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Headstarting involves ex situ rearing of vulnerable life stages, then releasing individuals into the wild once they are larger and less vulnerable to predation. Sometimes, headstarted animals display underdeveloped behaviors that may lead to an acclimation period of reduced survival and growth after release. Using data from a 6‐year headstarting program, we tested whether the early release condition affected survival, body condition, and somatic growth rate in 2 groups of headstarted Blanding's turtles (Emydoidea blandingii) released into Rouge National Urban Park (RNUP) in Toronto, Ontario, Canada. The first group included turtles released directly into the wild (i.e., hard release). The second group included turtles released into an in situ enclosure in which individuals remained for a week without food supplementation before being fully released into the wild (i.e., delayed release). Release condition did not affect survival or growth rate. In the delayed‐release group, body condition initially declined rapidly and remained low for up to 1 year after release. Given the lack of wild juveniles in RNUP, we compared body condition of headstarted turtles at various time points since release to similar‐sized wild juveniles from 2 other Ontario populations, one from Algonquin Provincial Park (APP) and one near Lake Erie (LE). Body condition of headstarted turtles was similar to those of wild APP turtles regardless of release method, and higher than those of wild LE turtles. Our results indicate that delayed release did not improve post‐release outcomes for headstarted turtles in an urban landscape and headstarted turtles sustain similar health metrics as wild turtles. [ABSTRACT FROM AUTHOR]

This study identifies the current spatial and temporal patterns of threats to at-risk freshwater fishes within Canada. Data for 65 at-risk freshwater fishes were collated from the Committee on the Status of Endangered Wildlife in Canada Assessment and Status reports with threat calculators. Using these data, the overall threat impact level and the threat impact of the 11 categories in the threat calculator were compared for all species and separately by conservation status, which indicates their risk of extinction. These threats were also compared temporally to a study completed in 2006 and spatially between National Freshwater Biogeographic Zones. The threats of invasive species and pollution had the highest impacts, accounting for 18.9% and 16.8% of the weighted impact on at-risk freshwater fishes, respectively. Since 2006, all threats have been increasing, except for natural disasters. The Great Lakes–Upper St. Lawrence River Biogeographic Zone had significantly more at-risk freshwater fishes and overall weighted threat impact than other zones, with pollution, invasive species, and natural system modification contributing the most to the imperilment in this region. [ABSTRACT FROM AUTHOR]

Understanding the relative roles of the historical, environmental, and anthropogenic processes underlying spatial biodiversity patterns is crucial to predict the impacts of global environmental changes. We quantified the relative roles of these factors in influencing species richness of total, native, non-native, and at-risk freshwater fishes in 985 tertiary watersheds across Canada while accounting for correlations among descriptors and spatial autocorrelation. Our findings indicate differences in factors influencing richness patterns among species categories. Environmental factors related to energy availability and historical factors related to post-glacial recolonization both played roles in shaping spatial variation in native species richness. In contrast, variation in non-native species richness was largely related to human activities increasing propagule pressure and habitat disturbance, which were greater for foreign species (i.e., not native to Canada) than for translocated native species. Anthropogenic processes and environmental conditions were both important determinants of at-risk species richness. Our study emphasizes the importance of an integrated approach that simultaneously considers natural and anthropogenic processes to better predict the fish biodiversity change at the landscape scale. [ABSTRACT FROM AUTHOR]

Invasive species denialism (ISD) is a controversial and hitherto underexplored topic, particularly with regard to its potential impacts on stakeholder engagement in support of invasive species management and policy. We examined how ISD is framed within the Great Lakes invasive species community, as well as the impacts of excluding and including those perceived as denialists in engagement efforts. We interviewed key informants in the region to gain an understanding of their framings of ISD, as well as focus groups allowing participants to discuss the impacts of exclusion and inclusion of stakeholders during the engagement process. ISD discussions were organised into three framings: 1) invasive species denialism; 2) invasive species cynicism; 3) invasive species nihilism. Participants raised concerns about outright exclusion of stakeholders and offered recommendations for mitigation of the impacts of inclusion of proponents of ISD in during stakeholder engagement. Our results have shown that a better understanding of the different framings of ISD is crucial to improve communication with stakeholders and to better inform responses and mitigation efforts. The newly defined framings of invasive species cynicism and invasive species nihilism demonstrate that more targeted responses to specific forms of ISD are needed to improve stakeholder engagement outcomes. [ABSTRACT FROM AUTHOR]

