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Fish populations rely on complex environmental conditions involving physical, chemical, and biological factors. Understanding the factors that control population persistence and productivity is essential for species management. We assessed the distribution and associated habitat features of a species at risk in Canada, Silver Shiner (Notropis photogenis), within Sixteen Mile Creek, a tributary of Lake Ontario. Using random forest models, we quantified a range of ecological factors (n = 25) to estimate habitat associations for sampled populations and life stages (juvenile, adult). A complex set of ecological factors were informative predictors of Silver Shiner distribution, including physical (stream morphology, water velocity, substrate type), and biological (aquatic and riparian vegetation) conditions. Juveniles were less responsive to habitat conditions but exhibited high seasonal variability in occurrence. Adults were most common in stream sections with greater than 0.5 m depth and stream velocity less than 0.6 m/s, and areas without silt substrate. Broadly, the models predicted Silver Shiner distribution with 68–92% accuracy in non-training data. Our findings describe the habitat conditions that Silver Shiner currently occupies in an urban drainage, which may serve as a point of reference for habitat protection and restoration. Further, predictive species distribution models can serve to identify habitat for further monitoring and restoration. [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]

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]

Investigation of the reproductive phenology and spawning behaviour of imperilled species in relation to environmental variability is needed to understand a critical component of species life history. In this study, we used redside dace (Clinostomus elongatus), a freshwater leuciscid listed as Endangered under Canada's Species at Risk Act, to model spawning phenology and make predictions about spawning initiation using historical and climate change projected thermal cues (measured as cumulative growing degree days), and provide an ethological description of spawning behaviour. Logistic regression models applied to 4 years of average daily stream water temperature data and field behavioural observations of the onset of spawning activity indicated a 50% probability of spawning initiation when cumulative growing degree days reached 214°C days and a 95% probability of spawning initiation at 288°C days. Using two climate change scenarios (i.e., a mid‐century 1.6°C increase and an end of century 3.6°C increase), spawning initiation was predicted to advance 3 days by the year 2050 and 7 days by the year 2100. Underwater video cameras placed at two sites within an urban stream captured 73 unique spawning events revealing that redside dace spawn in pairs as well as in dense, tightly packed groups (more than 20 individuals). Moreover, there is evidence of redside dace having a polygynandrous mating system, as female redside dace spawned with multiple males in 45.2% of the total spawning events recorded. Taken together, this study provides important insights into redside dace spawning initiation and behaviour, key life‐history traits having conservation implications for future reproductive success and, ultimately, population dynamics. [ABSTRACT FROM AUTHOR]

The Lake Chubsucker (Erimyzon sucetta) is a small member of the Catostomidae family requiring clear, still, well-vegetated waters. In Canada, it is found in watersheds of southern Lake Huron through Lake Erie. The species was first assessed as Special Concern by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) in 1994, reassessed as Threatened in 2001, and was listed as Threatened under Schedule 1 of the Species at Risk Act (SARA) in June 2003. Lake Chubsucker was subsequently re-assessed by COSEWIC in 2008 (and again most recently in May 2021) as Endangered and is listed as Endangered under SARA owing to a decline in suitable habitat and extant locations, and multiple habitat-related threats. The Recovery Potential Assessment (RPA) provides background information and scientific advice needed to fulfill various requirements of SARA. This research document provides the current state of knowledge of the species including its biology, distribution, population trends, habitat requirements, and threats, with updated information from 2011 through 2020. Limited information exists to adequately assess the status of most populations, as records generally represent few individuals caught over a limited number of sampling events using varied sampling protocols. A threat assessment identified the greatest threats to Lake Chubsucker in Ontario as aquatic invasive species, natural system modifications, pollution, and climate change; however, the impacts of these threats are not well understood. Mitigation measures and alternative activities related to the identified threats are presented. Important knowledge gaps remain regarding population trends, physiological tolerances to environmental conditions and pollutants, and habitat requirements by life stage. [ABSTRACT FROM AUTHOR]

The young-of-year (YOY) habitat of many fishes listed under the Species at Risk Act (SARA) is poorly described, yet identifying critical habitat is essential to ensure species recovery. Past research on the Endangered spotted gar (Lepisosteus oculatus Winchell, 1864) in Canada has focused on the habitat use of adults and juveniles, but little is known about the occurrence and habitat use of YOY. Dip net and aquatic habitat sampling were performed in nearshore (lakefront, agricultural drain), mid-channel (agricultural drain), and offshore sites within Rondeau Bay to determine the fine-scale habitat occupancy patterns of age-0 spotted gar. Habitat preference analysis indicated YOY spotted gar strongly preferred shallow (0.5–1.0 m), vegetated, nearshore (lakefront and agricultural drain) habitat and avoided offshore habitat. An association between submerged aquatic vegetation (SAV) and fish size was also found, as dependence on SAV diminished as total length increased. Our study represents the first capture and assessment of habitat associations of early-stage YOY spotted gar in Canada. Given our findings, management efforts should focus on protecting the vegetated nearshore habitat in Rondeau Bay and other occupied locations in Lake Erie to ensure the long-term persistence of spotted gar in Canada. [ABSTRACT FROM AUTHOR]

The reproductive period is a critical part of a species' life history. Estimating species-specific fecundity can improve demographic models aimed at developing recovery targets for imperilled species. We provide egg diameter and fecundity estimates and develop a length–fecundity relationship for silver shiner, Notropis photogenis (Cope, 1865), a small-bodied freshwater species listed as Threatened under Canada's Species at Risk Act. Furthermore, we document the incidence of an acanthocephalan parasite, the thorny-headed worm, Leptorhynchoides thecatus (Linton, 1891), in the gastrointestinal tract of silver shiner, which is the first published record of the parasite in this species. Silver shiner egg diameters (mean ± standard deviation) were 0.61 ± 0.15 mm and ranged from 0.13 to 0.92 mm. Fecundity ranged from 311 to 2768 eggs and was significantly higher in age 2–3+ fish (1475 ± 570 eggs) compared with age 1+ fish (576 ± 270 eggs). We highlight that parasite infection negatively impacted the body condition of individuals and that additional work is needed to determine the impact of parasite infestation on reproductive output, recruitment, susceptibility to predation, and survival of silver shiner in Canada. The fecundity and egg diameter estimates for Canadian silver shiner provided here can be incorporated into future populations modelling for this threatened species. [ABSTRACT FROM AUTHOR]

Stage‐specific abiotic and biotic associations are often poorly described for imperilled freshwater fishes, including Silver Shiner (Notropis photogenis; Threatened), which may limit species protection and recovery efforts. Here, we used fish and habitat sampling data from an urban drainage in southern Ontario, Canada to quantify abiotic and biotic associations for juvenile and adult Silver Shiner, while considering the potential effects of imperfect detection on sampled fishes. Detection probability of Silver Shiner was high (>0.80) across life‐stages, but occupancy models for adults and juveniles included different covariates. The top‐selected occupancy model (lowest Akaike's Information Criterion [AICc]) for adults included a positive effect of site depth, whereas sampling year was included in the top‐selected occupancy model for juveniles. A redundancy analysis suggested unique stage‐specific biotic associations; a positive association was observed between the abundance of adult Silver Shiner and Rosyface Shiner (Notropis rubellus), whereas positive associations were observed between juvenile Silver Shiner and the abundance of Fathead Minnow (Pimephales promelas) and Smallmouth Bass (Micropterus dolomieu). Overall, the results of this study advance the knowledge of stage‐specific abiotic and biotic associations of Silver Shiner, and the probability of species detection, which will inform future monitoring and protection of the species in Canada. More broadly, continued efforts are needed to quantify early life‐stage habitat requirements for informing the recovery of imperilled freshwater species. [ABSTRACT FROM AUTHOR]

