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The ecological impact of dreissenid mussel (e.g., quagga and zebra) populations and their empty shells on native fauna in large rivers and lakes has been extensively studied. However, there is limited information on their effects in small wadable streams. Although established mussel populations in these systems are uncommon, their shells are found in high densities in benthic environments and may adversely impact stream communities. Shell densities were quantified using quadrats in two wadable streams to assess impacts on native benthic macroinvertebrates and fish. Eight reaches of each river were sampled, four with dreissenids and four without, totaling 16 locations. Macroinvertebrate and fish communities were characterized using diversity and environmental tolerance indices. Shell densities were significantly higher in dreissenid-invaded sites compared to sites with only native bivalves in both rivers. Dense shell beds had degraded biological conditions with fewer sensitive macroinvertebrates, but bed density did not affect overall macroinvertebrate or fish diversity. These findings differ from lake and large river studies, which found a greater impact of dreissenid shell deposition on macroinvertebrate and fish diversity than we observed in small wadable streams. Thus, a different approach to management and restoration may be necessary to maintain a natural community composition in wadable streams. [ABSTRACT FROM AUTHOR]

The trade-off between current and future reproduction remains a central issue for understanding the diversity of fish life-histories along a slow-fast continuum. Fish living in rivers of tropical oceanic islands generally have a fast type life-history, but variations in key reproductive traits can occur in response to spatial changes in selection pressures. Here, we investigated the reproductive strategies of two sympatric amphidromous gobies widely distributed in Caribbean streams, Sicydium plumieri (n = 308) and Sicydium punctatum (n = 383), along a river gradient of Guadeloupe Island. Beyond the new insights provided on the reproductive traits (ovarian organization, gonadal development, length at maturity, and spawning season), the histological observations of testes and ovaries revealed variation in reproductive strategies. Sicydium punctatum showed a time-minimizing strategy, featuring early reproduction, a high spawning frequency, an extended reproductive period, and a broad spawning area along the river course. Sicydium plumieri displayed a size-maximizing strategy, featuring a delayed maturity, lower spawning frequency, and a shorter reproductive period restricted to the upper reaches of rivers. We discuss the advantages provided by these two strategies in response to the spatial changes in predation and disturbance levels along the upstream–downstream continuum, which probably affects the survival rate and mortality risk before the first reproduction. [ABSTRACT FROM AUTHOR]

Anthropogenic land use has caused a major crisis to the biodiversity of stream fishes in recent decades, especially with regard to biotic homogenisation. Understanding the response of stream fishes to anthropogenic land use will help to promptly implement effective conservation measures. In this study, we investigated the effects of agriculture on fish diversity in streams in the Wannan Mountains, China. We predicted that agriculture would influence fish diversity by affecting local habitat conditions. The results showed that habitat conditions (e.g. water temperature, water width, water depth) differed significantly between disturbed and reference sites. The disturbed sites had high species richness due to the addition of translocated species outpacing the loss of endemic species. Moreover, fish assemblages showed taxonomic differentiation accompanied by functional homogenisation, which mainly resulted from the addition of translocated species with redundant functional traits. However, the emergence of homogenisation shows a time delay. The biotic differentiation of fish assemblages in agroecosystems is temporary in the Wannan Mountains, and homogenisation may eventually develop as stress intensifies. Thus, it is urgent and necessary to take effective conservation measures to delay or prevent fish assemblages from worsening in agroecosystems before homogenisation develops. [ABSTRACT FROM AUTHOR]

Understanding consumer–resource interactions is essential for understanding the trophic dynamics of species-rich fish communities. Woodland et al. (Oikos 125:556–565, 2016) assumed that trophic position (TP) distributions of primary consumers and tertiary species are restricted versus intermediate consumers tending to be omnivores with broader TP distribution, where these omnivores often dominate the overall biomass. With rare evidence supporting this hypothesis in a river, we tested it in the species-rich Pearl River fish assemblage, China. Using bulk stable isotope (SI) approach (δ13C, δ15N), the TPs, SI distribution parameters, isotopic niche sizes (as standard ellipse areas, SEA) and interspecific niche overlap were calculated for the abundant fish species. Fishes of intermediate TPs (i.e. omnivores) had larger δ13C variance/ range, broader isotopic niches and higher niche overlap compared to fishes at low TPs and high TPs, indicating a higher degree of trophic redundancy among the omnivores, whereas high TP fish had narrower niche and lower niche overlap, indicating trophic partitioning among tertiary species. These omnivores at intermediate TPs between 2.4 and 2.8 dominated fish biomass. The results not only support the Woodland et al. (Oikos 125:556–565, 2016) hypothesis in the river, but also provide a novel explaining in how niche sizes and overlap vary by TP. [ABSTRACT FROM AUTHOR]

For shallow lakes, the most dramatic ecosystem shift is that from a clear-water, macrophyte-dominated regime to a turbid, phytoplankton-dominated regime. Whereas many studies have focussed on the factors that trigger such shifts, it is still unclear how these changes shape fish diversity. In the present study, we characterised the fish communities taxonomically and functionally in Lake Taihu, China, along a spatial gradient of habitat types, i.e. algal-dominated, macrophyte-dominated, open-lake and aquaculture conversion zones. Random Forests regression was then applied to examine how fish diversities were related to environmental conditions. Our results showed that the taxonomic and functional composition of the fish community varied among different habitat regimes. Macrophyte and water quality were identified as the most important factors affecting the fish diversity indices. Habitats with a high macrophyte biomass and low nutrient concentration supported higher functional diversity. Moreover, our analysis revealed that although functional diversity indices were strongly correlated with species richness, they appeared more sensitive to changes in habitat conditions. Overall, our study highlights the importance of macrophyte-dominated state in maintaining fish diversity in freshwater ecosystems and provides new insight into how functional diversity can improve our understanding of the response of biodiversity to ecological processes. [ABSTRACT FROM AUTHOR]

Human activities are one of the main causes of biodiversity loss and the reduction of ecosystem services. These activities, together with seasonality and the associated ecological and physicochemical changes, are the main modulators of fish communities in subtropical streams. Using data from 62 streams from Uruguay, we analyzed the effect of environmental variables on several attributes of fish community structure. First, we evaluated the effect of climatic seasonality on fish biomass, density, mean body length and weight using a paired t-test. Secondly, we analyzed the relationship between seasonality, environmental variables (environmental degradation, watershed area, and habitat diversity), and species richness with fish biomass using a linear mixed model. Fish biomass and density were higher in summer meanwhile, mean length was higher in winter. We found a humped relationship between biomass and environmental degradation in winter and summer, with low biomass in sites with high and low quality. Our model shows that species richness increase generates an increase in biomass, with the magnitude of this increase being greater during winter. In view of this results, we highlight that the humped pattern founded in our work should have special management attention to avoid misinterpretation of biomass increases caused by environmental degradation. [ABSTRACT FROM AUTHOR]

