species such as fish, individuals must use behavioral thermoregulation mechanisms to optimize physiological performance. In the present study, thermal preference was tested in groups of wild-type zebrafish, Danio rerio, screened for proactive and reactive animal personalities. Three replicate groups of proactive, reactive, and naive randomly sampled non-screened controls were used for the experiments. The frequency distribution of the animals was recorded in a custom-built multichamber tank under both constant temperature (temperature restricted conditions: T R) and a continuous thermal gradient profile (temperature choice: T Ch ranging from 21°C to 35°C). Proactive and reactive animal personalities expressed significantly different thermal preferences and general activity within the temperature gradient. Our results show that proactive fish, generally characterized as being more aggressive, bold risk takers, and prone to routine formation , have a preference for higher temperature environments. Reactive fish, which are shy, less risk-prone, and more flexible, favor medium colder temperatures. This is the first report of thermopreferendum in zebrafish where individual animal personality coupled to freedom of thermal choice has been applied to understand variation in individual preferences within a population.
In recent years the use of operant conditioning procedures has shown that species as diverse as chimpanzees, honeybees, and mosquitofish can be trained to discriminate between sets containing different numbers of objects. However, to succeed in this task, subjects can use two different strategies: either select the array containing a specific number of items (an absolute numerosity rule), or select the set containing the larger (or smaller) quantity of items (a relative numerosity rule). In the latter case, subjects need not only be able to judge whether two numerosities are equal or different but also be able to order numerosities. Here, in two experiments, we address whether fish can perform both kinds of judgment by training them with specific numerosities and testing their generalization to new numerosity contrasts. In experiment 1, subjects were initially trained to select between visual arrays of 6 and 12 shapes, and were then tested with a contrast pairing the previously trained numerosity (either 6 or 12) with a novel numerosity (respectively, 3 or 24). Spontaneously, subjects selected the novel numerosity, in accordance with a relative numerosity rule. The second experiment tested whether guppies can also learn to select one specific number against all others, if appropriately trained. Fish trained to select an array of 4 shapes against several alternatives (4 vs. 1, 4 vs. 2, 4 vs. 8, 4 vs. 10) learned to recognize the number four against all alternatives and proved able to generalize their discrimination to novel, more difficult contrasts (4 vs. 3 and 4 vs. 6 items). In summary, although guppies preferentially opt for relative comparisons, they can flexibly learn either relative or absolute decision criteria on numerosity stimuli, depending on the context.
Dominance hierarchies are ubiquitous in social species. Social status is established initially through physical conflict between individuals and then communicated directly by a variety of signals. Social interactions depend critically on the relative social status of those interacting. But how do individuals acquire the information they need to modulate their behaviour and how do they use that information to decide what to do? What brain mechanisms might underlie such animal cognition? Using a particularly suitable fish model system that depends on complex social interactions, we report how the social context of behaviour shapes the brain and, in turn, alters the behaviour of animals as they interact. Animals observe social interactions carefully to gather information vicariously that then guides their future behaviour. Social opportunities produce rapid changes in gene expression in key nuclei in the brain and these genomic responses may prepare the individual to modify its behaviour to move into a different social niche. Both social success and failure produce changes in neuronal cell size and connectivity in key nuclei. Understanding mechanisms through which social information is transduced into cellular and molecular changes will provide a deeper understanding of the brain systems responsible for animal cognition.
In this quick guide, Gordon Burghardt considers the criteria for ascribing a particular animal behavior as "play", and in particular the evidence for play in fishes, frogs and reptiles.
Copyright © 2015 Elsevier Ltd. All rights reserved.
Whether play occurs in fishes has long been a contentious issue, but recent observations document that social, object, and locomotor play can all be found in some species of teleosts. However, quantitative studies and those documenting individual differences are rare. We recorded hundreds of occurrences of an unusual behavior in three male Tropheus duboisi. The target behavior of attacking and deflecting an object that rapidly returned to its upright position not only fit the criteria for play behavior, but differed quantitatively and qualitatively among the individuals. This behavior has not been observed in other species of cichlids and other kinds of fishes. The presence or absence of food or other fish either within the aquarium or visible in an adjacent aquarium had no marked or consistent effect on the occurrence of the behavior. Various explanations for the origin and function of the behavior are discussed.
