Natal homing and straying are behavioural tactics of migratory animals that return to nursery habitats to breed as adults. Straying has evolutionary and ecological importance for species flexibility, interpopulation connectivity and success of invasive species in new environments. This study aimed to estimate the relative importance of straying and homing in introduced brown trout Salmo trutta spawning

We tested for effects of two dams on fish assemblages in the St. Joseph River, Indiana. Fishes were collected by boat electrofisher twice annually, at 23 sites from 1998 to 2018. Fish collection data were aggregated into CPUE counts of species per 500 m, and CPUE were pooled across sites above and below the dams. We used multivariate analyses to test for spatial and temporal variation for assemblages

Efforts to restore river ecosystem connectivity focus predominantly on diadromous, economically important fish species, and less attention is given to nonmigratory, small‐bodied, benthic fish species. Data on benthic fish swimming performance and behaviour in comparison with ecologically similar native species are especially relevant for the study of one of the most successful invaders in the last

The Cichlidae are among the most diversified families of fish in the Neotropics and represent an important component of aquatic biodiversity. Understanding cichlid nest‐site selection is important for assemblages facing uncertain futures due to species invasions and environmental change. This information could be used to predict how inter‐ and intraspecific competition for reproductive space may affect

The introduction of exotic species has the potential to cause resource competition with native species and may lead to competitive exclusion when resources are limiting. On the other hand, information is lacking to predict under what alternate trophic conditions coexistence may occur. Comparing diets of native yellow perch Perca flavescens and nonindigenous white perch Morone americana, we examined

Offspring growth is greatly influenced by both the maternal and paternal genotypes. However, although the effects of maternal genotype on offspring growth are recognised widely, ecological studies of the paternal genotype have not focused on the links with physiological traits, especially at the embryo stage. In this study, we conducted three experiments to determine the effects of two contrasting

Understanding spatial variation in non‐native fish species population ecology is imperative, where environmental, biotic and invasion‐related mechanisms contribute to spatial heterogeneity. Established populations of invasive silver carp Hypophthalmichthys molitrix are currently found throughout a large portion of the upper Mississippi River (UMR) basin. Despite their recent invasion and broad environmental

Documenting responses of biotic assemblages to coal‐mining impacts is crucial to informing regulatory and reclamation actions. However, attributing biotic patterns to specific stressors is difficult given the dearth of preimpact studies and prevalence of confounding factors. Analysing species distributions and abundances, especially stratified by species traits, provides insights into how assemblage

Swimming performance is a determinant characteristic for the survival of fish species and is related to their response to environmental disturbance. In this study, we evaluated how seasonal environmental variability of Mediterranean intermittent rivers influences swimming performance of a resident Iberian fish, the ruivaco, Achondrostoma oligolepis. Approximately forty fish of A. oligolepis were captured

Clearing land for the establishment of pasture is the principal cause of deforestation in the Amazon basin. We investigated how stream habitats and the taxonomic and functional structure of the fish fauna respond to the effects of the conversion of forest to pasture in the eastern Brazilian Amazon. We sampled 13 streams located in areas of forest and 13 streams within a pasture matrix. The structure

Recent large influxes of non‐native Pacific pink salmon (Oncorhynchus gorbuscha) to North European rivers have raised concern over their potential negative impacts on native salmonids and recipient ecosystems. The eggs and carcasses of semelparous pink salmon may provide a significant nutrient and energy subsidy to native biota, but this phenomenon has not been widely documented outside the species'

Bartram's Bass Micropterus sp. cf. cataractae is a rare black bass endemic to the Savannah River of the south‐eastern United States and is threatened by habitat degradation and hybridisation with nonnative Alabama Bass Micropterus henshalli. While Bartram's Bass has been functionally extirpated from reservoirs, some populations persist in tributaries. Understanding the mechanisms affecting hybridisation

Through their multiple functions, refuges may be important for stream‐living fishes, particularly during stressful events such as seasonal low flow or drought. Coastal Cutthroat Trout Oncorhynchus clarkii clarkii is an ideal study organism to understand the importance of refuge. During seasonal low flow, lower water levels limit access to refuge and emigration, survival of fish is low, and predation

Trophic partitioning, defining how individuals or populations differ in their resource use, is expected to promote coexistence of sympatric species by reducing resource overlap. We used stable isotope measurements (δ13C and δ15N) to address niche characteristics (δ13C and δ15N ranges, isotope convex hull and standard ellipse areas, mean nearest neighbour distances and trophic positions) and trophic