The Three Gorges Reservoir is one of the largest reservoirs in the world. Previous studies uncovered longitudinal changes in fish assemblages among riverine, transitional, and lacustrine zones, but whether they vary at small-scale habitats and how tributaries contribute to fish conservation is poorly understood. We selected three neighboring tributaries with different habitat characteristics within and among tributaries and hypothesized that the small-scale habitat heterogeneity within or among tributaries could shape spatial and temporal variation in fish assemblages. We analyzed spatial (among tributaries, pelagic versus benthic, lower versus upper reach) and seasonal patterns of fish assemblage and their relationship with the environment. Piscivorous, limnophilic, and mid-pelagic species dominated the fish assemblage in different habitats. Fish assemblage structure varied spatially between lower and upper reaches and among tributaries. Fish assemblages also varied seasonally, mainly related to environmental variability (i.e., water depth, water temperature, pH, specific conductivity, riparian slope, and vegetation coverage). Catch per unit effort was similar between pelagic and benthic habitats but exhibited horizontal and seasonal changes. The most influential environmental variables were water depth, water temperature, dissolved oxygen, and pH. Our results supported the hypothesis, and indicated that we should protect tributaries that provide important areas for fish diversity in large reservoirs. [ABSTRACT FROM AUTHOR]

The fish communities in the Yangtze River (YR) basin is in a degraded state due to the influence of human factors. Here, we used environmental DNA (eDNA) metabarcoding technology to conduct a survey on the fish diversity in the upper reaches of the YR from Jiangjin to Fuling to search for better monitoring methods. We set up 12 sampling sites in this river section, collected 36 environmental samples, and obtained 5,067,423 valid sequences. After conducting an annotated comparative analysis utilizing the NCBI public database, a total of 104 freshwater fish species were identified, belonging to 8 orders, 24 families, and 72 genera. This included six nationally protected fish species, as well as endemic, introduced, and previously unrecorded species within this basin. The results of this survey indicate a trend toward miniaturization of species and a decline in endemic fish species as well as an increase in exotic fish species in the region, which implied the fish communities in the upper YR region remains in a degraded state. However, the species composition at the family level has remained relatively stable over the past decade. Furthermore, the diversity analysis revealed that fish composition and diversity exhibit variability across different locations. [ABSTRACT FROM AUTHOR]

Variation in fin shape is one of the most prominent features of morphological diversity among fish. Regulation of fin growth has mainly been studied in zebrafish, and it is not clear whether the molecular mechanisms underlying shape variation are equally diverse or rather conserved across species. In the present study, expression levels of 37 candidate genes were tested for association with fin shape in the cichlid fish Lamprologus tigripictilis. The tested genes included members of a fin shape-associated gene regulatory network identified in a previous study and novel candidates selected within this study. Using both intact and regenerating fin tissue, we tested for expression differences between the elongated and the short regions of the spade-shaped caudal fin and identified 20 genes and transcription factors (including angptl5, cd63, csrp1a, cx43, esco2, gbf1, and rbpj), whose expression patterns were consistent with a role in fin growth. Collated with available gene expression data of two other cichlid species, our study not only highlights several genes that were correlated with fin growth in all three species (e.g., angptl5, cd63, cx43, and mmp9), but also reveals species-specific gene expression and correlation patterns, which indicate considerable divergence in the regulatory mechanisms of fin growth across cichlids. [ABSTRACT FROM AUTHOR]

In Morocco, no work has been carried out on parasitic monogeneans of cichlid fish as far. An examination of the gills of 375 fish from three native species of Cichlidae: Oreochromis aureus, Coptodon zillii and Coptodon guineensis from different localities, revealed the presence of two monogenean species (1328 monogenean specimens were recovered from 56 fish specimens) belonging to the family Dactylogyridae and to the genus Cichlidogyrus: three morphotypes of C. cirratus were identified from O. aureus and C. zillii; and C. cubitus was identified from C. guineensis. This is the first time that these monogeneans were collected and identified in Morocco. In addition, O. aureus was revealed as a new host for C. cirratus. The low parasite species richness and intensity, appear to support the enemy release hypothesis, and have probably promoted the lateral transfer of parasites in natural populations between O. aureus and C. zillii, and the synxenic diversification of C. cirratus. [ABSTRACT FROM AUTHOR]

Variation in jaw protrusion is critical to cichlid fish trophic diversification. For instance, jaw protrusion distance can influence suction, attack speed, as well as bite force, and jaw protrusion angle is associated with exploiting prey from different substrates. Interestingly, premaxillary ascending process length has been shown to influence the maximum distance some cichlid fishes protrude their oral jaws, but its relationship to jaw protrusion angle is unclear. Using phylogenetic comparative methods, morphometrics, and field measurements in Malawi cichlid species, we tested the relationship between the length of the premaxillary ascending process and two components of jaw protrusion. In Malawi, the premaxilla's ascending process length ranged from 6.9 to 15.2% with respect to standard length. Maximum jaw protrusion ranged from 1.4 to 9.1% of standard length and jaw protrusion angle varied from 17° to 76°. Although jaw protrusion angle was not associated with premaxillary ascending process length, phylogenetically adjusted correlations between the ascending process and maximum jaw protrusion distance were highly significant. Evolutionary change in the premaxilla is likely critical for determining the maximum distance, but not the angle, of Malawi cichlid jaw protrusion. Examinations of this type of potential phenotypic multi-functionality will continue to illuminate the mechanisms contributing to cichlid fish diversity. [ABSTRACT FROM AUTHOR]

As human-induced environmental changes reduce niche opportunities from global to local scales, permanent shifts in species traits alter ecosystem processes. Disentangling multiscale mechanisms driving temporal changes in coastal fish biodiversity is thus critical to conservation aims. From seasonal to multiyear periods, we investigated how local environmental variation and landscape features shape temporal beta diversity (abundance-based and trait-based dissimilarities, and their components of replacement and nestedness) per zones in bays and coastal lagoons, Southeastern Brazil. At larger temporal dimensions, unaccounted processes in individual systems influenced primarily taxonomic dissimilarity, whereas functional responses to variation in marine influence varied between types of system and zones. From 2 years to seasons, taxonomic and functional dissimilarities decreased with abundance-based species replacement, and both trait-based components, respectively. Replacement processes were primarily related to marine influence (transparency, salinity, pH, and tidal phase) at larger temporal dimensions, and habitat availability (mangroves and nearby estuaries) and complexity (forest cover and landscape urbanization) in seasons. Seasonal variations in tidal phase (lower) and pH (higher), respectively, promoted taxonomic (abundance gradients) and functional (fish trait loss) nestedness under shorter environmental gradients. Spatial and temporal balances between marine influence, habitat quality, and seascape connectivity drive temporal dissimilarities in coastal fish assemblages. [ABSTRACT FROM AUTHOR]