Variation in the structural complexity of a habitat is known to have significant affects on the evolution of different populations
and can shape behavior, morphology, and life-history traits. Here, we investigated whether habitat complexity influences a
species’ capacity for spatial learning and cue choice by comparing the performance of 4 goby species from 2 contrasting habitats
in a spatial task. Gobies were collected from dynamic, homogenous sandy shores and stable, spatially complex rock pool habitats.
We trained fish to use a T-maze to find a hidden reward and asked whether they used local visual landmarks or body-centered
methods for orientation (i.e. turn direction) to do so. It was expected that fish from rock pools would learn the spatial
task much faster and use different orientation cues than fish from sandy shores. We found that rock pool species learnt the
location of the reward arm much faster, made fewer errors and used both types of cues available (visual landmarks and turn
direction) to locate the reward, whereas sand species relied on turn direction significantly more than plant landmarks to
orientate. The results of this study provide support for the hypothesis that the spatial complexity of habitats in marine
environments has a significant effect on the evolution of fish cognition.
For the majority of animals, the ability to orient in
familiar locations is a fundamental part of life, and spatial
memory allows individuals to remember key locations such as
food patches, shelter, mating sites or areas regularly occupied
by predators. This study determined if gobies collected from
rocky platforms and sandy beaches differ in their ability to
learn and memorise the locations of tide pools in a simulated
rocky intertidal zone. Intertidal rock pool gobies show acute
homing abilities and, therefore, should be expected to display
superior learning and memory capabilities. In contrast, it is
unlikely that natural selection would favour similar learning
skills in sandy shore fishes because they simply shift back and
forth with the tides. The learning abilities of gobies were
tested using small replica rock platforms, containing four tide
pools that retained varying depths of water at simulated low
tide. Gobies were categorised as having learnt the task if they
were able to consistently locate the tide pool that retained the
most water at simulated low tide as the pool with the most
favourable conditions. Rock pool species were able to locate
the deepest pool to wait out low tide for ~95 % of the trials,
while species from sandy shores were found in the deepest
pool ~10 % of trials. Despite repeated stranding, sandy shore
fish continued to follow the tide out. We propose that rock
pool species memorised the location of rock pools during
simulated high tide enabling them to relocate the best refuge
for low tide.
Fish are one of the most highly utilised vertebrate taxa by humans; they are harvested from wild stocks as part of global fishing industries, grown under intensive aquaculture conditions, are the most common pet and are widely used for scientific research. But fish are seldom afforded the same level of compassion or welfare as warm-blooded vertebrates. Part of the problem is the large gap between people's perception of fish intelligence and the scientific reality. This is an important issue because public perception guides government policy. The perception of an animal's intelligence often drives our decision whether or not to include them in our moral circle. From a welfare perspective, most researchers would suggest that if an animal is sentient, then it can most likely suffer and should therefore be offered some form of formal protection. There has been a debate about fish welfare for decades which centres on the question of whether they are sentient or conscious. The implications for affording the same level of protection to fish as other vertebrates are great, not least because of fishing-related industries. Here, I review the current state of knowledge of fish cognition starting with their sensory perception and moving on to cognition. The review reveals that fish perception and cognitive abilities often match or exceed other vertebrates. A review of the evidence for pain perception strongly suggests that fish experience pain in a manner similar to the rest of the vertebrates. Although scientists cannot provide a definitive answer on the level of consciousness for any non-human vertebrate, the extensive evidence of fish behavioural and cognitive sophistication and pain perception suggests that best practice would be to lend fish the same level of protection as any other vertebrate.
Over a decade of comparative studies, researchers have found that
rudimentary numerical abilities are widespread among vertebrates.
While experiments in mammals and birds have employed a variety
of stimuli (visual, auditory and tactile), all fish studies involved visual
stimuli and it is unknown whether fish can process numbers in other
sensory modalities. To fill this gap, we studied numerical abilities in
Phreatichthys andruzzii, a blind cave-dwelling species that evolved
in the phreatic layer of the Somalia desert. Fish were trained to
receive a food reward to discriminate between two groups of objects
placed in opposite positions of their home tank. In Experiment 1,
subjects learned to discriminate between two and six objects, with
stimuli not controlled for non-numerical continuous variables that covary
with numbers, such as total area occupied by stimuli or density.
In Experiment 2, the discrimination was two versus four, with half of
the stimuli controlled for continuous quantities and half not controlled
for continuous quantities. The subjects discriminated only the latter
condition, indicating that they spontaneously used non-numerical
information, as other vertebrates tested in similar experiments. In
Experiments 3 and 4, cavefish trained from the beginning only with
stimuli controlled for continuous quantities proved able to learn the
discrimination of quantities based on the sole numerical information.
