Social networks in elasmobranchs and teleost fishes

Over the last decade, there has been an exponential increase in studies using social network analysis to describe the structure of animal societies. In this synthesis, we examine the contribution of social network analysis towards developing our understanding of the social organization of elasmobranchs and teleost fishes. We review and discuss the current state of knowledge of the mechanisms and functions underpinning social network structure in fishes with particular emphasis on cooperation, familiarity, site fidelity, population structure and the welfare of captive populations. We also discuss important methodological issues (e.g. how to identify and mark fish) and highlight new developments in this area of research and their implications for the study of fish behaviour. Finally, we outline promising future research areas for the application of social network analysis to teleost fishes and elasmobranchs.     

Can fish really feel pain?

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 misinterpreted and not replicable, so claims that fish feel pain remain unsubstantiated. Comparable problems exist in studies of invertebrates. In contrast, an extensive literature 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 elasmobranchs studied to date. A‐delta nociceptors, not yet found in elasmobranchs, but relatively common in teleosts, likely serve rapid, less noxious injury signaling, triggering 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 unwarranted 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.     

Are fish the victims of ‘speciesism’? A discussion about fear, pain and animal consciousness

Fish welfare is currently a hotly debated topic; this is mainly due to the issue of whether or not fish have the capacity for conscious awareness, or subjective states. Because of the contentious nature of animal consciousness, the subject is often avoided in many welfare arguments, but it is argued that since welfare should be about how animals feel, this issue is unavoidable. There is also good reason to believe that the issue of assessing subjective states is not as insurmountable as some believe.     

西藏雅鲁藏布江中游裂腹鱼类优先保护等级定量评价

西藏地区雅鲁藏布江中游分布有6种特有裂腹鱼类,是地方重要的土著经济物种。近年来,受人类活动和环境变化的影响,裂腹鱼类资源已严重衰退而处于濒危,急需开展裂腹鱼类的资源现状调查及保护等级评价工作。本课题组分别于2015年和2017年的春季(4—5月),对雅鲁藏布江中游的渔业资源进行调查监测,参阅相关文献资料,采用珍稀性、物种价值和人为干扰共3个一级指标和5个二级指标建立优先保护等级的定量评价体系,对6种裂腹鱼类的资源状况及濒危状况进行评价,根据评分标准与优先保护综合评价值(R)确定裂腹鱼类的优先保护等级。研究结果表明,尖裸鲤(Oxygymnocypris stewartii)为一级优先保护鱼类,双须叶须鱼(Ptychobarbus dipogon)为二级优先保护鱼类,拉萨裂腹鱼(Schizothorax waltoni)和巨须裂腹鱼(Schizothorax macropogon)为三级优先保护鱼类,异齿裂腹鱼(Schizothorax o’connori)和拉萨裸裂尻鱼(Schizopygopsis younghusbandi)为四级优先保护鱼类。评价分级结果与实际情况相符,真实地反映了6种裂腹鱼类优先保护顺序。本研究对雅鲁藏布江中游的鱼类保护等级提出建议,为鱼类资源的科学保护管理等提供参考和依据。     

硬骨鱼类免疫球蛋白分类及多样性产生机制研究进展

鱼类是最先出现免疫球蛋白的低等脊椎动物,对研究免疫球蛋白的起源、进化具有重要的意义。IgM和IgD是最先被人类发现和认识的鱼类免疫球蛋白,随着科技进步和研究深入,陆续在斑马鱼（Danio rerio）、虹鳟（Oncorhynchus mykiss）及鲤鱼（Cyprinus carpio）中发现了IgZ、IgT、IgM-Z等。与哺乳动物的免疫球蛋白一样,不同种鱼,甚至同种鱼不同个体间,免疫球蛋白的形态结构、基因类型、生物学功能等均有差异。为了进一步认识鱼类免疫球蛋白及其免疫应答的机制,本文综述了鱼类免疫球蛋白的分类和多样性机制等。     

Trait‐based ecology of fishes: A quantitative assessment of literature trends and knowledge gaps using topic modelling

