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When managing invasive fishes, permanent barriers may be best in preventing spread; however, they may not be feasible due to costs and logistical constraints. Alternatively, non-permanent barriers using electricity, light, sound, pressure, bubbles, CO2, and other stimuli are being developed and deployed in efforts to limit the spread of aquatic invasive species or to achieve fish guidance and conservation. However, the effectiveness of these barriers is quite variable and testing is often lacking for both target and non-target species. We conducted a series of laboratory trials to examine the effects of a vertical electric barrier on behaviour of common carp Cyprinus carpio (Linnaeus, 1758). In response to the electric field, common carp reduced passing the electric barrier significantly, exhibiting different behaviours when interacting with the electric barrier, and spent more time away from the electric barrier when it was turned on during the stimulus period compared to preand post-stimulus periods. Our results suggest that a relatively weak electric gradient (i.e., voltage gradient: 0.2-0.4 V·cm-1, power density: 3-42 μW·cm-3) can inhibit the movement of common carp. Our results also highlight the importance of detailed examination of behavioural responses of target species when evaluating and considering fish-deterrent technologies. [ABSTRACT FROM AUTHOR]

The native ranges of many species in North America reach their northern extent in southern Canada, which results in several aquatic species with core populations found farther south being assessed as at risk by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) and receiving protection under the Species at Risk Act (SARA)., To determine traits that predict at-risk status for freshwater fishes in Canada a classification and regression tree analysis was performed using a suite of ecological and life-history traits, and the species' distributions in Canada., Range-edge distribution in Canada was a significant predictor of a species assessed as at risk by COSEWIC and to be listed as at risk under SARA. Other predictive traits included Balon reproductive guild, reproductive age/maximum age ratio, and lifespan. Species with economic value were also not likely to be assessed as at risk by COSEWIC. Analyses showed greater inconsistency in listing status under SARA than COSEWIC assessment, and a bias toward not listing species, despite predicted at-risk status, was evident., The predictive models may prove useful in making future conservation decisions and highlight species that should have their status (re)assessed. [ABSTRACT FROM AUTHOR]

A spatially explicit metapopulation viability model was created within RAMAS-GIS to address questions related to the conservation and management of a freshwater species at risk ( Notropis anogenus). Population viability analysis was conducted to evaluate extinction risk and sensitivity analyses were undertaken to identify the most important spatial and non-spatial parameters influencing extinction and decline., As biodiversity offsets are increasingly used to compensate for habitat loss, the population model was also used to explore the effectiveness of four potential offsetting mechanisms. In particular, this study addressed whether the impact of habitat loss on a species at risk could be compensated by: (i) increasing habitat elsewhere; (ii) increasing vital rates; (iii) increasing abundance; and (iv) increasing connectivity., Results suggest that extinction risk is low for this metapopulation and that the risk of extinction was most sensitive to vital rates., Compensating habitat loss with habitat gain, the most straightforward approach explored, was by far the most effective type of compensation. Increasing vital rates was the second most promising approach. Although increasing abundance and increasing connectivity could not be categorically ruled out, their effectiveness was much more limited., Overall, this study provided insight into the influence of spatial and non-spatial parameters on abundance, patch occupancy, and extinction risk of an aquatic species. This approach can be applied to a wide variety of species to evaluate the effect of ecosystem perturbations and inform management options. [ABSTRACT FROM AUTHOR]

Darwin's naturalization conundrum describes the paradigm that community assembly is regulated by two opposing processes, environmental filtering and competitive interactions, which predict both similarity and distinctiveness of species to be important for establishment. Our goal is to use long-term, large-scale, and high-resolution temporal data to examine diversity patterns over time and assess whether environmental filtering or competition plays a larger role in regulating community assembly processes. We evaluated Darwin's naturalization conundrum and how functional diversity has changed in the Laurentian Great Lakes fish community from 1870 to 2010, which has experienced frequent introductions of non-native species and extirpations of native species. We analyzed how functional diversity has changed over time by decade from 1870 to 2010 at three spatial scales (regional, lake, and habitat) to account for potential noninteractions between species at the regional and lake level. We also determined which process, environmental filtering or competitive interactions, is more important in regulating community assembly and maintenance by comparing observed patterns to what we would expect in the absence of an ecological mechanism. With the exception of one community, all analyses show that functional diversity and species richness has increased over time and that environmental filtering regulates community assembly at the regional level. When examining functional diversity at the lake and habitat level, the regulating processes become more context dependent. This study is the first to examine diversity patterns and Darwin's conundrum by integrating long-term, large-scale, and high-resolution temporal data at multiple spatial scales. Our results confirm that Darwin's conundrum is highly context dependent. [ABSTRACT FROM AUTHOR]

Determining the occurrence and site occupancy of rare and endangered species can be challenging, particularly without causing harm or stress to the species of concern., Environmental DNA (eDNA) detection was used to assess habitat occupancy by spotted gar ( Lepisosteus oculatus), which is federally listed as Threatened in Canada, with known occurrences limited to a small number of locations in southern Ontario., Quantitative polymerase chain reaction (qPCR) assays were developed to detect spotted gar eDNA, which was detected in all but one previously recorded location. The eDNA method was shown to be more effective than traditional netting for detecting spotted gar habitat use., The use of qPCR allowed for quantification of substantial variation in detection strength (copy number) among replicate eDNA samples, with implications for establishing sampling designs for detection and surveillance., The use of eDNA for detection and monitoring of aquatic species of conservation concern shows great potential as a non-invasive method for assessing species occurrences and habitat occupancy, as well as for informing targeted sampling by conventional capture methods., Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The Anthropocene Epoch is characterized by novel and increasingly complex dependencies between the environment and human civilization, with many challenges of biodiversity management emerging as wicked problems. Problems arising from the management of biological invasions can be either tame (with simple or obvious solutions) or wicked, where difficulty in appropriately defining the problem can make complete solutions impossible to find. We review four case studies that reflect the main goals in the management of biological invasions - prevention, eradication, and impact reduction - assessing the drivers and extent of wickedness in each. We find that a disconnect between the perception and reality of how wicked a problem is can profoundly influence the likelihood of successful management. For example, managing species introductions can be wicked, but shifting from species-focused to vector-focused risk management can greatly reduce the complexity, making it a tame problem. The scope and scale of the overall management goal will also dictate the wickedness of the problem and the achievability of management solutions (cf. eradication and ecosystem restoration). Finally, managing species that have both positive and negative impacts requires engagement with all stakeholders and scenario-based planning. Effective management of invasions requires either recognizing unavoidable wickedness, or circumventing it by seeking alternative management perspectives. [ABSTRACT FROM AUTHOR]