However, their numerical acuity was lower than that reported in other
teleost fish tested with visual stimuli.
Brain evolution has often been correlated with the cognitive demands of social life. Further progress depends on our ability to link cognitive processes to corresponding brain part sizes and structures, and, ultimately, to demonstrate causality. Recent research suggests that fishes are suitable to test general hypotheses about vertebrate social cognition and its evolution: brain structure and physiology are rather conserved among vertebrates, and fish are able to perform complex decisions in social context. Here, we outline the opportunities for experimentation and comparative studies using fish as model systems, as well as some current shortcomings in fish social cognition research.
It has been known for more than a century that interacting people can generally achieve more accurate decisions than single individuals. Here we show that interacting guppy fish (Poecilia reticulata) achieve a superior level of numerosity discrimination well beyond the average ability of the isolated individual fish. This enhancement of numerical acuity was observed in dyadic interactions when (Experiment 1) the dyad chose which larger shoal of guppies to join and when (Experiment 2) the dyad chose the higher or the lower numerosity among two decision options after having learned the task individually. Dyadic accuracy and that of the more competent member of each dyad matched closely, supporting the hypothesis that meritocratic leadership arises spontaneously between dyadically interacting fish, rather than the 'many wrongs' principle that has been used to explain group superiority in many species.
Grouping behaviour is widespread in animals. One important reason for grouping is the reduction of individual predation risk; the larger a group, the greater the protection for the individual. Fishes, in particular, have become a model taxon in experimental research to study proximate and ultimate causes of grouping. Accordingly, numerous studies have so far demonstrated that fishes prefer to shoal with larger groups. Thus far these studies have usually examined small groups, with up to 20 individuals. However, in nature groups are often much bigger (up to several hundreds of individuals), and theory predicts that benefits, for example due to dilution effects, decline exponentially with increasing group size. Furthermore, discrimination might be absent because of limited cognitive ability. Thus, it is essential to test whether the findings from small groups also apply to large groups. Here, we examined group size preferences in the three-spined stickleback, Gasterosteus aculeatus, a small fish that forms large shoals in nature. In five experiments, subadult sticklebacks were given the choice between two shoals differing in group size (numerical contrasts: 15 versus 60, 20 versus 60, 30 versus 60, 40 versus 60 and 50 versus 60). Test fish on average preferred the larger group; this preference was stronger in the beginning of the respective trial and decreased over time. Moreover, preferences for the larger shoal decreased with decreasing group size differences, implying context-dependent preferences. We found significant discrimination up to numerical contrasts of 40:60. Our results are in accordance with the findings of shoal size discrimination in small groups and with optimality hypotheses, but might also reflect the impact of cognitive constraints.
The acquisition of information such as the location and quality of food, mates or shelter is a key survival
requirement for animals. Individuals can acquire information through personal experience (private information)
or through observing and interacting with others (social information). Environmental spatial
and temporal heterogeneity can mean that sometimes social information conflicts with private knowledge.
We tested how personality affected the importance placed on public versus private information in
wild female guppies when these two information sources came into conflict.We found that boldness and
sociality affected decisions to use conflicting social and private information. Bolder females used social
information to avoid competition and/or potential patch depletion, whereas highly social individuals
preferred the presence of conspecifics over rich foraging opportunities. There was no evidence of a speed
eaccuracy trade-off in a spatial associative learning task; rather, bold female guppies learned both more
quickly and more accurately than shy females. We found no evidence of a behavioural syndrome between
boldness and sociality which is consistent with previous studies on this population.
The theory of ecological cognition poses that the brains and behaviour of animals are shaped by the environmental challenges they face in their everyday lives. Site fidelity and homing ability was tested for five species of intertidal rock pool fish by tagging and displacing them to new rock pools at various distances from their ‘home’ rock pools. Three of the species were rock pool specialists whilst the remaining two spend a small proportion of their life in rock pools during early ontogeny. The three specialists showed strong site fidelity with >50 % of individuals found in the same pool 42 days after tagging. In contrast, the non-specialist species showed low fidelity and poor homing abilities. Homing success in the rock pool specialists remained relatively stable as displacement distance increased. The effect of body size on homing ability was species dependent, with only one species showing a significantly greater tendency to home with increasing size.