Species traits are a new data currency to enhance our understanding of ecological patterns and processes. Trait‐based studies of fishes are numerous in comparison with other animal groups, reflecting the diversity of fish forms and functions they provide to aquatic ecosystems. We conduct a retrospective examination of literature to identify knowledge gaps and provide guidance for future research in trait‐based fish ecology. We apply an automated text mining and topic modelling to track the evolution of research topics within peer‐reviewed articles of functional traits in marine and freshwater fishes published over the past half century, explore the inter‐connections among those topics and identify emerging avenues for investigation. By mapping the topic landscape of the literature, 16 latent topics emerged that vary in their prevalence. Our results show a decline in the frequency of studies using reproductive traits to model and explore the way fish allocate energy for reproduction, and increase in studies reporting functional diversity metrics and utilizing the concept of multivariate functional space. Research focused on contributions of fish traits to ecosystem functioning also has increased in frequency. We revealed large gaps in information between growing and decreasing topics and that these gaps were derived from different types of traits being considered. We suggest that scientists break‐free from the traditions of their research field by targeting investigations that: (a) apply functional diversity metrics to a broader assortment of traits, (b) focus on traits influencing energy allocation to growth/reproduction and (c) integrate trophic‐web and behavioural studies with other topics.     

长江口青草沙水库正式供水前的鱼类群落结构特征

为研究上海青草沙水库的鱼类物种组成、多样性及其空间变化,2010年7--10月在该水库共捕获鱼类993尾,隶属5目,18种,其中淡水鲤形目鱼类最多,占总物种数的72.2％.群落优势种为贝氏(鳖)、刀鲚、鲫、光泽黄颡鱼.聚类分析表明,鱼类群落类型存在较显著的空间差异,刺网网目大小对渔获物物种组成有较显著的影响.物种多样性与丰富度和均匀度均显著正相关,但更多地受丰富度的影响.单因素方差分析表明,鱼类物种多样性在空间上无显著差异.4种摄食功能群中,无脊椎动物食性(44.4％)和杂食性(33.3％)鱼类物种数比例较高;4种生态类群中,定居性鱼类占绝对优势(77.8％).青草沙水库鱼类群落表现出淡水或长江口低盐淡水区鱼类区系的主要特征,与以近海鲈形目鱼类为优势的长江口邻近水域的鱼类群落差异巨大,推测水库建设导致的隔离与盐度下降是形成该水库鱼类群落趋于淡水区系的主要原因.     

The implications of a feelings-based approach to fish welfare: a reply to Arlinghaus et al.

The welfare of fish is a topic of increasing debate touching on a number of complex scientific and ethical issues and constructive dialogue between groups with differing approaches to the topic requires mutual understanding from both perspectives. In a recent review aimed at stimulating debate on this topic, Arlinghaus et al. (2007) explore the question of fish welfare in the particular context of recreational angling, by means of a critique of a review of fish welfare in general written by ourselves ( Huntingford et al. 2006 ). We entirely agree with the desirability of debate on this topic and recognize a number of valuable qualities in the commentary by Arlinghaus et al. However, we argue that the critique has some serious flaws. In the first place, by rejecting a feelings‐based approach to welfare, it fails to address the aspect of welfare that is at the heart of much legitimate public concern. Secondly, while advocating an objective, scientific approach to fish welfare, Arlinghaus et al. fail to present their own agenda (that recreational angling is morally acceptable) in a transparent way. Thirdly, they seriously misrepresent the position taken in Huntingford et al. (2006) on a number of important issues. In this reply, we address these points and then discuss briefly the areas of agreement and constructive disagreement between the two reviews.     