The objectives of this study were to investigate the food resources consumed by two species of detritivorous fishes along the Apodi‐Mossoró River reservoir cascade system, located in the tropical semi‐arid region of Brazil. The hypotheses tested were as follows: (a) the diet, niche breadth and niche overlap of the species in the reservoirs downstream of the cascade are different due to the blockage

Resource use by organisms is mainly influenced by factors such as the morphology of individuals and the diversity and abundance of resources. For omnivores, the influence of these factors is more complex, as they have a morphology adapted to access different trophic levels, and any change in the environment can affect the quality or availability of resources. The aim of this study was to evaluate the

We investigated how the taxonomic and functional structures of fish assemblages in the lower Amazon River floodplain responded to seasonal hydrological variations. Fishes were sampled in 440 aquatic habitats across a floodplain area of 17,673 km2 during periods of high, receding, low and rising water. In addition, we recorded local environmental and landscape variables known to affect fish assemblages

Ecological studies have traditionally treated fish species or populations as homogenous groups; however, numerous studies have shown that intrapopulation variation in resource use is widespread. Within‐species diet differences are evident in small and large freshwater systems and may influence trophic and population dynamics. In a previous study of young yellow perch, spatial intrapopulation diet variation

Riparian forest may represent a key subsidy to aquatic food webs. While most research has been done in running waters, the origin of resources subsidising biomass and the role of riparian coverage in food webs remains largely unstudied in reservoirs. This research evaluated the role of forest riparian zones as food web subsidies in a recently formed reservoir of Ijuí River, Brazil. The diet of fish

Facultative migration occurs when, in response to prevailing conditions, individuals in a population may (or may not) undertake a migration. The brown trout (Salmo trutta) is a species that exhibits facultative migration, where some individuals within populations may move to mainstem rivers (fluvial–adfluvial migration), lakes (lacustrine–adfluvial migration), estuaries (partial anadromy) or sea (anadromy)

Populations of generalist fish can be composed of individuals specialised to a small subset of food resources, a process known as individual specialisation. In this study, we hypothesised that variation in the diet and morphology of individuals is related to habitat complexity and that greater levels of individual specialisation are found at intermediate levels of macrophyte biomass. Fish and aquatic

Variation in life history traits within and across species is known to reflect adaptations to different environmental drivers through a diversity of mechanisms. Trait variation can also help buffer species and populations against extinction in fluctuating environments and against anthropogenic disturbances. Here, we examine the distribution and drivers of Ocean‐type Chinook salmon (Oncorhynchus tschawytscha)

The Baltic Sea is a unique ecosystem and the largest body of brackish water in the world. It is inhabited by several originally freshwater fish species, one of them being pike (Esox lucius), which is adapted to the mesohaline conditions of the southern Baltic Sea and colonises its south‐western bays and lagoons. Using twelve microsatellite markers, we analysed the genetic structure of 407 Baltic Sea

The impacts of climate change on cold‐water fishes will likely negatively manifest in populations at the trailing edge of their distributions. Rio Grande cutthroat trout (Oncorhynchus clarkii virginalis, RGCT) occupy arid south‐western U.S. streams at the southern‐most edge of all cutthroat trout distributions, making RGCT particularly vulnerable to the anticipated warming and drying in this region

The recruitment of anadromous brown trout smolt from a small Baltic stream, frequently exposed to summer drought, was quantified for 9 years, and the effect from drought on smolt number and age composition analysed. Drought was quantified by, (a) a newly developed index quantifying the severity of summer drought (Drought Severity Index—DSI—based on amount of precipitation, monthly mean temperature

The Atlantic salmon (Salmo salar) population of the River Minho represents the southern natural distribution edge of the species. In line with the general trend for Atlantic salmon, this population has been declining over the years and is now at a critically low level. With river connectivity compromised by a large dam just 80 km upstream the River Minho's outlet, and an expected deterioration of climatic

In high‐latitude lakes, air temperature is an important driver of ice cover thickness and duration, which in turn influence water temperature and primary production supporting lake consumers and predators. In lieu of multidecadal observational records necessary to assess the response of lakes to long‐term warming, we used otolith‐based growth records from a long‐lived resident lake fish, lake trout

Migrating fish species are worldwide in decline due to several global changes and threats. Among these causes are man‐made structures blocking their freshwater migration routes. Shipping canals with navigation locks play a dual role in this. These canals can serve as an important migration route, offering a short cut between freshwater and the sea. In contrast, the navigation locks may act as barriers

The classical debate about the roles of endogenous factors and external drivers in regulating populations continues to be a very active area of scientific research, and these roles are even more complex in populations located in geographically marginal areas. We tested three hypotheses on two separate brown trout populations inhabiting the southernmost basins of the Iberian Peninsula, with the aims