The numerosity of any set of discrete elements can be depicted by a genuinely abstract number representation, irrespective of whether they are presented in the visual or auditory modality. The accumulator model predicts that no cost should apply for comparing numerosities within and across modalities. However, in behavioral studies, some inconsistencies have been apparent in the performance of number comparisons among different modalities. In this study, we tested whether and how numerical comparisons of visual, auditory, and cross-modal presentations would differ under adequate control of stimulus presentation. We measured the Weber fractions and points of subjective equality of numerical discrimination in visual, auditory, and cross-modal conditions. The results demonstrated differences between the performances in visual and auditory conditions, such that numerical discrimination of an auditory sequence was more precise than that of a visual sequence. The performance of cross-modal trials lay between performance levels in the visual and auditory conditions. Moreover, the number of visual stimuli was overestimated as compared to that of auditory stimuli. Our findings imply that the process of approximate numerical representation is complex and involves multiple stages, including accumulation and decision processes.
There is controversy in comparative psychology about whether on the one hand non-symbolic number estimation of small (≤4) and large numbers involves a single mechanism (an approximate number system), or whether on the other hand enumeration of the numbers 1-4 is accomplished by a separate mechanism, an object tracking system. To date, support for the latter hypothesis has come only from the different ratio-dependency of performance seen in the two numerical ranges, a reading that has been criticized on several grounds. In humans, the two-system hypothesis is supported by evidence showing that manipulation of the physical properties of the stimuli (e.g., the motion of the items) has dissimilar effects on small- and large-number discrimination. In this research, we studied this effect on guppies. Initially, fish were trained to simultaneously discriminate two numerical contrasts having the same easy ratio (0.50): one in the small-number (2 vs. 4) range and one in the large-number (6 vs. 12) range. Half of the fish were presented with moving items; the other half were shown the same stimuli without motion. Fish were then subjected to non-reinforced probe trials in the presence of a more difficult ratio (0.75: 3 vs. 4 and 9 vs. 12). Under both static and moving conditions, the fish significantly discriminated 6 versus 12, but not 9 versus 12 items. As regards small numbers, both groups learned to discriminate a 0.50 ratio, but only fish tested with moving stimuli also discriminated 3 and 4 items. This differential effect suggests that fish may possess two separate systems for small- and large-number discrimination.
We review studies claiming that fish feel pain and find deficiencies in the methods used for pain identification, particularly for distinguishing unconscious detection of injurious stimuli (nociception) from conscious pain. Results were also frequently mis-interpreted and not replicable, so claims that fish feel pain remain unsubstantiated. Comparable problems exist in studies of invertebrates. In contrast, an extensive litera-ture involving surgeries with fishes shows normal feeding and activity immediately or soon after surgery. C fiber nociceptors, the most prevalent type in mammals and responsible for excruciating pain in humans, are rare in teleosts and absent in elas-mobranchs studied to date. A-delta nociceptors, not yet found in elasmobranchs, but relatively common in teleosts, likely serve rapid, less noxious injury signaling, trigger-ing escape and avoidance responses. Clearly, fishes have survived well without the full range of nociception typical of humans or other mammals, a circumstance according well with the absence of the specialized cortical regions necessary for pain in humans. We evaluate recent claims for consciousness in fishes, but find these claims lack adequate supporting evidence, neurological feasibility, or the likelihood that consciousness would be adaptive. Even if fishes were conscious, it is unwar-ranted to assume that they possess a human-like capacity for pain. Overall, the behavioral and neurobiological evidence reviewed shows fish responses to nociceptive stimuli are limited and fishes are unlikely to experience pain.
For a diversity of species, differences in sexual and parental roles, along with differences in body morphology, often result in males and females having different diets, distinct predators and even different patterns of habitat use. As a consequence, the two sexes often face different environmental challenges and selection may favour the evolution of sex differences in cognition. We tested this prediction in the guppy (Poecilia reticulata). Under perceived hazard, individual guppies join the larger available social group, a behaviour that is thought to minimise predation risk. In this species, females are more frequently exposed to predation and more averse to predation risk; we therefore expected greater accuracy in shoal size discrimination in females. We compared the accuracy of male and female guppies in discriminating shoals of 4 and 6 conspecifics, which represents the upper limit of discrimination for this species. Overall, we found no sex differences in the accuracy of discriminating the two shoals. However, while females showed this ability at the beginning of the test, males began to select the larger group only after several minutes. In three control experiments, we found indications that this sex difference cannot be accounted for by differences in motivation or antipredator strategies between the two sexes, suggesting female guppies are more efficient at rapidly estimating shoal size.
