Native Fish Communities Research Articles

Initial sightings and derby data from the red lionfish invasion (Pterois volitans) (Scorpaeniformes: Scorpaenidae) in Barbados.

BackgroundNative to the Indo-Pacific region, the lionfish (Pterois volitans and P. miles) has been classified as an alien invasive species which has rapidly invaded the North-western Atlantic and the Caribbean. The primary concerns regarding lionfish pertain to their broad diet, general habitat use and their potential threat on fisheries resources, native fish communities and human health. Away from natural predators, lionfish populations can easily become established and pose a serious threat to local fish species and ecosystem functioning. The first confirmed sighting of the red lionfish (Pterois volitans) in Barbados was in November 2011. Throughout 2012, fishermen and recreational divers were encouraged to report sightings of lionfish via an established hotline. Where possible, sightings were confirmed by way of the fish being captured and handed over to the Barbados Fisheries Division or the East Coast Conservation Organisation (ECCO) Inc. (an environmental NGO) for confirmation. In addition to confirmation, biological data (such as length, weight, sex and maturity) were also collected. Genetic research conducted on confirmed specimens collected between 2011-2013 identified the presence of only one species, P. volitans. Since the first confirmed sighting of the red lionfish in Barbados, it is believed that population numbers have steadily increased. One of the methods utilised in Barbados to control this alien invasive lionfish species is that of an annual derby. On 5 and 6 December 2015 and 13 November 2016, teams of divers (both free divers and SCUBA divers) took to the local waters to hunt for and kill lionfish. Caught lionfish were landed at scoring stations to be counted and allowed for the collection of basic biological data (such as length, weight, sex and maturity). In addition to biological data, teams (observers) also provided information on dive sites (locations) and associated geographic information (i.e. GPS coordinates), where available.New informationThese two datasets, initial sightings (2012) and derby data (2015 and 2016), present the first collected data for the red lionfish (P. volitans) in Barbados. The two datasets are occurrence datasets which document the identification of >1500 lionfish removed from the waters of Barbados between 2011 and 2016.

Temporal and ontogenetic changes in the trophic signature of an invasive marine predator

Many successful invasive species have generalist diets, but the extent to which they can track changing resources has seldom been documented. Stable isotope analysis was used to measure dietary shifts with ontogeny and over time in relation to changes in prey availability for Indo-Pacific lionfish (Pterois sp.). These are invasive predators that are well established throughout the western North Atlantic and Caribbean where they have caused significant decreases in native reef fish populations in some areas. Samples and observations were made off New Providence Island, Bahamas during the summers of 2008 and 2010. Lionfish δ15N and δ13C values increased only weakly with body length, suggesting that processes other than growth also contribute to stable isotope variability. The trophic niche of lionfish changed significantly between years, concomitant with large changes in native fish prey abundance and community structure. The trophic niche of large lionfish expanded, increasing in trophic diversity at the population level and showing lower individual trophic similarity, while that of small lionfish remained similar in size but shifted towards more 15N-enriched and 13C-depleted prey sources. The ability of lionfish to modify their diet over time may have facilitated their expansion and persistence at high densities in some areas despite local prey depletion.

Habitat use and population structure of the shoal chub (Macrhybopsis hyostoma) in the upper Mississippi River basin

Anthropogenic alterations of river systems may have a profound effect on native fish community and habitat use; however, it’s difficult to understand the extent of these impacts without establishing well-defined habitat preferences. We investigated the Shoal chub, Macrhybopsis hyostoma, a native obligate river species from nine sampling locations in the upper Mississippi River Basin (UMRB). Field surveys demonstrated that overall Shoal chubs preferred tributaries, yet this was statistically significant only for gravid females. Diet analysis and comparative morphology suggested that the Shoal chub is insectivorous and prefer benthic habitats. Our analysis of habitat use suggested that juvenile Shoal chubs preferred sand substrate and adults preferred medium to large gravel. Shoal chubs developed more melanophores as they aged, which is a likely an adaptation to their habitat shifts. The field survey identified possible sites where spawning was occurring and may be important for future conservation efforts for the Shoal chub. In addition, we conducted population genomic analysis of Shoal chub samples collected from the streams in three Midwest states (Illinois, Missouri, and Nebraska) and found low genetic diversity among the chubs that raises a concern in conservation. This preliminary study provides insights into further investigation of the impact caused by stream habitat alteration on native species and into the conservation of Shoal chubs in the UMRB.