Understanding the biological and socio-economic risks associated with existing and potential aquatic invasive species is essential for an aquatic invasive species program to be successful. Effective programs are based on risk analyses, in which risk assessment informs risk management and both are communicated to resource managers and the public. Risk assessments provide valuable information that can be applied to many areas of an aquatic invasive species program. Based on biological and socio-economic risk assessments, appropriate risk management actions related to prevention, early detection and rapid response, and control can be undertaken. In particular, biological risk assessments inform both socio-economic risk assessment and subsequent preventative, monitoring, and control management actions. The uncertainty and knowledge gaps identified in risk assessments help identify and prioritize future research. Risk assessments are used to identify the riskiest aquatic invasive species and pathways and can be used to identify effective management, policy, and legislative actions to minimize risk. This, in turn, allows for the optimal allocation of limited resources to combat aquatic invasive species; therefore, risk assessment should be considered the cornerstone of a successful aquatic invasive species program. This article describes the risk analysis of aquatic invasive species, with emphasis on biological risk assessment and how they can be managed using marine and freshwater examples, with particular emphasis on the risk assessment of Bigheaded Carps in North America. [ABSTRACT FROM PUBLISHER]

Quantifying spatial genetic structure can reveal the relative influences of contemporary and historic factors underlying localized and regional patterns of genetic diversity and gene flow - important considerations for the development of effective conservation efforts. Using 10 polymorphic microsatellite loci, we characterize genetic variation among populations across the range of the Eastern Sand Darter (Ammocrypta pellucida), a small riverine percid that is highly dependent on sandy substrate microhabitats. We tested for fine scale, regional, and historic patterns of genetic structure. As expected, significant differentiation was detected among rivers within drainages and among drainages. At finer scales, an unexpected lack of within-river genetic structure among fragmented sandy microhabitats suggests that stratified dispersal resulting from unstable sand bar habitat degradation (natural and anthropogenic) may preclude substantial genetic differentiation within rivers. Among-drainage genetic structure indicates that postglacial (14 kya) drainage connectivity continues to influence contemporary genetic structure among Eastern Sand Darter populations in southern Ontario. These results provide an unexpected contrast to other benthic riverine fish in the Great Lakes drainage and suggest that habitat-specific fishes, such as the Eastern Sand Darter, can evolve dispersal strategies that overcome fragmented and temporally unstable habitats. [ABSTRACT FROM AUTHOR]

Predictive models of species distribution are useful tools to identify habitats of imperilled species for protection, inventory and restoration. Critical aspects of such models include the influence of scale, uncertainties associated with imperfect detection and spatial autocorrelation and transferability of model predictions., We addressed these issues in developing occupancy models of the imperilled eastern sand darter ( Ammocrypta pellucida) based on surveys of the Grand and Thames Rivers, Ontario, Canada., Eastern sand darter detection probabilities were remarkably different between streams, but factors affecting site occupancy were similar. The proportion of sand and fine gravel was most important, but water clarity and biotic indices also received support in additive models. Accounting for spatial autocorrelation reduced the effect of important covariates., Occupancy was more closely related to substratum at the site level than factors at broader scales (reach and valley segment), further emphasising the substratum specificity of this species., Almost all of the top-ranked site and reach occupancy models had good predictive performance based on assessments of transferability. These models indicate that three formerly occupied Ontario catchments have a high probability of supporting the species and deserve consideration for repatriation., Our methods demonstrate how a comprehensive approach to occupancy modelling can be used to help guide recovery efforts for imperilled species. [ABSTRACT FROM AUTHOR]