Understanding population-level habitat requirements is important for the effective conservation of imperilled species, especially for those with fragmented distributions. This study examined fine-scale distribution of the threatened pugnose shiner (Notropis anogenus) in the upper St. Lawrence River, Ontario, Canada. Occupancy modelling, multivariate analyses, and co-occurrence modelling were used to identify environmental correlates of pugnose shiner distribution and species associations in an embayment area, Thompson's Bay. The pugnose shiner was most abundant in outer bay sites that were cooler, less turbid, had a higher pH, and had more submerged aquatic vegetation than the inner bay sites. The probability of pugnose shiner occupancy increased with distance from the inner bay and with the presence of Chara vulgaris, and decreased with increasing conductivity. The pugnose shiner positively co-occurred with seven species, including the blackchin shiner and blacknose shiner, and negatively co-occurred with bluegill. Centrarchid species were dominant across Thompson's Bay. This has important conservation implications because some native centrarchid predators are increasing in abundance, coincident with climate change, which may threaten the persistence of rare and imperilled cyprinids such as pugnose shiner. [ABSTRACT FROM AUTHOR]

For freshwater fishes, elevated water temperatures associated with climate warming and hypoxia can co-occur and are likely to interact as both affect oxidative metabolism. We quantified the effects of acclimation to elevated temperature and hypoxia on the thermal tolerance of pugnose shiner (Notropis anogenus), a cyprinid fish threatened in its Canadian range. In one experiment, pugnose shiner underwent two-week sequential acclimations to six increasing temperatures. Fish acclimated to warmer waters increased their critical thermal maximum (CTmax), while the agitation temperature (Tag) was 3.4 °C lower than the CTmax. In another experiment, fish were acclimated to three dissolved oxygen treatments (>95%, ∼56%, or ∼40% air saturation) for two weeks and tested under >95% and 40% conditions. CTmax was lower when measured under 40% for normoxia-acclimated fish but not for hypoxia-acclimated fish. Hypoxia-acclimated fish had higher Tag and smaller agitation windows than normoxia-acclimated fish, suggesting that hypoxia acclimation improves aspects of thermal tolerance. We examine the plasticity of thermal tolerance of pugnose shiner, showing that they may be more vulnerable to high temperatures compared with other non-imperiled Notropis species. [ABSTRACT FROM AUTHOR]

Aim: A better understanding of native and non‐native species responses to environmental conditions, historical processes, and human pressures is crucial in the face of global environmental changes affecting biodiversity. Here, we evaluate the relative roles of environmental, historical and anthropogenic factors in influencing species richness of native and non‐native freshwater fishes in watersheds across North America. Location: North America (exclusive of Mexico). Time period: Recent. Major taxa studied: Freshwater fishes. Methods: We compiled an extensive dataset of native and non‐native fish richness in 2,993 watersheds across North America, together with corresponding data for environmental (climatic, geographic), historical and anthropogenic factors. We used variance partitioning and hierarchical partitioning to quantify the relative importance of environmental, historical and anthropogenic factors in explaining richness variation in native and non‐native [overall, and by geographic origin (foreign/translocated) and pathway (authorized/unauthorized)] fishes, while accounting for correlations among explanatory variables and spatial autocorrelation. Results: Overall importance of environmental and anthropogenic factors was greater than historical factors in explaining both native and non‐native richness. Precipitation‐related factors were more important in explaining native richness, whereas non‐native richness was largely associated with temperature‐related factors. However, richness related to authorized introductions was less constrained by temperature than unauthorized introductions. Dam density, road density and urbanization gradient were major anthropogenic factors related to non‐native richness, yet their relative importance varied among origin‐ and pathway‐based categories. Conclusions: Our findings indicate different environmental drivers influence native and non‐native fish richness patterns in North America. The accumulation of non‐native species in watersheds depends on the interaction between environmental conditions and anthropogenic‐based processes related to introduction history including geographic origin, introduction pathway, and propagule pressure, where the latter likely plays a major role. Warmer regions with high human population densities and more impoundments are more prone to fish invasions, mostly via unauthorized introductions. [ABSTRACT FROM AUTHOR]