A small native predator reduces reproductive success of a large invasive fish as revealed by whole-lake experiments.

The extent to which native fish communities might control the success of invasive fish has been of interest to ecologists, but it has been rarely addressed using experiments. We conducted an experiment in six small lakes in the Upper Mississippi Region to test the effects of a small native predator, bluegill sunfish (Lepomis macrochirus) on the recruitment of a large, invasive fish, the common carp (Cyprinus carpio). Bluegills are predominant throughout the region and were previously shown to consume carp eggs and larvae. We stocked both lakes at each of our 3 sites with adult carp (spawners) and one lake at each site with bluegills. We repeated the experiment at two of the three sites for two consecutive years. In each lake we assessed the abundance of post-larval carp one month after spawning (backpack electrofishing surveys) and at the end of the season (mark-recapture). For each site/year combination, catch rate of post-larval carp was typically an order of magnitude higher in control than bluegill lakes, but it often declined quickly over time. The abundance of end-of-seasonal juveniles was significantly higher (no 95% CI overlap) in control lakes than in bluegill lakes, except for one pair of lakes during one year when both the control and bluegill lake had similar, low abundance of end-of-season carp. Overall, our results support the hypothesis that common carp recruitment is substantially reduced in habitats dominated by bluegills. We also suggest our results may be applicable to other species, and that managers should explore how predation on early life stages may control other invasive species.

Temperature—Not Flow—Predicts Native Fish Reproduction with Implications for Climate Change

AbstractHabitat alterations and introduction of nonnative fishes reduced the distributions of the Flannelmouth Sucker Catostomus latipinnis, Bluehead Sucker C. discobolus, and Roundtail Chub Gila robusta to less than 50% of their historical ranges. Climate change models generally predict decreased streamflows and increased water temperatures that may further affect these species. Understanding the effects of flow and water temperature on their life histories should lead to better assessments of climate change impacts on extant populations and more informed management for species conservation. Basinwide larval fish sampling and hatch dates derived from otolith daily increment counts showed that water temperature was the dominant environmental factor cueing reproduction in the upper White River basin, Colorado. Reproduction for all three species began in spring, occurring first at warmer, lower‐elevation, downstream locations and progressing upriver to higher elevations as water temperatures increased. Warmer water temperatures in tributaries initiated earlier reproductive activity compared to adjacent cooler main‐stem habitat. Presence of larvae in samples and estimated hatch dates demonstrated a distinct, predictable upstream progression of reproduction associated with warming water and clear upstream limits to reproduction for all three species. Larval presence and hatching dates revealed earlier reproductive activity in 2012 than in 2013, driven by lower flow and earlier stream warming. A regression model predicted stream temperature during fish spawning seasons under different climate change scenarios and showed expanded upstream limits of thermally suitable reproductive habitat and earlier reproduction for our study species. The long‐term implications of climate change are unknown, but managers should strive to perpetuate the valuable and relatively pristine native fish community in the upper White River drainage as a vestige of those that formerly existed throughout the Colorado River basin.