ABSTRACT The use of non-lethal experiments to elucidate behavioural and physiological thresholds to environmental stressors can provide valuable data for identifying threats to, and critical habitat of, imperilled species. Increased turbidity contributes to population declines and loss of fish diversity globally, but the complex direct and indirect effects of this stressor on imperilled species are not well understood., Response to turbidity was examined in a group of closely related North American fishes ( Notropis spp.), including four imperilled shiners: pugnose shiner ( N. anogenus), bridle shiner ( N. bifrenatus), blacknose shiner ( N. heterolepis), blackchin shiner ( N. heterodon), and the more common mimic shiner ( N. volucellus). Two experiments quantified (i) the behavioural response of each species to progressively increasing turbidity, and (ii) critical swimming speed of fishes acclimated in turbid- and clear-water treatments to provide insights into effects of low turbidity on aerobic performance., Very low levels of turbidity (<10 NTU) altered schooling behaviour of pugnose and bridle shiners, both imperilled. Critical swimming speed was lower in pugnose shiner acclimated to low turbidity than fish acclimated to clear waters, while the opposite pattern was observed in bridle shiner. Low turbidity did not affect behaviour or critical swimming speed in the other three shiner species, suggesting that they are more tolerant of low levels of turbidity., The demonstration of alterations in ecologically significant measures of behaviour and performance in the pugnose and bridle shiners, provides evidence required to identify and implement conservation and recovery actions related to turbidity of human origin. In addition, it is suggested that species-specific responses should be evaluated, where possible, when defining critical habitat., Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The use of live baitfish is a cultural norm in many jurisdictions across North America. Because baitfish are often harvested from mixed stocks in the wild, the potential for bycatch exists, leading to the inadvertent relocation of nontarget species via distribution networks and anglers; therefore, like many fisheries, core issues revolve around selective fishing. We assess selectivity of bait fisheries in Ontario, focusing on the prevalence of bycatch within the commercial supply chain and the propensity for nontarget species introductions by anglers. Selection for target stocks was strong; however, species assemblages in retail tanks and angler purchases included game, imperiled, invasive, and other nontarget species. The combination of bycatch, a large volume of angling trips, and risky angler behavior results in high probabilities of introducing the suite of nontarget species contained incidentally. Pathway approaches to management provide opportunities to increase selectivity, manage the risk of species introductions, and sustain the integrity of bait operations throughout North America. RESUMEN: el uso de carnada viva es una norma cultural en varias jurisdicciones de Norte América. Debido a que los peces que se utilizan como carnada a veces son capturados junto con una mezcla de stocks silvestres, existe el potencial de que se vuelvan fauna de acompañamiento, lo que tiene como consecuencia que especies no objetivo sean reubicadas de forma inadvertida a través pescadores y de redes de distribución; por esta razón, como sucede en muchas pesquerías, el problema medular gira en torno a la pesca selectiva. En este trabajo se evalúa la selectividad de las pesquerías de carnada en Ontario, Canadá, haciendo enfasis en la prevalencia de la fauna de acompañamiento en la cadena productiva y en la propensión que existe por parte de los pescadores a reubicar especies no objetivo. La selectividad que existe para los stocks objetivo es intensa, sin embargo las asociaciones de peces que comercializan los pescadores incluyen especies de pesca deportiva, especies en peligro, especies invasivas y otras especies no objetivo. La combinación de fauna de acompañamiento, una enorme cantidad de viajes de pesca y un comportamiento riesgoso por parte de los pescadores, da como resultado una alta probabilidad de introducir una amplia gama de especies no objetivo que son contenidas incidentalmente. El manejo utilizando corredores, podria incrementar la selectividad, controlar la introducción de especies y mantener la integridad de las operaciones pesqueras con carnada a lo largo de Norte América. [ABSTRACT FROM AUTHOR]

A primary goal of ecosystem-based fishery management is to reduce non-target stock impacts, such as incidental harvest, during targeted fisheries. Quantifying incidental harvest has generally incorporated fishery-dependent catch data, yet such data may be biased by gear non-retention, observation difficulties, and non-random harvest patterns that collectively lead to an impartial understanding of non-target stock capture. To account for such issues and explicitly recognize the combined influence of ecological and harvest factors contributing to incidental capture within targeted fisheries, we demonstrate a probabilistic modelling framework that incorporates: (i) background rates of target and non-target stock co-occurrence as the primary ecological basis for incidental harvest; (ii) the probability of harvesting at localities exhibiting co-occurrences; (iii) the probability of selecting for non-target species with fishery gear; and, (iv) as a function of harvest effort, the overall probability of incidental capture for any non-target stock contained in the species pool available for harvest. To illustrate application of the framework, simulation models were based on fishery-independent data from a freshwater fishery in Ontario, Canada. Harvest simulations of empirical stock data indicated that greatest species-specific capture values were over 4000 times more likely than for species with lowest values, indicating highly variable capture probabilities because of the combined influence of stock heterogeneity and harvest dynamics. Estimated bycatch-effort relationships will allow forecasting incidental harvest on the basis of effort to evaluate future shifts in fishing activity against specific ecosystem-based fishery management objectives, such as reducing the overall probability of bycatch while maintaining target landings. [ABSTRACT FROM AUTHOR]

The invasion of round goby Neogobius melanostomus into tributaries of the Laurentian Great Lakes poses concerns for the conservation of native fish communities and the functioning of stream ecosystems. In streams, where standard methods for detection are lacking, development of sensitive sampling methods to identify round goby-invaded sites is a prerequisite for the implementation of effective management strategies. We sampled 34 stream sites that spanned a range of goby densities with two active gears (electrofishing and seining) and one passive gear (minnow traps) to compare gear efficiency at detecting invasive round goby. Naive occupancy, defined as the number of sites where goby were detected with each gear divided by the total number of sites, was 0.79 (27/34 sites) for seining, 0.68 (23/34) for electrofishing, and 0.50 (17/34) for traps. The probability of detecting a single round goby in a single pass (determined with single-season, constant-probability models) was 0.75 ± 0.065 (mean ± SE) for minnow traps, 0.69 ± 0.056 for seining, and 0.47 ± 0.075 for electrofishing. Mean ± SE catch per unit effort (CPUE; round goby/min) was 0.716 + 0.158 for seining, 0.137 ± 0.043 for electrofishing, and 0.078 ± 0.022 for minnow traps, seining being significantly more efficient than minnow traps and electrofishing. The CPUE did not differ between electrofishing and traps. Mean goby size did not differ among gear types, but a size bias was detected when data from a related study were included in the analysis, seining capturing smaller round goby. Based on the sensitivity and efficiency of seining, we conclude that when stream conditions allow, this gear is a practical means of detecting round goby and determining their abundance in streams. Received August 11, 2011; accepted January 4, 2012 [ABSTRACT FROM AUTHOR]

