An evaluation of current perspectives on consciousness and pain in fishes

There is growing societal and scientific interest in the welfare status of fish used for commercial enterprise. As animal welfare is primarily concerned with the quality of life of a conscious, sentient organism, the question of whether fishes are even capable of consciousness must first be addressed in order to assess their welfare status. Recently, there has been a resurgence of research investigating the biological basis for human consciousness, and our current understanding of the cognitive mechanisms underlying fish behaviour has likewise improved significantly. Combined, these research perspectives create an opportunity to better comprehend the phylogeny of traits associated with consciousness, as well as the emergence of consciousness itself during vertebrate evolution. Despite the availability of this literature, contemporary reviews or published studies investigating the probability of conscious states occurring in fishes often do so without considering new perspectives or data. In this paper, we review and critique recent publications that report equivocal conclusions favouring the absence or presence of consciousness in various fishes. By introducing other data into these analyses, we demonstrate that there are alternative perspectives which support the existence of consciousness in fishes as a plausible concept. An accurate assessment of the mental capacity of fishes will require enhanced knowledge of their forebrain neuroanatomy, an understanding of how such structures mediate behavioural responses, and an analysis of that information within the context of contemporary theory related to the evolution of consciousness in higher vertebrates.     

Methods for studying spatial behaviour of freshwater fishes in the natural environment

Spatial behaviour of fishes in fresh and brackish water ranges in temporal scales between localized diel movements, often associated with foraging and predator evasion, to seasonal or life‐cycle related events involving movements between freshwater habitats or freshwater and marine biotopes. Recent technological advances have resulted in dramatic improvements in the range of techniques available for the study of spatial behaviour of freshwater fishes in the natural environment, and broadly may be divided into two categories: capture dependent and capture independent. The former incorporates those methods that rely on sampling marked fish (mark–recapture) or unmarked fish (density estimates, catch per unit effort) over defined scales of time and space in order to derive information on distribution and movement. Captured fish may also be tagged with transmitters that radiate energy, enabling the fish to be tracked and/or environmental data to be gathered. Biochemical analysis of samples from fish, requiring non‐destructive sampling (genetic analysis and scale microchemistry) or destructive sampling (otolith microchemistry) may also provide information on migration and ontogenetic processes. Capture independent techniques include visual observation and video techniques, hydroacoustics and automated fish counting. Catch per unit effort and mark–recapture techniques are most efficient where long‐term fishery or monitoring studies are in place and data on crude spatial and temporal scales are acceptable. They also have the advantages of low technical requirements and low equipment costs. Where specific management or ecological questions are pertinent, recapture independent techniques may be more appropriate. Telemetric methods can provide high resolution information at the individual level, while hydroacoustics is increasingly providing information at the population level in large lake and river environments. Biochemical methods are becoming increasingly useful in determining the extent of population segregation, where DNA analysis is used, and in the study of migration and ontogenetic changes in behaviour, where otolith microchemistry and stable isotope analysis is used.     

The role of learning in shark behaviour

The role of learning in behaviour is well known for many animal taxa, including teleost fishes, insects, birds and mammals. However, its importance to sharks in everyday behavioural processes has rarely been considered. Almost 50 years ago the first learning experiments on sharks were conducted; our first section discusses these studies and places them in a framework of associative and non‐associative learning. These experiments showed that sharks were capable of different forms of learning, such as operant and classical conditioning and habituation. Sharks could learn associations as rapidly as other vertebrates and also remember training regimes for several months. However, much of this experimental evidence was based on small sample sizes and few shark orders, such as Carcharhiniformes and Orectobliformes, leaving large gaps in our knowledge of the general learning capabilities of other shark orders. We also examine recent research that has tested for, or inferred learning in behavioural processes. This section reveals that sharks, like teleost fishes use learning to improve prey search and capture to potentially navigate and orientate in their home range and recognize conspecifics, heterospecifics and mates. Learning is also discussed in relation to ecotourism and fisheries. Findings indicated that these activities may lead to conditioning of sharks and that considerable effort should go into investigating what impact this could have on the shark species involved. Finally, we discuss the importance of combining laboratory experiments with field studies, the use of new experimental techniques, the role of model species and research priorities for future work.     