Impacts of freshwater aquaculture on fish communities: A whole‐ecosystem experimental approach

Abstract Aquaculture is a growing global industry; freshwater aquaculture has significant potential for expansion in Canada, but growth of the freshwater sector has been slow due to concerns over potential environmental impacts and a lack of information on potential impacts to native fish communities. To provide guidelines and target variables for evaluating aquaculture impacts on freshwater fish communities, we operated an experimental aquaculture farm as a whole‐lake experiment where 10,000 rainbow trout (Oncorhynchus mykiss) were raised annually from 2003 to 2007. Impacts were assessed using up to 8 years of pre‐impact and 8–10 years of post‐impact data. Prey fish abundance increased dramatically during aquaculture but declined sharply following the experiment. High abundance of littoral minnows in autumn was not observed during spring and, combined with size distribution data, suggests high overwinter mortality of adult minnows. White sucker (Catostomus commersonii) abundance and body condition declined during and after aquaculture, with evidence of overwinter juvenile recruitment failure in the last 2 years of operation, although size‐at‐age increased. The adult abundance of lake trout (Salvelinus namaycush) doubled during aquaculture, due to a combination of (a) increased growth rates of young trout and (b) earlier age and larger sizes at maturation. Within 2 years following aquaculture, lake trout abundance declined by nearly 50% to background levels, suggesting a large increase in lake trout mortality once operations ceased. These changes were not observed in nearby reference lakes. While aquaculture appeared to benefit some species (slimy sculpin [Cottus cognatus], minnows, lake trout), prolonged declines in white sucker abundance and condition and continued depression of Mysis densities and optimal oxythermal habitat availability nearly a decade following operations suggest potentially long‐term impacts at this magnitude. Importantly, this experiment highlights important indicator species and life history traits for monitoring of freshwater aquaculture impacts on native fish communities.

Diversity patterns of native and exotic fish species suggest homogenization processes, but partly fail to highlight extinction threats

AbstractAimExotic species are a major threat to biodiversity and have modified native communities worldwide. Invasion processes have been extensively studied, but studies on species richness and beta diversity patterns of exotic and native species are rare. We investigate such patterns among exotic and native fish communities in upland and lowland rivers to explore their relationship with environmental drivers.LocationNorthern Italy.MethodsExotic and native fish beta diversity patterns were investigated separately in lowland and upland sites using Local Contribution to Beta Diversity (LCBD) and Species Contribution to Beta Diversity (SCBD) analyses. To examine the main environmental variables affecting the LCBD, a Boosted Regression Trees (BRT) method was used. Community dispersion among and within stream orders was investigated with the PERMDISP test.ResultsIn lowland sites, exotic species richness was higher than native species richness, especially in large rivers and drainage canals. An opposite trend was found in upland sites, where native species richness was higher than exotic species richness, especially in large rivers. No clear LCBD patterns were found along stream orders in the lowland, whereas higher stream orders in the upland showed the highest LCBD. Its patterns in upland and lowland sites were related to a number of factors, such as total suspended solids and total phosphorus. Community dispersion among stream orders did not show a relationship with environmental heterogeneity. SCBD values were positively correlated with species occupancy in the study area, and native species showed higher SCBD values than exotic species only in the uplands.Main conclusionsLarge rivers in the uplands are important in maintaining native fish diversity and should be protected against invasive fish. In contrast, most lowland rivers have suffered from biological homogenization. Some rare native species can show low contribution to beta diversity, but still need conservation actions due to their risk of local extinction.

An invasive species, Carassius gibelio, alters the native fish community through trophic niche competition

Carbon and nitrogen stable isotope analyses were used to determine isotopic niche width of the invasive fish species Carassius gibelio to help assess the niche overlap and potential impact of this species on the native fish fauna in the Karamenderes River, northwest Turkey. C. gibelio had the highest niche area of the coexisting species. The greatest overlap of isotopic niche was between C. gibelio and Mugil cephalus in the river mouth. The freshwater species displayed similar patterns when taking into consideration their relative abundance and isotopic overlap. While C. gibelio is likely to outcompete some species at some localities, the species was found co-occurring with others by maximum tolerable overlap degree and apparently utilised vacant niche space at some stations. Overall our results indicate that C. gibelio has extensive niche overlap with the native fish species making it a strong competitor, and because of its high abundance and high niche width this invasive species represents a serious threat to the native fish fauna, particularly in the river mouth.