The addition of nonnative species and loss of native species has modified the composition of communities globally. Although changes in β‐diversity have been well documented, there is a need for studies incorporating multiple time periods, more than one dimension of biodiversity, and inclusion of nestedness and turnover components to understand the underlying mechanisms structuring community composition and assembly. Here, we examined temporal changes in functional dissimilarity of fish communities of the Laurentian Great Lakes and compared these changes to those of taxonomic dissimilarity by decade from 1870 to 2010. Jaccard‐derived functional dissimilarity index was used to quantify changes in functional β‐diversity within communities, between all possible pairs of communities, and using a multiple‐site index among all communities. β‐diversity was partitioned into components of nestedness and turnover, and changes were examined over time. Similar to patterns in taxonomic dissimilarity, each community functionally differentiated from the historical community of 1870, with Lake Superior changing the most (~24%) and Lake Ontario the least (~14%). Although communities have become taxonomically homogenized, functional β‐diversity among all communities has increased over time, indicating functional differentiation. This is likely due to functional similarity between the communities being historically high (i.e., ~88% similar in 1870). The higher taxonomic relative to functional turnover indicates that the species being replaced between communities are functionally redundant, which could occur given the harsh environmental conditions of the region and/or as a result of the recent glacial history of the region. High functional nestedness across communities reflects dispersal limitations, with smaller communities being functional subsets of large communities closer to source populations. The functional differentiation observed is likely due to nonnative species with functional traits unique to the region establishing or the loss of functionally redundant native species; however, it is important to note that patterns of homogenization were periodically observed through time. Our study demonstrates the possible factors regulating diversity in the Laurentian Great Lakes fish communities, that patterns of taxonomic and functional β‐diversity are dynamic over time and vary in the magnitude and direction of change, and that taxonomic diversity should not be used to predict changes in functional diversity. [ABSTRACT FROM AUTHOR]

Aim: As a result of the loss of native species and the spread of non‐native species, fish communities are becoming increasingly homogenous globally. In the Laurentian Great Lakes, 21 native fish species have been extirpated from one or more lakes as a result of habitat alteration and destruction, overexploitation and invasive species since the 1800s. Over the same time period, 30 non‐native species became established in at least one lake as a result of authorized and unauthorized introductions. This study examines temporal changes in taxonomic dissimilarity over 15 time periods spanning the last 150 years. Location: Laurentian Great Lakes, North America. Methods: Changes to the Great Lakes fish fauna were summarized in species lists by decade from 1870 to 2010. Taxonomic dissimilarity between and within communities was calculated using Jaccard's dissimilarity coefficient; the relative contribution of turnover (species replacement) and nestedness (species loss) to total taxonomic dissimilarity was also calculated. To test whether the Great Lakes have homogenized, we conducted a regression on multiple‐site dissimilarity values over time. Results: Native species richness in the Great Lakes exhibits a latitudinal gradient that reflects post‐glacial history and current climate. We demonstrate that the establishment of non‐native species and extirpation of native species has changed fish communities in each of the Great Lakes, with communities in Lake Superior differentiating the most (~23%) and in Lake Ontario the least (~12%) since 1870. Multiple‐site dissimilarity ranges between ~50% and 53% per decade, and communities have become ~5.9% more similar over time since 1870. Main Conclusions: Species introductions and extirpations have changed community composition, resulting in the fish communities becoming significantly more similar to one another over time and, thus, homogenized. As a result, ongoing management should prevent range expansion of native and non‐native species to preserve the current distinctiveness of the Great Lakes fish communities. [ABSTRACT FROM AUTHOR]

Watersheds in southern Ontario are of high conservation concern due to their diverse fish communities, productive environments, and threats from numerous anthropogenic stressors. The Credit River watershed, located west of the Greater Toronto Area, has over 60 fish species, and multiple stressors including urbanization, climate change, and aquatic invasive species. This study examines fish community change in the Credit River watershed. Historical fish datasets collected in the watershed from 1954 to 2015 were analyzed to examine richness patterns, temporal trends in species distributions, and faunal similarity at the site and sub-watershed levels. Species richness increased over time at the site and sub-watershed level, displaying predictable richness patterns due to anthropogenic introductions and changes in sampling methods. Species distribution patterns remained largely stable over time with decreases in some species (e.g. Redside Dace) and increases in others (e.g. Largemouth Bass). Faunal similarity also increased over time at the site and sub-watershed level, indicating that the fish communities in the Credit River are homogenizing. [ABSTRACT FROM AUTHOR]