Identifying the spatial patterns of fish diversity is essential for the conservation and management of stream fishes. Many studies highlight the need to comprehensively consider diversity rather than a unique index to enact conservation strategies. However, understanding spatial patterns along environmental gradients and the correlation of multifaceted diversity in stream fish communities remains limited. Thus, we surveyed fishes along an upstream–downstream gradient in the Qiupu River, an important tributary of the Yangtze River, China. We aimed to explore the spatial variation and congruence of the multifaceted diversity of fish communities, as measured by taxonomic (TR), functional (FR), and phylogenetic (PR) richness, along the longitudinal gradient. Both TR and PR had a positive linear relationship with distance from the headwaters, although this trend was not significant for FR due to functional trait redundancy. There was high spatial congruence between TR and PR but relatively low-congruence between TR and FR. Spatial autocorrelation patterns were identified for TR and FR, but not for PR. Our results suggest that along the continuum, each diversity metric reflected different spatial patterns, and the results support the importance of using multiple facets of diversity in assessing community structure and developing conservation strategies. [ABSTRACT FROM AUTHOR]

Rocky reefs and kelp forests form conspicuous habitats that promote species diversity and support livelihoods in coastal communities. However, taxonomic approaches often disregard biological identity and differences between species. In this study, we explore the relationship between functional diversity of fish communities and habitat complexity in temperate reefs and test if greater habitat complexity, such as rugosity or kelp three-dimensional structure, would result in higher functional diversity. We conducted fish surveys using SCUBA in four kelp forest sites and rocky reef sites. Although the rocky reef and kelp forest sites showed differences in habitat complexity, no significant differences in fish taxonomic or functional diversity were found between the two habitat types. However, we did find differences at smaller spatial scales for the kelp forest sites, where number of stipes, stipe bundle diameter, and kelp density influenced functional richness, but not species richness, highlighting the importance of functional approaches in certain ecosystems. The differences found among kelp forest sites may be linked with small-scale spatiotemporal oceanographic drivers of productivity such as upwelling exposure or nutrient availability. We recommend considering small-scale spatial drivers when aiming to understand how habitat characteristics link with functional diversity. [ABSTRACT FROM AUTHOR]

The objective of this research was to evaluate changes in fish diversity in streams subjected to different intensities of aquaculture production. The differences in the percentage of occupation by aquaculture ponds were used as a proxy for the propagule pressure of Oreochromis niloticus in natural environments and allowed for the classification of streams into three propagule pressure categories: no propagule, moderate, and intense. A species-rank abundance in the three propagule categories was conducted. Fish presence and absence data, and abundance of fish species were used as proxy to test the effect of aquaculture on fish assemblages. A total of 70 species were sampled, and O. niloticus was captured only in streams where aquaculture was developed. We found that O. niloticus increases its abundance as aquaculture propagule pressure also increases. Oreochromis niloticus was the 17th most abundant species in the moderate category, and the 6th species in the intense category. Fish composition (presence x absence, and abundance data) differed significantly among the propagule pressure categories, with species richness greater in no propagule pressure. These findings reinforce the role of aquaculture as a vector of invasive fish into Neotropical streams, where they can develop self-sustainable populations and impact native fish diversity. [ABSTRACT FROM AUTHOR]

Functional diversity metrics have been suggested as important indicators of ecosystem functioning. We investigated the effects of land use mediated by local environmental variables on the fish assemblages' functional structure in 18 headwater streams distributed in the Upper Paraná and Iguaçu ecoregions. The species were characterized according to habitat use, food resource use, life history, and hypoxia tolerance. We calculated functional diversity indices [richness (FRic), evenness (FEve), divergence (FDiv), dispersion (FDis), diversity (RaoQ)] and functional rarity indices [distinctiveness (Disti), uniqueness (Uni)], and evaluated the effects of regional and local variables on these indices using generalized linear models. The results highlighted the occurrence of the most functionally distinct and unique species in the forested streams. Moreover, we observed higher FRic in streams sampled in argisol, with a high ammonia load and low habitat diversity. Forested and agricultural covers positively affected FDis and RaoQ. Urban cover had a negative effect on FDis and RaoQ, mainly due to the increase in generalist functional groups in urban streams. Our findings emphasize the importance of forested cover in maintaining specialized species in fish assemblages of streams and preserving functional diversity and ecosystem functioning. Furthermore, these results contribute to direct conservation and recovery measures in freshwater environments. [ABSTRACT FROM AUTHOR]

The lack of knowledge about freshwater biodiversity in remote areas like montane Andean rivers is noticeable and hinder the development of efficient conservation plans for aquatic ecosystems. Habitat requirements of tropical Andean fishes have been poorly analysed, despite the relevance of these ecological features on the fish conservation strategies. The present study aimed to examine fish assemblages along the altitudinal gradient in tropical Andean rivers and their relationship to habitat features to detect the most relevant abiotic factors and their implication on conservation. This study was conducted on a regional scale, along six basins located in tropical Andes (500 to 2,692 m a.s.l.). We studied fish diversity and distribution and their habitats along these elevation gradients. We found 6,320 specimens from 53 genera. Our analysis for the six most common and widely distributed genera (Astroblepus, Brycon, Bryconamericus, Chaetostoma, Pimelodella and Trichomycterus) underlines the relevance of hydromorphological variables on fish community structure in the Andean montane rivers, whereas human alterations seem to be less significant. These findings could be useful for current management and conservation strategies considering present threats over tropical montane rivers. [ABSTRACT FROM AUTHOR]

Large-scale deforestation not only modifies the landscape, but also affects in the structure of the habitat, and threaten the functional structure of the aquatic biota. This study evaluates the partitioning of the functional beta diversity of stream fish along a gradient of environmental impact and determines which functional traits are associated with the gradient. Biological, environmental, and landscape variables were sampled in 2014 and 2015. The functional structure of the fish fauna was characterized using 12 functional traits. The functional beta diversity and functional replacement were influenced by changes in local abiotic and landscape conditions, caused by modifications in forest cover, with the functional traits varying systematically in accordance with environmental features. We found no association between environmental variables and functional traits. Our results raise concerns with regard to the transformation of the landscapes in which streams are found caused by changes in land use, and we would recommend the preservation of an adequate buffer of good quality riparian vegetation in management or restoration projects to guarantee the long-term conservation of stream ecosystems. [ABSTRACT FROM AUTHOR]