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Background: DNA barcoding aims to provide an efficient method for species-level identifications using an array of species specific molecular tags derived from the 59 region of the mitochondrial cytochrome c oxidase I (COI) gene. The efficiency of the method hinges on the degree of sequence divergence among species and species-level identifications are relatively straightforward when the average genetic distance among individuals within a species does not exceed the average genetic distance between sister species. Fishes constitute a highly diverse group of vertebrates that exhibit deep phenotypic changes during development. In this context, the identification of fish species is challenging and DNA barcoding provide new perspectives in ecology and systematics of fishes. Here we examined the degree to which DNA barcoding discriminate freshwater fish species from the well-known Canadian fauna, which currently encompasses nearly 200 species, some which are of high economic value like salmons and sturgeons. Methodology/Principal Findings: We bi-directionally sequenced the standard 652 bp ''barcode'' region of COI for 1360 individuals belonging to 190 of the 203 Canadian freshwater fish species (95%). Most species were represented by multiple individuals (7.6 on average), the majority of which were retained as voucher specimens. The average genetic distance was 27 fold higher between species than within species, as K2P distance estimates averaged 8.3% among congeners and only 0.3% among concpecifics. However, shared polymorphism between sister-species was detected in 15 species (8% of the cases). The distribution of K2P distance between individuals and species overlapped and identifications were only possible to species group using DNA barcodes in these cases. Conversely, deep hidden genetic divergence was revealed within two species, suggesting the presence of cryptic species. Conclusions/Significance: The present study evidenced that freshwater fish species can be efficiently identified through the use of DNA barcoding, especially the species complex of small-sized species, and that the present COI library can be used for subsequent applications in ecology and systematics. [ABSTRACT FROM AUTHOR]

We examined the relationship between microhabitat variables and fish distributions in a large connecting channel, the Detroit River. Fishes were sampled by boat seine at 60 sites in shallow (<2.5 m) Canadian waters in May, July, and September 2004. Length-frequency distributions were used to separate species into small- and large-species size categories. Fish-microhabitat associations were examined by applying canonical correspondence analysis separately for each season. Small fishes were often more strongly associated with microhabitat variables than large conspecifics. For example, small centrarchids were more strongly associated with complex macrophytes than large centrarchids in the spring; however, this pattern varied among seasons. We attribute the stronger microhabitat associations of small fishes to predator avoidance. Small-bodied species also selected habitats that provided protection against predation: the spotfin shiner preferred shallow water, and the round goby preferred coarse substrate. We observed a strong difference in microhabitat preferences between the small and large size categories of a species. Fish size played a greater role than season in determining fish-microhabitat associations. We found that macrophytes with a complex morphological structure were the most important factor in determining fish distributions in all seasons, while depth ranked second or third in importance. Fishes use an array of microhabitats in the Detroit River, and habitat heterogeneity is essential for promoting a diverse fish assemblage. [ABSTRACT FROM AUTHOR]

Point sampling by electrofishing is often used to study fishes in large rivers and lakes whereby a specific location is electrofished without moving the anode. Short (l-5-s) samples are taken under the belief that many small samples are preferred over a few large ones for statistical analyses. However, this typically results in relatively little time spent sampling fishes compared with time spent measuring abiotic factors and traveling among sites. We evaluated the optimal sampling duration and number of replicates per site to balance sample size and number for community-level studies. In 2004, 165 point samples were taken from shallow Canadian waters of the Detroit River. Sites were continuously electrofished for 2 min (eight 15-s intervals), and a second replicate of 2 min was taken after a pause. Subsets of the data were used to compare various designs of sampling duration and number of replicates. A sampling design of two replicates of 1 min appeared to be ideal because it balanced a large gain of information with a small increase in effort. This design would allow 35-50 sites to be sampled per day, depending on the detail of abiotic measurements. Compared with data from the first 15-s interval only, sampling for two replicates of 1 rain resulted in fewer null (no fishes captured) samples (19% instead of 53%). The number of common (found at >5% of Samples) species also increased from 12 to 19. By increasing the effort for point sampling by electrofishing at each site, a better understanding of the fish assemblage was obtained. This allows for more complete analyses of community composition and habitat preference. [ABSTRACT FROM AUTHOR]

Few studies of fish assemblages have been conducted in large rivers owing to the difficulties of sampling such complex systems. We evaluated the effectiveness of six different gear types (seine nets, boat electrofishers, hoop nets, Windermere traps, trap nets, and minnow traps) in sampling the fish assemblage at 30 sites in the shallow offshore waters of the middle Detroit River in July and August 2003. A total of 2,449 fish representing 38 species in 15 families were captured by seining (1,293 fish, 29 species), boat electrofishing (398 fish, 23 species), hoop nets (524 fish, 26 species), and Windermere traps (234 fish, 14 species). Trap nets and minnow traps were not effective in sampling offshore littoral sites. Significantly higher fish species richness and abundance were obtained and more unique species were captured by seine nets than by any other gear type. When effort is constant, the highest richness and abundance are obtained by seine nets. Windermere traps produced significantly lower abundance and richness than all other gear types, but proportionally more benthic species. Total species accumulation rates were not markedly reduced when Windermere trap data were excluded. Use of additional Windermere traps at each site could increase abundance, but samples taken by Windermere traps had the lowest rarefied richness among gear types at any level of abundance. Nonmetric multidimensional scaling showed that seine-net catches, which were dominated by midwater schooling species (brook silverside Labidesthes sicculus, emerald shiner Notropis atherinoides, and mimic shiner N. volucellus), were most dissimilar from Windermere trap catches, which were dominated by centrarchids. Seine nets were the most effective gear for sampling offshore waters. [ABSTRACT FROM AUTHOR]

The article presents a study which examines the potential smallmouth bass introductions into lakes of central Ontario to better guide prevention efforts. The study uses artificial neural network to predict lakes that are likely to be invaded by bass based on the local and regional environmental variables for 3046 central Ontario lakes. The study concludes the optimization of efforts to prevent further impacts by focusing on the vulnerable subset of lakes.