The ability to discriminate between different quantities has important ecological relevance for animals when engaging in behaviours such as forming groups, foraging or trying to avoid predators. Quantity discrimination has been shown in a diversity of human and nonhuman animal species. In angelfish this discrimination ability has been investigated using dichotomous choice tests when the numerically different stimulus groups (shoals) of conspecifics were fully visible to the test fish. Here, using a new procedure we investigated whether test fish were able to discriminate between the contrasting shoals using their memory. After a period of full visual access to the contrasted shoals on the two sides of their test tank, the test fish was required to make a choice while being able to see only a single member of the stimulus shoals on each side. With this cognitively more demanding procedure we tested discrimination between numerically large shoals (≥ four fish per stimulus shoal). As in our previous studies, we found that angelfish consistently chose the larger of the two shoals when the shoals differed by a 2:1 or higher ratio, but not those that differed by a 3:2 or 4:3 ratio. The results followed Weber's law in that performance became poorer as the ratio between the two stimulus shoals approached one. In addition, when we kept the absolute difference between the contrasted shoals constant, discrimination was less accurate as the shoal sizes increased. This pattern of results lends support for the analogue magnitude representational system in the angelfish, a nonverbal approximation system believed to be employed by a diversity of human and nonhuman animal species. Furthermore, our results also demonstrate that angelfish remember the different shoals presented to them, i.e. they make their choice based upon mental representation of the different quantities.
Recent developments in the study of pain in animals have demonstrated the potential for pain perception in a variety of wholly aquatic species such as molluscs, crustaceans and fish. This allows us to gain insight into how the ecological pressures and differential life history of living in a watery medium can yield novel data that inform the comparative physiology and evolution of pain. Nociception is the simple detection of potentially painful stimuli usually accompanied by a reflex withdrawal response, and nociceptors have been found in aquatic invertebrates such as the sea slug Aplysia. It would seem adaptive to have a warning system that allows animals to avoid lifethreatening injury, yet debate does still continue over the capacity for non-mammalian species to experience the discomfort or suffering that is a key component of pain rather than a nociceptive reflex. Contemporary studies over the last 10 years have demonstrated that bony fish possess nociceptors that are similar to those in mammals; that they demonstrate pain-related changes in physiology and behaviour that are reduced by painkillers; that they exhibit higher brain activity when painfully stimulated; and that pain is more important than showing fear or anti-predator behaviour in bony fish. The neurophysiological basis of nociception or pain in fish is demonstrably similar to that in mammals. Pain perception in invertebrates is more controversial as they lack the vertebrate brain, yet recent research evidence confirms that there are behavioural changes in response to potentially painful events. This review will assess the field of pain perception in aquatic species, focusing on fish and selected invertebrate groups to interpret how research findings can inform our understanding of the physiology and evolution of pain. Further, if we accept these animals may be capable of experiencing the negative experience of pain, then the wider implications of human use of these animals should be considered.
Quantitative ability in non-human animals represents one of the topics most investigated in cognitive ethology during the last decade. Vertebrates as diverse as mammals, birds, and fish proved able to discriminate between two quantities in several ecological contexts. Recently, there has been a wide debate as to whether non-human animals share a single mechanism of numerical representation (commonly referred to as the “approximate number system”, ANS) or instead have also a distinct mechanism for enumerating small numbers (≤ 4), referred to as “subitizing”. To date, little attention has been devoted to assess whether individual differences exist in quantity abilities within the boundaries of the two supposed mechanisms.
In the present study, we compared the performance of guppies (Poecilia reticulata) in small- and large-quantity discrimination. Subjects were inserted in an unfamiliar tank where two groups of conspecifics differing in numerosity were visible, and their spontaneous preference of joining the larger shoal was taken as a measure of their numerical acuity. Each subject was tested in two numerical contrasts: 2 vs 3 and 6 vs 10. A positive correlation in the performance in the two numerical contrasts was found: subjects showing a better performance in the subitizing range also showed a better performance in the ANS range. Our data do not contradict the hypothesis of two distinct mechanisms of numerical representation but may be more parsimoniously explained by the existence of a single ANS mechanism across the whole numerical range.