Shallow coastal habitats are ruled by fluctuating environmental conditions, which lead to shifts in fish communities. Functional groups of habitat use and trophic strategy were used to address the responses of fish composition and diversity, since comparisons of rich tropical systems are often complex through species-based approaches. We hypothesized that fish groups will have specific affinities in response to the prevailing environmental conditions, especially those reflecting the prevalence of oceanic or estuarine conditions, where guilds of habitat use would perform better as indicators. Despite the importance of other environmental factors (i.e. temperature and transparency), salinity was the key structuring factor irrespective of the coastal lagoon. Although harbouring the greatest biomass of piscivores, the harsh environmental conditions at Araruama lagoon were related to low diversity. A great number of indicator species, typically of marine affinity, was found at the Saquarema lagoon, probably due to the continuous and broad connection to the sea leading to the predominance of euhaline conditions. Despite the presence of non-native species (i.e. Oreochromis niloticus), the Maricá lagoon function as an important refuge for freshwater groups. Our results stressed the key role played by coastal lagoons of varied water conditions in supporting fish diversity at regional levels. [ABSTRACT FROM AUTHOR]

Despite decades of investigation, there are few ecological studies on the Amazonian fish fauna that have looked both at the main factors shaping the fish assemblages at a regional scale and used environmental, spatial and historical approaches simultaneously. The current study aimed to measure the relative influence of environmental aspects, spatial distance and historical processes on fish genera assemblages in the upper Amazon basin (Peru and Ecuador). Climate, slope and elevation were used as environmental variables; watercourse was used to represent the spatial distance between sites and phylogenetic relationships were used as a proxy for historical processes. A partial Redundancy Analysis (pRDA) was used to compute the influence of each group of factors (environment, space and historical processes) on the fish genera assemblage. Our analysis indicated historical processes had the greatest influence on fish genera assemblages, followed by spatial distance and environment. Such patterns are most likely due to the extinction processes caused by environmental filters generated by the Andean orogeny and possible speciation in each sub-basin. The results suggest that the use of phylogeny, in addition to environment and space, provides a useful tool with which to assess the drivers responsible for fish assemblages at a regional scale. [ABSTRACT FROM AUTHOR]

Exploring the seasonal dynamics of different components of biodiversity (alpha, beta, and zeta) and identifying the factors driving these patterns can help to reveal the health conditions and changes of ecosystems across different seasons. Seasonal differences in coastal fish biodiversity components were determined based on data of species abundance, traits, and mitochondrial genes. We then used multiple models to assess the relative importance of environmental and geographic variables in shaping the spatial patterns of different components of diversity. The results showed that the variation patterns of alpha diversity indices among seasons were inconsistent. All beta diversity indices showed significant seasonal variations. The rate of zeta diversity decline was highest in winter, and the compositional turnover showed no significant variations among the other three seasons. In spring, longitude was the most important factor influencing variations in alpha and beta diversity, while sea surface temperature and distance from mainland were important drivers for fish zeta diversity. Distance from mainland, sea surface temperature, and salinity were the most critical factors shaping the spatial pattern of diversity in summer, autumn, and winter, respectively. Our results suggest that environmental and geographic factors play an important role in shaping the patterns of coastal fish diversity. [ABSTRACT FROM AUTHOR]

Fish hosts are critical for freshwater mussels. However, correlation between mussel and fish species richness (SR) is variable. Here, we examine how the environment affects this variability. We calculated mussel–fish SR ratios for 459 stream sites to capture the different responses of mussel and fish SR to environmental variables. We used Random-Forests (RF) to model how the SR ratio varied with environmental gradients. We also modeled the percent SR of mussel guilds with different hosting and life-history strategies. The SR ratio was generally low, but highly variable across sites. The ratio variability strongly affected mussel-fish SR correlations and can be explained by environmental factors. Given that environmental gradients also differ among datasets or regions, mussel-fish SR correlation can be expected to vary. The responses of the SR of mussel guilds agree with the expectations. However, land-use and climate co-vary with other environmental variables, and their effects are difficult to assess. We conclude that mussel and fish respond differently to many environmental variables; the importance of fish SR to mussel SR may vary with the environmental settings of streams but often appears to be low. Thus, environmental data may be generally sufficient for mussel-SR modelling and mussel diversity conservation planning. [ABSTRACT FROM AUTHOR]

Our understanding of the factors determining stream community assembly has mainly been built upon taxonomic diversity. Additionally, most investigations of factors governing assembly are limited in scope and use of spatial model testing. Therefore, we combine a sizeable environmental dataset (local and landscape level) with robust spatial analysis to model the factors determining multiple facets of stream fish diversity—across a region and within four drainages. We found that total dissimilarity was more explained by replacement than nestedness. Fish diversity was governed by spatial and environmental factors, although the degree depended on the diversity facet and drainage. Adjusted R2 for combined models (i.e., spatial plus environment) of fish beta diversity was as high as 0.65. Local instream habitat variables were the most explanatory factors. Spatial factors based on overland Euclidean distance and asymmetric (directional) distance revealed more explanatory power than symmetric hydrologic distance. The purely spatial variation was often as high as 33% explained. Multiple facets were strongly correlated and provided similar results—albeit some differences arose, especially within different drainages; these differences highlight how difficult it is to generalize the multifaceted approach. However, the importance of exploring spatial models for determining the role of spatial processes on community assembly cannot be overstated. [ABSTRACT FROM AUTHOR]

In the neotropics, potamodromous fish species are among the most severely impacted by dams, which can lead to blocking of the migratory routes, elimination of the breeding areas, and population isolation in this group. However, growing evidence has indicated that free-flowing tributaries along fragmented watersheds provide important contributions to the reproductive migration and recruitment of migratory fish. If this is really occurring, we could expect low or undetectable population differences in different reservoirs and respective unimpeded tributaries along watersheds fragmented by dams. Aiming to test this hypothesis, we assessed the genetic diversity and population structure of Pimelodus maculatus, a migratory catfish species, in seven reservoirs and nine tributaries along the Paranapanema River basin, Paraguay-Paraná-Plata system, South America. As predicted in our initial hypothesis, after analyzing nine microsatellite loci and a 406-bp mitochondrial DNA sequence (D-Loop) in 640 individuals, we found high nuclear genetic diversity and non-significant genetic substructuring among each reservoir and its tributaries, contrasting with the results between samples separated by dams. Our findings reinforce the idea that free‐flowing tributary rivers are contributing to maintenance of wider population distributions, larger effective population sizes, and satisfactory genetic diversity levels. [ABSTRACT FROM AUTHOR]

In this study, we present a new method to compare the distribution of knowledge regarding the biodiversity of a taxa with the distribution of environments inhabited by that taxa, in order to identify the main geographical gaps in biodiversity knowledge. We compared the geographical distribution of studies describing freshwater fish assemblages in Argentina with the distribution of freshwater bodies, delimiting priority areas that require additional sampling effort in order to achieve a more balanced understanding of this taxa's diversity throughout the country. Our results show a substantial geographical bias in the distribution of knowledge regarding freshwater fish assemblages in Argentina, with most of the studies concentrating on a few areas of the country. Many sectors appear as undersampled, and most of the country has been studied only recently, after many sites have undergone severe impact by anthropic activities. The absence of fish assemblages descriptions previous to habitat changes in these sites considerably limits our capacity to understand changes in biodiversity that anthropic habitat modifications might have generated or even the ones they are generating now. We show the areas of Argentina where freshwater fish diversity needs to be studied most urgently based on the distribution of freshwater habitats. [ABSTRACT FROM AUTHOR]