Environmental DNA (eDNA) metabarcoding has the potential to significantly improve surveys of biodiversity in freshwater systems. However, this methodology is still infrequently used in global hotspots of endemic species, in part because of two major barriers to the success of eDNA metabarcoding: (1) insufficient regional taxonomic representation in public reference sequence databases; and (2) inconsistent species incidence and abundance estimates when compared to conventional surveys. We sampled eDNA and conducted visual surveys in the headwaters of two rivers in the Cape Fold aquatic ecoregion, South Africa. A reference sequence database was generated for the regional diversity of fishes to improve taxonomic classification of endemic species. We also compared the consistency of incidence data and relative abundance estimates of fishes from eDNA metabarcoding sequencing results and visual surveys (snorkel and underwater cameras) at each site sampled. Only 1% of eDNA metabarcoding reads could be classified to fish species without the supplementation of reference sequence databases for local endemic species. Once regional reference sequences were added, a total of nine species were detected and >99% reads classified. A strong positive relationship (Φ = 0.75) was observed between the patterns of detections using eDNA and visual approaches. However, eDNA metabarcoding detected more species than visual methods. In addition, the relative read frequency and abundance observed in visual surveys was significantly correlated (R2 = 0.85–0.88, p < 0.001) in the majority of the small pools surveyed. Incomplete public reference sequence databases hinder the use of eDNA metabarcoding in regions of high endemicity. Local reference sequence libraries can overcome these challenges. When appropriately implemented, eDNA metabarcoding shows promise, producing results consistent or better than the more frequently used and labour‐intensive visual surveys. Efficient survey methods like eDNA metabarcoding are urgently needed to improve aquatic monitoring efforts globally. Understanding how eDNA metabarcoding sequencing results relate to conventional survey methods is a key step in its implementation in ecoregions with high endemicity. [ABSTRACT FROM AUTHOR]

Aim: Here, we use an integrative, comprehensive risk assessment framework as a screening tool to evaluate how the invasion risk of previously failed introduced freshwater fish species, commonly found in the live‐trade pathway, will change under future climate‐change scenarios. Location: Laurentian Great Lakes, North America. Methods: The 34 species screened for invasion risk previously failed to establish populations, likely due to poor environmental suitability, low propagule pressure, and/or biotic resistance from the recipient community, and are most commonly found in the increasingly important live‐trade pathway. Using established trait‐based models, we quantified the probability of establishment success and probability of having high ecological impact in the decade of first introduction and present‐day communities (2020) based on known species extirpations, introductions and establishments between 1870 and 2020. We completed a climate match analysis under future climate‐change scenarios based on 16 bioclimatic variables. This approach identified a list of species that should be prioritized in surveillance management. Results: We identified seven species that have an increased climate match with the region and an increased probability of establishment success. Five of these species have an increased probability of high ecological impacts. Twenty‐four species have a current probability of establishment success greater than 50% and 33 species have a current probability of high ecological impacts greater than 50%. Climate match was dynamic under future climate‐change scenarios with 14 species experiencing a better match between their native geographical range and the Laurentian Great Lakes region. Main conclusions: Our models identify and predict the invasion risk of non‐native freshwater fish species present in pathways relevant to the Great Lakes region and provide a comprehensive framework for future management that prioritize efforts to species of highest risk. This framework could be applied to different taxa, pathways, and/or ecosystems to estimate current and predicted invasion risk under multiple scenarios. [ABSTRACT FROM AUTHOR]

Background: The winter tick (Dermacentor albipictus) has garnered significant attention throughout North America for its impact on wildlife health, and especially for moose (Alces alces), where high tick burdens may result in host hair loss, anemia, and can prove fatal. The environmental transmission of D. albipictus larvae to a host is a critical event that has direct impact on infestation success, yet in-field observations of this life stage are lacking. In Yukon, Canada, D. albipictus had previously been found on hosts, but its larval life stage had not been detected in the field, despite previous sampling attempts. Methods: We sampled for D. albipictus larvae using traditional flagging methods in Ibex Valley and Braeburn, Yukon. Sites were sampled repeatedly for D. albipictus larvae by flagging from late August to end of October in 2018 and late August to end of November 2019. Results: Larvae of D. albipictus were collected throughout Ibex Valley, at approximate densities ranging from 0.04 to 4236 larvae/100 m2. Larvae were present primarily on grassy vegetation on south-facing slopes in the Ibex Valley region and in Braeburn. Highest average larval numbers suggest peak questing activity was towards the end of September and beginning of October, as elsewhere in North America. Conclusions: To the best of our knowledge, we report the first successful collection of the off-host, larval life stage of D. albipictus by flagging, north of 60° latitude in Yukon, Canada. These new observations provide critical information on the spatial distribution of the host-seeking life stage of D. albipictus and confirm that this species is completing its whole life cycle in southern Yukon. Understanding the environmental conditions where larvae spend their vulnerable period off-host in this northern location can inform both management strategies and projections of future range expansion which may occur with a changing climate. [ABSTRACT FROM AUTHOR]

The greenside darter, Etheostoma blennioides is a small benthic fish found in fast-flowing streams in eastern North America. In Canada, this species is native to three, and introduced into one, Great Lakes tributaries in southwestern Ontario. It is currently listed as a species of Special Concern. To characterize population genetic structure and diversity in the Canadian populations of greenside darter, eight polymorphic microsatellite markers were developed for the species. The polymerase chain reaction primers were tested between 32 and 60 individuals from the Sydenham River and yielded a high number of alleles (four to 42 per locus), and observed heterozygosities ranging from 0.14 to 0.82. [ABSTRACT FROM AUTHOR]

A preface for the 2006 issue of the "Aquatic Ecosystem Health & Management" is presented.