The implications for aquaculture practice of epigenomic programming of components of the endocrine system of teleostean embryos: lessons learned from mammalian studies

Epigenetics is the study of changes in gene expression patterns that occur without any modification of the underlying nucleotide sequence of the DNA. Modifications of the so‐called epigenome include complex transient or permanent chemical changes of the DNA or histone proteins resulting in the suppression or enhancement of gene expression, together with an array of post‐translational events that modify the translational products. Epigenomic programming (EP) of the genome is an essential component of embryonic development in animals from the totipotent fertilized egg to the pluripotent stem cells, stem cell differentiation and final tissue and organ formation. Many of these EP processes are influenced transiently and some permanently by environmental influences. In eutherian mammals, environmentally related EP of embryos is linked to permanent changes in the phenotype of the progeny, some of which have been associated with adult onset metabolic disorders. Moreover, because some of the epigenetic remodelling occurs in both the soma and germ line, the resultant phenotypic characteristics (some of which are linked to disease states) may be heritable. Although far less is known about the effects of environmentally linked EP on the ontogeny of fishes, the available information suggests that the EP processes are similar amongst all vertebrates, and there are clear parallels between fish and mammals that are discussed in this paper. Our perspective takes the well‐established findings in mammals and uses them to proactively extrapolate to the as yet under‐recognized implications of EP for fish biology and for fish production in intensive aquaculture.     

Influences of local habitat and stream spatial position on fish assemblages in a dammed watershed,the Qingyi Stream,China

Abstract – Identifying the underlying mechanisms that explain the spatial variation in stream fish assemblages is crucial for the protection of species diversity. The influences of local habitat and stream spatial position on fish assemblages were examined from first‐order through third‐order streams within a dammed watershed, the Qingyi Stream, China. Based on linear regression models, the most important environmental variables influencing fish species richness were water temperature and wetted width, but stream spatial position variables were less important. Using canonical correspondence analysis, five environmental variables were identified to significantly influence fish assemblages, including three habitats (elevation, substrate and water depth) and two spatial variables (C‐link and Link). Our results suggest that, in a heavily dammed watershed, by blocking the migration routes of fishes, dams weaken the influence of stream spatial position on fish species richness. However, fish species compositions are significantly influenced by both local habitat environment and stream spatial position, which is perhaps owing to the distribution of fish species according to ecological requirements not related to spatial processes.     

Non‐diadromous life history and limited movement in northern lineages of Australian smelt: Evidence from otolith chemistry analysis

A comprehensive knowledge of migratory behaviour is paramount for the effective management and conservation of fishes in coastal drainages. The Australian smelt (Retropinna semoni) is a common fish distributed throughout coastal and inland drainages in south‐eastern Australia. Multiple life history patterns (potamodromy, facultative diadromy, estuarine residence) in the southern regions of its geographic distribution have been reported, and it is possible that some of these differences reflect characteristic behaviours of cryptic species within the group. To elucidate the life history patterns of smelt at the northern extent of their range and to identify any differences in migratory behaviour between two genetically distinct lineages (“SEQ‐N”, “SEQ‐S”) in this region, the movement patterns of Australian smelt were assessed using otolith chemistry. No evidence of marine residence was found based on otolith Sr:Ca and Ba:Ca transects for either group, suggesting that both are non‐diadromous. Significant differences in multi‐elemental otolith chemistry signatures were found among rivers and between paired sites within some rivers, suggesting no connectivity among drainages and limited dispersal of individuals over large spatial scales within rivers. These findings provide key insights into the migratory patterns of northern Australian smelt populations and, in combination with previous research, suggest that life history variation in the Australian smelt complex may occur primarily at the intra‐population level rather than among genetically distinct lineages. Conservation and management strategies for Australian smelt should take limited dispersal and individual life history variation into consideration in order to protect the components of this important species complex.     

Effects of anthropogenic disturbances on α and β diversity of fish assemblages and their longitudinal patterns in subtropical streams,China