Guest editors: David J. Hoeinghaus, Jaquelini O. Zeni, Gabriel L. Brejão, Rafael P. Leitão & Renata G. Frederico / Neotropical Stream Fish Ecology in a Changing Landscape The Neotropical Region holds the richest diversity in the world in both terrestrial and aquatic ecosystems. Such impacts can compromise the conservation of the biodiversity and hamper the ecosystem services provided by fish (Pelicice et al., [12]), particularly in these highly biodiverse Neotropical freshwater ecosystems. Roa-Fuentes et al. ([13]) investigated agroecosystems and highlighted the importance of local drivers for maintaining stream fish biodiversity in these ecosystems. [Extracted from the article]

This study investigated the effects of environmental variation on fish diversity patterns in two coastal streams in northwestern Ecuador. Specifically, we examined the role of topography, instream conditions (pH, conductivity), and human influence (land-use modifications) on fish species richness, diversity and evenness as well as body size diversity and size evenness. Study region comprised 19 sites sampled bimonthly during the dry and wet seasons in 2016–2017. The results showed that the contribution of each measure of fish diversity responded differently to the local drivers. For size-based metrics, fish assemblages displayed greater size diversity (more diversity of body sizes) at lower pH and conductivity levels. Taxonomic metrics showed a negative relationship between the number of species and the downstream–upstream gradient. In both measures of diversity, human influence negatively affected size evenness and Shannon diversity, with less equitable abundance distribution and fewer species in more human-altered locations. These results improve our understanding of how assembly processes operate in shaping local fish assemblages in Neotropical coastal streams. [ABSTRACT FROM AUTHOR]

The high diversity of fish species found in Brazilian streams has attracted scientific interest in recent years. However, it is not clear how studies have addressed biodiversity knowledge shortfalls. We conducted a scientometric analysis of stream fish studies in Brazil to identify trends and gaps in how objectives, spatial coverage, and biodiversity knowledge shortfalls have been studied. Our review covered 690 articles published between 1981 and 2019, and we found an increase in the number of publications, the spatial scale of studies, and the number of streams studied. We also found biases in the distribution of publications concerning regions, biomes, basins, and biodiversity knowledge shortfalls. The Southeast region, the Paraná River basin, the Atlantic Forest biome, and the Hutchinsonian shortfall contributed to a greater number of studies while the Northeast region, the Pantanal biome, Parnaíba basin, Western Northeast Atlantic basin, and the Prestonian shortfall were less represented. Therefore, to improve our knowledge about stream fish, we recommend new collection efforts in under-sampled regions and new studies focused on filling less-addressed biodiversity knowledge shortfalls. Moreover, we emphasize the importance of standardized sampling protocols, a complete sharing of data, and an increase in scientific collaboration. [ABSTRACT FROM AUTHOR]

Lake Tanganyika cichlids - targeting the patterns and origin of phenotypic and behavioral varia... Lake Tanganyika is the oldest of the East African Great Lakes (Cohen et al., [9]) and thus harbors the morphologically, behaviorally, ecologically, and genetically most diverse cichlid species assemblage (Snoeks, [53]). South American cichlids - new insights into their visual system Cichlid species have undergone extensive diversification in visual systems, and there is now substantial evidence of selection on visual opsins driving divergence in spectral sensitivity (Trezise & Collin, [63]). Cichlid parasites Parasites are strong drivers of natural selection, and over recent years there have been several studies investigating links between ectoparasite faunas and cichlid diversification (Raeymaekers et al., [43]; Vanhove et al., [66]; Gobbin et al., [22]). A fossil cichlid radiation The cichlid fossil record is tremendously important for our understanding of cichlid evolution. [Extracted from the article]

Small nearshore fishes are an important part of lacustrine and functional diversity and link pelagic and benthic habitats by serving as prey for larger nearshore and offshore fishes. However, the trophic complexity of these small nearshore fishes is often unrecognized and detailed studies of their role in food webs are lacking. Here, we examined niche space patterns of small nearshore fish species using Bayesian analyses of carbon and nitrogen stable isotope data in nine freshwater lakes that are among the largest lakes in Minnesota. We found considerable variability in niche areas within species and high variability in niche overlap across species. At the assemblage level, niche overlap (average diet overlap of all species pairs at a lake) decreased as whole-lake species richness increased, possibly indicating a greater degree of resource specialization in more speciose lakes. Overall fish niche space was weakly but significantly related to niche space of their invertebrate prey. Although nearshore benthic resources contributed to fish diets in all lakes, all fish species also had non-negligible and variable contributions from pelagic zooplankton. This inter- and intraspecific variability in trophic niche space likely contributes to the multi-level trophic complexity, functional diversity, and potentially food web resilience to ecosystem changes. [ABSTRACT FROM AUTHOR]

The use of artificial habitats as tool for management and conservation of lentic freshwater ecosystems has been most studied in North America, with dominance of Centrarchidae fish. Contrary to north temperate ecosystems, Cichlidae species appear to be prevalent on artificial habitats in Neotropical reservoirs. Currently, due to the rapid expansion of non-native fish introductions globally, these two fish families are increasingly expected to coexist in the same environments. This study aimed to test experimentally the use of artificial habitats by fish in two Neotropical reservoirs between: (i) kind of habitats, (ii) Cichlidae and Centrarchidae, (iii) native and non-native species, and (iv) size classes. The results showed a higher number of individuals and species in pipes and rocks habitats. The dominance of Cichlidae over Centrarchidae in pipes, rocks and control habitats suggests a kind of partitioning between these groups. Native Cichlidae (< 80 mm) were predominant in pipes whereas native and non-native species seemed to share tree and rock habitats. Artificial habitats can potentially increase local abundance and diversity of fish species, however, it is essential to consider the species' origin (i.e. native or non-native) associated with each kind of artificial habitat in order to prevent invasive species from benefiting of artificial structures deployment in freshwater systems. [ABSTRACT FROM AUTHOR]

Species introductions often coincide with loss of genetic diversity and natural enemies. Anthropogenic translocation of the North-American pumpkinseed Lepomis gibbosus (L., 1758) (Centrarchidae) and its further spread have resulted in recent species establishment in most European countries. This study determines genetic differentiation of non-native European pumpkinseed populations and identifies how their genetic structure relates to the distribution and abundance of parasite species. Microsatellite analysis indicated presence of three genetic lineages, which were well supported by discriminant analysis based on parasite abundance data. The first lineage clustered pumpkinseed populations from northern and southern France and showed high allelic richness, heterozygosity and parasite richness. The second included populations along the "Southern invasion corridor" connecting the rivers Rhine, Main and Danube. The fish exhibited low to high genetic and parasite diversity and generally high parasite abundance. The third lineage clustered populations with low genetic and parasite diversity, located in Portuguese reservoirs and water bodies along the upper Elbe. Parasite species richness was significantly associated with host microsatellite heterozygosity and allelic richness, a trend partially affected by richness of North-American parasites. Furthermore, our results indicate that parasite community composition may serve as a useful biological tool to discriminate non-native fish populations and their inter-relationships. [ABSTRACT FROM AUTHOR]