Understanding resident fish population responses to restored connectivity would enhance decision‐making on dam removal and fish passage. Since such evaluations are limited in the Great Lakes region of North America, we compared abundance, survival, and growth of resident brook trout and brown trout between sets of Michigan streams where populations were or were not interacting with salmonid species

The Chishui River is the last free‐flowing tributary of the upper Yangtze River, China, which has an important role in fish conservation. This study aimed to explore the spatial organisation of fish assemblages in this river. Field sampling was conducted biannually between 2015 and 2017 at 41 sites from its headwater and downstream. One hundred and twenty‐two fish species were captured, including 34

Migrations of juvenile salmon smolts are generally high‐risk, with predation often implicated in reduced survival. In theory, smolts can maximise survival via depensation, or synchronising movements to swamp predators. Depensation, however, is difficult to assess in the wild. Accounting for depensation could also generate more realistic telemetry‐based survival estimates for management. Here, we assess

Rising temperatures caused by climate change are likely to affect cool‐water and warm‐water fishes differently. Yet, forecasts of anticipated temperature effects on fishes of different thermal guilds are lacking, especially in freshwater ecosystems. Towards this end, we used spatially explicit, growth rate potential (GRP) models to project changes in seasonal habitat quality for a warm‐water piscivore

Estimating species’ potential distribution is one of the main objectives of macroecology, especially when sampling biases can affect knowledge on how environmental variables affect species distribution. Ecological niche models estimate species’ environmental niches from different variables and their occurrences. Using the presence‐only data from eight Amazonian fish species, which inhabit rivers and

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

Lake sturgeon (Acipenser fulvescens) have been negatively impacted by barriers to migration, pollution and overharvest. Biological data such as the timing of spawning activity and larval drift have provided a better understanding of larval production success or failure on a site‐specific basis. However, many river systems that serve as reproductive locations for remnant lake sturgeon populations remain

Stable isotope ratios of nitrogen (δ15N) have been used to estimate trophic position (TP) of organisms due to the predictable enrichment of nitrogen‐15 in consumer tissues relative to their diet. We explored estimates of trophic position using liver and muscle δ15N and stomach content analysis in a broad size range of Arapaima sp. from Amazonian floodplain lakes. Estimates of TP based on liver δ15N

Climate change will increase the temperature of rivers and will lead to more extreme events, such as floods. Temperature increases and floods will likely alter the phenology of freshwater species differently and have the potential to significantly disturb prey–predator interactions. In spring, an increase in temperature triggers an increase in primary production and controls the timing of the emergence

The conservation, management and monitoring of aquatic resources should benefit from understanding their spatial structuring. In this paper, we used the reference condition approach (RCA) to test if the variability in biotic communities, riverine fish assemblages in the present case, is better controlled with a spatial delineation based on ecoregions or by grouping rivers with local catchment characteristics

Volitional dispersal is a ubiquitous strategy characteristic of species across major faunal groups. Dispersal during the juvenile life stage is of interest because early performance can be critical for determining future success (survival/reproduction). For salmonids, dispersal can influence local density, competition, individual growth and survival, though drivers of dispersal at meso‐scales are rarely

The catadromous life cycle of the European eel encompasses a spawning migration to the Sargasso Sea. Prior to their migration, eels develop a silver coloration being referred to as “silver eels.” Due to the dramatic European eel recruitment decline, it is crucial to quantify silver eel escapement to evaluate the success of measures taken under Eel Management Plans (Regulation EC (1100/2007)). Thus

The establishment of national parks are an important and often‐used tool to protect biodiversity. However, when considering freshwater ecosystems, many of these areas in Brazil are habitat mosaics in which a small part of the ecosystem is protected and strongly influenced by the surrounding environment. By assessing the fish fauna and their diversity patterns in five national parks (NPs) within the

Alternative life‐history tactics of masu salmon Oncorhynchus masou are well documented. Subsequent to the freshwater parr stage (age ≥ 1 + years), an anadromous form migrates to the sea after smolting, while a resident form matures without seaward migration. In addition to this typical migratory dimorphism, anecdotal reports based on field observations have indicated that some underyearling masu salmon

Smolt lengths are increasingly recognised as an important determinant of salmonid marine survival rates. Overwintering growth rates could thus strongly influence adult return rates. In Atlantic salmon Salmo salar, most overwintering studies focus on rivers in harsh climates with minimal growth, yet in more southerly rivers, overwintering growth rates can be relatively high. Here, the factors influencing

