Embryos of many valued salmonid species incubate in the hyporheic zone of boreal streams over winter. Influence of individual winter‐related environmental variables on salmonid embryo success has been previously investigated. However, how multiple variables act together to influence embryo incubation remains poorly understood. Using a naturally spawning population of Atlantic salmon (Salmo salar) in the Miramichi River basin (New Brunswick, Canada), we related variation in the abiotic embryo incubation habitat in different streams (spatial) and over the course of two winters (temporal) to embryo mortality between fertilisation and hatch. Over two years (2013–2014 and 2014–2015), we introduced fertilised eggs to six simulated salmon redds in each of three riffles in each of five active spawning reaches (nredds = 90) with a range of hyporheic conditions. Embryo mortality was quantified at an early sampling event (March; pre‐freshet and during late embryonic development) and a late sampling event (May; post‐freshet and post‐hatch). We extracted 22 abiotic predictor variables for statistical analyses from continuous records of hyporheic environmental conditions, collected for the duration of the incubation period in each study reach. Through partial least squares regression analyses, 37.6% of the total variation in mortality was explained by the predictor variables. Each group of predictor variables explained similar proportions of variation (water temperature: 8.4%, water level: 7.4%, dissolved oxygen: 7.1%, ice conditions: 7.2%, and substrate characteristics: 7.5%), which suggests that mortality is influenced by multiple interacting abiotic conditions, rather than a single variable in isolation, and that the factors contributing to ideal salmonid incubation habitats are complex and interconnected. Our research highlights the value of a multi‐faceted research perspective and provides a baseline from which future changes in threatened salmonid populations can be measured and compared in an effort to identify relevant species‐ or population‐specific differences.
Debates around fishes' ability to feel pain concern sentience: do reactions to tissue damage indicate evaluative consciousness (conscious affect), or mere nociception? Thanks to Braithwaite's discovery of trout nociceptors, and concerns that current practices could compromise welfare in countless fish, this issue's importance is beyond dispute. However, nociceptors are merely necessary, not sufficient, for true pain, and many measures held to indicate sentience have the same problem. The question of whether fish feel pain – or indeed anything at all – therefore stimulates sometimes polarized debate. Here, we try to bridge the divide. After reviewing key consciousness concepts, we identify “red herring” measures that should not be used to infer sentience because also present in non-sentient organisms, notably those lacking nervous systems, like plants and protozoa (P); spines disconnected from brains (S); decerebrate mammals and birds (D); and humans in unaware states (U). These “S.P.U.D. subjects” can show approach/withdrawal; react with apparent emotion; change their reactivity with food deprivation or analgesia; discriminate between stimuli; display Pavlovian learning, including some forms of trace conditioning; and even learn simple instrumental responses. Consequently, none of these responses are good indicators of sentience. Potentially more valid are aspects of working memory, operant conditioning, the self-report of state, and forms of higher order cognition. We suggest new experiments on humans to test these hypotheses, as well as modifications to tests for “mental time travel” and self-awareness (e.g., mirror self-recognition) that could allow these to now probe sentience (since currently they reflect perceptual rather than evaluative, affective aspects of consciousness). Because “bullet-proof” neurological and behavioral indicators of sentience are thus still lacking, agnosticism about fish sentience remains widespread. To end, we address how to balance such doubts with welfare protection, discussing concerns raised by key skeptics in this debate. Overall, we celebrate the rigorous evidential standards required by those unconvinced that fish are sentient; laud the compassion and ethical rigor shown by those advocating for welfare protections; and seek to show how precautionary principles still support protecting fish from physical harm.
Aquaculture is a growing industry worldwide and Canadian finfish culture is dominated by marine salmonid farming. In part due to increasing public and stakeholder concerns around fish welfare protection, the first-ever Canadian Code of Practice for the Care and Handling of Farmed Salmonids was recently completed, following the National Farm Animal Care Council's (NFACC) rigorous Code development process. During this process, both the Scientific (responsible for reviewing existing literature and producing a peer-reviewed report that informs the Code) and Code Development (a diverse group of stakeholders including aquaculture producers, fish transporters, aquaculture veterinarians, animal welfare advocates, food retailers, government, and researchers) Committees identified research gaps in tandem, as they worked through the literature on salmonid physiology, health, husbandry, and welfare. When those lists are combined with the results of a public “top-of-mind” survey conducted by NFACC, they reveal several overlapping areas of scientific, stakeholder, and public concern where scientific evidence is currently lacking: (1) biodensity; (2) health monitoring and management, with a focus on sea lice infection prevention and management; (3) feed quality and management, particularly whether feed restriction or deprivation has consequences for welfare; (4) enclosure design, especially focused on environmental enrichment provision and lighting design; and (5) slaughter and euthanasia. For each of these five research areas, we provide a brief overview of current research on the topic and outline the specific research gaps present. The final section of this review identifies future research avenues that will help address these research gaps, including using existing paradigms developed by terrestrial animal welfare researchers, developing novel methods for assessing fish welfare, and the validation of new salmonid welfare indices. We conclude that there is no dearth of relevant research to be done in the realm of farmed salmonid welfare that can support crucial evidence-based fish welfare policy development.