Aim: We assess climate similarity among global freshwater and terrestrial ecoregions under historical and future climate scenarios to determine where climate change will impact the climate filter of invasion process. Location: Global. Methods: We used the Climatch algorithm to conduct a climate‐match analysis to quantify the climate similarity between freshwater and terrestrial ecoregions of the world. Climate match was modelled between all freshwater and terrestrial ecoregions. The analysis was conducted under historical climates and projected climates of 2081–2100 (2090) under three shared socioeconomic pathways SSP2‐4.5, SSP3‐7.0, SSP5‐8.5. Climate matches of each ecoregion were presented as mean climate match to all other ecoregions of the same set. Friedman's non‐parametric rank sum two‐way analysis of variance with repeated measures was used to examine differences in mean climate match between climate scenarios. Results: Mean climate match of ecoregions was projected to increase significantly with small effect sizes for freshwater ecoregions (recipients: 0.132; sources: 0.105), and moderate and small effect sizes for terrestrial ecoregions (recipients: 0.330; sources: 0.259). Climate change was predicted to increase mean climate match in North America and Eurasia, particularly in the Arctic by 2090 under each SSP. Ecoregions in central Africa and South America were predicted to have reduced mean climate match. Ecoregions within larger countries (e.g. Australia, Canada, USA) showed variation in mean climate match. Main Conclusion: Climate change projections of bioclimatic predictors of species invasions were shown to increase in homogeneity under higher emissions scenarios. Furthermore, we demonstrate how climate change will provide opportunities for invasive species transported among ecoregions to survive under new conditions and identify where the climate filter of the invasion process will be most affected. Findings can be used to inform conservation actions for mitigating the impacts of introduced species by identifying potential risky source regions of future freshwater and terrestrial invasions under climate change. [ABSTRACT FROM AUTHOR]

When dealing with invasive fishes, permanent barriers may inhibit spread, but may not be feasible due to costs and logistical constraints. Alternatively, non-permanent barriers using electricity, light, sound, pressure, bubbles, and CO2 are being developed and deployed in efforts to limit and prevent 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 invasive and native species. We conducted a laboratory experiment to investigate the impact of vertical electric barrier on behaviour of Rainbow Trout, Oncorhynchus mykiss. In response to electric current, Rainbow Trout responded by significantly decreasing passage through the electric barrier zone and spending more time away from the electric barrier when it was turned on during the stimulus period compared to pre-stimulus period. Moreover, when interacting with electric barrier, Rainbow Trout exhibited certain behaviours (e.g. stunned and remained on the same side of the barrier, stunned and crossed the barrier) more than others (e.g. approach and retreat, deflected, and paralyzed). Moreover, it appears that Rainbow Trout remained distant from the electric barrier even after the electric barrier was turned off. Our results indicate that 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 Rainbow Trout. Our results also highlight the importance of detailed investigation of behavioural responses of target species when evaluating and considering fish-deterrent or guidance technologies. [ABSTRACT FROM AUTHOR]

Biodiversity loss is a serious issue for freshwater fishes in temperate climates and there is a need for more information in this area. A study was conducted to assess fish community changes in the littoral zone of 22 lakes over a 45 year period (compared years 1969-1979 and year 2014). To compare fish communities, historical seining records were compiled for 22 inland lakes and compared with contemporary data sampled using the same protocol. Fish abundance data analyzed using a multivariate approach identified a shift from cyprinid-dominated communities to centrarchid-dominated communities between time periods. There was no evidence to support a strong influence of invasive species on these communities, but there have been significant changes in temperature and land use around these lakes since the historical data sets were collected. This is an important contribution to our understanding of biodiversity change in North American freshwater fish communities and may influence fisheries management approaches in the future. [ABSTRACT FROM AUTHOR]

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]

Aim: We employed a climate‐matching method to evaluate potential source regions of freshwater invasive species to an introduced region and their potential secondary spread under historical and future climates. Location: Global source regions, with primary introductions to the Laurentian Great Lakes and secondary introductions throughout North America. Methods: We conducted a climate‐match analysis using the CLIMATE algorithm to estimate global source freshwater ecoregions under historical and future climates with an ensemble of global climate models for climate‐change scenario SSP5‐8.5. Given existing research, we use a climate match of ≥71.7% between ecoregions to indicate climatic conditions that will not inhibit the survival of introduced freshwater organisms. Further, we estimate the secondary spread of freshwater invaders to the ecoregions of North America under historical and future climates. Results: We identified 54 global freshwater ecoregions with a climate match ≥71.7% to the recipient Laurentian Great Lakes under historical climatic conditions, and 11 additional ecoregions were predicted to exceed the threshold under climate change. Three of the 11 ecoregions were located in South America, a continent where no matches existed under historical climates and eight were located in the southern United States, southern Europe, Japan and New Zealand. Further, we identify 34 North American ecoregions of potential secondary spread of freshwater invasions from the Great Lakes under historical climatic conditions, and five ecoregions were predicted to exceed the threshold under climate change. Main Conclusion: We provide a climate‐match method that can be employed to assess the sources and spread of freshwater invasions under historical and future climate scenarios. Our climate‐match method predicted increases in climate match between the recipient region and several potential source regions, and changes in areas of potential spread under climate change. The identified ecoregions are candidates for detailed biosecurity risk assessments and related management actions. [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]