Reproductive phenology and the length of the growing season vary in response to interannual environmental variability, with implications for population dynamics of freshwater fishes. Understanding the reproductive phenology of imperilled species in relation to environmental conditions is needed to better evaluate potential responses to changing environmental conditions, estimate future population dynamics and develop comprehensive recovery strategies. We examined Silver Shiner, a species listed as “Threatened” under Canada's Species at Risk Act, during spring 2018 and 2019 to better understand the reproductive phenology of the species at the northern edge of its range in Canada. The initiation of Silver Shiner spawning occurred on the descending limb of the hydrograph and was completed before the onset of the extended period of low summer flow. In addition, both the initiation and cessation of spawning occurred in response to a cumulative growing degree day base 5 (GDD5) cue, with logistic regression models indicating a 50% probability the population initiated and ceased spawning when GDD5 reached 68ºC•days and 368ºC•days, respectively. Logistic regression incorporating GDD5 effectively predicted spawning initiation and cessation, providing useful models for examining the impacts of alterations to the thermal regime on reproductive phenology and improving the ability to evaluate changes in the larval growth period. Furthermore, the models can facilitate the development of real-time estimates of spawning activity, and therefore ensure that disturbance to the species is minimized during the sensitive reproductive period. [ABSTRACT FROM AUTHOR]

Nontarget management effects Nontarget management effects refer to the situation in which management actions implemented to benefit one species (species A) negatively affect the state of another species (species B; Figure 2). Keywords: conflict resolution; decision-making; fishery management; invasive species control; unintended consequences; control de especies invasoras; consecuencias no deseadas; manejo de pesquerías; resolución de conflictos; toma de decisiones EN conflict resolution decision-making fishery management invasive species control unintended consequences control de especies invasoras consecuencias no deseadas manejo de pesquerías resolución de conflictos toma de decisiones 1 14 14 03/02/22 20220201 NES 220201 INTRODUCTION Wildlife provide multiple benefits to humans, including recreational, economic, health, historic, and scientific benefits (Conover, 2002). Conflict-generating species In situations with conflict-generating species, there is a trade-off when management of an intermediate species (species C) benefits one species (species A) and negatively affects another (species B; Figure 1). In this case, management efforts to increase a target species (species A; Figure 2) are either hindered by the other species (species B; Figure 2 prey focused), or can be achieved by reducing the state of the other species (species B; Figure 2 competitor and predator focused). Single-species management Management narrowly focused on a single species may miss the consequences of single-species decisions on other important species (e.g., bycatch [Gilman et al., 2019]) and can create perceived trade-offs due to incomplete knowledge of community structure and interspecific interactions (e.g., Caribbean spiny lobster [ I Panulirus argus i ] and grey snapper [ I Lutjanus griseus i ] vs. goliath grouper [ I Epinephelus itajara i ] [Frias-Torres, 2013]). [Extracted from the article]

Under Section 73(3) of Canada's Species at Risk Act, the competent minister may not authorize an activity that jeopardizes the survival or recovery of a SARA-listed species. Since 2004, the concept of jeopardizing survival and recovery has received considerable attention from DFO's Science Sector in the form of allowable harm advice; however, allowable harm is a species, not project-specific concept, and to date has not typically incorporated habitat effects, which are expected with development projects in and around aquatic ecosystems. Here, an overview of allowable harm advice is presented as it relates to interpreting Section 73(3). Components of a science-based framework to assess the impact of development activities under Section 73(3) are then presented. The three components are: 1) the ability to relate individual projects to changes in habitat condition; 2) relationships between habitat condition and species vital rates, including considerations for behavioural and sub-lethal effects; and, 3) the relationship between population growth rate and vital rates, explored through elasticity analysis for 143 COSEWICassessed species (fishes, freshwater mussels, marine mammals, marine turtles) across five population states (crashing, declining, stable, growing, booming). These components are combined to estimate changes to a species' population growth rate resulting from a single development activity, and thus also provide an accounting framework to evaluate harm from all activities in a permitting period. The components will require future work to inform taxa-specific functional responses, especially concerning relationships between habitat and vital rates, and sub-lethal effects. Further work is also required to determine the ability to achieve measurable gains in vital rates and populations through offsetting measures, if applied. If adopted into a decision support tool, this body of work would ensure that project decisions around Section 73(3) can be made in a rigorous, transparent, and nationally consistent manner. [ABSTRACT FROM AUTHOR]

The Lake Whitefish (Coregonus clupeaformis) is a coldwater benthivore with a broad distribution and highly variable ecological and morphological traits across Canada. A species pair of Lake Whitefish in Lake Opeongo, consisting of a large-bodied and small-bodied form, was first discovered in 1940. Both forms (now considered separate Designatable Units, DUs) were assessed as Threatened by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) in April 2018. The reason for this designation was that both DUs are known only from Lake Opeongo, Algonquin Provincial Park, Ontario, and the introduction of aquatic invasive species could disrupt the unique ecological processes that drove divergence and maintains the species pair (COSEWIC 2018). The Recovery Potential Assessment provides background information and scientific advice needed to fulfill various requirements of the federal Species at Risk Act. This research document provides the current state of knowledge of the species pair including its biology, distribution, population trends, habitat requirements, and threats, which will be used to inform recovery plans. Limited information exists to adequately assess the status of either DU, particularly the small-bodied form. A threat assessment identified the greatest threats to the large- and small-bodied DUs of Lake Whitefish in Lake Opeongo as aquatic invasive species, climate change, and human disturbances; however, the impacts of these threats are not well understood. Mitigation measures and alternative activities related to the identified threats are presented, as appropriate. Important knowledge gaps remain regarding population trends, as well as differences in niche occupancy and impacts of current and anticipated threats on the two DUs. [ABSTRACT FROM AUTHOR]

Understanding the factors underlying species establishment is critical for the management of invasive fishes, yet the roles of propagule pressure and environmental factors are infrequently quantified in joint models. We estimated the establishment likelihood of the invasive black carp (Mylopharyngodon piceus) by examining the relative influence of propagule pressure (introduction size and age structure) and environmental factors (temperature-driven young-of-year [YOY] overwinter survival, adult survival, age at maturity, and longevity). Simulations demonstrated that both propagule pressure and environmental factors can act as non-linear bottlenecks to establishment. When the model was applied to 12 Great Lakes tributaries and nearshore areas, black carp establishment was probable with sufficient propagules and under most environmental conditions (median p = 0.21–0.73, 0.70–1.00, and 0.46–0.97 for 100 pairs of age 4, age 9, and age 16 fish, respectively), except for YOY (p < 0.01). Our analysis is one of the few studies to examine the relative role of propagule pressure and environmental conditions on establishment, indicating that both factors can lead to establishment failure independently or concurrently within an ecosystem. [ABSTRACT FROM AUTHOR]