Land use effects in riverscapes: Diversity and environmental drivers of stream fish communities in protected, agricultural and urban landscapes

Increasing agriculture and urbanization inevitably lead to changes in the biodiversity of stream ecosystems. However, few studies examined comprehensively how biodiversity is distributed within and among protected, agricultural and urban land use types in streams. We studied environmental characteristics of streams and patterns of species richness and other community attributes of stream fish communities in these three characteristic land use types in the catchment of the Danube River, Hungary. Land use separated streams to some degree based on their environmental characteristics. However, both between stream environmental and fish community variability were high in most types, and comparable to land use type level differences in case of many streams. A variety of environmental gradients influenced fish community structure rather independently of land use type, which was also influenced by spatial drivers. Non-native fishes modified the structure of native fish communities, especially in agricultural streams, although their modification effect varied more among individual streams than among land use types. In conclusion, land use type proved to be a poor predictor of fish communities in this human modified landscape. We found that even intensively managed areas (i.e. agricultural and urban) can contribute to the maintenance of fish diversity in this biogeographic region, or at least their potential can be comparable to those streams which flow in protected areas. Thus, conservation management should focus on maintaining streams in more natural condition in protected areas and/or use the potential of non-protected agricultural and urban streams in maintaining fish diversity in human modified landscapes.

Detection and removal efficiency of invasive lionfish in the northern Gulf of Mexico

Mitigating the negative impacts of invasive lionfish (Pterois volitans/miles complex) is a top priority for marine reef fisheries management, with human removals considered the most viable approach to population control. Control efforts via diver spearfishing removals have annually removed tens of thousands of lionfish throughout their invasive range, but the effectiveness of removal efforts to remove 100% or achieve target lionfish densities in a given reef system has not been fully evaluated. Accounting for detection and removal efficacy is necessary for developing and evaluating lionfish management targets, as population- and community-level effects of lionfish removals may be diminished by undetected lionfish remaining in the system. This study quantified lionfish detection, catchability, and removal efficiency to evaluate the effectiveness of lionfish surveys and removal efforts on northern Gulf of Mexico (nGOM) artificial and natural reefs. Detection was assessed during crepuscular and midday time periods via diver and remotely operated vehicle (ROV) video surveys, with covariates for time of day and survey methodology assessed using generalized linear mixed models. Catchability and removal efficiency were estimated via depletion models based on serial removals via spearfishing on 6 artificial reefs and 9 natural reefs. A priori, we had expected lionfish detection to be higher during crepuscular periods given lionfish in the Caribbean and in their native range have been shown to forage more actively away from reefs then. However, we found lionfish detection was not significantly different between midday and crepuscular periods. Survey methodology affected detection, with 24% fewer lionfish being detected via ROV surveys versus diver surveys at artificial reefs and 72% fewer lionfish detected via ROV surveys at natural reefs. Therefore, density estimates on nGOM natural reefs, which constitute of >99% of the region’s habitat, may be higher than previously reported and problematic for lionfish management. Mean catchability for spearfishing lionfish was 0.88 on artificial reefs and 0.69 on natural reefs standardized for area. Mean removal efficiency for the first removal event was 87% on artificial reefs and 67% on natural reefs, higher than removal efficiency computed for Caribbean reefs (47%). Incomplete detection and <100% removal efficiency, in concert with density-dependent processes, may explain recent findings that sustained lionfish removal efforts had no discernible positive impacts on native reef fish communities.