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 AUTHOR]

The secondary invasion of the round goby (Neogobius melanostomus) into tributaries of the Laurentian Great Lakes has resulted in ecological impacts on many native benthic species. However, the ecological impacts on white sucker (Catostomus commersonii), a native benthic species has not been examined. A comparative control and invaded site study design was used to examine diet overlap and the dietary impact of the round goby invasion on white sucker's trophic niche. We found significant diet overlap between round goby and white sucker, and white sucker in sympatry with round goby shift their feeding strategy to be more generalist when compared to white sucker in uninvaded locations. No influence of diet competition with round goby on the trophic niche of white sucker was found in this study. Our results support the hypothesis that white sucker are experiencing competition for prey items with round goby. These increased competitive interactions may exacerbate the observed declines in white sucker abundance as round goby continue their invasion upstream in Lake Ontario tributaries. [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]

Freshwater turtle populations are declining globally as a result of anthropogenic activities. Threats to turtles in urban areas are exacerbated by road mortality and subsidized predators, which can lead to catastrophic shifts in population size and structure. Headstarting is used as a conservation tool to supplement turtle populations that may otherwise face extirpation. A headstarting program began in 2012 to recover a functionally extinct population of Blanding's Turtles (Emydoidea blandingii) 26in Rouge National Urban Park (RNUP), Ontario, Canada. The original population included five adults and one juvenile turtle. From 2014 to 2020, 270 headstarted turtles were released. The population has been monitored annually since 2014 using visual-encounter surveys, radio-telemetry, and live trapping (from 2018 onwards). We used mark-recapture and radio-telemetry data to quantify abundance, survival, and sex ratio of the headstarted turtle population. Using a Jolly-Seber model, we estimated abundance to be 183 turtles (20 turtles/ha) in 2020. Estimated survival of headstarted turtles approached 89%, except for turtles released in 2019 when survival was 43% as a result of a known mass mortality event at the study site. Pre- and post-release sex ratios were not significantly different (χ2 = 1.92; p = 0.16), but shifted from 1:1.5 to 1:1 male:female post-release. Given that the headstarted turtles have not yet reached sexual maturity, it is unclear whether headstarted turtles will reach adulthood and successfully reproduce to maintain a self-sustaining population. Thus, to evaluate the success of the headstarting program, long-term monitoring is required. [ABSTRACT FROM AUTHOR]

Aim: Biological communities are the result of a stepwise spatiotemporal filtering process, driven by large‐scale historical and local contemporary determinants. The biogeographical pattern and species richness of North American fishes are predominantly determined by historical processes of past glaciations and postglacial dispersal and by contemporary environmental and ecological processes. We evaluated the effects of postglacial dispersal through glacial Lake Agassiz and habitat heterogeneity, represented by lake surface area, on contemporary freshwater fish species richness patterns of northwestern Ontario lakes. Location: Northwestern Ontario, Canada. Taxon: Freshwater fishes. Methods: Applying the theory of island biogeography and species–area curves, we examined the effects of isolation from the past dispersal corridor of glacial Lake Agassiz and habitat heterogeneity on species richness across 264 contemporary lakes. While controlling for correlations among the predictor variables, generalized linear models were constructed between species richness, as the response variable and the explanatory variables of lake elevation and surface area, and connection to the dispersal corridor. Results: Differential cover by glacial Lake Agassiz led to variation in fish species richness across contemporary lakes and it is higher in lakes that were covered by Lake Agassiz relative to basins remaining outside of the boundaries of the glacial lake. Lake surface area is the strongest predictor of species richness, while lake elevation is the strongest factor predicting isolation. Main Conclusions: Habitat heterogeneity and postglacial colonization have led to differences in fish richness within the same geographical region, which increases with lake surface area and decreases with elevation. These are likely driven by greater niche diversity facilitating the assembly of more diverse communities and isostatic rebound and fluctuating levels of Lake Agassiz isolating lakes at high elevations from the dispersal route earlier during the colonization process, respectively. These patterns underscore the importance of incorporating historical and environmental community determinants in biodiversity studies. [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]

Science-based approaches for selecting among single-species, community-, and ecosystem-based recovery plans are needed to conserve imperilled species. Selection of recovery plans has often been based on past success rates with other taxa and systems or on economic cost, but less on the ecology of the system in question. We developed a framework for selecting a recovery plan based on the distributions and ecology of imperilled and nonimperilled species across available habitat types and applied it to fishes in the Sydenham River, Ontario, Canada. We first tested whether distributions of fishes were adequately predicted by habitat features hypothesized to limit the distributions of imperilled fishes versus a broader set of habitat features known to predict fish distributions. We then tested whether imperilled species occurred in similar or disparate habitat types. For the Sydenham River, an ecosystem-based recovery plan was deemed most appropriate because imperilled species occur in disparate habitat types. We lastly provide decision criteria to facilitate applications of our framework to the selection of recovery plans for other species and systems. [ABSTRACT FROM AUTHOR]