Life‐history and other vital rate information is important for effective species conservation by informing demographic trends and aspects of population viability. However, species‐specific information is lacking for many small‐bodied freshwater fishes, which can make it difficult to relate demographic trends to threats or recovery actions. Silver Shiner (Notropis photogenis), a small‐bodied species listed as Threatened under Canada's Species at Risk Act, lacks well‐informed age and vital rate information. We aged 254 Silver Shiner using opercular and otolith structures and determined that Silver Shiner is short‐lived, with a probable maximum age of 4. Three years of field collections (2017–2019) were used to parameterize growth models and to estimate adult (age 1–3+) mortality rates. Silver Shiner captured in urban reaches exhibited altered growth and higher mortality compared to non‐urban reaches, indicating that urbanization may have demographic impacts on the species. Results highlight the importance of detailed age and vital rate information for assessing threats and informing effective conservation approaches for imperilled fishes. Furthermore, the potential negative impact of urbanization on the growth and survival of this species highlights the urgency of better understanding the influence of urbanization on small‐bodied freshwater fishes in general. [ABSTRACT FROM AUTHOR]

More than 15 years have passed since Canada's Species at Risk Act was enacted. To evaluate scientific progress in support of the Act, we identified research accomplishments up to 2017 for imperilled aquatic species in the Great Lakes – St. Lawrence River basin based on recovery documents and an expert survey, spanning 1182 activities across 68 research topics for 45 fish and mussel species. Greatest progress was observed for population ecology (38% of activities with major progress) and habitat science (28%), with comparably less progress on threats (mechanisms and impacts; 19%) and recovery (threat mitigation and reintroduction; 21%). As a result of lagging progress, threat and reintroduction topics were prioritized for a Canadian Freshwater Species at Risk Research Network (SARNET; 2017–2020), which focused on addressing key knowledge gaps with novel applications. This special issue outlines the SARNET projects, which span novel field, laboratory, and analytical activities. Continued research investment into novel and existing approaches is necessary to advance scientific achievements for fishes and mussels in support of the Species at Risk Act in Canada. [ABSTRACT FROM AUTHOR]

The aquarium, water garden, and live seafood trades are major pathways for the introduction of aquatic species into Canada. If released, some imported species may become invasive, with negative consequences for Canadian ecosystems. This research document describes the movement of live aquatic (freshwater, brackish, and marine) organisms including fishes, invertebrates, and plants in trade into and within Canada, identifies aquatic species previously or presently in trade, describes end user participation and the release of aquatic organisms to the wild, develops spatially explicit estimates of propagule pressure, and identifies possible critical control points. A total of 4,296,188 aquarium organisms, representing 844 taxa, were imported into Canada from 40 source countries during a four-month period in 2018. The top three ports of entry, by trade volume, were Windsor, ON; Mirabel, QC; and, Calgary, AB. Imported aquarium organisms were distributed within Canada via major distribution hubs in Innisfil, ON; LaSalle, QC; and, Calgary, AB. Aquarium retailers tended to aggregate around major urban centers. A baseline scenario assuming a 10.6% participation rate and a 3.9% release rate estimated that 57,799 households released 347,650 aquarium organisms per year. During the same four-month timeframe, 3,758,224 water garden organisms, representing 199 taxa, were imported into Canada from 19 source countries. Major ports of entry and distribution hubs for water garden organisms were the same as the aquarium pathway. Water garden retailers were also found around major cities. An estimated 50,769 households released 305,367 water garden organisms per year, based on an assumed 9.2% participation rate and 3.9% release rate. About 82,434,924 live seafood organisms, representing 84 taxa, were imported into Canada from 20 source countries during the same four-month period. Major ports of entry for live seafood organisms included Ottawa, ON; Richmond, BC; St-Stephen, NB; and, Toronto, ON. Montebello, QC; Chilliwack, BC; and, Cap-Pelé, NB were major distribution hubs for live seafood organisms. Similar to the other pathways, live seafood retailers clustered around major cities. An estimated 47,964 users released 288,502 live seafood organisms per year, based on an assumed 3.5% participation rate and 3.9% release rate. Critical control points that allow the greatest volume of organisms in trade to be encountered were identified. For all three pathways, these included the major ports of entry, key distribution hubs, and urban centres where aggregations of retailers, end users, and releasers occur. Results of sensitivity analyses suggested that all parameters considered had an equal effect on the propagule pressure estimates for all pathways, though they had a disproportionate effect on the spatial distribution of end users and releasers. Despite uncertainty around model parameters, statistically significant hot spots of introduction risk were identified. Maintaining detailed import records and characterizing the human dimensions of the aquarium, water garden, and live seafood trades would reduce uncertainty and refine spatially explicit estimates of propagule pressure associated with each pathway. [ABSTRACT FROM AUTHOR]

Bayluscide, a chemical lampricide, is used by government agencies to assess and control invasive Sea Lamprey (Petromyzon marinus) in the Great Lakes basin. The toxicity of Bayluscide to non-target fishes has been previously investigated. However, the potential mortality of fishes and mussels assessed by COSEWIC or listed under Canada's Species at Risk Act as Endangered, Threatened, or Special Concern has not been evaluated based on the factors that dictate species responses in the wild. To assess the potential for mortality, the likelihood that fishes and mussels of conservation concern will be exposed to, and experience toxicity-induced mortality from, granular Bayluscide in the Detroit, St. Clair, Thames, and Sydenham rivers in southwestern Ontario were quantitatively estimated. Simulation models were based on: 1) habitat associations that predispose fishes and mussels species to occur in areas targeted for application; 2) population densities susceptible to exposure; and, 3) the toxicity of the compound, based on: i) assumed Bayluscide concentrations in the environment; ii) taxonomic or habitat match with surrogate species; and, iii) four dose-response relationships, using Sea Lamprey LC50 and LC99.9 concentrations as a benchmark (fishes) or a single point estimate (mussels). Population effects were evaluated by combining estimates of Bayluscideinduced mortality with age-structured models of Eastern Sand Darter (Ammocrypta pellucida; SARA Threatened), Northern Madtom (Noturus stigmosus; SARA Endangered), Channel Darter (Percina copelandi; Lake Erie DU, SARA Endangered), and Ichthyomyzon spp. In most cases, simulated applications resulted in no or low mortality of fishes and mussels. However, in some cases (≤ 5%), mortality of ones to tens of fishes and potentially hundreds of freshwater mussels and Silver Lamprey (Ichthyomyzon unicuspis) or Northern Brook Lamprey (I. fossor) occurred following a single application cycle. Based on a model in which recovery from Bayluscide effects does not occur, the 50-100 year effect of repeated Bayluscide application could reduce abundance by as much as 100% from baseline for some species (Northern Madtom, Ichthyomyzon spp.) or up to 90% for others (Eastern Sand Darter) if populations are small and applications occurred annually but would be less severe if populations are large. Estimated mortality varied with the frequency and size of applications but relationships were non-linear. Several uncertainties were identified including: 1) environmentally relevant concentrations of Bayluscide; 2) species-specific Bayluscide toxicity and appropriateness of surrogates; 3) incidence and effect of avoidance behavior; 4) occurrence, density, and habitat associations based on a limited number of field studies; and, 5) unknown population abundance and trajectory for most species of conservation concern. Results indicate that in some cases, Bayluscide may result in mortality and population effects for species of conservation concern but mortality may be mitigated by several factors associated with the application cycle. [ABSTRACT FROM AUTHOR]