Macroecology of fish community biomass – size structure: effects of invasive species and river regulation

The biomass of organisms of different sizes is increasingly being used to explore macroscale variation in food-web and community structure. Here we examine how invasive species and river flow regulation affect native fish biomass and fish community log10biomass – body mass scaling relationships in Australia’s largest river system, the Murray–Darling. The log10biomass – body mass scaling exponent (scaling B) of invasive fishes (95% CI: −0.14 to −0.18) was less negative than for native fishes (95% CI: −0.20 to −0.25), meaning that invasive species attained a higher biomass in larger size-classes compared to native species. Flow alteration and invasive common carp (Cyprinus carpio) biomass were correlated with severe reductions in native fish biomass ranging from −47% to −68% (95% CI). Our study provides novel evidence suggesting that invasive and native communities have different biomass – body mass scaling patterns, which likely depend on differences in their trophic ecology and body size distributions. Our results suggest that restoration efforts using environmental flows and common carp control has potential to boost native fish biomass to more than double the current level.

Prey fish communities of the Laurentian Great Lakes: A cross-basin overview of status and trends based on bottom trawl surveys, 1978-2016

Annual bottom trawl surveys were initiated in the 1970s in Laurentian Great Lakes Superior, Huron, Michigan and Ontario and in 1990 in Erie to provide annual assessments of the status and trends of prey fish communities. Native Cisco Coregonus artedi and Bloater C. hoyi dominated the prey fish community of Lake Superior. Prey fish communities in lakes Huron and Michigan were dominated by nonnative Rainbow Smelt Osmerus mordax and Alewife Alosa pseudoharengus for much of 1978-2016, but Bloater was an important species during the 1980-1990s and more recently has become the dominant prey species in these lakes. Alewife dominated the prey fish community of Lake Ontario during all 1978-2016. While nonnatives dominated the prey fish community in Lake Erie, native Emerald Shiner Notropis atherinoides was an important species and occasionally the dominant prey fish after the establishment of Round Goby Neogobius melanostomus in the late 1990s. During the 1980s-1990s Bythotrephes cederstroemi, Dreissena polymorpha, and Dreissena bugensis caused profound changes in Laurentian Great Lakes ecosystems and likely contributed to declines in fish community biomass in lakes Michigan and Huron. The impacts of these invaders were more muted in lakes Erie and Ontario. Lake Superior stands out as the Laurentian Great Lakes success story: Lake Trout Salvelinus namaycush was restored, and native prey fishes dominate and support a viable fishery. Although the abundance of Bloater has increased recently in lakes Huron and Michigan, recovery of native prey fishes remains uncertain. The absence of native species among the principal prey fish in Lake Ontario indicates a lack of progress in native fish recovery. Recovery of native prey fishes remains unclear in Lake Erie. The ever-changing state of the Laurentian Great Lakes caused by the impacts of invasive species and ongoing climate and ecosystem change will continue to challenge restoration of native fish communities in the 21st Century.

Tag retention and survival of juvenile bighead carp implanted with a dummy acoustic tag at three temperatures

Bighead carp Hypophthalmichthys nobilis and silver carp Hypophthalmichthys molitrix (together, the bigheaded carps) are invasive fishes in North America that have resulted in substantial negative effects on native fish communities and aquatic ecosystems. Movement and behavior of adult bigheaded carps has been studied previously using telemetry, while similar studies with juvenile bigheaded carps have yet to be attempted. Recent technological advances in telemetry transmitters has increased the availability of tags sufficiently small enough to implant in juvenile carps. However, the effects of surgical implantation of telemetry tags on juvenile bigheaded carps have not been evaluated. We determined tag retention and survival associated with surgical implantation of acoustic telemetry tags into juvenile bighead carp (range 128–152 mm total length) at three temperatures (13, 18, and 23°C). In addition, we assessed the effect of surgically implanted transmitters on the fitness, defined as changes in weight or critical swimming speed, of carp implanted with transmitters. Survival was high among tagged fish (85%) with 47% of tags retained at the conclusion of the 45‐day study. No substantial decline in fitness of the fish was observed in tagged fish compared to untagged fish.

