Welfare Challenges Influence the Complexity of Movement: Fractal Analysis of Behaviour in Zebrafish

Toxicity evaluation of neonicotinoids to earthworm (Eisenia fetida) behaviors by a novel locomotion tracking assay

Pesticides are substances used for controlling, preventing, and repelling pests in agriculture. Among them, neonicotinoids have become the fastest-growing class of insecticides because of their efficiency in targeting pests. They work by strongly binding to nicotinic acetylcholine receptors (nAChRs) in the central nervous system of insects, leading to receptor blockage, paralysis, and death. Despite their selectivity for insects, these substances may be hazardous to non-target creatures, including earthworms. Although earthworms may be invasive in some regions like north America, they contribute to the development of soil structure, water management, nutrient cycling, pollution remediation, and cultural services, positively impacting the environment, particularly in the soil ecosystem. Thus, this study aimed to develop a novel earthworm behavior assay since behavior is a sensitive marker for toxicity assay, and demonstrated its application in evaluating the toxicity of various neonicotinoids. Here, we exposed Eisenia fetida to 1 and 10 ppb of eight neonicotinoids (acetamiprid, clothianidin, dinotefuran, imidacloprid, nitenpyram pestanal, thiacloprid, thiametoxam, and sulfoxaflor) for 3 days to observe their behavior toxicities. Overall, all of the neonicotinoids decreased their locomotion, showed by a reduction of average speed by 24.94-68.63% and increment in freezing time movement ratio by 1.51-4.25 times, and altered their movement orientation and complexity, indicated by the decrement in the fractal dimension value by 24-70%. Moreover, some of the neonicotinoids, which were acetamiprid, dinotefuran, imidacloprid, nitenpyram, and sulfoxaflor, could even alter their exploratory behaviors, which was shown by the increment in the time spent in the center area value by 6.94-12.99 times. Furthermore, based on the PCA and heatmap clustering results, thiametoxam was found as the neonicotinoid that possessed the least pronounced behavior toxicity effects among the tested pesticides since these neonicotinoid-treated groups in both concentrations were grouped in the same major cluster with the control group. Finally, molecular docking was also conducted to examine neonicotinoids' possible binding mechanism to Acetylcholine Binding Protein (AChBP), which is responsible for neurotransmission. The molecular docking result confirmed that each of the neonicotinoids has a relatively high binding energy with AChBP, with the lowest binding energy was possessed by thiametoxam, which consistent with its relatively low behavior toxicities. Thus, these molecular docking results might hint at the possible mechanism behind the observed behavior alterations. To sum up, the present study demonstrated that all of the neonicotinoids altered the earthworm behaviors which might be due to their ability to bind with some specific neurotransmitters and the current findings give insights into the toxicities of neonicotinoids to the environment, especially animals in a soil ecosystem.

Pain management in zebrafish : Report from a FELASA Working Group

Empirical evidence suggests fishes meet the criteria for experiencing pain beyond a reasonable doubt and zebrafish are being increasingly used in studies of pain and nociception. Zebrafish are adopted across a wide range of experimental fields and their use is growing particularly in biomedical studies. Many laboratory procedures in zebrafish involve tissue damage and this may give rise to pain. Therefore, this FELASA Working Group reviewed the evidence for pain in zebrafish, the indicators used to assess pain and the impact of a range of drugs with pain-relieving properties. We report that there are several behavioural indicators that can be used to determine pain, including reduced activity, space use and distance travelled. Pain-relieving drugs prevent these responses, and we highlight the dose and administration route. To minimise or avoid pain, several refinements are suggested for common laboratory procedures. Finally, practical suggestions are made for the management and alleviation of pain in laboratory zebrafish, including recommendations for analgesia. Pain management is an important refinement in experimental animal use and so our report has the potential to improve zebrafish welfare during and after invasive procedures in laboratories across the globe.