Habitat structure and predation are major factors that influence the distribution of zooplankton species and functional traits. Here, we analyzed how the structure provided by macrophytes (richness, Shannon's diversity, and biomass) and potential predation by small-bodied fishes (richness and abundance) determine the richness of species and functional traits of zooplankton, as well as the spatial dissimilarity (beta-diversity) of species and traits. Zooplankton, fish, and macrophytes were simultaneously sampled across a gradient of 30 multi-species macrophyte beds. We assessed spatial patterns of zooplankton under taxonomic and functional approaches, using linear regression models, Generalized Dissimilarity Models, a Structural Equation Model, and a Fourth-Corner Analysis. Zooplankton taxonomic beta-diversity was most represented by the turnover component and zooplankton functional beta-diversity by nestedness. Zooplankton taxonomic richness and taxonomic beta-diversity were positively related to macrophyte biomass, richness, and Shannon's diversity, whereas zooplankton functional richness and functional beta-diversity were positively related to fish richness and abundance. Macrophyte biomass and diversity oppositely influenced fish structure, which had influence on zooplankton structure. Macrophytes also negatively influenced the zooplankton traits such as body size, reproduction type, habitat, lifespan, and predatory escape response and positively influenced the trait feeding type. Fish were negatively related to the trait body size. The spatial structure generated by macrophyte beds and fish community determined the distribution of zooplankton species and functional traits. [ABSTRACT FROM AUTHOR]

We aimed to study the responses of fish functional diversity to El Niño Southern Oscillation (ENSO) in different environments from the upper Paraná River floodplain (UPRF), Brazil. We predicted that (i) El Niño events intensify floods in the UPRF and, consequently, promote functional convergence of the fish assemblage and (ii) different functional traits will be favored in El Niño or La Niña events. The functional convergence was measured through functional dispersion and functional redundancy indexes, wherein lakes presented higher similarity during El Niño and lower similarity during La Niña. ENSO did not have a strong effect in rivers. The functional richness and functional evenness did not respond to ENSO events. Fish with parental care and invertivorous fish were favored during El Niño, while piscivorous and herbivorous fish were favored during La Niña. Due to their distinct lifecycles, long-distance migratory fish responded to this climatic oscillation 1 year after El Niño. Overall, the influence of ENSO on fish diversity in the UPRF is a complex phenomenon. However, even with other local and regional factors acting on the ichthyofauna, fish diversity responded to these climatic fluctuations. [ABSTRACT FROM AUTHOR]

We investigated how the riverine network influences taxonomic and functional beta diversity patterns of fish assemblages in the mainstem/headwater (lateral) and upstream/downstream (longitudinal) gradients in a Neotropical river system. We investigated the following questions: which component (turnover or nestedness) explains taxonomic and functional beta diversity in both gradients? Is this component a consistent pattern for different lateral sections of the river basin? Is this component influenced by the spatial extent? Finally, how are taxonomic and functional beta diversity structured by space and environment along the longitudinal gradient? Taxonomic and functional turnover were the main patterns found for the lateral gradient and they were consistent for all lateral sections considered. Taxonomic and functional turnover were also the main patterns for the longitudinal gradient, increasing with the spatial extent increase and being structured by space and spatially structured environments. Our study demonstrates that the dendritic nature of riverine systems constrains species and traits occurrence along lateral and longitudinal gradients in a Neotropical region, generating taxonomic and functional turnover patterns due to the influence of space and spatially structured environments on niche- and dispersal-based processes. These results show that Neotropical riverine systems conservation must go beyond traditional approaches and consider the metacommunity perspective. [ABSTRACT FROM AUTHOR]

Beta diversity quantifies changes in assemblages among sites and can identify how anthropogenic changes affect species distributions patterns. We investigated how spatial and temporal beta diversity of fish assemblages responded to recent environmental changes within an established agroecosystem and investigated whether the observed pattern of spatial and temporal beta diversity was different from null expectations. Fish assemblages in 38 streams were sampled in 2003 and 2013, and local and regional variables were quantified in both periods. Species were classified into functional groups based on 15 ecomorphological traits. We tested for relationships between spatial and temporal patterns of beta diversity and its components (turnover and nestedness) and environmental distances and degree of changes over time, and for differences with null expectations. Spatial beta diversity was mostly due to turnover and remained relatively unchanged between periods. Spatial beta diversity was not different from randomness. Temporal beta diversity was lower than expected by null models and not correlated with environmental changes. Past environmental filters related to a long history of agricultural development homogenized habitats and fish assemblages by selecting for habitat-generalist species. In this context, contemporary fish assemblage dynamics in these streams are driven primarily by stochastic processes, likely stochastic local species loss. [ABSTRACT FROM AUTHOR]

Non-native freshwater fish introduced via the aquarium trade can cause major changes at the community level over time and space, resulting in dynamics context dependencies within homogenization process. We investigated fish biodiversity in anthropogenically impacted headwater creeks (i.e., under elevated propagule pressure) located in southeastern Brazil, through a standardized sampling program. We assessed ichthyological community composition with the aim of quantifying spatio-temporal dynamics across creeks. We divided the sampling period according to decades, in which "2000s" represented 2003, 2004, 2005, and 2006, while "2010s" represented 2015. Changes in pairwise community similarity indicated biotic homogenization in the 2000s (i.e., communities became more similar over time). In contrast, changes in pairwise similarity in the 2010s indicated biotic differentiation. We suggest that these changes are caused by the extirpation of both native and non-native species due to environmental degradation and the occurrence of six new non-native species. The beta-diversity increased between sampling seasons and creeks across decades, also indicating biotic differentiation. Our study provides strong evidence for a transition phase from biotic homogenization to differentiation of fish communities over time, caused by interaction between older environmental degradation and more recent impacts from the Brazilian aquarium trade, reinforcing the importance of simple, practical, and inexpensive long-term studies to understand biodiversity-related processes. [ABSTRACT FROM AUTHOR]