Spatial variability in the somatic growth of pikeperch Sander lucioperca, an invasive piscivorous fish

AbstractIntroduced fishes can develop invasive populations that impact native species and ecosystems. Understanding the population ecology of introduced species in their extended ranges and how this compares to their native ranges is therefore important for informing their management. Here, the age and somatic growth rates of the piscivorous freshwater fish pikeperch Sander lucioperca were analysed across their invasive and native ranges to determine their spatial patterns and drivers. Analyses were initially completed in their invaded range in central and western England. Populations varied spatially in their growth rates; being slowest for a population in a narrow and shallow canal and fastest in a large, impounded lowland river. A meta‐analysis of parameters of the von Bertalanffy growth model then revealed that across their native and invasive ranges, their theoretical ultimate lengths (L∞) and growth coefficients (K) were significantly related to latitude, but not longitude. Their relationships with latitude were nonlinear, with higher values of L∞ and lower values of K being evident towards their northerly and southerly range limits. Faster growth rates were evident in the middle of their range (45 to 55°N), suggesting temperatures here were most optimal for growth, but were in a trade‐off with reduced ultimate lengths. These spatial patterns suggest that whilst introduced S. lucioperca can colonise new waters across a wide area, the expression of their life‐history traits will vary spatially, with potential implications for how invasive populations establish and integrate into native fish communities.

River science and management issues in Chile: Hydropower development and native fish communities

AbstractThe magnitude of hydropower developments in emerging regions threatens the sustainability of their riverine landscapes. Fragmentation of river networks by multiple barriers and the imposition of new hydrological regimes influences the ability of these river ecosystems to absorb and adapt to these developments and other stressors. Direct transfer of paradigms built from a restricted geographical base to a global context is fraught with issues because of regional differences in eco‐hydro‐geomorphology, biological communities, and nonlinear interactions between the two. In this manuscript, some impacts of hydropower development on Chilean riverine ecosystems are presented. To understand the context of hydropower, we provide the political context of energy development in Chile. Interactions between hydropower generation and Chilean river ecosystems with special reference to native Chilean fish fauna are outlined. Three case studies are presented that considers: (a) habitat alteration downstream of the Rucúe Dam, (b) the effects of daily hydropeaking in the Biobío River, and (c) mitigation strategies to reduce habitat alteration upstream of the San Pedro Dam. These case studies illustrate the expanding scientific knowledge on Chilean riverine landscapes. Finally, new measures to reduce ecosystem impacts of hydropower development on native Chilean fish communities are outlined. Although specific scientific information is available, developing regional ecohydrological models and improving knowledge of ecosystem and sustainability science is required. The scientific approach on which solutions are sought to address present and future river ecosystem problems in Chile are inherently interdisciplinary nature.

Some biological characteristics of Carassius gibelio (Bloch, 1782) (Teleostei: Cyprinidae) in the Azad dam Lake in Western Iran

The freshwater Prussian carp, Carassius gibelio (Bloch, 1782) is a cyprinid, known as a hazardous species for native fish communities. In the present study, some population parameters, including length-weight relationship ( LWR ), condition factor ( KF ), relation condition factor ( K n ), age and growth of C. gibelio in the Azad dam, Kordestan Province, Iran were estimated. The LWR indicating a positive allometric growth pattern. The von Bertalanffy growth parameters were estimated as L ∞ =337mm, K =0.255 yr -1 , t 0 =-0.21 yr. There was a significantly positive correlation between TL and KF ( r 2 =0.89). The average of K n was lower than 1 which suggested that the well-being of the fish was not good in the Azad dam region.