A comprehensive painkillers screening by assessing zebrafish behaviors after caudal fin amputation

Recently, the usage of zebrafish for pain studies has increased in the past years, especially due to its robust pain-stimulated behaviors. Fin amputation has been demonstrated to induce a noxious response in zebrafish. However, based on the prior study, although lidocaine, the most used painkiller in zebrafish, has been shown to ameliorate amputated zebrafish behaviors, it still causes some prolonged effects. Therefore, alternative painkillers are always needed to improve the treatment quality of fin-amputated zebrafish. Here, the effects of several analgesics in recovering zebrafish behaviors post-fin amputation were evaluated. From the results, five painkillers were found to have potentially beneficial effects on amputated fish behaviors. Overall, these results aligned with their binding energy level to target proteins of COX-1 and COX-2. Later, based on their sub-chronic effects on zebrafish survivability, indomethacin, and diclofenac were further studied. This combination showed a prominent effect in recovering zebrafish behaviors when administered orally or through waterborne exposure, even with lower concentrations. Next, based on the ELISA in zebrafish brain tissue, although some changes were found in the treated group, no statistical differences were observed in most of the tested biomarkers. However, since heatmap clustering showed a similar pattern between biochemical and behavior endpoints, the minor changes in each biomarker may be sufficient in changing the fish behaviors.

How Free Swimming Fosters the Locomotion of a Purely Oscillating Fish-like Body

The recoil motions in free swimming, given by lateral and angular rigid motions due to the interaction with the surrounding water, are of great importance for a correct evaluation of both the forward locomotion speed and efficiency of a fish-like body. Their contribution is essential for calculating the actual movements of the body rear end whose prominent influence on the generation of the proper body deformation was established a long time ago. In particular, the recoil motions are found here to promote a dramatic improvement of the performance when damaged fishes, namely for a partial functionality of the tail or even for its complete loss, are considered. In fact, the body deformation, which turns out to become oscillating and symmetric in the extreme case, is shown to recover in the water frame a kind of undulation leading to a certain locomotion speed though at the expense of a large energy consumption. There has been a deep interest in the subject since the infancy of swimming studies, and a revival has recently arisen for biomimetic applications to robotic fish-like bodies. We intend here to apply a theoretical impulse model to the oscillating fish in free swimming as a suitable test case to strengthen our belief in the beneficial effects of the recoil motions. At the same time, we intend to exploit the linearity of the model to detect from the numerical simulations the intrinsic physical reasons related to added mass and vorticity release behind the experimental observations.

Entropy and Fractal Techniques for Monitoring Fish Behaviour and Welfare in Aquacultural Precision Fish Farming-A Review

In a non-linear system, such as a biological system, the change of the output (e.g., behaviour) is not proportional to the change of the input (e.g., exposure to stressors). In addition, biological systems also change over time, i.e., they are dynamic. Non-linear dynamical analyses of biological systems have revealed hidden structures and patterns of behaviour that are not discernible by classical methods. Entropy analyses can quantify their degree of predictability and the directionality of individual interactions, while fractal dimension (FD) analyses can expose patterns of behaviour within apparently random ones. The incorporation of these techniques into the architecture of precision fish farming (PFF) and intelligent aquaculture (IA) is becoming increasingly necessary to understand and predict the evolution of the status of farmed fish. This review summarizes recent works on the application of entropy and FD techniques to selected individual and collective fish behaviours influenced by the number of fish, tagging, pain, preying/feed search, fear/anxiety (and its modulation) and positive emotional contagion (the social contagion of positive emotions). Furthermore, it presents an investigation of collective and individual interactions in shoals, an exposure of the dynamics of inter-individual relationships and hierarchies, and the identification of individuals in groups. While most of the works have been carried out using model species, we believe that they have clear applications in PFF. The review ends by describing some of the major challenges in the field, two of which are, unsurprisingly, the acquisition of high-quality, reliable raw data and the construction of large, reliable databases of non-linear behavioural data for different species and farming conditions.