Identifying the spatial patterns of α and β diversity of biotics is an important yet little‐understood area of basic and applied ecological research. Although the upstream–downstream patterns of α diversity of stream fishes are numerously reported, β diversity has received less attention. In this study, we surveyed fishes along the upstream–downstream gradients in three headwater streams of the Qingyi River, China, which were affected by different extents of human activities. We aimed to assess how anthropogenic disturbances affect α and β diversity of stream fishes and their upstream–downstream patterns. We found that, compared with that in the Shuxi Stream disturbed less, endemic species decreased and cosmopolitan species increased in the Maxi and Puxi Stream disturbed heavily. The streams disturbed heavily showed lower α diversity and higher β diversity than that in the stream disturbed less. This among‐stream variations in fish diversity only occurred at the mid‐downstream, not upstream segments. α diversity increased downstream and β diversity decreased downstream from headwaters to mouth in the stream disturbed less, whereas this upstream–downstream pattern in fish diversity shifted in the streams disturbed heavily, in which both α and β diversity showed the quadratic distributions with the hump‐shape for α diversity and the U‐shape for β diversity respectively. Our results suggest that anthropogenic disturbances cause some cosmopolitan fishes replacing many endemic fishes in upland streams. This replacement processes result in α diversity decreasing and β diversity increasing, and shift the spatial patterns in fish diversity along the upstream–downstream gradient.     

The complementary role of lentic and lotic habitats for Arctic grayling in a complex stream‐lake network in Arctic Alaska

Lakes can be important to stream dwelling fishes, yet how individuals exploit habitat heterogeneity across complex stream‐lake networks is poorly understood. Furthermore, despite growing awareness that intermittent streams are widely used by fish, studies documenting the use of seasonally accessible lakes remain scarce. We studied Arctic grayling (Thymallus arcticus) in a small seasonally flowing (June–October) stream‐lake network in Alaska using PIT telemetry. Overall, 70% of fish visited two lakes, 8% used a single lake, and 22% used only stream reaches. We identified five distinct behavioural patterns that differed in dominant macrohabitat used (deep lake, shallow lake or stream reaches), entry day into the network and mobility. Some juvenile fish spent the entire summer in a shallow seasonally frozen lake (average 71 days), whereas others demonstrated prospecting behaviour and only entered the stream channel briefly in September. Another group included adult and juvenile fish that were highly mobile, moving up to 27 km while in the 3‐km stream‐lake network, and used stream reaches extensively (average 59 days). Lentic and lotic habitats served differing roles for individuals, some fish occupied stream reaches as summer foraging habitat, and other individuals used them as migration corridors to access lakes. Our study emphasises the importance of considering stream‐lake connectivity in stream fish assessments, even to shallow seasonally frozen habitats not widely recognised as important. Furthermore, we demonstrate that individuals may use temporary aquatic habitats in complex and changing ways across ontogeny that are not captured by typical classifications of fish movement behaviour.     

The demography of introduction pathways,propagule pressure and occurrences of non‐native freshwater fish in England

• 1. Biological invasion theory predicts that the introduction and establishment of non‐native species is positively correlated with propagule pressure. Releases of pet and aquarium fishes to inland waters has a long history; however, few studies have examined the demographic basis of their importation and incidence in the wild.
• 2. For the 1500 grid squares (10×10 km) that make up England, data on human demographics (population density, numbers of pet shops, garden centres and fish farms), the numbers of non‐native freshwater fishes (from consented licences) imported in those grid squares (i.e. propagule pressure), and the reported incidences (in a national database) of non‐native fishes in the wild were used to examine spatial relationships between the occurrence of non‐native fishes and the demographic factors associated with propagule pressure, as well as to test whether the demographic factors are statistically reliable predictors of the incidence of non‐native fishes, and as such surrogate estimators of propagule pressure.
• 3. Principal coordinates of neighbour matrices analyses, used to generate spatially explicit models, and confirmatory factor analysis revealed that spatial distributions of non‐native species in England were significantly related to human population density, garden centre density and fish farm density. Human population density and the number of fish imports were identified as the best predictors of propagule pressure.
• 4. Human population density is an effective surrogate estimator of non‐native fish propagule pressure and can be used to predict likely areas of non‐native fish introductions. In conjunction with fish movements, where available, human population densities can be used to support biological invasion monitoring programmes across Europe (and perhaps globally) and to inform management decisions as regards the prioritization of areas for the control of non‐native fish introductions.

© Crown copyright 2010. Reproduced with the permission of her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd.     