Pugnose minnow (Opsopoeodus emiliae) is a small, reclusive species that is widespread in North America, but is one of the rarest fishes in Canada, found in less than 12 known localities in southwestern Ontario. In contrast to most pugnose minnow populations across the global range, Canadian populations are primarily found in turbid systems, potentially indicating persistence in suboptimal conditions. We used data from a multi‐gear species and habitat survey in the Canard River, Ontario, a system dominated by agricultural inputs and the best‐known capture site of the species in Canada, to parameterise multi‐gear occupancy models for understanding the relationship between pugnose minnow occupancy and microhabitat features, including the role of turbidity. Almost 300 pugnose minnow were captured, representing the largest single collection of the species in Canadian history. The best occupancy model indicated that the probability of pugnose minnow occupancy was highest in the deepest sites with the lowest water clarity (i.e. high turbidity); however, competing models suggested that occupancy was highest at sites with wild celery (Vallisneria americana) and higher water clarity, signifying that habitats with low turbidity may be utilised if sufficient physical cover exists. Together, our results suggest that Canadian pugnose minnow populations occupy and potentially favour turbid conditions, possibly to avoid visual predators in clearer habitats. It remains uncertain whether this abiotic association represents a long‐term, viable, local adaptation or whether persistence of pugnose minnow in the Canard River is at risk unless significant water quality improvements can be made. [ABSTRACT FROM AUTHOR]

Freshwater ecosystems are among the most threatened environments on our planet. Disturbances across the terrestrial landscape accrue within freshwater ecosystems and, combined with global stressors such as climate change and invasive species, create a complex situation for recovering imperilled fishes. Given the drastic global decline of freshwater fishes, similarly extreme efforts are needed for their conservation and recovery — repatriation represents one such opportunity. Species repatriation describes the act of releasing a species in areas where extirpation has occurred. Paradoxically, a long history of fish introductions for recreational purposes exists, yet examples of repatriation for imperilled fishes are relatively rare compared with terrestrial species. Stemming from the restoration and species introduction literature, we identify five ecological themes to consider when evaluating repatriation potential of freshwater fishes and suggest that repatriation represents the "drastic" approach needed to achieve meaningful conservation milestones. [ABSTRACT FROM AUTHOR]

Fishes are among the most threatened taxa in Canada with over 70 species, subspecies, and (or) designatable units presently listed for protection under the Species at Risk Act (SARA). Protecting these species requires a diverse set of strategies based on the best-available data and information. One approach identified under SARA and in Canadian federal recovery strategies for improving the status of SARA-listed fishes is species reintroduction, which involves the release of individuals into areas from which they have been extirpated with the goal of re-establishing self-sustaining populations. The success of reintroduction relies on a comprehensive understanding of species ecology and life history, with considerations around population genetics and genomics. However, SARA-listed species are some of the most poorly known species in Canada due to their rarity and relative lack of research investment prior to the enactment of SARA. As a result, SARA-listed species have the most to lose if reintroduction activities are not carefully researched, planned, and executed. Therefore, the purpose of this review is to present an accessible summary on the state of reintroduction science for SARA-listed fishes in Canada with the hope of motivating future research to support reintroduction activities. We focus our review on 14 SARA-listed freshwater or anadromous fishes identified as candidates for reintroduction in federal recovery strategies. We follow the species-specific summaries with guidance on how basic research questions in population ecology, habitat science, and threat science provide a critical foundation for addressing knowledge gaps in reintroduction science. Subsequently, we identify the importance of genetic and genomic techniques for informing future research on the reintroduction of SARA-listed species. We conclude with recommendations for active, experimental approaches for moving reintroduction efforts forward to recover Canadian fishes. [ABSTRACT FROM AUTHOR]

Anthropogenic stressors such as agriculture and urbanization can increase river turbidity, which can negatively impact fish gill morphology and growth due to reduced oxygen in the benthic environment. We assessed the gill morphology, field metabolic rate (FMR), and two hypoxia tolerance metrics (oxygen partial pressure at loss of equilibrium, PO2 at LOE, and critical oxygen tension, Pcrit) of eastern sand darter (Ammocrypta pellucida), a small benthic fish listed as threatened under the Species at Risk Act in Canada, from rivers in southern Ontario. Field trials were conducted streamside in the Grand River (August 2019; mean NTU 8) and in the comparatively more turbid Thames River (August 2020; mean NTU 94) to test the effect of turbidity on each physiological endpoint. Gills were collected from incidental mortalities and museum specimens, and were assessed using hematoxylin and eosin and immunofluorescent staining. The between‐river comparison indicated that turbidity significantly increased interlamellar space and filament width but had no significant influence on other gill morphometrics or FMR. Turbidity significantly increased PO2 at LOE (i.e., fish had a lower hypoxia tolerance) but did not significantly impact Pcrit. Therefore, although turbidity influences hypoxia tolerance through LOE, turbidity levels were not sufficiently high in the study rivers to contribute to measurable changes in gill morphology or metabolism in the wild. Determining whether changes in gill morphology or metabolism occur under higherturbidity levels would help resolve the ecological importance of turbidity on species physiology in urban and agricultural ecosystems. [ABSTRACT FROM AUTHOR]

Understanding the functional relationship between the sample size and the performance of species richness estimators is necessary to optimize limited sampling resources against estimation error. Nonparametric estimators such as Chao and Jackknife demonstrate strong performances, but consensus is lacking as to which estimator performs better under constrained sampling. We explore a method to improve the estimators under such scenario. The method we propose involves randomly splitting species-abundance data from a single sample into two equally sized samples, and using an appropriate incidence-based estimator to estimate richness. To test this method, we assume a lognormal species-abundance distribution (SAD) with varying coefficients of variation (CV), generate samples using MCMC simulations, and use the expected mean-squared error as the performance criterion of the estimators. We test this method for Chao, Jackknife, ICE, and ACE estimators. Between abundance-based estimators with the single sample, and incidence-based estimators with the split-in-two samples, Chao2 performed the best when CV < 0.65, and incidence-based Jackknife performed the best when CV > 0.65, given that the ratio of sample size to observed species richness is greater than a critical value given by a power function of CV with respect to abundance of the sampled population. The proposed method increases the performance of the estimators substantially and is more effective when more rare species are in an assemblage. We also show that the splitting method works qualitatively similarly well when the SADs are log series, geometric series, and negative binomial. We demonstrate an application of the proposed method by estimating richness of zooplankton communities in samples of ballast water. The proposed splitting method is an alternative to sampling a large number of individuals to increase the accuracy of richness estimations; therefore, it is appropriate for a wide range of resource-limited sampling scenarios in ecology. [ABSTRACT FROM AUTHOR]