Pain Recognition in Fish

Empirical evidence has demonstrated that fish experience pain, and so to ensure their good welfare, it is vital that we can recognize and assess pain. A range of general, behavioral, and physiologic indicators can be used when assessing pain in fish. Many of these can be used at the tank side and are termed operational welfare indicators, whereas some require further computer or laboratory analysis. Behavioral indicators are valid and have been shown to profoundly differ between nonpainful and painful treatments in fish. However, these are not universal, and species-specific differences exist in behavioral responses to pain.

Impact of Lidocaine on Pain-Related Grooming in Cuttlefish

Nociception is the neural process of encoding noxious stimuli and is typically accompanied by a reflex withdrawal response away from the potentially injurious stimulus. Studies on nociception in cephalopods have so far focused on octopus and squid, with no investigations to our knowledge on cuttlefish. Yet, these are an important species both in scientific and commercial use. Therefore, the present study demonstrated that a standard pain stimulus, acetic acid, induced grooming behaviour directed towards the injection site in cuttlefish and that the injection of lidocaine reduces grooming behaviours in acetic-acid-injected cuttlefish. Wound-directed behaviour demonstrates that the animal is aware of the damage; thus, when subjecting these animals to any painful treatments in the laboratory, researchers should consider alleviating pain by the administration of pain-relieving drugs.

Evaluation of Locomotion Complexity in Zebrafish after Exposure to Twenty Antibiotics by Fractal Dimension and Entropy Analysis

Antibiotics are extensively used in aquaculture to prevent bacterial infection and the spread of diseases. Some antibiotics have a relatively longer half-life in water and may induce some adverse effects on the targeted fish species. This study analyzed the potential adverse effects of antibiotics in zebrafish at the behavioral level by a phenomic approach. We conducted three-dimensional (3D) locomotion tracking for adult zebrafish after acute exposure to twenty different antibiotics at a concentration of 100 ppb for 10 days. Their locomotor complexity was analyzed and compared by fractal dimension and permutation entropy analysis. The dimensionality reduction method was performed by combining the data gathered from behavioral endpoints alteration. Principal component and hierarchical analysis conclude that three antibiotics: amoxicillin, trimethoprim, and tylosin, displayed unique characteristics. The effects of these three antibiotics at lower concentrations (1 and 10 ppb) were observed in a follow-up study. Based on the results, these antibiotics can trigger several behavioral alterations in adult zebrafish, even in low doses. Significant changes in locomotor behavioral activity, such as total distance activity, average speed, rapid movement time, angular velocity, time in top/bottom duration, and meandering movement are highly related to neurological motor impairments, anxiety levels, and stress responses were observed. This study provides evidence based on an in vivo experiment to support the idea that the usage of some antibiotics should be carefully addressed since they can induce a significant effect of behavioral alterations in fish.

Acute and Chronic Effects of Fin Amputation on Behavior Performance of Adult Zebrafish in 3D Locomotion Test Assessed with Fractal Dimension and Entropy Analyses and Their Relationship to Fin Regeneration

Simple Summary

Fin amputation is a routinely conducted procedure for various experiments, especially in zebrafish. However, no study compares the acute and chronic effects of the amputation of each fin on their behaviors. In addition, although some analgesics have been applied after the fin amputation procedure, the long-term effects of these drugs in have not been evaluated yet. In this study, we found that amputation in the caudal fin resulted in the most pronounced behavior alterations and their behavior was fully recovered before the caudal fin was fully regenerated, indicating that these behavioral changes came from pain elicited from the fin amputation. Finally, while lidocaine treatment could ameliorate the behavioral effects after the amputation procedure, it did not accelerate the behavior recovery process; instead, it caused the fish to display some slight side effects.