Stocking density and welfare of cage farmed Atlantic salmon: application of a multivariate analysis

The welfare of fish is receiving increasing attention and attempts have been made to control welfare in farmed fish through regulation of management practices, including stocking density. However, there is little published information on the influence of stocking density on welfare of fish in marine cages. This present study examined welfare in Atlantic salmon (Salmo salar) in cages on a commercial marine farm, exposed to densities ranging from 9.7 to 34 kg m⁻³. On three occasions over a period of 10 months, fish were sampled from each cage, weighed and measured; their fin condition assessed and blood samples taken for measurement of glucose and cortisol. A multivariate analysis was used to combine four commonly used measures of fish welfare (condition of body and fins and plasma concentrations of glucose and cortisol) into a single welfare score. As well as objectively reflecting a coherence within the data, this score was consistent with the evaluation of welfare by experienced farmers. A generalized linear model indicated that the median welfare score for each cage was significantly related to sampling period, to stocking density (mean over the previous 3 months) and to location of the cage. A model with all the data from individual fish proved to be more robust and also identified sample period, stocking density (mean over 3 months) and position of the cage as significant predictors of the welfare score. There was no significant association between the welfare score and the length of time since grading or lice treatment. Further analysis of the relationship between stocking density and the welfare score suggested that there was no trend up to an inflection point ca. 22 kg m⁻³, after which increasing stocking density was associated with lower welfare scores. This study suggests that, while stocking density can influence the welfare of Atlantic salmon in production cages, this is only one influence on their welfare and on its own cannot be used to accurately predict or to control welfare.     

Spatial cognition and its neural basis in teleost fishes

The present review is focused on recent laboratory studies revealing that the spatial behaviour of fishes is as complex and elaborate as described in land vertebrates. In addition, the data presented here indicate that the remarkable richness and plasticity of spatial behaviour in fishes are based on learning and memory mechanisms and cognitive processes that depend on particular brain circuits, possibly homologous to those identified in mammals and birds. For example, there is evidence that the fish hippocampal pallium is essential for processing and encoding complex spatial information to form map‐like representations of the environment. In contrast, body‐centred orientation strategies or emotional learning are subserved by different cerebral structures, such as the optic tectum, the cerebellum or the amygdalar pallium. These results that suggest a striking similarity in some cognitive processes and their neural basis between fish and land vertebrates are consistent with the possibility that these vertebrate groups share a common basic pattern of brain and behaviour organisation inherited from a common ancestor and conserved through a long history of separate evolution.     

Do postlarval amphidromous fishes transport marine‐derived nutrients and pollutants to Caribbean streams?

Diadromous fishes are known biotransport vectors that can move nutrients, energy and contaminants in an upstream direction in lotic ecosystems. This function has been demonstrated repeatedly in anadromous salmonids, but the role of other diadromous species, especially tropical taxa, as biotransport vectors is less studied. Amphidromous fish species exhibit potential to act as upstream vectors of nutrients and contaminants in their postlarval and juvenile stages, but this role is largely unknown because of limited understanding of larval growth habitats. Moreover, because some species are harvested in artisanal fisheries as postlarvae, and postlarvae are consumed by riverine and estuarine predators, heavy contaminant loads may present a human or wildlife health concern. This research incorporates stable isotope and contaminant analyses to infer larval habitats and contaminant accumulation of amphidromous fishes on the Caribbean island of Puerto Rico. The isotopic signatures of postlarval amphidromous fishes indicated marine basal sources and food web components, rather than those from riverine habitats. Additionally, postlarvae did not contain concentrations of anthropogenic pollutants that would be of ecological or human health concern. These findings are the first and strongest evidence that amphidromous fish postlarvae function as biotransport vectors of marine nutrients into and up river ecosystems without posing a health threat to the receiving food web or human consumers.     

The physiological consequences of catch‐and‐release angling: perspectives on experimental design,interpretation, extrapolation and relevance to stakeholders