Redside Dace (Clinostomus elongatus) is a small minnow with a limited distribution in southern Ontario and is listed as Endangered under the Species at Risk Act. The draft federal recovery strategy for Redside Dace outlines the need to develop a monitoring program to quantify the abundance and distribution of the species in Canada. A repeat-survey design, whereby surveys are replicated spatially and temporally, could be used to inform models for assessing the abundance and distribution of Redside Dace and subsequent management decisions that may impact the species. An introduction to Redside Dace monitoring is presented, including a summary of previous and current monitoring efforts. Potential objectives of a Redside Dace monitoring program are described as well as an introduction to the use of a repeat-survey design for estimating species detection and occupancy. Considerations around the allocation of effort for a Redside Dace monitoring program are presented, including: (i) the effect of scale on site definition and subsequent implications for total monitoring effort and statistical power; (ii) targeted versus random sampling; and, (iii) how stratified random sampling across different gradients (e.g., space, time, threats) can inform the conservation status of the species. Occupancy is emphasized over an abundance-based approach as it provides relatively greater power per sampling effort for generating conclusions. Nevertheless, sampling Redside Dace using repeated surveys within and between sampling seasons can be used to inform abundance estimates. Overall, stratification of sampling effort for Redside Dace spatially (i.e., across populations) and over time will allow statistically powerful conclusions about changes in occupancy and (or) abundance at the local, population, and Canadian scale. Implementation of such a monitoring approach would inform management activities such as the review of development and instream work proposals, population status assessments, and future restoration projects. [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]

Fish gills are complex organs that have direct contact with the environment and perform numerous functions including gas exchange and ion regulation. Determining if gill morphometry can change under different environmental conditions to maintain and/or improve gas exchange and ion regulation is important for understanding if gill plasticity can improve survival with increasing environmental change. We assessed gill morphology (gas exchange and ion regulation metrics), hematocrit and gill Na+/K+ ATPase activity of wild-captured blackside darter (Percina maculata), greenside darter (Etheostoma blennioides), and johnny darter (Etheostoma nigrum) at two temperatures (10 and 25 °C) and turbidity levels (8 and 94 NTU). Samples were collected August and October 2020 in the Grand River to assess temperature differences, and August 2020 in the Thames River to assess turbidity differences. Significant effects of temperature and/or turbidity only impacted ionocyte number, lamellae width, and hematocrit. An increase in temperature decreased ionocyte number while an increase in turbidity increased lamellae width. Hematocrit had a species-specific response for both temperature and turbidity. Findings suggest that the three darter species have limited plasticity in gill morphology, with no observed compensatory changes in hematocrit or Na+/K+ ATPase activity to maintain homeostasis under the different environmental conditions. [Display omitted] • Temperature and turbidity caused minimal changes in gill morphology. • There are species-specific differences in hematocrit. • Closely related species have differences in gill morphology. [ABSTRACT FROM AUTHOR]

For freshwater fishes and mussels listed under the Species at Risk Act (SARA), a federal recovery strategy or management plan identifies recovery measures for best achieving population and distribution objectives. Recovery strategies and management plans for SARAlisted freshwater fish and mussel species often identify conservation translocation, specifically supplementation or reintroduction, as a potential approach for improving survival and/or recovery. However, there has been limited progress in undertaking conservation translocations primarily due to basic information gaps on species ecology and uncertainty about how to assess the potential ecological benefits and risks to freshwater species and ecosystems. The objectives of this research document were to: 1) identify and evaluate the potential benefits and risks of conservation translocation as a tool for improving the survival, recovery, or management of SARA-listed freshwater fish and mussel species; and, 2) identify science-based considerations and methods for determining when conservation translocation would be expected to improve the survival, recovery, or management of SARA-listed freshwater fishes and mussels. Benefits and risks of conservation translocations to the focal species and broader ecosystem components are presented, including a decision support framework for evaluating the potential benefits and risks of conservation translocation for SARA-listed freshwater fishes and mussels. The decision support framework consists of five steps: 1) Identify fundamental and means objectives for conservation translocations; 2) Assess the probability of achieving the fundamental and means objectives; 3) Identify and assess the likelihood and magnitude of unintended consequences; 4) Compile and weigh the scientific evidence to inform the translocation decision; and, 5) Implement and monitor the conservation translocation. Using the decision support framework can help determine if and when the ecological benefits of conservation translocations outweigh the uncertainties and ecological risks when attempting to improve the survival and recovery of SARA-listed freshwater fishes and mussels. Future refinement of the decision support framework would benefit from several case studies in addition to those presented in the appendices. [ABSTRACT FROM AUTHOR]

Early detection and response programs can prevent or delay species invasions. The potential to detect and remove species during response activities can be informed by the relationships between species abundance, sampling scheme, the probability of capture, and response effort. These relationships were investigated for Asian carps, which have been the subject of recent response efforts in the Great Lakes basin. Simulation models were used to examine the response effort required to detect and remove Asian carps in a fixed 75 ha area. The mean relative effort to detect a single fish ranged from 0.07 to 13.48 passes of the response area given: abundances from 1 to 25 fish (0.01 to 0.33 fish/ha), probabilities of capture from 0.05 to 0.70, and an assumed systematic sampling design. Response effort required for detection decreased in a nonlinear manner as fish abundance or the probability of capture increased. The mean relative effort required for local removal was 0.72 to 69.55 passes of the response area, and a similar nonlinear relationship was observed where small increases in the probability of capture above 0.05 led to substantial decreases in effort required for local removal. Completing five passes of the response area with non-detections (and an assumed low probability of capture, i.e., < 0.15) resulted in a moderate probability (p > 0.45) that fish remained within the response area. In addition, the probability of capture needed to be > 0.25 for low abundances (i.e., 1 fish) and > 0.55 for high abundances (i.e., 20 fish) to result in a high probability of local removal (p > 0.80) with five passes of the response area. Factors including fish aggregation behaviour, the size of the response area, sampling scheme (i.e., systematic, random, repeat, and informed sampling), and fish avoidance were also examined to determine their influence on effort required for detection and local removal. Improved knowledge of occupied fish habitat and resulting informed sampling had the greatest influence on effort required for detection and local removal under most probabilities of capture and fish abundances. These results provide a preliminary assessment of the potential effort required to successfully detect and remove Asian carps during response activities in the Great Lakes basin. [ABSTRACT FROM AUTHOR]

The use of translocations to recover populations requires a sufficiently large number of individuals from source populations, but removing too many individuals could lead to source population collapse. To understand the trade-off between the probabilities of source population extirpation and translocation success, matrix population models that incorporate Allee effects, density dependence, and demographic and environmental stochasticity were combined with a model that simulates removals from source populations. We apply these models to eastern sand darter (Ammocrypta pellucida; Species at Risk Act status: Threatened) translocation scenarios in Canada. The results suggest that translocations most often require source populations >20 000 individuals, as source population extirpation probability increased with the number and frequency of removals. Transport mortality or losses immediately following introduction further affected translocation success. Uncertainty around life-history parameters and the strength of Allee effects led to additional uncertainty about the required source population size. Although stochastic processes affected the probability of translocation success, factors such as stocking density and frequency can be controlled, and translocation may therefore be a viable strategy for eastern sand darter recovery, even when applying cautious thresholds to guard against uncertainty. [ABSTRACT FROM AUTHOR]