Reintroduction is an increasingly common conservation tool used to recover populations of imperilled species, but its success depends on the suitability of the introduced animals' phenotype for their new habitat. For fishes, thermal tolerance may be a key trait in urbanized habitats. We compared thermal tolerance (CTmax) among three lineages (western, central, eastern) of imperilled redside dace (Clinostomus elongatus). CTmax of eastern adults was 3–4 °C lower than that of the other lineages, but adults of each lineage had similar thermal acclimation responses. In contrast, the acclimation response of juveniles differed by ∼80% between the central and western lineages. Using these data, we predicted how each lineage would fare in a hypothetical reintroduction to relatively warm urbanized habitats. Owing to the differences in juvenile acclimation responses, predicted thermal safety margins for the central lineage were double those predicted for the western lineage. Overall, we suggest that CTmax is a useful trait to incorporate into the source population selection process; however, there is an urgent need for the establishment of captive experimental research populations of imperilled species to address remaining uncertainties. [ABSTRACT FROM AUTHOR]

Quantifying the responses of rare and vulnerable species to environmental stressors poses special challenges. This study examined the responses of vulnerable fish species listed under the Species at Risk Act to environmental stressors in lakes, streams, and wetlands of the Canadian Great Lakes basin. We used a joint species distribution model (JSDM) to improve the estimates of responses of vulnerable species to environmental stressors, and the effects of functional traits on those responses, by "borrowing information" from abundant species for which we have more information. We measured abundance, functional traits, and taxonomic relationships for 115 freshwater fish species (including 12 vulnerable species), and environmental features, at 1972 sites. The JSDM yielded more precise estimates of responses than single-species models fitted to each vulnerable species. Habitat associations inferred from the JSDM showed substantial overlap with those provided in COSEWIC status reports. Model-derived responses to environmental stressors can provide a management-friendly basis for species classification in terms of species' tolerances to various forms of environmental change, and supplement the qualitative criteria for habitat requirements currently used in assessments of species vulnerability. [ABSTRACT FROM AUTHOR]

Despite the promising applications of genome-wide information to conservation, the field of conservation genomics remains hindered by a research-practice gap. Identifying the benefits from genomics in relation to fish conservation planning and decision-making could contribute to bridging this gap. The goals of our study were twofold. First, we reviewed the fish conservation genomic literature to determine how genomic information has been used to inform conservation decision making; and second, we examined how genomic information can be linked to an existing conservation decision framework. Our review showed that, as fish conservation genomics studies accumulate over time, collaborations between researchers and conservation practitioners are becoming increasingly frequent. While the field is dominated by studies of economically important families (e.g. salmonids, acipenserids) in first-world countries (North America, Europe), it has a broad taxonomic coverage where species of both local and global conservation concern are well represented. We also show that genomic information can readily be harnessed to guide decisions within existing conservation decision frameworks, from the conceptualization (identification of conservation targets and threats) to the implementation and the monitoring of conservation actions. In addition, our review identifies some limitations related to genomic inferences for conservation and proposes solutions to address these uncertainties and improve communication between conservation genomic scientists and practitioners. For genomic researchers, we outline how conservation decisions are made; for practitioners, we illustrate how genomic information can inform decision-making. [ABSTRACT FROM AUTHOR]

Similar to many freshwater ecosystems, the Laurentian Great Lakes of North America have undergone numerous anthropogenic stressors resulting in considerable loss of biodiversity and habitat. Among Great Lakes fishes, the coregonine sub-family has endured the most extensive declines, including extinction of several species (Coregonus johannae, C. alpenae, and C. kiyi orientalis) and at least 10 instances of local extirpations of other species (C. nigripinnis, C. reighardi, C. zenithicus, C. hoyi, and C. artedi) across all 5 lakes, much of which occurred prior to the 1960s owing to overfishing, interactions with non-indigenous species, and habitat loss. Despite these declines, no federal-, provincial-, or state-mandated actions were ever implemented to conserve coregonine diversity, potentially because so much of the coregonine declines occurred prior to the enactment of federal conservation legislation. Possible explanations for inaction since enactment of that legislation include insufficient data on biological vulnerability or threats, unresolved taxonomy, and limited support from the fishery management agencies and their stakeholders prior to the 2000s. In recent decades, however, several fishery management agencies have undertaken efforts to re-introduce coregonine diversity. These efforts helped lead to development of a science-based framework to restore coregonines that was universally endorsed by fishery managers representing eight U.S. states, four U.S. tribal organizations, and the province of ON, Canada, in May 2018. The basin-wide framework is based on principles of conservation biology and adaptive management. We describe details of its key steps, including planning, restoring, and evaluating, while also describing recent implementation efforts to develop methods, improve available resources, and enhance coordination across the basin. Although our paper describes a regional effort to restore native coregonines, our adaptive-management approach could be used by other multi-agency stakeholders seeking to conserve or restore native fishes. [ABSTRACT FROM AUTHOR]

Detection of early life stages of fishes is important for understanding life history patterns and critical spawning habitats. When feasible, identifying early life stages of fishes using morphology requires taxonomic expertise and can be challenging, time consuming, and imprecise. In this study, we used DNA metabarcoding to identify egg and larval batch samples from two sites in the species-rich East Sydenham River, Ontario, Canada. We used a two-step PCR metabarcoding approach to amplify a highly variable region of the mitochondrial COI gene from 1075 mixed species batch samples. Amplicon libraries were sequenced with Illumina Mi-seq and the sequencing reads were filtered and assembled using the software package mothur. Barcodes were then classified using a reference library comprised of Great Lakes fishes and potential invaders. In total, 34 species, including three at-risk species and three invasive species, were detected at the two sampling sites. This study shows the potential utility of metabarcoding for detection and identification of early life stage Great Lake fishes. [ABSTRACT FROM AUTHOR]