As nonindigenous species are a major threat to global biodiversity, cost-effective management requires identification of areas at high risk of establishment. Here we predict suitable environments of 14 high-profile species of nonindigenous snakehead (Channidae) and Asian carp (Cyprinidae) species in North America based upon ecological niche modelling and compare the driving environmental variables for the two fish groups. Snakeheads distributions were correlated with thermal factors, whereas those of Asian carps were related mainly to precipitation. Predicted suitable ranges for these nonindigenous species can be divided into three main areas: Mexico and the southern United States (five species); Mexico and the United States up to ~35 °N (three species); and most of Mexico, continuous United States, and southern Canada (six species). For the province of Ontario, we combined the number and location of aquarium stores and live fish markets with predicted areas of suitable environments to identify areas at risk of introduction and establishment. We identified several watersheds draining into northwestern Lake Ontario as having the highest risk, highlighting the increased predictive value of this approach. [ABSTRACT FROM AUTHOR]

Climate change will ultimately affect the supply and quality of freshwater lakes and rivers throughout the world. This study examines the potential impacts of climate change on freshwater fish distributions in Canada. Climate normals data (means from 1961 to 1990) from Environment Canada were used to map current climate found throughout the tertiary watersheds of Canada. Logistic regressions based on these climate data were used to develop predictive presence-absence equations for (a) common commercially and recreationally important species and (b) an Arctic freshwater species and a freshwater fish species of conservation significance listed by the Committee on the Status of Endangered Wildlife (COSEWIC). The Canadian Centre for Climate Modelling and Analysis Global Coupled Model 2(IS92a) provided forecasts of Canada's climate in 2020 and 2050. The data from this scenario and the logistic regressions provided a ready framework for predicting the potential distributions of the fishes. Physical and ecological barriers would have to be overcome for the distribution of these species to actually change in response to climate change. Generally, coldwater species may be extirpated from much of their present range while cool and warm-water species may expand northward. Species that are limited to the most southern regions of the country may expand northwards. A conceptual framework for assessing potential climate change impacts on fishes and the variety of management strategies required to deal with these impacts are discussed. Our forecasts demonstrate the need for climate change assessments in species at risk as well as for common species. [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]

Human activity can put non‐game fishes at higher risk of extinction because of inappropriate management action. Eastern sand darter (Ammocrypta pellucida), a small benthic fish classified as threatened across much of its northern range, inhabits increasingly fragmented sandy habitats and, as a non‐game fish, may be easily overlooked in conservation efforts. In this study, the authors use genotype data from nine microsatellite loci and cytochrome oxidase I (COI) sequencing data across its northern native range to re‐assess genetic structure and to characterize a newly discovered, geographically disjunct population. Previous microsatellite marker analyses had identified seven distinct population genetic clusters across the region sampled; the analysis of this study showed that the newly discovered population (West Lake, Ontario) exhibits a divergent structure. COI haplotype analysis suggests that a single haplotype recolonized the Great Lakes and surrounding water bodies after the Wisconsinan glacial period, and subsequent fluctuation in water levels and habitat fragmentation resulted in divergence of genetic clusters. Although the novel West Lake population has a common ancestral source with other populations in the broader region, its divergent genetic signature merits its consideration as a separate conservation unit. The analyses of this study highlight the potential conservation implications of the discovery of new populations, particularly those of at‐risk species, even within a region that has been genetically well characterized. [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]

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]