Species reintroduction efforts can improve the recovery of imperiled species, but successful implementation of this conservation strategy requires a thorough understanding of the abiotic and biotic factors influencing species viability. Species interactions are especially understudied, in particular by omitting the effect of imperfect detection on negative, neutral, or positive associations within a community. Using repeat surveys from 5 southern Ontario, Canada, Great Lakes tributaries, we quantified species co‐occurrence patterns with the eastern sand darter (ESD) (Ammocrypta pellucida), listed as federally threatened, and characterized how imperfect detection during sampling can influence inference regarding these relationships. We used a probabilistic framework that included 3 approaches of increasing complexity: probabilistic co‐occurrence analysis ignoring imperfect detection; single‐species occupancy models with subsequent co‐occurrence analysis; and 2‐species occupancy models. We then used our occupancy models to predict suitable sites for potential future reintroduction efforts while considering the influence of negative species interactions. Based on the observed data, ESD showed several positive associations with co‐occurring species; however, species associations differed when imperfect detection was considered. Specifically, a negative association between ESD and rosyface shiner (Notropis rubellus) was observed only after accounting for imperfect detection in the Grand River. Alternatively, positive associations in the Grand River between ESD and northern hogsucker (Hypentelium nigricans) and silver shiner (Notropis photogenis) were observed regardless of whether imperfect detection was accounted for. Our models predicted several potential reintroduction sites for ESD in formerly occupied watersheds with high levels of certainty. Overall, our results demonstrate the importance of investigating imperfect detection and species co‐occurrence when planning reintroduction efforts. Article impact statement: Species co‐occurrence patterns can be affected by imperfect detection and are an important consideration for species reintroduction. [ABSTRACT FROM AUTHOR]

Niche specificity can predispose species to population declines during periods of resource limitation, yet trophic niche specificity is poorly known for many small-bodied freshwater fishes. Applying a two-tiered approach involving stomach content and stable isotope analyses, we examined the diet and trophic niche of the threatened eastern sand darter (Ammocrypta pellucida (Putnam, 1863)) and co-occurring fishes in the Thames River, Ontario, Canada. As with previous studies, stomach content analysis revealed that eastern sand darter consumed a variety of benthic organisms including Chironomidae, Cladocera, Ostracoda, Oligochaeta, and Ephemeroptera; however, proportional contributions of prey groups differed based on stable isotope analysis, highlighting the potential for seasonal variation in prey consumption. Despite evidence of a generalist strategy, stable isotope analysis indicated eastern sand darter exhibited a relatively narrow trophic niche relative to co-occurring fishes. Trophic niche overlap was relatively minor between eastern sand darter and drift-feeding fishes (spotfin shiner (Cyprinella spiloptera (Cope, 1867)), emerald shiner (Notropis atherinoides Rafinesque, 1818), and buffalo sp. (genus Ictiobus Rafinesque, 1820)), but was more evident between eastern sand darter and benthic and benthopelagic fishes (johnny darter (Etheostoma nigrum Rafinesque, 1820) and blackside darter (Percina maculata (Girard, 1859))), indicating that competition with these species may be more likely during periods of prey scarcity. [ABSTRACT FROM AUTHOR]

For more than two decades the Great Lakes Fishery Commission has sought tactics to complement, and potentially replace, the use of barriers and lampricides to control sea lamprey (Petromyzon marinus) in the Great Lakes, but thus far without success. This paper examines the potential of modern genetic technology to suppress these invasive populations. We identified six recombinant options that appeared to be moderately to highly feasible, most of which were judged by an expert panel as extremely low or low risk, and for which research and development was broadly supported by stakeholders. The two options judged to overall best combine high efficacy and low risks were a Mendelian "sex ratio drive" and genetically modifying a prey species combined with killing or sterilizing sea lamprey that fed on it. Core issues regarding use of genetic biocontrol in the Great Lakes include technical problems associated with maintaining a sea lamprey brood line, information gaps for most options, the extent of broader public support, and the extent and nature of national and international consultation required in making decisions about control options. [ABSTRACT FROM AUTHOR]

A correction notice is presented regarding Fig. 3 in the originally published article, where sites BC1 and CC1 were incorrectly highlighted as part of the "Medium impact" grouping; the corrected versions of Fig. 3.

Abstract Understanding recreational demand in aquatic ecosystems is necessary to relate ongoing environmental change to anthropogenic factors. We investigated whether factors influencing patterns of boating activity by recreational fishers (boat fishers) differed from those of other recreational boaters at Ontario, Canada lakes. Count data from aerial roving creel surveys flown for one year between 2008 and 2012 and across 643 lakes in Ontario indicated that greater accessibility of lakes, lake size, and human development around lakes were associated with higher activity for both boat fishers and other recreational boaters. Other recreational boating activity was greater at lakes with more human development (as measured by the density of docks) and was more concentrated in southern Ontario than was boat fishing activity. Boat fishing activity was greater at larger-sized lakes with tourism establishments and greater walleye biomass densities and less within lakes located in parks than was other recreational boating activity. The reduced importance of human development and increased importance of walleye for boat fishers was associated with boat fishing having a greater spatial footprint than other recreational boating. This different footprint can result in different impacts from the two activities across a large area such as the province of Ontario. Although boat fishers travelled further afield than other recreational boaters, large lakes with tourism establishments were especially attractive to these fishers. Consequently, these lakes are especially susceptible to impacts from boat fishers including the arrival of non-indigenous species. The boat fishing and other recreational boating models had strong predictive power (correlation coefficient > 0.80) when validated with a separate evaluation dataset comprised of 456 lakes and activity counts measured between 2013 and 2017. [ABSTRACT FROM AUTHOR]

Over 90% of recent human‐caused extinctions are wild species known from only one nation. These nationally endemic species represent one of the greatest global conservation responsibilities for any country. To meet this responsibility, we must first identify nationally endemic species. We developed the first comprehensive inventory of the 308 plant, animal, and fungi species and infraspecies only found in Canada, of which approximately 90% are of global conservation concern. Our analysis also identified 27 spatial concentrations of endemic species, many of which are associated with glacial refugia, islands, coasts, and unique habitats. Nationally endemic species have not been the primary focus of endangered species conservation in Canada and other countries. Our analysis provides a case study on how national inventories of endemic species can be developed and applied to support species assessments and place‐based conservation. Prioritizing endemic species for conservation can build on sentiments of sense of place and national responsibility to foster public interest. We propose a species conservation framework that highlights the critical role of national endemism in preventing global extinctions. Greater conservation focus on endemic species will support national and international biodiversity conservation targets, including the post‐2020 Global Biodiversity Framework. [ABSTRACT FROM AUTHOR]