The number of animals bred, raised, and slaughtered each year is on the rise, resulting in increasing impacts to welfare. Farmed animals are also becoming more diverse, ranging from pigs to bees. The diversity and number of species farmed invites questions about how best to allocate currently limited resources towards safeguarding and improving welfare. This is of the utmost concern to animal welfare funders and effective altruism advocates, who are responsible for targeting the areas most likely to cause harm. For example, is tail docking worse for pigs than beak trimming is for chickens in terms of their pain, suffering, and general experience? Or are the welfare impacts equal? Answering these questions requires making an interspecies welfare comparison; a judgment about how good or bad different species fare relative to one another. Here, we outline and discuss an empirically-based methodology that aims to improve our ability to make interspecies welfare comparisons by investigating welfare range, which refers to how good or bad animals can fare. We begin our proposal with a theory of welfare. We operationalize that theory of welfare by identifying metrics that are defensible proxies for measuring welfare, including cognitive, affective, behavioral, and neuro-biological measures. We assign differential weights to those proxies that reflect their evidential value for the determinants of welfare, such as the “Delphi'' structured deliberation method with a panel of experts. Then we review the evidence and score its quality to ascertain whether a particular taxa may possess the proxies in question to construct a taxa-level welfare range profile. Finally, we use a Monte Carlo simulation to generate an overall estimate of comparative welfare range relative to our hypothetical index species - humans. Interspecies welfare comparisons will help facilitate empirically informed decision-making to streamline the allocation of resources and to ultimately better prioritize and improve animal welfare.
Current frameworks for designing and evaluating good enclosures and “enrichments” typically focus on animals' active interactions with these features. This has undoubtedly improved the welfare of zoo‐housed animals over the last 30 years or more. However, literature reviews from this same period identify persistent gaps in how such frameworks are applied: experiences and behaviors that do not rely on active interaction with stimuli or resources are largely ignored, when evaluating the welfare value of enclosures and enrichments within them. Here, we review research evidence demonstrating that active interaction is not always a reliable measure of welfare value, showing that items that elicit little or no interaction can nevertheless still reduce stress and improve well‐being. This evidence largely comes from research on humans, lab animals and farm animals, but also from some zoo studies too. We then investigate why. We review psychology and ethology literatures to show that such welfare benefits can arise from five, non‐mutually exclusive, processes or mechanisms that are well‐understood in humans and domestic animals: (1) some motivations are sated quickly by interaction with resources, yet still have large welfare benefits; (2) active interaction may just be a way to achieve a goal or solve a problem, without being beneficial for welfare in itself; (3) having opportunities for choice and control may be inherently beneficial, even when not acted on; (4) some enclosure features meet social needs for structure, landmarks, and blocked sightlines; and (5) some stimuli may be preferred because they signaled good environments to an animal's ancestors. We use this information to identify improved ways of enhancing and assessing zoo animal welfare. Incorporating these concepts should expand the scope of behaviors and subjective experiences that are targeted, to now include those that involve little active interaction and yet still are important for good welfare.
Deformities in fish embryos are important for their survival in later life stages. However, a consistent way to refer to and classify salmonid embryo deformities does not exist. Expanding on reports of alevin deformities, we developed a classification tool for distinguishing the deformities observed in a collection of preserved Atlantic salmon (Salmo salar) embryos. Deformities were classified based on the deformed body part and a qualitative subtype. This classification tool uses external morphology, requires minimal equipment and can be applied from the first appearance of optic vesicles to hatch.
Billions of animals across many taxa are extensively farmed, with critical impacts on animal welfare. Societal efforts to reduce animal suffering lack rigorous and systematic approaches that facilitate maximising welfare improvements, such as informed funding allocation decisions. We present a multi-measure, cross-taxa framework for modelling differences in pain, suffering, and related cognition to assess whether certain animals have larger welfare ranges (how well or badly animals can fare). Measures include behavioural flexibility, cognitive sophistication, and general learning. We evaluated 90 empirically detectable proxies for cognition and welfare range (henceforth 'proxies') in pigs, chickens, carp, salmon, octopus, shrimp, crabs, crayfish, bees, and silkworms. We grouped a subset of proxies into: A) 10 ideal proxies and B) 10 less ideal proxies but with sufficient data for interspecies comparisons. We graded the strength of evidence per proxy across taxa, and constructed a cognition and welfare range profile, with overall judgement scores (ranging from likely no/low confidence to yes/very high confidence). We discuss the implications of comparisons and highlight key avenues for future research. This work is timely, given recent indications of significant political will towards reducing animal suffering, such as the inclusion of cephalopods and decapods in the Animal Welfare (Sentience) Bill following a UK government-commissioned research review. Given the novelty and robustness of our review, we believe it sets a new standard for investigating interspecies comparisons of cognition and welfare ranges and helps inform future research. This should help streamline funding allocations and improve the welfare of millions of farmed animals.
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