Detection of invasive species is critical for management but is often limited by challenges associated with capture, processing and identification of early life stages. DNA metabarcoding facilitates large‐scale monitoring projects to detect establishment early. Here, we test the use of DNA metabarcoding to monitor invasive species by sequencing over 5000 fishes in bulk ichthyoplankton samples (larvae and eggs) from four rivers of ecological and cultural importance in southern Canada. We were successful in detecting species known from each river and three invasive species in two of the four rivers. This includes the first detection of early life‐stage rudd in the Credit River. We evaluated whether sampling gear affected the detection of invasive species and estimates of species richness, and found that light traps outperform bongo nets in both cases. We also found that the primers used for the amplification of target sequences and the number of sequencing reads generated per sample affect the consistency of species detections. However, these factors have less impact on detections and species richness estimates than the number of samples collected and analysed. Our analyses also show that incomplete reference databases can result in incorrectly attributing DNA sequences to invasive species. Overall, we conclude that DNA metabarcoding is an efficient tool for monitoring the early establishment of invasive species by detecting evidence of reproduction but requires careful consideration of sampling design and the primers used to amplify, sequence and classify the diversity of native and potentially invasive species. [ABSTRACT FROM AUTHOR]

Predicting how quickly populations expand their range and whether they will retain genetic diversity when they are introduced to new regions or track environmental conditions suited to their survival is an important applied and theoretical challenge. The literature suggests that long‐distance dispersal, landscape heterogeneity and the evolution of dispersal influence populations' expansion rates and genetic diversity. We used individual‐based spatially explicit simulations to examine these relationships for Tench (Tinca tinca), an invasive fish expanding its geographical range in eastern North America since the 1990s. Simulated populations varied greatly in expansion rates (1.1–28.6 patches year−1) and genetic diversity metrics, including changes in observed heterozygosity (−19 to +0.8%) and effective number of alleles (−0.32 to −0.01). Populations with greater dispersal distances expanded faster than those with smaller dispersal distances but exhibited considerable variation in expansion rate among local populations, implying less predictable expansions. However, they tended to retain genetic diversity as they expanded, suggesting more predictable evolutionary trajectories. In contrast, populations with smaller dispersal distances spread predictably more slowly but exhibited more variability among local populations in genetic diversity losses. Consistent with empirical data, populations spreading in a longer, narrower dispersal corridor lost more neutral genetic variation to the stochastic fixation of alleles. Given the unprecedented pace of anthropogenic environmental change and the increasing need to manage range‐expanding populations, our results have conservation ramifications as they imply that the evolutionary trajectories of populations characterised by shorter dispersal distances spreading in narrower landscapes are more variable and, therefore, less predictable. [ABSTRACT FROM AUTHOR]

Environmental DNA (eDNA) monitoring methods have played a significant role in improving fisheries management decisions. Yet, their impact to date has been rather limited in Canada, where eDNA sampling and analyses are only beginning to be used to inform management and conservation decisions, practices, and policies. Studies investigating hurdles to the incorporation of eDNA evidence into fisheries management decisions generally focus on technical challenges (i.e., risks of false-positive and false-negative detections). We set out to identify challenges that eDNA researchers and conservation practitioners must overcome to fully unlock the benefits of eDNA sampling for fish management in the Canadian context. We discuss aspects of the broad and heterogeneous geography, preponderance of regions located far from densely populated areas, complex political landscape, and cultural diversity of Canada that may complicate the design of reliable eDNA monitoring tools or restrict their use if not adequately addressed. To advocate for the wider use of eDNA sampling, we outline a number of action items that would facilitate the broad adoption of eDNA sampling as a monitoring tool at the Canadian scale. [ABSTRACT FROM AUTHOR]

A globally invasive fish, Eurasian tench ( Tinca tinca) is spreading through the St. Lawrence River and poses an imminent invasion threat to the Great Lakes. Following its illegal release into a tributary of the St. Lawrence River in 1991, tench has spread throughout the river's main stem over the past decade, and its abundance in commercial fishing bycatch in the river has grown exponentially. The tench is a generalist benthic consumer with largely undocumented ecological impacts in North America. Reports from other invaded regions indicate that it can compete with other benthic fishes, host a diverse assemblage of parasites and pathogens, degrade water clarity in shallow lakes, limit submerged macrophyte growth, reduce gastropod populations, and promote benthic algal growth through top-down effects. Risk assessments and climate-match models indicate that the Great Lakes are vulnerable to tench invasion, and they signal the need for timely comprehensive actions, including development and implementation of monitoring and rapid-response protocols, including prevention or slowing of natural dispersal through canals. [ABSTRACT FROM AUTHOR]

Although electrosedation is becoming a frequently used technique to anaesthetize fish for a variety of commercial, management, and research applications, limited information is available on the effectiveness of different settings (e.g., voltage, frequency, shocking duration) and target species. We examined recovery times and short-term survival while using a commercially available electroanaesthesia unit to prepare fishes for transmitter implantation surgeries and ran experimental tests without surgery on different electrosedation settings. Our results indicate that electrosedation is a quick and efficient form of anaesthesia, with full anaesthesia achieved, surgeries completed, and recovery in under 10 min for common carp ( Cyprinus carpio L., 1758), goldfish ( Carassius auratus (L. 1758)), and others. We had zero mortality over at least 24 h associated with electrosedation. We found no significant differences in recovery times related to species or mass, nor did we find any significant changes to recovery time when changing voltage applied, frequency, shocking duration, or when changing the type of pulse applied (e.g., burst pulses vs. standard pulse). Although further researches are needed to address the sublethal and long-term effects of eletrosedation, these findings are important to researchers for selecting suitable target species and optimizing recovery time and survival for a quick release after surgery, tagging, or any time fish sedation is required. [ABSTRACT FROM AUTHOR]