Abstract

The fin is known to play an important role in swimming for many adult fish, including zebrafish. Zebrafish fins consist of paired pectoral and pelvic with unpaired dorsal, anal, and caudal tail fins with specific functions in fish locomotion. However, there was no study comparing the behavior effects caused by the absence of each fin. We amputated each fin of zebrafish and evaluated their behavior performance in the 3D locomotion test using fractal dimension and entropy analyses. Afterward, the behavior recovery after the tail fin amputation was also evaluated, together with the fin regeneration process to study their relationship. Finally, we conducted a further study to confirm whether the observed behavior alterations were from pain elicited by fin amputation procedure or not by using lidocaine, a pain-relieving drug. Amputation in the caudal fin resulted in the most pronounced behavior alterations, especially in their movement complexity. Furthermore, we also found that their behavior was fully recovered before the caudal fin was fully regenerated, indicating that these behavioral changes were not majorly due to a mechanical change in tail length; instead, they may come from pain elicited from the fin amputation, since treatment with lidocaine could ameliorate the behavioral effects after the amputation procedure. However, lidocaine did not accelerate the behavior recovery process; instead, it caused the fishes to display some slight side effects. This study highlights the potential moderate severity of fin amputation in zebrafish and the importance of analgesia usage. However, side effects may occur and need to be considered since fin amputation is routinely conducted for various research, especially genomic screening.

Automated analysis of activity, sleep, and rhythmic behaviour in various animal species with the Rtivity software

Behavioural studies provide insights into normal and disrupted biological mechanisms. In many research areas, a growing spectrum of animal models—particularly small organisms—is used for high-throughput studies with infrared-based activity monitors, generating counts per time data. The freely available software to analyse such data, however, are primarily optimized for drosophila and circadian analysis. Researchers investigating other species or non-circadian behaviour would thus benefit from a more versatile software. Here we report the development of a free and open-source software—Rtivity—allowing customisation of species-specific parameters, and offering a versatile analysis of behavioural patterns, biological rhythms, stimulus responses, and survival. Rtivity is based on the R language and uses Shiny and the recently developed Rethomics package for a user-friendly graphical interface without requiring coding skills. Rtivity automatically assesses survival, computes various activity, sleep, and rhythmicity parameters, and performs fractal analysis of activity fluctuations. Rtivity generates multiple informative graphs, and exports structured data for efficient interoperability with common statistical software. In summary, Rtivity facilitates and enhances the versatility of the behavioural analysis of diverse animal species (e.g. drosophila, zebrafish, daphnia, ants). It is thus suitable for a broad range of researchers from multidisciplinary fields such as ecology, neurobiology, toxicology, and pharmacology.

Data Driven Insight Into Fish Behaviour and Their Use for Precision Aquaculture

Aquaculture, or the farmed production of fish and shellfish, has grown rapidly, from supplying just 7% of fish for human consumption in 1974 to more than half in 2016. This rapid expansion has led to the growth of Precision Aquaculture concept that aims to exploit data-driven management of fish production, thereby improving the farmer's ability to monitor, control, and document biological processes in farms. Fundamental to this paradigm is monitoring of environmental and animal processes within a cage, and processing those data toward farm insight using models and analytics. This paper presents an analysis of environmental and fish behaviour datasets collected at three salmon farms in Norway, Scotland, and Canada. Information on fish behaviour were collected using hydroacoustic sensors that sampled the vertical distribution of fish in a cage at high spatial and temporal resolution, while a network of environmental sensors characterised local site conditions. We present an analysis of the hydroacoustic datasets using AutoML (or automatic machine learning) tools that enables developers with limited data science expertise to train high-quality models specific to the data at hand. We demonstrate how AutoML pipelines can be readily applied to aquaculture datasets to interrogate the data and quantify the primary features that explains data variance. Results demonstrate that variables such as temperature, wind conditions, and hour-of-day were important drivers of fish motion at all sites. Further, there were distinct differences in factors that influenced in-cage variations driven by local variables such as water depth and ambient environmental conditions (particularly dissolved oxygen). The framework offers a transferable approach to interrogate fish behaviour within farm systems, and quantify differences between sites.