Freshwater biodiversity is declining from impacts associated with anthropogenic stressors. Here, we use carbon (δ13C) and nitrogen (δ15N) stable isotopes to assess food web effects following a coal mine spill that displaced biota and altered biophysical stream characteristics. We compared isotopic niche metrics of benthic macroinvertebrates and the fish community, including non-native brook trout (Salvelinus fontinalis) and endangered Athabasca rainbow trout (Oncorhynchus mykiss), to infer spatial differences in site-specific resource use along a habitat disturbance gradient. Predatory benthic macroinvertebrate trophic position was elevated where impacts from the spill were most pronounced. Autochthonous carbon contribution to consumer diets was lowest in biota sampled at the most highly impacted site from the mine spill, leading to an unexpected expansion of the isotopic niche size of rainbow trout and the aquatic invertebrate community. Collectively, our results suggest variation in trophic resource assimilation across multiple levels of the food web, fueled by the allochthonous energy pathway in highly impacted study sites. We conclude this reflects a biotic response to altered basal aquatic resources following a major industrial disturbance. [ABSTRACT FROM AUTHOR]

Aquatic biota often face multiple anthropogenic threats such as river fragmentation and climate change that can contribute to high rates of aquatic species imperilment world-wide. Temperature-induced hypoxia is one under-explored mechanism that can threaten aquatic species in fragmented rivers with reduced flows. We applied ecosystem metabolism models to define the effect of water temperature on net ecosystem production (NEP) of oxygen at 12 sites of a fragmented river channel that supports three fish species at risk and experiences hypoxia. We found that water temperature and precipitation events at 75% of our sites were significantly and negatively correlated to NEP estimates and explained 28% of the variation in NEP within sites. Temperature-induced reductions in NEP at these sites likely contributed to hypoxic conditions threatening the three species at risk as NEP explained 41% of the variation in dissolved oxygen near all sites. Our results have applications for understanding drivers of hypoxic stress in fragmented watercourses, integrating water temperature–NEP effects with oxygen demands of sensitive fish species, and modeling future effects of climate change on aquatic species. [ABSTRACT FROM AUTHOR]

Captive breeding programs are widely applied by conservation practitioners as a means of conserving, reintroducing, and supplementing populations of imperilled freshwater fishes and mussels. We conducted a systematic map to provide an overview of the existing literature on the effectiveness of captive breeding and release programs. A key finding is that there is limited evaluation of the effectiveness of such programs at all three stages (i.e., broodstock collection, rearing/release methods, and post-release monitoring). We identified clusters of evidence for evaluating supplementation associated with rearing/release methods for fish growth and survival metrics, and the monitoring stage for fish genetic diversity, growth, and survival metrics, primarily focused on salmonids. However, many studies had inadequate experimental designs (i.e., lacked a comparator). Overall, there was a paucity of studies on the effectiveness of captive breeding programs for imperilled freshwater mussels, highlighting the need to make such information broadly available when studies are undertaken. Outputs from this systematic map (i.e., the map database and heatmaps) suggest that the effectiveness of captive breeding and release programs requires further systematic evaluation. [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]

Freshwater biodiversity loss is one of the greatest environmental threats in our changing world. Although declines have been reported extensively in the literature, much less attention has been devoted to solving the freshwater biodiversity crisis relative to other ecosystems. The recently proposed Emergency Recovery Plan for Freshwater Biodiversity (Tickner et al., 2020, BioScience, 70(4), 330–342) outlines an ambitious but necessary set of overarching actions that can help "bend the curve" for freshwater biodiversity declines. This plan is timely given the present opportunity to adjust freshwater biodiversity targets in international biodiversity agreements and to encourage meeting targets of relevant Sustainable Development Goals. Yet, relying solely on a trickle down from such agreements to national and local scales will likely take too long, given the immediate urgency of the situation. Here, we advocate for a broader, concerted effort from all actors to ensure the Emergency Recovery Plan meaningfully influences the actions of practitioners at a local scale. We outline the roles and responsibilities of actors involved with policy, research, professional bodies and societies, advocacy, and industry, as well as practitioners themselves, in achieving this goal. It is our hope that this overview facilitates the real‐world actions needed to execute the Emergency Recovery Plan so that we can indeed "bend the curve" for freshwater biodiversity. [ABSTRACT FROM AUTHOR]

We project how human population change (2018 to 2046) and aquatic invasive species (AIS) establishment events of bigheaded carps (Hypophthalmichthys spp.) and grass carp (Ctenopharyngodon idella) might combine to affect future Canadian recreational fishing activity for the Laurentian Great Lakes. Human population change is expected to affect the total number of fishing trips (increase of about 143 000 trips or 11.4%) more than any of the AIS establishment events (maximum decrease of about 44 000 trips or 3.5%). The projected 11.4% increase to the number of fishing trips from human population change, however, lags the 38% projected increase to Ontario, Canada's population from 2018 to 2046. Increasing urbanization and an aging population, which are associated with reduced rates of fishing participation, were responsible for this difference. The combined effects of human population change and AIS establishment illustrate the importance of accounting for human population change as it reverses the conclusions and results in a projected net increase of between 92 000 and 125 000 in the number of fishing trips. The combined model also identifies potential growth areas for fishing such as shore fishing by urbanites on the western portion of Lake Ontario. [ABSTRACT FROM AUTHOR]

Bayluscide, a chemical lampricide, is used by government agencies in the Great Lakes basin to assess Sea Lamprey (Petromyzon marinus) as part of bi-national efforts to control the species. The use of granular Bayluscide has been highly successful in identifying and suppressing Sea Lamprey populations. However, the ecological risk of Bayluscide for fishes and mussels listed under Canada's Species at Risk Act and other species of conservation concern is not well understood. This document: 1) identifies potential pathways (direct, indirect) and mechanisms (physiological, non-physiological) by which the application of granular Bayluscide may influence fishes and mussels of conservation concern; 2) evaluates the relative ecological risk of applications based on four metrics (spatial distribution, application intensity, habitat associations that predispose species to exposure, toxicity); 3) identifies mitigation measures that may reduce potential impacts to non-target species; and, 4) identifies uncertainties needed to refine risk estimates. Spatial analyses indicated that between 2011 and 2017, Bayluscide applications occurred within the distribution of 21 fish and 15 mussel species of conservation concern including areas identified as critical habitat for 16 species (6 fishes, 10 mussels). For fishes, relative risk was greatest for native lampreys (Silver Lamprey [Ichthyomyzon unicuspis] and Northern Brook Lamprey [Ichthyomyzon fossor]) followed by Lake Sturgeon (Acipenser fulvescens) and Northern Madtom (Noturus stigmosus). Native lampreys exhibited high relative risk given habitat preferences and the toxicity of Bayluscide to those species. Northern Madtom ranked highly due to exposure (spatial and temporal patterns of application) and toxicity. Lake Sturgeon ranked highly due to exposure, though results were not directly comparable with other species due to assessment methods. For mussels, relative risk was greatest for Salamander Mussel (Simpsonaias ambigua), Threehorn Wartyback (Obliquaria reflexa), and Hickorynut (Obovaria olivaria). Salamander Mussel and Threehorn Wartyback ranked highly due to exposure and toxicity. A high risk ranking for Hickorynut occurred due to exposure and habitat preference. Mitigation measures to reduce the ecological consequences of Bayluscide applications are numerous and include modifying the frequency and timing of treatments, decreasing the size of application sites, and avoiding areas near critical habitat. However, the effect of potential mitigation measures should be rigorously tested to ensure that desired outcomes for species of conservation concern are realized while avoiding unintended consequences. Lastly, as reduced control effectiveness of Sea Lamprey would have undesirable effects on species of conservation concern susceptible to parasitism by Sea Lamprey (e.g., Lake Sturgeon), optimization measures may be warranted to account for such trade-offs. [ABSTRACT FROM AUTHOR]