Managing non‐native fish in the environment

Non‐native fishes are frequently used to enhance aquaculture and fisheries; if introduced into the wider environment, then the majority will have negligible effects on native biodiversity. However, a minority will become invasive, causing adverse ecological effects, and so management actions may be needed to minimize their dispersal and impacts. These actions include eradication attempts from specific waters or well‐defined spatial areas, population control by suppression (e.g. through removal programmes) and containment of existing populations to prevent their further spread. These remedial actions have generally only been undertaken across large spatial areas in developed countries; experience suggests a fundamental constraint is a lack of selective removal methods that target the non‐native fish species only. For example, eradication methods tend to be limited to low technology, ‘scorched‐earth’ techniques (e.g. biocide chemicals) whose use is generally constrained to relatively small and enclosed water bodies. Risk management of non‐native fishes should ensure that actions taken are commensurate with the level of risk posed by that species in the environment; although pre‐introduction risk assessment schemes have been developed, there remains a lack of decision support tools for post‐introduction situations. Although this inhibits the management of non‐native fishes in the environment, control programmes such as those against common carp Cyprinus carpio in Australia and topmouth gudgeon Pseudorasbora parva in England and Wales suggest there is potential for invasions to be managed and controlled within large spatial areas, even if their eradication may not be feasible.     

The proximate architecture for decision‐making in fish

Evolution has since the very beginning resulted in organisms which can sort fitness‐related information from noise, evaluate it and respond to it. In animals, the architecture for proximate control of behaviour and physiology has been gradually evolving since before the Cambrian explosion of animal phyla. It integrates many different survival circuits, for example for danger, feeding and reproduction, and operates through reflexes, instincts, homeostatic drives and precursors to human emotions. Although teleost brains differ substantially from the much better understood brains of terrestrial vertebrates, their anatomy, physiology and neurochemistry all point towards a common and malleable architectural template with strong and flexible effects on fish behaviour and elements of personality. We describe the main components of this architecture and its role in fish behaviour from the perspectives of adaptation, evolutionary history and gene pools. Much research is needed, as several of the basic assumptions for architectural control of behaviour and physiology in teleosts are not thoroughly investigated. We think the architecture for behavioural control can be used to change ecosystem models from a bottom‐up perspective to also include behaviourally mediated trophic cascades and trait‐mediated indirect effects. We also discuss the utility of modelling based on proximate architectural control for fish welfare studies.     

Movement ecology of imperilled fish in a novel ecosystem: River‐reservoir movements by razorback sucker and translocations to aid conservation

1. Reservoirs and associated river fragments are novel ecosystems not experienced by fishes in their evolutionary history, yet they are now commonplace across the globe. Understanding how fishes use these novel habitats is vital to conservation efforts in contemporary riverscapes.
2. Movement patterns of the endangered razorback sucker (Xyrauchen texanus) synthesized from tagging efforts in the upper Colorado River basin, USA, illustrate the applications of tagging technology and data sharing by multiple agencies to better understand the spatial ecology of large river fishes.
3. Tagging studies between 2014 and 2018 in Lake Powell and its two main tributary rivers, the Colorado (unfragmented) and San Juan (waterfall‐fragmented), were used to quantify movement of razorback sucker within this river–reservoir habitat complex. In addition, facilitated translocations of fish upstream of a waterfall barrier in the San Juan River were assessed in 2016–2017.
4. Extensive movement of fish occurred within and across river and reservoir habitats. Of 722 fish captured in the Colorado River arm of Lake Powell, 36% of re‐encounters occurred upstream in the Colorado or Green rivers, or fish dispersed through the reservoir and were detected in the San Juan River arm. Fourteen fish moved more than 600 km. In the San Juan arm of the reservoir, 29% and 20% of fish in 2017 and 2018, respectively, had moved ~30–40 km upstream below the waterfall in the San Juan River within a year. In 2016–2017, 303 fish were translocated upstream of the waterfall into the San Juan River, but 80% were re‐encountered downstream of the waterfall within a year.
5. Long‐distance movements by razorback sucker were common within and among rivers and reservoirs illustrating how large river fish, in general, might maintain population connectivity in highly altered ecosystems.

     

A meta‐analysis of fish behavioural reaction to underwater human presence

In an increasingly anthropic world, humans have profound impacts on the distribution and behaviour of marine fishes. The increased human presence has modified fishes’ antipredator behavioural responses, and consequently flight decisions, as a function of their changed perceptions of risk. Understanding how fish react to human presence can help identify the most vulnerable functional groups/species and estimate impacts caused by human disturbance. Shoal and body size are known to influence fish flight initiation distance (FID; the distance between the predator and prey when the prey begins to escape); however, few studies attempt to test the moderators of these relationships. Here, we present a comprehensive meta‐analysis evaluating FID of fish in response to human presence. Specifically, we investigated six candidate moderators that could influence the relationship between FID with shoal and body size. Our results showed that individual fish size was strongly and positively correlated with FID and the most important moderator that explained the variance in individual body size‐FID relationship was shoaling behaviour. However, and somehow surprisingly, we detected no significant relationship between shoal size and FID. We discuss how these results can inform the development of fish conservation strategies and ultimately assist in the management of marine protected areas.     