Identification of Individual Zebrafish (Danio rerio): A Refined Protocol for VIE Tagging Whilst Considering Animal Welfare and the Principles of the 3Rs

In aquatic ecology, studies have commonly employed a tagging technique known as visible implant elastomer (VIE). This method has not been widely adopted by the zebrafish research community and also lacks refinement with regard to animal welfare. The current paper introduces a new VIE tagging protocol, with the aim of improving existing tagging techniques by placing particular emphasis on the Three Rs. To improve animal welfare and fish survival, we added the use of an analgesic compound (lidocaine) through the marking procedure, followed by after-treatment with antiseptics (melaleuca, aloe vera, and PVP-I as active ingredients) to improve tissue regeneration and healing. The newly improved protocol has been quantitatively evaluated on different populations and age groups of zebrafish. This study will be useful to the scientific zebrafish community and to the wider field including biologist and aquarists, especially in consideration of animal welfare, where tagging techniques are considered as a potential noxious stimulus for fish.

Auditory environmental enrichment prevents anxiety-like behavior, but not cortisol responses, evoked by 24-h social isolation in zebrafish

The zebrafish (Danio rerio) is widely used as a promising translational model organism for studying various brain disorders. Zebrafish are also commonly used in behavioral and drug screening assays utilizing individually tested (socially isolated) fish. Various sounds represent important exogenous factors that may affect fish behavior. Mounting evidence shows that musical/auditory environmental enrichment can improve welfare of laboratory animals, including fishes. Here, we show that auditory environmental enrichment mitigates anxiogenic-like effects caused by acute 24-h social isolation in adult zebrafish. Thus, auditory environmental enrichment may offer an inexpensive, feasible and simple tool to improve welfare of zebrafish stocks in laboratory facilities, reduce unwanted procedural stress, lower non-specific behavioral variance and, hence, collectively improve zebrafish data reliability and reproducibility.

Skin swabbing is a refined technique to collect DNA from model fish species

Model fish species such as sticklebacks and zebrafish are frequently used in studies that require DNA to be collected from live animals. This is typically achieved by fin clipping, a procedure that is simple and reliable to perform but that can harm fish. An alternative procedure to sample DNA involves swabbing the skin to collect mucus and epithelial cells. Although swabbing appears to be less invasive than fin clipping, it still requires fish to be netted, held in air and handled—procedures that can cause stress. In this study we combine behavioural and physiological analyses to investigate changes in gene expression, behaviour and welfare after fin clipping and swabbing. Swabbing led to a smaller change in cortisol release and behaviour on the first day of analysis compared to fin clipping. It also led to less variability in data suggesting that fewer animals need to be measured after using this technique. However, swabbing triggered some longer term changes in zebrafish behaviour suggesting a delayed response to sample collection. Skin swabbing does not require the use of anaesthetics and triggers fewer changes in behaviour and physiology than fin clipping. It is therefore a more refined technique for DNA collection with the potential to improve fish health and welfare.

Antinociceptive activity of 3β-6β-16β-trihydroxylup-20 (29)-ene triterpene isolated from Combretum leprosum leaves in adult zebrafish (Danio rerio)