Wetlands are increasingly in peril as a result of human activities. In the Laurentian Great Lakes, coastal wetlands provide essential habitats for many fishes. Consequently, efficient sampling approaches for wetland fishes are needed for effective management. We employed a repeat-sampling strategy using a seine to collect fishes from seven wetlands. The data set was used to develop guidance for optimizing wetland fish sampling. To meet richness targets, the required number of sampling sites decreases as sampling intensity increases. Half the number of sites was required when three seine hauls per site were done compared with one haul. On average, 97 one-haul sites were required to detect 90% of species, whereas only 47 three-haul sites were required. Sampling effort is predicted to be greater in areas with more species and larger wetlands. The number of individuals and sites needed to detect 90% of species increased exponentially as species richness increased, and the number of individuals needed was positively related to wetland area. The use of block nets did not improve species detection or affect the composition. [ABSTRACT FROM AUTHOR]

Introduced and geographically expanding populations experience similar eco‐evolutionary challenges, including founder events, genetic bottlenecks, and novel environments. Theory predicts that reduced genetic diversity resulting from such phenomena limits the success of introduced populations. Using 1900 SNPs obtained from restriction‐site‐associated DNA sequencing, we evaluated hypotheses related to the invasion history and connectivity of an invasive population of Tench (Tinca tinca), a Eurasian freshwater fish that has been expanding geographically in eastern North America for three decades. Consistent with the reported history of a single introduction event, our findings suggest that multiple introductions from distinct genetic sources are unlikely as Tench had a small effective population size (~114 [95% CI = 106–123] individuals), no strong population subdivision across time and space, and evidence of a recent genetic bottleneck. The large genetic neighbourhood size (220 km) and weak within‐population genetic substructure suggested high connectivity across the invaded range, despite the relatively large area occupied. There was some evidence for a small decay in genetic diversity as the species expanded northward, but not southward, into new habitats. As eradicating the species within a ~112 km radius would be necessary to prevent recolonization, eradicating Tench is likely not feasible at watershed—and possibly local—scales. Management should instead focus on reducing abundance in priority conservation areas to mitigate adverse impacts. Our study indicates that introduced populations can thrive and exhibit relatively high levels of genetic diversity despite severe bottlenecks (<1.5% of the ancestral effective population size) and suggests that landscape heterogeneity and population demographics can generate variability in spatial patterns of genetic diversity within a single range expansion. [ABSTRACT FROM AUTHOR]

Aim: Most studies focusing on terrestrial ecosystems have shown that non‐native species are more likely to invade phylogenetically clustered communities, that the introduction of non‐native species increases phylogenetic clustering in the recipient communities, and that the latter is more conspicuous for recipient communities at a larger spatial scale. However, whether these patterns hold for aquatic ecosystems is rarely tested. Here, we investigate the phylogenetic structure of native and non‐native freshwater fish assemblages at a continental spatial extent. Location: The continental United States and Canada. Time period: Current. Methods: We collated native and naturalized non‐native species lists of freshwater fishes for each watershed at local and regional spatial scales. Two phylogenetic metrics (MPDses and MNNDses) representing different evolutionary depths were used to quantify the phylogenetic dispersion of each watershed fish assemblage and were related to temperature and precipitation using correlation and regression analyses. Values of the metrics were compared between the two spatial scales. Results: Our study found that (1) phylogenetically more diverse fish communities tended to be invaded by fewer non‐native fish species, and that non‐native species more frequently invaded communities with lower phylogenetic dispersion (i.e. higher phylogenetic clustering), (2) introduction of non‐native fishes reduced phylogenetic clustering in some watershed but increased clustering in others, (3) introduction of non‐native species caused phylogenetic dispersion to increase in watersheds with low phylogenetic diversity and to decrease in watersheds with high phylogenetic diversity and (4) phylogenetic clustering for fish assemblages at the larger spatial scale was smaller than that at the smaller spatial scale. Main conclusions: Support for Darwin's naturalization and preadaptation hypotheses in freshwater fish assemblages depends on the phylogenetic diversity of assemblages within the invaded watersheds. Our results are contrary to previous studies that found that the introduction of non‐native species increases phylogenetic clustering in the recipient communities more strongly at a larger spatial scale. [ABSTRACT FROM AUTHOR]

One of the greatest challenges for researchers today is understanding climate-change impacts on fish populations, particularly in vulnerable and understudied ecosystems such as the Canadian Arctic. Among other impacts, northern fishes will undergo thermal stress as atmospheric and sea surface temperatures are projected to rise globally. Models that consider how both environmental factors such as temperature and potential species interactions will impact population extirpation and species’ range contraction can help project the future distribution of a species in the face of a warming climate. Here, we investigate the climate-change impacts of rising temperatures and the potential northward distributional shift of brook charr (Salvelinus fontinalis) on Arctic charr (Salvelinus alpinus), Canada’s northernmost freshwater fish species. Specifically, we used a logistic regression model to establish baseline relationships between the current distribution of Arctic charr and the variables, degree-days (a key climate variable), geographical location, and brook charr occurrence. We developed the model applying the expected changes in degree-days to 2050 (25–50% increase from the average of 1976–2005) and 2080 (50–100% increase) while incorporating the historical distribution of Arctic charr to estimate the change in Arctic charr distribution over that time. We found that growing degree-days, longitude, latitude, and brook charr occurrences correctly classified 93% of Arctic charr historical occurrences in Canada. We estimate that in a high-carbon scenario, where degree-days are expected to increase by 50 to 100%, Arctic charr range is projected to decrease by 18% in Canada by 2051–2080 and decrease even further by 3% with the presence of brook charr. The Canadian high Arctic may provide refuge for Arctic charr, likely maintaining temperatures optimal for species persistence. Regardless, management that considers the climate stresses on Arctic charr populations will be important to preserve this highly valued resource that is pivotal for food security and traditional ways of life for northerners. [ABSTRACT FROM AUTHOR]