Non‐structural deterrents may limit invasive fish dispersal and range expansion without altering waterflow or navigation. Despite extensive research in laboratory and artificial environments, few studies have been conducted in situ and, of those, few have evaluated the full community response of fishes interacting with the deterrent. We deployed acoustic deterrents within a physical trap‐and‐sort fishway at Cootes Paradise, Ontario, Canada, to determine the avoidance responses of a community of fishes attempting to disperse into the wetland.To test the effectiveness of an acoustic deterrent, the catch rates of fishes entering Cootes Paradise were compared when the deterrent was off (control) and on (treatment). Community diversity was fit to candidate generalised linear models, and common carp catch abundance was fit to candidate generalised additive models, both of which were compared with backwards selection. The presence of a phylogenetic signal in fish responses was assessed with Pagel's λ and Blomberg's K indices of trait evolution.Over 11,500 fishes, representing 16 species and 12 families, were captured. The acoustic deterrent did not alter the Shannon diversity of fishes challenging the fishway, but a significant phylogenetic signal in species‐specific avoidance responses was observed. There was a modest decrease in the catch rates of common carp (ambient trials = 1.03 fish/hr, deterrent trials = 0.84 fish/hr), a species of major management concern.Fish avoidance responses to acoustic deterrents were widely variable, and species specific. The avoidance response of common carp, the target species, was weak, probably due to a complex acoustic environment surrounding the fishway. Group size did not alter deterrent efficacy, but precipitation, water temperature, and turbidity did.Our study successfully quantified acoustic deterrent responses across an entire community of wetland fishes, including both native and invasive species. We are the first to demonstrate that there is a phylogenetic component to deterrent responses across species. We also identify environmental parameters that alter deterrent efficacy in the field, and describe important considerations for the deployment of non‐structural deterrents in the field. [ABSTRACT FROM AUTHOR]

Freshwater ecosystems have been substantially altered, threatening the survival and recovery of aquatic species at risk. Estimating the likelihood and magnitude of future extinctions (extinction debt; ED) is integral for conserving biodiversity and requires accurate species composition lists. Using species‐area relationships, we estimated ED for fishes in historically disturbed wetlands in the Lake Erie basin. Then, we used simulated data sets to assess how ED varied when species lists used to derive species‐area relationships had an increasing proportion of undetected species. When species lists were incomplete, ranging from 0.99 to 0.75, 15% fewer wetlands were estimated to have species in ED and, on average, 50% fewer species were expected to go extinct per wetland. Imperfect detection ultimately biased conservation prioritization among wetlands. Our findings suggest that if imperfect detection is not accounted for when projecting future extinctions, the severity of future species loss across a landscape, and the subsequent need for immediate restorative action, can be greatly underestimated. [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]

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]

Deterrents that limit the dispersal of non-native fishes into waterways are important tools for managing aquatic invasions. Acoustic and stroboscopic stimuli may be used to limit the dispersal of common carp (Cyprinus carpio), a widely invasive species. This study exposed wild-caught common carp to stroboscopic, acoustic, or combined-stimuli treatments, to observe changes made in their activity and in the number of passes made across the deterrent. Mixed-effects models determined that for all treatments, common carp spent more time moving actively during the stimulus and post-stimulus periods than during the control period. Common carp deterrent passes differed according to treatments. In the stroboscopic treatment, passes only increased during the post-stimulus period, in the acoustic treatment there were no significant differences across stimulus periods, and in the combined treatment passes decreased during the stimulus period. These results indicate that stimulus-induced behavioural changes may be sustained for short periods of time (> 30 min) after the deactivation of a stimulus deterrent. Our study found a muted avoidance response in comparison to other acoustic deterrent studies, likely due to the lack of sufficient stimulus refuge. Finally, individuals that were exposed to both stimuli did not express additive behavioural responses in comparison to individuals that were only exposed to one stimulus type. Our findings highlight important considerations for deterrent technologies and directly quantify the behavioural response of combined deterrent stimuli. [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]

Abstract: The extraction and characterization of DNA from aquatic environmental samples offers an alternative, noninvasive approach for the detection of rare species. Environmental DNA, coupled with PCR and next‐generation sequencing (“metabarcoding”), has proven to be very sensitive for the detection of rare aquatic species. Our study used a custom‐designed group‐specific primer set and next‐generation sequencing for the detection of three species at risk (Eastern Sand Darter, Ammocrypta pellucida; Northern Madtom, Noturus stigmosus; and Silver Shiner, Notropis photogenis), one invasive species (Round Goby, Neogobius melanostomus) and an additional 78 native species from two large Great Lakes tributary rivers in southern Ontario, Canada: the Grand River and the Sydenham River. Of 82 fish species detected in both rivers using capture‐based and eDNA methods, our eDNA method detected 86.2% and 72.0% of the fish species in the Grand River and the Sydenham River, respectively, which included our four target species. Our analyses also identified significant positive and negative species co‐occurrence patterns between our target species and other identified species. Our results demonstrate that eDNA metabarcoding that targets the fish community as well as individual species of interest provides a better understanding of factors affecting the target species spatial distribution in an ecosystem than possible with only target species data. Additionally, eDNA is easily implemented as an initial survey tool, or alongside capture‐based methods, for improved mapping of species distribution patterns. [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]

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]

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]