Drugs used to treat pain are associated with adverse effects, increasing the search for new drugs as an alternative treatment for pain. Therefore, we evaluated the antinociceptive behavior and possible neuromodulation mechanisms of triterpene 3β, 6β, 16β-trihydroxylup-20(29)-ene (CLF-1) isolated from Combretum leprosum leaves in zebrafish. Zebrafish (n = 6/group) were pretreated with CLF-1 (0.1 or 0.3 or 1.0 mg/mL; i.p.) and underwent nociception behavior tests. The antinociceptive effect of CFL-1 was tested for modulation by opioid (naloxone), nitrergic (L-NAME), nitric oxide and guanylate cyclase synthesis inhibitor (methylene blue), NMDA (Ketamine), TRPV1 (ruthenium red), TRPA1 (camphor), or ASIC (amiloride) antagonists. The corneal antinociceptive effect of CFL-1 was tested for modulation by TRPV1 (capsazepine). The effect of CFL-1 on zebrafish locomotor behavior was evaluated with the open field test. The acute toxicity study was conducted. CLF-1 reduced nociceptive behavior and corneal in zebrafish without mortalities and without altering the animals' locomotion. Thus, CFL-1 presenting pharmacological potential for the treatment of acute pain and corneal pain, and this effect is modulated by the opioids, nitrergic system, NMDA receptors and TRP and ASIC channels.

Acute and chronic stress prevents responses to pain in zebrafish: evidence for stress-induced analgesia

The state of an animal prior to the application of a noxious stimulus can have a profound effect on their nociceptive threshold and subsequent behaviour. In mammals, the presence of acute stress preceding a painful event can have an analgesic effect whereas the presence of chronic stress can result in hyperalgesia. While considerable research has been conducted on the ability of stress to modulate mammalian responses to pain, relatively little is known about fish. This is of particular concern given that zebrafish (Danio rerio) are an extensively used model organism subject to a wide array of invasive procedures where the level of stress prior to experimentation could pose a major confounding factor. This study, therefore, investigated the impact of both acute and chronic stress on the behaviour of zebrafish subjected to a potentially painful laboratory procedure, the fin clip. In stress-free individuals, those subjected to the fin clip spent more time in the bottom of the tank, had reduced swimming speeds and less complex swimming trajectories; however, these behavioural changes were absent in fin-clipped fish that were first subject to either chronic or acute stress, suggesting the possibility of stress-induced analgesia (SIA). To test this, the opioid antagonist naloxone was administered to fish prior to the application of both the stress and fin-clip procedure. After naloxone, acutely stressed fin-clipped zebrafish exhibited the same behaviours as stress-free fin-clipped fish. This indicates the presence of SIA and the importance of opioid signalling in this mechanism. As stress reduced nociceptive responses in zebrafish, this demonstrates the potential for an endogenous analgesic system akin to the mammalian system. Future studies should delineate the neurobiological basis of stress-induced analgesia in fish.

Summary: Exposure of zebrafish to acute or chronic stress prior to fin clipping prevents behavioural changes normally seen after fin clip; naloxone treatment prevented this effect, demonstrating stress-induced analgesia.

Evolution of nociception and pain: evidence from fish models

In order to survive, animals must avoid injury and be able to detect potentially damaging stimuli via nociceptive mechanisms. If the injury is accompanied by a negative affective component, future behaviour should be altered and one can conclude the animal experienced the discomfort associated with pain. Fishes are the most successful vertebrate group when considering the number of species that have filled a variety of aquatic niches. The empirical evidence for nociception in fishes from the underlying molecular biology, neurobiology and anatomy of nociceptors through to whole animal behavioural responses is reviewed to demonstrate the evolutionary conservation of nociception and pain from invertebrates to vertebrates. Studies in fish have shown that the biology of the nociceptive system is strikingly similar to that found in mammals. Further, potentially painful events result in behavioural and physiological changes such as reduced activity, guarding behaviour, suspension of normal behaviour, increased ventilation rate and abnormal behaviours which are all prevented by the use of pain-relieving drugs. Fish also perform competing tasks less well when treated with a putative painful stimulus. Therefore, there is ample evidence to demonstrate that it is highly likely that fish experience pain and that pain-related behavioural changes are conserved across vertebrates. This article is part of the Theo Murphy meeting issue 'Evolution of mechanisms and behaviour important for pain'.