Introduced European smelt (Osmerus eperlanus) affects food web and fish community in a large Norwegian lake

Invasive and introduced fishes can affect recipient ecosystems and native species via altered competitive and predatory interactions, potentially leading to top-down and bottom-up cascading impacts. Here, we describe a case from a large lake in southern Norway, Storsjoen, where the illegal introduction of a small, predominantly planktivorous fish species, European smelt (Osmerus eperlanus), has led to changes in the native fish community and lake food web. Survey fishing data collected before (2007) and after (2016) the introduction indicates that smelt has become the numerically dominant fish species both in benthic and pelagic habitats, with concurrent reductions in the relative abundance of native European whitefish (Coregonus lavaretus) and Arctic charr (Salvelinus alpinus) populations. Stable isotope (δ13C and δ15N) data indicate minor changes in the trophic niches of native whitefish and Arctic charr despite partly overlapping niches with the introduced smelt. In contrast, brown trout (Salmo trutta) showed an earlier shift to piscivory, a more pelagic niche and increased growth rate, likely because of the smelt induced increase in pelagic prey fish abundance. The main trophic pathway supporting top predators (i.e., large brown trout) in Storsjoen has, therefore, shifted from a littoral to a more pelagic base. Our study demonstrates that small-sized introduced fishes can alter lake food-web dynamics, with contrasting impacts on native fishes. This knowledge is vital for future evaluation and mitigation of potential impacts of smelt introductions on lake ecosystems.

Fish Occurrence in a Seasonally Inundated Floodplain of the Willamette River, Oregon

The dynamic nature of large rivers is often diminished by anthropogenic alterations resulting in simplified stream networks with decreased floodplain connectivity and ecological function which adversely impact native organisms. However, little is known about the importance of large river floodplains to fish communities in the Pacific Northwest, especially during winter high flows. Our objectives were to document seasonal use of a Willamette River floodplain for native and non-native fish by measuring: 1) fish community characteristics (species richness, native versus non-native status, relative abundance), 2) spawning and rearing, 3) timing of use and movement, and 4) use by federally protected juvenile spring Chinook salmon (Oncorhynchus tshawytscha). During fall 2011 through spring 2012, a floodplain was sampled with a backpack electrofisher and out-migrant trap. A total of 12 native and 11 non-native species were detected. During nine electrofishing samples, 691 fish were collected, of which 95% were native. An estimated 42,297 fish were captured by the out-migrant trap; 98% of which were native and most were age-0 threespine stickleback (Gasterosteus aculeatus). Native species were detected on the floodplain prior to non-native species and tended to emigrate from the floodplain before non-native species, leading to a higher potential of stranding for non-native species as waters recedes. This study documents use of floodplain habitat by native and non-native fish species for seasonal flood refuge, rearing and spawning. Our results demonstrate native fish communities could potentially benefit from conservation of existing floodplains and restoration of floodplains changed by land use practices and altered flow regimes.

Correction: Isotope niche dimension and trophic overlap between bigheaded carps and native filter-feeding fish in the lower Missouri River, USA

[This corrects the article DOI: 10.1371/journal.pone.0197584.].

Phylogenetic and environmental DNA insights into emerging aquatic parasites: implications for risk management

Species translocation leads to disease emergence in native species of considerable economic importance. Generalist parasites are more likely to be transported, become established and infect new hosts, thus their risk needs to be evaluated. Freshwater systems are particularly at risk from parasite introductions due to the frequency of fish movements, lack of international legislative controls for non-listed pathogens and inherent difficulties with monitoring disease introductions in wild fish populations. Here we used one of the world’s most invasive freshwater fish, the topmouth gudgeon, Pseudorasbora parva, to demonstrate the risk posed by an emergent generalist parasite, Sphaerothecum destruens. Pseudorasbora parva has spread to 32 countries from its native range in China through the aquaculture trade and has introduced S. destruens to at least five of these. We systematically investigated the spread of S. destruens through Great Britain and its establishment in native fish communities through a combination of phylogenetic studies of the host and parasite and a novel environmental DNA detection assay. Molecular approaches confirmed that S. destruens is present in 50% of the P. parva communities tested and was also detected in resident native fish communities but in the absence of notable histopathological changes. We identified specific P. parva haplotypes associated with S. destruens and evaluated the risk of disease emergence from this cryptic fish parasite. We provide a framework that can be applied to any aquatic pathogen to enhance detection and help mitigate future disease risks in wild fish populations.