Pygmy Whitefish (Prosopium coulterii) was first captured in Lake Superior in 1952. In November 2016, COSEWIC assessed Pygmy Whitefish, Great Lakes-Upper St. Lawrence populations (DU5) as Threatened. The reason given for this designation was that "this small-bodied freshwater fish has experienced dramatic declines in abundance over the last several decades, with an overall estimated decline of 48% since 2000. The continued presence of invasive fishes and recovery of native predatory fishes may threaten or limit recovery, respectively" (COSEWIC 2016). The Recovery Potential Assessment (RPA) provides background information and scientific advice needed to fulfill various requirements of the federal Species at Risk Act. This research document provides the current state of knowledge of the species including its biology, distribution, population trends, habitat requirements, and threats, which will be used to inform recovery plans. A population status assessment indicated that the density of Pygmy Whitefish in Lake Superior has declined since 2013. A threat assessment indicated that the greatest threats to Pygmy Whitefish within DU5 are climate change, invasive species, and pollution; however, the impact of these threats is currently unknown. Predation from top predators such as Lake Trout (Salvelinus namaycush) and Burbot (Lota lota) may be limiting population growth. [ABSTRACT FROM AUTHOR]

Emerging diseases of wildlife are an existential threat to biodiversity, and human-mediated movements of live animals are a primary vector of their spread. Wildlife disease risk analyses offer an appealing alternative to precautionary approaches because they allow for explicit quantification of uncertainties and consideration of tradeoffs. Such considerations become particularly important in high-frequency invasion pathways with hundreds of thousands of individual vectors, where even low pathogen prevalence can lead to substantial risk. The purpose of this study was to examine the landscape-level dynamics of human behavior-mediated pathogen introduction risk in the context of a high-frequency invasion pathway. One such pathway is the use and release of live fish used as bait by recreational anglers. We used a stochastic risk assessment model parameterized by angler survey data from Minnesota, USA, to simulate one year of fishing in Minnesota and estimate the total number of risky trips for each of three pathogens: viral hemorrhagic septicemia virus, the microsporidian parasite Ovipleistophora ovariae , and the Asian fish tapeworm Schizocotyle acheilognathi. We assessed the number of introductions under four scenarios: current/baseline conditions, outbreak conditions (increased pathogen prevalence), source-focused control measures (decreased pathogen prevalence), and angler-focused control measures (decreased rates of release). We found that hundreds of thousands of introduction events can occur per year, even for regulated pathogens at low pathogen prevalence. Reducing the rate of illegal baitfish release had significant impact on risky trips in scenarios where a high number of anglers were involved, but was less impactful in circumstances with limited outbreaks and fewer affected anglers. In contrast, reducing pathogen prevalence in the source populations of baitfish had relatively little impact. In order to make meaningful changes in pathogen introduction risk, managers should focus efforts on containing local outbreaks and reducing illegal baitfish release to reduce pathogen introduction risk. Our study also demonstrates the risk associated with high-frequency invasion pathways and the importance of incorporating human behaviors into wildlife disease models and risk assessments. [ABSTRACT FROM AUTHOR]

Freshwater biodiversity is in a state of crisis. The recent development of a global emergency recovery plan to "bend the curve" for freshwater biodiversity lacks the necessary details for implementation in a regional context. Using Canada as an example, we describe a toolbox intended to equip decision-makers and practitioners with evidence-based tools for addressing threats to freshwater biodiversity. The toolbox includes two rubric-based scoring tools to inform users about the level of the reliability (e.g., transparent methods, critical appraisal) and relevancy to Canadian freshwater systems (e.g., habitat, species) of an evidence synthesis. Those scoring tools were applied to 259 evidence syntheses, also included in the toolbox, across fifty freshwater management actions. Habitat Creation, Invasive Species Removal, and Revegetation were found to have reliable evidence syntheses but there remain several actions for which the syntheses are not robust and where the evidence base is unreliable. We suggest the need for more rigorously conducted empirical tests of freshwater management actions, further evidence synthesis, and clearer conveyance of implications for decision-makers and practitioners. Decision-makers and practitioners should use the two scoring tools on syntheses outside this project and tailor them to their regions. Given the global interest in addressing the freshwater biodiversity crisis and the necessity to engage and empower decision-makers and practitioners on a regional basis, we anticipate this toolbox will serve as a model for regions beyond Canada. Future studies to understand if and how the toolbox is used will be needed to make refinements and ensure it benefits freshwater biodiversity. • Current management of freshwater ecosystems fails to address the global freshwater biodiversity crisis • Evidence syntheses and reviews are a valuable resource to decision-makers and practitioners for informing conservation actions • The toolbox consists of over 250 freshwater management evidence syntheses, scored based on the included appraisal tools • Syntheses demonstrate a poor systematic review conduct but show a strong potential for regional relevance and applicability [ABSTRACT FROM AUTHOR]

Understanding the implications of different management strategies is necessary to identify best conservation trajectories for ecosystems exposed to anthropogenic stressors. For example, science-based risk assessments at large scales are needed to understand efficacy of different vector management approaches aimed at preventing biological invasions associated with commercial shipping. We conducted a landscape-scale analysis to examine the relative invasion risk of ballast water discharges among different shipping pathways (e.g., Transoceanic, Coastal or Domestic), ecosystems (e.g., freshwater, brackish and marine), and timescales (annual and per discharge event) under current and future management regimes. The arrival and survival potential of nonindigenous species (NIS) was estimated based on directional shipping networks and their associated propagule pressure, environmental similarity between donor-recipient ecosystems (based on salinity and temperature), and effects of current and future management strategies (i.e., ballast water exchange and treatment to meet proposed international biological discharge standards). Our findings show that current requirements for ballast water exchange effectively reduce invasion risk to freshwater ecosystems but are less protective of marine ecosystems because of greater environmental mismatch between source (oceanic) and recipient (freshwater) ecoregions. Future requirements for ballast water treatment are expected to reduce risk of zooplankton NIS introductions across ecosystem types but are expected to be less effective in reducing risk of phytoplankton NIS. This large-scale risk assessment across heterogeneous ecosystems represents a major step towards understanding the likelihood of invasion in relation to shipping networks, the relative efficacy of different invasion management regimes and seizing opportunities to reduce the ecological and economic implications of biological invasions. [ABSTRACT FROM AUTHOR]