Over the past 20 years, there has been a dramatic increase in the use of physiological tools and experimental approaches for the study of the biological consequences of catch‐and‐release angling practices for fishes. Beyond simply documenting problems, physiological data are also being used to test and refine different strategies for handling fish such that stress is minimised and survival probability maximised, and in some cases, even for assessing and facilitating recovery post‐release. The inherent sensitivity of physiological processes means that nearly every study conducted has found some level of – unavoidable – physiological disturbance arising from recreational capture and subsequent release. An underlying tenet of catch‐and‐release studies that incorporate physiological tools is that a link exists between physiological status and fitness. In reality, finding such relationships has been elusive, with further extensions of individual‐level impacts to fish populations even more dubious. A focus of this article is to describe some of the challenges related to experimental design and interpretation that arise when using physiological tools for the study of the biological consequences of catch‐and‐release angling. Means of overcoming these challenges and the extrapolation of physiological data from individuals to the population level are discussed. The argument is presented that even if it is difficult to demonstrate strong links to mortality or other fitness measures, let alone population‐level impacts of catch‐and‐release, there remains merit in using physiological tools as objective indicators of fish welfare, which is an increasing concern in recreational fisheries. The overarching objective of this paper is to provide a balanced critique of the use of physiological approaches in catch‐and‐release science and of their role in providing meaningful information for anglers and managers.     

Fish under exercise

Improved knowledge on the swimming physiology of fish and its application to fisheries science and aquaculture (i.e., farming a fitter fish) is currently needed in the face of global environmental changes, high fishing pressures, increased aquaculture production as well as increased concern on fish well-being. Here, we review existing data on teleost fish that indicate that sustained exercise at optimal speeds enhances muscle growth and has consequences for flesh quality. Potential added benefits of sustained exercise may be delay of ovarian development and stimulation of immune status. Exercise could represent a natural, noninvasive, and economical approach to improve growth, flesh quality as well as welfare of aquacultured fish: a FitFish for a healthy consumer. All these issues are important for setting directions for policy decisions and future studies in this area. For this purpose, the FitFish workshop on the Swimming Physiology of Fish () was organized to bring together a multidisciplinary group of scientists using exercise models, industrial partners, and policy makers. Sixteen international experts from Europe, North America, and Japan were invited to present their work and view on migration of fishes in their natural environment, beneficial effects of exercise, and applications for sustainable aquaculture. Eighty-eight participants from 19 different countries contributed through a poster session and round table discussion. Eight papers from invited speakers at the workshop have been contributed to this special issue on The Swimming Physiology of Fish.     

Genetics of neotropical fish: from chromosomes to populations

The Neotropical freshwater fish fauna is very rich—according to the most recent catalogue 71 families and 4,475 species have been described. However, only a small amount of general information is available on the composition of Neotropical marine fishes. In Brazil, 1,298 marine species have been recorded. General analysis of available cytogenetic and population genetic data clearly indicates research has been mainly concentrated on freshwater fishes. Thus, today, cytogenetic information is available for 475 species of Characiformes, 318 species of Siluriformes, 48 species of Gymnotiformes, 199 freshwater species that do not belong to the superorder Ostariophysi, and only 109 species of marine fishes. For the species studied, only about 6% have sex chromosomes and about 5% have supernumerary or B chromosomes. A review of the cytogenetic studies shows that these data have provided valuable information about the relationships between fish groups, the occurrence of cryptic species and species complexes, the mechanism of sex determination and sex chromosome evolution, the distribution of nucleolus organizer regions, the existence supernumerary chromosomes, and the relationship between polyploidy and evolution. In relation to populations in Neotropical marine waters, the studies have shown the presence of cryptic species, which has important implications for fishery management. Different levels of genetic structuring can be found among Neotropical freshwater migratory fish species. This raises important implications for fish population genetic diversity and consequently its sustainable utilization in inland fisheries and aquaculture, specifically for conservation of ichthyo-diversity and survival.     