Dramatic environmental changes and species invasions are increasingly threatening the diverse fish fauna of the Yellow River, China. This study examines temporal changes in the alpha and beta components of fish taxonomic, functional and phylogenetic diversity in relation to anthropogenic environmental changes over the past 50 years. We hypothesized that temporal trends in multifaceted components of diversity would be highly congruent, but that the relative importance of anthropogenic disturbances would differ in shaping spatial patterns of fish diversity. We found that all three components of alpha diversity increased over time but at different rates (19.1%, 21.3% and 15.3% for taxonomic, functional and phylogenetic diversity, respectively). Fish faunas of the Yellow River have also become homogenized over time, but this was much greater for functional and phylogenetic components of beta diversity than for taxonomic diversity (change in beta diversity = − 0.11, − 0.24 and − 0.02, respectively). Temporal changes in alpha and beta diversity were strongly related to invasion of non-native fish species and changes in temperature, sediment load, reservoir capacity and aquaculture area. Our results underscore the ongoing need for threat mitigation (particularly relating to dams and aquaculture) to conserve the unique biodiversity of one of the world's largest rivers. [ABSTRACT FROM AUTHOR]

Hydroelectric expansion has affected the functioning of most tropical rivers in the world. However, community reassembly in Neotropical impoundments remains poorly understood, because long-term studies are incipient. In this context, we evaluated temporal changes in fish diversity before and after the construction of Peixe Angical Dam, Upper Tocantins River, Amazon Basin. Specifically, we investigated changes in taxonomic (richness, abundance and species composition) and functional diversity (trait richness and composition) over a period of a decade. Fish assemblages were sampled at five sites along the river, between 2004 and 2014 (before and after river regulation). As predicted, taxonomic and trait richness declined in the impoundment, and the composition shifted over the years, with increasing dissimilarity between sites. We also observed significant changes in species abundance and trait composition. However, changes were abrupt and a novel community state emerged after the fifth year of the impoundment. After this period, richness and abundance tended to stabilize at low levels, with different species/trait composition when compared to the pre-damming period. Our results indicate that major changes in community structure occurred during the first years of the impoundment, with relevant losses in taxonomic and functional diversity, along with a rapid change towards a new state. [ABSTRACT FROM AUTHOR]

Many multi-regional studies investigating how available habitat area, energy availability, and historical refugia drive freshwater fish diversity have emphasized Northern Hemisphere and tropical areas. Furthermore, while many such studies have examined diversity drivers on basin-scale species richness (i.e., gamma diversity), they typically have not evaluated beta diversity or phylogenetic diversity nor included representative numbers of Southern Hemisphere basins unassociated with tropical rainforests. Here, we examine 784 basins and present the first comprehensive evaluation of the driving effects of gamma diversity and the patterns of beta and phylogenetic diversity across extra-tropical Southern Hemisphere (ETSH) freshwater fish communities. We find that ETSH gamma diversity does not show a strong historical legacy associated with glaciations, and is influenced more by factors related with habitat area and available energy. Additionally, ETSH regions show high beta and phylogenetic diversity and low levels of diadromy, except New Zealand, which shows narrow species diversity and cosmopolitan species dominance. Finally, phylogenetic diversity indicates how the endemism of the three ETSH Mediterranean-climate regions is characteristic of long-term isolation and persistence. These results demonstrate ETSH freshwater fish diversity to be distinct from both the tropics and their Northern Hemisphere latitudinal counterparts. [ABSTRACT FROM AUTHOR]

The biogeography and conservation of elasmobranch species was increasingly addressed in the recent past, but the southwestern Atlantic Ocean fauna is still one of the least studied. Reliable delimitation of the distribution range of species is fundamental to conservation and development of fisheries management strategies. A recent molecular study of the cryptic Aetobatus narinari species complex restricted that species to western and eastern coasts of the New World. However, the current distribution of A. narinari and phylogenetic relationships within the genus Aetobatus have yet to be clarified, the goal of this phylogeographic analysis. Using mitochondrial and nuclear markers we investigated specimens from the Atlantic coast of Brazil and the Pacific coast of Mexico and related them to previously analyzed specimens from other regions. Our analysis indicates that Aetobatus narinari is present only in the western Atlantic, formed by a single genetic lineage that ranges between Florida and southeastern Brazil, while the Pacific New World lineage is in fact assigned to Aetobatus laticeps. Analysis of divergence times revealed that biogeographic events such as the closure of the Tethys Sea, the formation of the Benguela barrier, and the Isthmus of Panama played major roles in diversification and dispersal of the genus Aetobatus. [ABSTRACT FROM AUTHOR]

The relationship between fish and amphibians is thought to be antagonistic because of the frequent amphibian extirpations after fish introductions, although some field observations show that amphibians and fish often co-occur in rivers. Here, we used surveys in north-eastern Spain (99,700 km2, 15 river catchments, N = 535 sites) to identify the most frequent fish–amphibian associations and the riverine conditions that might concurrently promote the diversity of native fish and of five widely distributed amphibian species. Overall, there was little congruence between native fish and amphibian-diversity measures (species richness and the Shannon, Simpson and Pielou diversity indices). Different riverine conditions appeared to be important for the two vertebrate groups. Alien fish richness, which was highly correlated with alien fish abundance, was negatively associated with amphibian richness and Shannon diversity but was positively associated with native fish richness. River water depth was negatively associated with amphibian occurrence. While our snap-shot surveys may be a transitional stage in the fish–amphibian relationships, we found that some widely distributed amphibian species co-occur with fish in rivers in north-eastern Spain. Small rivers, such as tributaries often have the most intact fish assemblages, and probably are the best locations to explore fish–amphibian associations in greater depth. [ABSTRACT FROM AUTHOR]

In order to generate a database of the auto-ecology and distribution of Argentinian North Patagonian ostracods (Argentina), a survey in 40 aquatic systems has been carried out. For this purpose, we report the ostracod diversity and assess the relationships between ostracod occurrence and abundance considering abiotic environmental variables. Twenty-two ostracod species have been found, three of which first record for Neotropical region and one for Argentina. Conductivity, temperature, and energy level have significantly explained ostracod distribution and abundance. Based on host waters features, three ostracod assemblages have been recognized: (1) temperate waters with moderate to high conductivity have presented in Sarscypridopsis aculeata, Potamocypris unicaudata, Heterocypris hyalinus, and Cypridopsis vidua as typical fauna; (2) environments with flowing waters were dominated by Ilyocypris ramirezi and Heterocypris incongruens, whereas (3) in cold and low conductivity environments, Tonnacypris lutaria, Eucypris virens, and Bradleystrandesia fuscata were the characteristic taxa. Our data indicate that Patagonian ostracods are largely influenced by host waters features, mainly conductivity and temperature. Likewise, due to the fact that eight of the twenty-two identified taxa in this survey were recovered in Holocene sequences from Patagonia, this study provides valuable information for future paleo-environmental reconstructions in North Patagonia. [ABSTRACT FROM AUTHOR]