Standard approaches to study the evolution and stability of helping either investigate how life history features like longevity and migration may yield conditions that select for rather unconditional helping or how specific game structures yield conditional helping strategies. Although the latter approach is more apt at explaining variable behavior within and between individuals, applicability seems limited due to strong compartmentalization of situations. Instead, recent evidence suggests that individuals are primarily under selection to display general social competence, that is, the ability to choose among the full range of available social behaviors the one that is appropriate to maximize fitness within the constraints of given circumstances. This view shifts the emphasis to general decision rules and the evolution of developmental mechanisms.
The capacity for specialization and radiation make fish an excellent group in which to investigate the depth and variety of animal cognition. Even though early observations of fish using tools predates the discovery of tool use in chimpanzees, fish cognition has historically been somewhat overlooked. However, a recent surge of interest is now providing a wealth of material on which to draw examples, and this has required a selective approach to choosing the research described below. Our goal is to illustrate the necessity for basing cognitive investigations on the ecological and evolutionary context of the species at hand. We also seek to illustrate the importance of ecology and the environment in honing a range of sensory systems that allow fish to glean information and support informed decision-making. The various environments and challenges with which fish interact require equally varied cognitive skills, and the solutions that fish have developed are truly impressive. Similarly, we illustrate how common ecological problems will frequently produce common cognitive solutions. Below, we focus on four topics: spatial learning and memory, avoiding predators and catching prey, communication, and innovation. These are used to illustrate how both simple and sophisticated cognitive processes underpin much of the adaptive behavioral flexibility exhibited throughout fish phylogeny. Never before has the field had such a wide array of interdisciplinary techniques available to access both cognitive and mechanistic processes underpinning fish behavior. This capacity comes at a critical time to predict and manage fish populations in an era of unprecedented global change. WIREs Cogn Sci 2015, 6:159-176. doi: 10.1002/wcs.1337 For further resources related to this article, please visit the WIREs website.
The authors have declared no conflicts of interest for this article.
© 2015 John Wiley & Sons, Ltd.
The central nervous system, and the brain in particular, is one of the most remarkable products of evolution. This system allows an individual to acquire, process, store and act on information gathered from the environment. The resulting flexibility in behavior beyond genetically coded strategies is a prime adaptation in animals. The field of animal cognition examines the underlying processes and mechanisms. Fishes are a particularly interesting group of vertebrates to study cognition for two reasons (Figure 1). First, they occupy a key position in the vertebrate phylogenetic tree: the common ancestor of the tetrapods was a bony fish. Thus, all vertebrates share key genetic features that code for the body structure, including the vertebrate brain. Similarities in brain structure and function are hence likely to be due to common ancestry. A second reason to study fish cognition is that fish have had their own independent evolution/radiation since they split from tetrapods. Bony fishes are by far the most species-rich vertebrate group. As a consequence, they provide the best options for a comparative approach that aims to link the evolution of cognition to a species’ ecology. Therefore, the study of fishes may reveal general principles of ecological effects on cognitive abilities in vertebrates.
The way animals move through space is likely to affect the way they learn and remember spatial information. For example, a pelagic fish, Astyanax fasciatus, moves freely in vertical and horizontal space and encodes information from both dimensions with similar accuracy. Benthic fish can also move with six degrees of freedom, but spend much of their time travelling over the substrate; hence they might be expected to prioritise the horizontal dimension. To understand how benthic fish encode and deploy three-dimensional spatial information we used a fully rotational Y-maze to test whether Corydoras aeneus (i) encode space as an integrated three-dimensional unit or as separate elements, by testing whether they can decompose a three-dimensional trajectory into its vertical and horizontal components, and (ii) whether they prioritise vertical or horizontal information when the two conflict. In contradiction to the expectation generated by our hypothesis, our results suggest that C. aeneus are better at extracting vertical information than horizontal information from a three-dimensional trajectory, suggesting that the vertical axis is learned and remembered robustly. Our results also showed that the fish prioritise vertical information when it conflicts with horizontal information. From these results, we infer that benthic fish attend preferentially to a cue unique to the vertical axis, and we suggest that this cue is hydrostatic pressure.
Recent empirical research, mostly done on humans, recognizes that individuals' physiological state affects levels of cooperation. An individual's internal state may affect the payoffs of behavioural alternatives, which in turn could influence the decision to either cooperate or to defect. However, little is known about the physiol