Differences in reproductive strategies of male and female fishes are presumably accompanied by differences in nutrient allocation and predicted to lead to divergence in body composition between the sexes. We compared patterns of variation in fatty acid profiles of lipids extracted from ova, liver, muscle and visceral fat between mature male and female walleye (Sander vitreus) sampled from two wild

Body shape variation should play a central role in determining the feeding ability of a fish species. We tested whether variations in feeding resource use of sympatric and closely related fish species could be explained by differences in ecologically relevant metrics, such as body morphology, trophic apparatus or combinations thereof. Fish were sampled at 14 sampling sites from Pelotas River and tributaries

There is concern that expanding beaver (Castor fiber) populations will negatively impact the important economic, recreational and ecological resources of Atlantic salmon (Salmo salar) and sea trout (Salmo trutta) populations in Europe. We studied how beaver dams influenced habitat, food resources, growth and movement of juvenile Atlantic salmon and trout on three paired beaver‐dammed and beaver‐free

Experimental predation studies were conducted to evaluate and compare the predation threats of 10 species of native and non‐native fishes on larvae of Pacific Lamprey, Entosphenus tridentatus, and Western Brook Lamprey, Lampetra richardsoni. The relative predatory threats were examined over four sets of binary factors, including the following: (a) short (2‐day) or long (7‐day) duration, (b) presence/absence

We investigated whether isotopic niche partitioning could mediate the coexistence between native (Hoplias sp. B) and non‐native (Hoplias mbigua) trahira in a Neotropical floodplain. We hypothesised that during the dry season both species inhabit isolated sites (i.e. lakes) and thus rely on distinct food resources to sustain their coexistence. We found evidence of trophic segregation among native and

Growth of fish is an important contributor to individual fitness as well as fish production. Explaining and predicting growth variation across populations is thus important from fundamental and applied perspectives, which requires knowledge about the ecological factors involved in shaping growth. To that end, we estimated environment‐dependent von Bertalanffy growth models for 13 gravel pit lake populations

Bayesian inference was used to estimate the main population parameters (sex ratio, L50, LWR and somatic growth) and to evaluate sexual dimorphism and growth patterns (isometric/allometric and monophasic/biphasic growth) of Astyanax paranae of the Upper Paraná River. This study brings three statistical differentials: (a) the reparametrisation of the logistic model as a function of L50; (b) the reparameterisations

Multiyear drought is projected to increase in frequency and duration in arid and semiarid regions across the world, threatening native species and ecosystem function. The effects of multiyear drought are often exacerbated by human water use, which manifest in reduced lake elevation, reduced stream discharge, and disruption in hydrologic connectivity for aquatic species. Here, we demonstrate that drought‐driven

Many species of salmonids have been stocked into waters outside of their native range. The invasiveness and impact of these species on native species varies depending on their biological traits, and on environmental conditions, such as climate. In Japan, rainbow trout and brown trout, both listed in 100 of the world's worst invasive alien species by the International Union for Conservation of Nature

Unravelling the effect of climate variability on species biology has been one of the main goals of ecological studies. Environmental factors such as river discharge and temperature have being proposed as triggers of reproductive cycle in fish. In temperate climates, fish reproduction is affected mainly by temperature, while is influenced by flood pulses in large tropical rivers. We evaluated the influence

The consequences of over‐exploitation may seriously impair the integrity and functioning of ecosystems. When loss of species is accompanied by the loss of ecological processes, the effects are no longer just taxonomic and may affect the stability of the environments. Ornamental fishing is one of the main economic activities of the middle Negro River. Such activity is directed to a small number of species

Trout and charr, members of the salmonid family, have high conservation value but are also susceptible to anthropogenic threats in part due to the specificity of their habitat requirements. Understanding historical and future threats facing these species is necessary to promote their recovery. Of freshwater trout and charr in the Canadian Rocky Mountain region, westslope cutthroat trout (Oncorhynchus

Understanding the spatial ecology of juvenile freshwater fish beyond summer months is an essential component of their life history puzzle. To this end, declines in the natural populations of sympatric Muskellunge (Esox masquinongy) and Northern Pike (Esox lucius) in the upper St. Lawrence River prompted study of spatiotemporal patterns and habitat requirements associated with earlier life stages of

We employed the trophic upsurge hypothesis as an analytical framework to describe the response of Neotropical fish communities to terrestrial inundation associated with river damming. Data were collected for the impact assessment of the Peixe Angical Dam, Tocantins River, Brazil. Monthly surveys were conducted at nine sites (seven upstream, two downstream) from 15 months before to 20 months after dam