This study aimed to characterize species composition and abundance of fish assemblages of low-order streams of the Machado River Basin and to identify the main environmental factors associated to fish assemblages along the elevational gradient. Fishes were collected by seine and dip nets, along an 80-m stretch of 71 streams. In each site, we recorded physical, chemical, and land–water ecotone variables. We collected 22,702 specimens of 91 species. Species richness and abundance varied negatively with elevation. Ordination and similarity analyses detected that streams located in higher and middle elevation ranges differed in species composition from those in the lower elevation range. Almost one-third of the recorded species were selected as indicator species. Species of the families Trichomycteridae, Cichlidae, Gymnotidae, and Characidae were closely associated with the land–water ecotone and structural characteristics of lower elevation range, whereas several other Characidae species were more abundant in middle elevation range, where aquatic vegetation cover and conductivity values were higher. By assuming that composition and relative abundance of fish respond to environmental changes, hydrological characteristics may be viewed as environmental filters for stream assemblages by ultimately selecting the pool of species able to reach for specific elevation ranges and meet their biological requirements. [ABSTRACT FROM AUTHOR]

Typified by heterogeneous habitats, large rivers host diversified communities throughout their course. As the spatial organisation of fish communities within these ecosystems remains little studied, longitudinal gradients and spatial heterogeneities of fish diversity were analysed in the large temperate St. Lawrence River, Canada. We used two distinct datasets obtained from either seine nets or gillnets from governmental standardised fish surveys (1995–2012) consisting of a total of 299,662 individuals from 76 fish species captured in 1,051 sites. Results from diversity indices and multivariate analysis revealed a gradual downstream increase in taxonomic diversity, and a gradual change of the community structure along the river. In addition, we observed different fish communities within fluvial lakes and corridors and found significant differences in fish community structure between opposite shores. The fish communities described along the river using seine nets are spatially more heterogeneous than when described using gillnets. This discrepancy is likely resulting both from the more mobile species targeted by gillnets and sampling sites located farther from the shallower shoreline habitat targeted by seine nets. The organisation of fish communities stresses the need to implement science-based policies and actions to preserve biodiversity and restore communities distributed over large heterogeneous ecosystems. [ABSTRACT FROM AUTHOR]

The rocky shore habitats of the African Great Lakes support high densities of cichlid fishes, including many closely related/ecologically similar species. Aggressive behaviours between conspecifics, and perhaps heterospecifics, influence this unusually high level of species coexistence. In dichotomous choice aggression trials, male Maylandia thapsinogen were presented simultaneously with two heterospecific intruders (Maylandia emmiltos and Maylandia zebra). M. thapsinogen were significantly more aggressive towards intruders from an allopatric species (similar orange dorsal fin colour—M. emmiltos), than towards a different allopatric species (blue dorsal fin—M. zebra). Aggression biases disappeared when colour differences were masked using monochromatic lighting. A second experiment compared female aggression biases between M. emmiltos with M. thapsinogen, species similarly coloured to one another, the former possessing a yellow, as opposed to a black throat as the latter does. M. thapsinogen preferentially attacked females of their own species in full but not monochromatic light, while female M. emmiltos showed no significant bias in aggression under any lighting. Responses were not affected by olfactory cues provided by the stimulus fish. These results indicate that divergence in colour might facilitate species coexistence in some cases, but not all, which could be important should populations rejoin through lake level drops. [ABSTRACT FROM AUTHOR]

Fish species of the genus Capoeta are known for their special mouth morphology (inferior mouth with the horny edge to the lower jaw), short dorsal fin with seven to nine branched rays, and their tumultuous taxonomic history. The genus Capoeta has had a complex evolutionary history with high diversification in the Middle East and is closely related with genus Luciobarbus. Earlier attempts to clarify the complex taxonomy of the group established four species groups, namely C. capoeta, C. damascina, C. tinca, and C. trutta species group. Based on this study, the C. capoeta group currently includes nine taxa (seven previous + two newly included members) and all reviewed in this paper based on morphological characters and mitochondrial genes. Capoeta macrolepis, revalidated as a distinct species, and Capoeta fusca are additional members of the C. capoeta group. Molecular time tree shows that the separation of Capoeta from its relative Luciobarbus was about 12.43-16.99 MYA. Based on the time tree presented herein, the high diversity of Capoeta in the Tigris-Euphrates system, the nesting of Capoeta within the tetraploid Luciobarbus in the mitochondrial trees and the high diversity of Luciobarbus in the Tigris-Euphrates system, it is proposed that the origination and diversification of Capoeta occurred in the palaeo-drainages of the Tigris-Euphrates system. From here, dispersion of Capoeta to the other nearby basins could have been possible through freshwater corridors during the Pliocene or Pleistocene. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate how distinct land uses can alter the trophic structure of fish communities in streams. For this purpose, nine streams under the influence of three distinct land uses (pasture, sugarcane, and natural cover) were evaluated. The structure and isotopic niche of the fish communities were investigated by calculating descriptive community-wide metrics based on stable isotopes of δC and δN. The largest isotopic niche was observed in fish communities in pasture streams, and the smallest in sugarcane streams. Pasture streams exhibited greater ranges of carbon sources exploited by fishes, higher trophic diversity, and lower trophic redundancy. In contrast, sugarcane streams had greater ranges of nitrogen exploited by fishes and showed the smaller trophic diversity, higher trophic redundancy, and uniformity. Sugarcane was also the only land use that exerted a negative influence on community isotopic niche width. Natural cover streams in turn, showed lower trophic uniformity and exhibited intermediate values for all remaining metrics. We conclude that fish communities residing in streams influenced by pastures displayed characteristics that led to greater trophic diversity, and fish communities influenced by sugarcane plantations were more negatively affected by this land use. [ABSTRACT FROM AUTHOR]

The Serrasalmidae is a speciose family of Neotropical freshwater fishes with diverse interspecies dietary preferences, from the herbivorous or frugivorous pacus to the omnivorous or carnivorous piranhas. The Serrasalmidae is an ideal comparative model to explore the biochemical correlates of dietary preference. For example, debate exists about whether variation in dietary preference among fishes influences the capacities for de novo glucose synthesis (gluconeogenesis) or glucose use as metabolic fuel (glycolysis). We predicted that carnivory in piranhas would be associated with an enhanced gluconeogenic capacity compared with the herbivorous pacus, because carnivores consume less carbohydrate. As a corollary, we expected similar glycolytic capacities at a major site of glucose use (heart) in fishes with different diets. We measured activities of key enzymes of gluconeogenesis and the opposing reactions of glycolysis in liver (the primary gluconeogenic site) and heart of five serrasalmid species showing an interspecies dietary gradient from herbivory to omnivory to carnivory. The interspecific variation in enzyme activities was, in general, unrelated to dietary preference. Glycolytic capacity in heart was lower in herbivores but this may be related to non-diet factors. Among serrasalmid fishes, the enzymatic capacities of glucose metabolism are not overtly influenced by interspecific divergence of dietary preference. [ABSTRACT FROM AUTHOR]