Latitudinal shifts in coral reef fishes: why some species do and others do not shift

Climate change is resulting in rapid poleward shifts in the geographical distribution of many tropical fish species, but it is equally apparent that some fishes are failing to exhibit expected shifts in their geographical distribution. There is still little understanding of the species‐specific traits that may constrain or promote successful establishment of populations in temperate regions. We review the factors likely to affect population establishment, including larval supply, settlement and post‐settlement processes. In addition, we conduct meta‐analyses on existing and new data to examine relationships between species‐specific traits and vagrancy. We show that tropical vagrant species are more likely to originate from high‐latitude populations, while at the demographic level, tropical fish species with large body size, high swimming ability, large size at settlement and pelagic spawning behaviour are more likely to show successful settlement into temperate habitats. We also show that both habitat and food limitation at settlement and within juvenile stages may constrain tropical vagrant communities to those species with medium to low reliance on coral resources.     

Turbine entrainment and passage of potadromous fish through hydropower dams: Developing conceptual frameworks and metrics for moving beyond turbine passage mortality

Potadromous fishes are vulnerable to involuntary entrainment through hydropower turbines. However, turbines can also provide a downstream passage route for potadromous fish. Here, we review evidence for turbine entrainment and passage in potadromous fish, and evaluate the effects of these processes on upstream and downstream populations. We develop conceptual frameworks and metrics to quantify vulnerability to turbine entrainment removals, and to quantify the efficiency of turbines as a downstream passage route. We highlight factors that influence these processes and provide case‐studies demonstrating their applicability. We found that juvenile potadromous fish are being entrained through turbines at rates high enough to impact upstream populations. Given that juvenile passage survival is often high, we argue that turbines provide an important downstream passage route for potadromous fish. We show that entrainment vulnerability is likely a function of interactions between in‐reservoir fish behaviour, habitat configuration and operations and thus not well captured by passage mortality estimates. Similarly, we show that while passage mortality can limit downstream passage efficiency, passage success is also dependent on reservoir and forebay navigation, along with survival and fitness in the downstream river. We advocate for a shift in focus away from estimates of passage mortality and injury, which have previously accounted for the majority of turbine passage research. Instead, we recommend an approach that focusses on quantification of the factors that influence downstream passage efficiency and entrainment vulnerability. Moreover, we highlight the need to better understand the broader scale impacts of these events on upstream and downstream populations.     

Evaluating potential competitive bottlenecks between invasive common carp and native bluegill and yellow perch

Processes influencing fish recruitment are often highly complex and inherently difficult to understand. Invasive species may complicate recruitment through habitat and food web modifications resulting in competitive bottlenecks. Common carp Cyprinus carpio have been distributed worldwide, and their introductions have resulted in destructive effects on aquatic ecosystems and food web dynamics. Common carp are highly fecund, and high densities of age‐0 carp may occur in some years that may reduce invertebrate prey resources and adversely affect native age‐0 fishes. We used enclosures and field observations to examine potential effects of age‐0 common carp on growth and survival of age‐0 yellow perch Perca flavescens and bluegill Lepomis macrochirus. Yellow perch and bluegill were stocked into enclosures with and without common carp (31 fish/m³) using a substitution experimental design, and fish growth and survival and invertebrate prey resources were assessed. Common carp reduced growth of yellow perch but not bluegill and did not affect survival of either species in mesocosms. Next, we used patterns of common carp, bluegill, and yellow perch abundance and total length across 38 lake‐years to evaluate potential interspecific interactions in natural systems. Age‐0 common carp abundance was not negatively related to size or abundance of bluegill or yellow perch. However, adult common carp and age‐0 yellow perch abundance were inversely related, suggesting a potential competitive bottleneck. Thus, age‐0 common carp may suppress growth of yellow perch when prey is limited, but adult common carp may have larger effects than early life stages on native juvenile fishes.     