Assessment of behaviour in groups of zebrafish (Danio rerio) using an intelligent software monitoring tool, the chromatic fish analyser

BACKGROUND

Zebrafish (Danio rerio) are an increasingly popular model species within a variety of biomedical and neurobiological contexts. Researchers are required to prevent any negative states, such as pain, when using experimental animals to optimise fish welfare but analysis tools for zebrafish are lacking.

NEW METHOD

The chromatic fish analyser (CFA) is a computer-based monitoring system that has the potential to identify changes in fish behaviour via spatial chromatic analysis of video images. The CFA was used to monitor the behaviour of groups of six fish, where none, one, three or six fish were given a fin clip. Additionally a drug with pain-relieving properties, lidocaine, was administered to determine if this ameliorated any alterations in behaviour. The CFA measured hue horizontally and vertically reflecting the position of the fish in their tank. Saturation (indicates clustering distribution) and lightness were measured to reflect overall zebrafish activity.

RESULTS

Changes in vertical hue demonstrated that all fin clipped animals were closer to the bottom of the tank relative to pre-treatment; this was not observed in control groups, and was alleviated in those treated with lidocaine. Saturation (clustering) and lightness alterations indicated fin clipped groups reduced activity after receiving the fin clip. Lidocaine was effective in preventing the behavioural changes when 1 or 3 fish were clipped.

CONCLUSIONS

The CFA proved powerful enough to identify significant changes in behaviour taken directly from video images. With further development this monitoring tool represents a step forward in detecting behavioural changes in groups of zebrafish indicating welfare.

Welfare of Fish—No Longer the Elephant in the Room

The concept of fish welfare is fairly recent and was overlooked for many years, based on a popular misconception that fish were “stupid” creatures devoid of any kind of sentience or mental capability [...]

Automated monitoring of behaviour in zebrafish after invasive procedures

Fish are used in a variety of experimental contexts often in high numbers. To maintain their welfare and ensure valid results during invasive procedures it is vital that we can detect subtle changes in behaviour that may allow us to intervene to provide pain-relief. Therefore, an automated method, the Fish Behaviour Index (FBI), was devised and used for testing the impact of laboratory procedures and efficacy of analgesic drugs in the model species, the zebrafish. Cameras with tracking software were used to visually track and quantify female zebrafish behaviour in real time after a number of laboratory procedures including fin clipping, PIT tagging, and nociceptor excitation via injection of acetic acid subcutaneously. The FBI was derived from activity and distance swum measured before and after these procedures compared with control and sham groups. Further, the efficacy of a range of drugs with analgesic properties to identify efficacy of these agents was explored. Lidocaine (5 mg/L), flunixin (8 mg/L) and morphine (48 mg/L) prevented the associated reduction in activity and distance swum after fin clipping. From an ethical perspective, the FBI represents a significant refinement in the use of zebrafish and could be adopted across a wide range of biological disciplines.

Ethical considerations in fish research

Fishes are used in a wide range of scientific studies, from conservation research with potential benefits to the species used to biomedical research with potential human benefits. Fish research can take place in both laboratories and field environments and methods used represent a continuum from non-invasive observations, handling, through to experimental manipulation. While some countries have legislation or guidance regarding the use of fish in research, many do not and there exists a diversity of scientific opinions on the sentience of fish and how we determine welfare. Nevertheless, there is a growing pressure on the scientific community to take more responsibility for the animals they work with through maximising the benefits of their research to humans or animals while minimising welfare or survival costs to their study animals. In this review, we focus primarily on the refinement of common methods used in fish research based on emerging knowledge with the aim of improving the welfare of fish used in scientific studies. We consider the use of anaesthetics and analgesics and how we mark individuals for identification purposes. We highlight the main ethical concerns facing researchers in both laboratory and field environments and identify areas that need urgent future research. We hope that this review will help inform those who wish to refine their ethical practices and stimulate thought among fish researchers for further avenues of refinement. Improved ethics and welfare of fishes will inevitably lead to increased scientific rigour and is in the best interests of both fishes and scientists.