Simple Summary: Surveying ticks on wildlife hosts consistently over time and across space presents many challenges. In Yukon, Canada, the winter tick, Dermacentor albipictus, is a blood-feeding parasite that can cause significant losses of hair and blood in moose and other wildlife. The impacts of winter tick infestation in wildlife hosts in this northern region are not well documented. To enhance existing surveillance of winter ticks in Yukon, we implemented a three-year citizen science program, the Yukon Winter Tick Monitoring Project (YWTMP) to engage hunters in the collection of underrepresented moose and caribou samples. Social media, participation incentives, and hide-sampling kits distributed to hunters increased the combined number of annual moose and caribou hide submissions almost 100-fold, and the geographical range of samples by almost 500 km, compared with submission numbers in the previous seven years. Citizen science samples were also used to detect previously unknown infection localities on moose in southeastern Yukon that are spatially separate to known infestations found on elk and deer, helping to build a better picture of infection dynamics on different host animals. Engaging with key demographic groups using structured citizen science programs like the YWTMP can significantly expand sampling efforts in remote areas while maintaining systematic sampling methods to monitor parasites of wildlife health concern. Sampling hides from harvested animals is commonly used for passive monitoring of ectoparasites on wildlife hosts, but often relies heavily on community engagement to obtain spatially and temporally consistent samples. Surveillance of winter ticks (Dermacentor albipictus) on moose (Alces alces) and caribou (Rangifer tarandus caribou) hosts in Yukon, Canada, has relied in part on voluntary submission of hides by hunters since 2011, but few samples were submitted. To enhance sampling efforts on underrepresented moose and caribou hosts, we implemented a three-year citizen science program, the Yukon Winter Tick Monitoring Project (YWTMP), to better engage with hunters in hide sample collection. A combination of in-person and social media outreach, incentivized engagement, and standardized hide sampling kits increased voluntary submissions of moose and caribou hides almost 100-fold since surveillance began. Citizen science samples expanded the northernmost geographic extent of existing sampling efforts for moose by 480 km and for caribou by 650 km to reach 67.5° N latitude. Samples also resulted in new detections of winter ticks on moose hides that are spatially separate to those submitted for other cervids in Yukon. Findings from the YWTMP have provided an essential baseline to monitor future winter tick host–parasite dynamics in the region and highlighted priority areas for ongoing tick surveillance. [ABSTRACT FROM AUTHOR]

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]

The eighth edition of "Common and Scientific Names of Fishes" documents 5089 species of fishes in the United States, Canada, and Mexico. It expands the geographic coverage to include all species found within the exclusive economic zones (EEZs) of these countries and includes countries of occurrence for all marine species. The publication aims to standardize the names of North American fishes, improving communication among fisheries biologists and others interested in fishes. It provides accepted scientific names and recommends common names in English, Spanish, and French. The edition also incorporates online resources for taxonomy and occurrence data. The first edition was published in 1948 and subsequent editions have expanded the list of species. Changes in names and occurrences are explained in the appendix, and the classification of fishes has been updated based on molecular data. The publication acknowledges the importance of fieldwork in understanding the diversity of fishes. [Extracted from the article]

Aim The successful conservation of endangered mussel communities requires, in part, a thorough understanding of the processes that shape their distribution. Therefore, we tested the prediction that (1) the distribution of host fishes explains a significant amount of variation in mussel community composition. In addition, because mussel distribution also depends on spatial processes and environmental variables, we predicted that (2) the distribution and community composition of mussels in Ontario varies across eight contiguous watersheds, flowing into three different basins of the Great Lakes (Huron, St. Clair and Erie); and (3) environmental variables also explain part of the mussel distribution. Location Watersheds in south-western Ontario, North America, Great Lakes Region. Methods Existing data on the distribution of mussels and fishes, and environmental and spatial information were compiled. Variation partitioning with redundancy analysis was used to examine what proportion of the variation in mussels' community composition was explained by watershed (as a spatial component), environmental differences and host fish presence. Redundancy analysis for mussel abundances was used to illustrate the similarities in the distributions of mussels and fishes, and the association of differences in community composition of mussels among watersheds with certain mussel species and environmental variables. Results Host fish presence explained 44%, watershed identity 28% and environmental factors 23% of the variation in mussel species composition. However, much of the explained variation was shared among these components, and all three components together explained 55% of the total variation in species composition. Even after statistically eliminating the other explanatory variables, host fish distribution was the most important group of predictor variables, although we used a subset of relevant environmental variables because of the scale of the study. Main conclusions Our results highlight the important role played by host fishes in shaping current distributions of freshwater mussels and underscore the necessity of incorporating these relationships in conservation efforts and management actions. [ABSTRACT FROM AUTHOR]