The origin of the mammalian form of GnRH in primitive fishes

The presence of neuroendocrine hormones in extant agnathan fishes suggests that a method of control involving these hormones was operating 500–600 million years ago in emerging vertebrates. Data on a limited number of species show that several members of the GnRH family of peptides may have arisen in non-teleost fishes. Lamprey (Petromyzon marinus) GnRH has a unique composition and has not been detected in other vertebrates. It is not yet clear whether the chicken II GnRH-like molecule arose in cartilaginous fishes, but a chromatographically and immunologically similar molecule is found in dogfish (Squalus acanthias) and ratfish (Hydrolagus colliei). Finally, a mammalian GnRH-like molecule is detected in three primitive bony fish: sturgeon (Acipenser transmontanus), reed fish (Calamoichthys calabaricus), and alligator gar (Lepidosteus spatula). Minor forms are also present, but are not yet characterized. Clearly, the basic structure of GnRH peptides was established in primitive fish. In contrast, at least three other identified forms of GnRH have been detected in teleosts or tetrapods: Salmon I, catfish I, and chicken I GnRH. Evidence for the presence of members of the GnRH family and the neurohypophysial hormone family in primitive fishes argues for the importance of neuroendocrine control throughout the history of vertebrates.     

罗非鱼链球菌病研究进展

链球菌（Streptococcus spp．）是一种广泛分布于自然界的革兰氏阳性菌,是人类的重要病原之一,也是其他多种脊椎动物包括猪、牛、鱼等的重要病原菌。目前已有多个国家报道了鱼类链球菌病的暴发与流行,受感染的鱼类包括多种海水和淡水鱼类,以温水性鱼类最为严重。近年中国罗非鱼链球菌感染的报道也呈现增加趋势,尤其在2009年,广东、海南、福建和广西地区养殖罗非鱼的链球病发病率为20％～50％,死亡率达50％～70％,甚至更高。链球菌病已严重危害着中国罗非鱼养殖业的健康发展。文章对罗非鱼链球菌病的病原、流行及防治方法作一综述,以期为今后开展罗非鱼链球菌病防控研究提供参考。     

Hundred-year decline of North Atlantic predatory fishes

We estimate the biomass of high‐trophic level fishes in the North Atlantic at a spatial scale of 0.5° latitude by 0.5° longitude based on 23 spatialized ecosystem models, each constructed to represent a given year or short period from 1880 to 1998. We extract over 7800 data points that describe the abundance of high‐trophic level fishes as a function of year, primary production, depth, temperature, latitude, ice cover and catch composition. We then use a multiple linear regression to predict the spatial abundance for all North Atlantic spatial cells for 1900 and for each year from 1950 to 1999. The results indicate that the biomass of high‐trophic level fishes has declined by two‐thirds during the last 50‐year period, and with a factor of nine over the century. Catches of high‐trophic level fishes increased from 2.4 to 4.7 million tonnes annually in the late 1960s, and subsequently declined to below 2 million tonnes annually in the late 1990s. The fishing intensity for high‐trophic level fishes tripled during the first half of the time period and remained high during the last half of the time period. Comparing the fishing intensity to similar measures from 35 assessments of high‐trophic level fish populations from the North Atlantic, we conclude that the trends in the two data series are similar. Our results raise serious concern for the future of the North Atlantic as a diverse, healthy ecosystem; we may soon be left with only low‐trophic level species in the sea.     

Taxonomic and functional diversity in a subtropical stream: A longitudinal pattern analysis

Identifying the spatial patterns of fish diversity in streams is basic for the conservation and management of stream fishes. The “upstream–downstream” patterns in the taxonomic α-diversity of stream fishes have been widely surveyed. However, the longitudinal patterns in the functional diversity and β-diversity of stream fishes have been given less attention. In this study, we surveyed fishes along an upstream–downstream gradient in a headwater stream of the Qiantang River, China, and examined the longitudinal variations in fish diversity. Our aims were to assess whether the longitudinal patterns in fish diversity were consistent between the taxonomic and functional metrics and between the α- and β-aspects of diversity. We found that both species richness and functional richness of fishes showed a hump-shaped relationship with the distance from headwaters, while both taxonomic and functional β-diversities presented the U-shaped distributions along the river continuum. Functional diversity related more to the distance from headwaters than taxonomic diversity. Despite their similar relationship with the distance from headwaters, taxonomic and functional β-diversities were dominated by species turnover and function nestedness components, respectively. Our results suggest that, along the river continuum in a subtropical stream, the α- and β-aspects of fish diversity present different longitudinal variations. Although the taxonomic and functional diversity shows similar relationships with distance from headwaters, their spatial variations are driven by different ecological processes.