漂流性鱼卵的孵化特性及水动力需求研究进展

明晰鱼卵运动规律是鱼类产卵场位置推算、水库生态调度和鱼类资源保护等研究的基础。尤其是对于产漂流性卵鱼类,当流水环境不足以维持鱼卵漂流时,鱼卵便下沉死亡而无法孵化成幼鱼。对照中国内陆鱼类名录,查阅了国内重要流域及地方鱼类志中有关产漂流性卵鱼类的繁殖条件,列举了典型产漂流性卵鱼类产卵水温、产卵月份和孵化时长等相关信息。针对现有鱼类志中对于鱼卵基本物理性质及鱼卵安全漂流孵化所需水动力条件几乎没有记载的情况,补充查阅了国内外相关文献,总结梳理了漂流性鱼卵安全漂流水动力条件的研究进展。一种观点认为鱼卵在水体中是否能安全漂流取决于水体的流速,另一种观点认为控制漂流性鱼卵悬浮或下沉的关键参数是湍流或剪切速度,而不是水流的线速度。现有漂流性鱼卵漂流的关键水动力条件和阈值尚有争议,仍需对鱼卵运动规律进行机理实验研究。在此基础上,总结梳理了目前国内外对鱼卵在水中漂流输移的研究方法和手段,主要是通过野外观测、室内实验和模型模拟三种方式进行。以上研究极大推进了对鱼卵运动机制的理解,但大多数研究都仅仅针对鱼卵运动规律本身进行单一的实验或模型研究,而对于如何通过水利工程生态调度创造满足漂流性鱼卵孵化所需的流水环境,提出水利水电工程生态环境效应多维调控方法是未来产漂流性卵鱼类保护研究的重要方向。     

Aristotle as an ichthyologist: Exploring Aegean fish diversity 2,400 years ago

In an attempt to trace the origins of the science of ichthyology, we studied Aristotle's zoological works (21 books in total), aiming to give an exhaustive catalogue of his fishes, suitable for use by modern marine biologists, and to evaluate the great philosopher's knowledge of fish biology. Our investigation yielded 135 ichthyonyms used to describe 109 individual fish taxa (13 fishes had multiple names) and 12 terms that corresponded either to fish developmental stages or behavioural patterns. Because of the variable amount of information given in the texts, 54 fishes were identified to species or genus level, 24 fishes to higher categories (family, order), 27 fishes could only be classified as Actinopterygii or Elasmobranchii, while four could not be classified at all. Among the most easily recognizable fishes were Lophius spp., Conger conger, Muraena helena, Anguilla anguilla and Mugil cephalus. The latter two and the tunas (Τhunnus spp.) were the most frequently recorded fishes. Aristotle's inquiry was not limited or focused on fish that were of human interest, but he also reported or described species that fascinated him by their peculiar life history. He was interested in a wide array of aspects of fish biology ranging from body structure and function, reproduction and development to fish feeding habits, migrations and diseases. As evidenced by his work, Aristotle should be considered the first ichthyologist, preoccupied with the zoological, scientific study of fish, and a review of his writings can prove useful for current ichthyological research.     

Fish welfare: a challenge to the feelings-based approach, with implications for recreational fishing

Fish welfare issues are increasingly appearing on social and political agendas and have recently gained prominence in fisheries literature. By focusing on examples from recreational fishing, this paper challenges some of the previous accounts of fish welfare. Issues of concern encompass: (1) the feelings‐based approach to fish welfare; (2) the artificial divide between human beings and nature; and (3) ways in which stakeholders can address fish welfare issues. The different approaches to characterizing the interaction of humans with animals are animal welfare, animal liberation and animal rights. We show that the suffering‐centred approaches to fish welfare and the extension of the moral domain to fish – characteristic of the concepts of animal liberation and animal rights – are not the cornerstone of animal welfare. This, however, does not question the need of fisheries stakeholders to consider the well‐being of fish when interacting with them. There are many ways in which recreational fishing stakeholders can modify standard practices to improve the welfare of fish, without questioning fishing as an activity per se. Examples are choice of gear and handling techniques. Previous accounts have failed to include discussions of the many efforts – voluntary or mandated – pursued by fisheries stakeholders to reduce fish stress, injury and mortality. Progress towards addressing fish welfare issues will be enhanced by avoiding the viewing of humans as ‘non‐natural’ disturbance to fishes and keeping three types of crucial question in separate compartments. The three questions cover the symptoms of good and poor welfare, the conscious experience of suffering, and the ethical attitudes towards animals. Fish biologists should focus on the first question – objective measurement of biochemical, physiological and behavioural indicators – to evaluate whether human interactions with fish impair the latters’ health or prevent them from receiving what they need, if held in captivity.