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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. La comprehension des roles relatifs des processus historiques, environnementaux et d'origine humaine qui soustendent les motifs spatiaux de biodiversite revet une importance cruciale pour la prediction des impacts des changements environnementaux planetaires. Nous quantifions les roles relatifs de ces facteurs en ce qui concerne leur influence sur la richesse specifique des poissons d'eau douce indigenes, non indigenes, en peril, ainsi que de l'ensemble des poissons d'eau douce dans 985 bassins versants tertiaires au Canada, en tenant compte des correlations entre descripteurs et de l'autocorrelation spatiale. Nos constatations revelent que les facteurs qui influencent les motifs de richesse varient selon la categorie d'especes. Des facteurs environnementaux associes a la disponibilite d'energie et des facteurs historiques associes a la recolonisation postglaciaire ont joue un role dans la modulation des variations spatiales de la richesse des especes indigenes, alors que les variations de la richesse des especes non indigenes sont en bonne partie associees a des activites humaines qui accroissent la pression de propagule et la perturbation d'habitats, qui sont plus grandes pour les especes non indigenes au Canada que pour les especes indigenes deplacees. Les processus d'origine humaine et les conditions ambiantes s'averent d'importants determinants de la richesse d'especes en peril. L'etude souligne l'importance d'une approche integree qui tient compte simultanement des processus naturels et d'origine humaine pour une meilleure prediction des variations de la biodiversite des poissons a l'echelle du paysage. [Traduit par la Redaction], Introduction Understanding the processes underlying the spatial variation in biodiversity is a central pursuit in macroecology (Ricklefs 2004). Historical, environmental, and anthropogenic processes are known to influence the taxonomic diversity [...]

Effective conservation requires that species recovery measures are informed by rigorous scientific research. For imperilled freshwater fishes and mussels in Canada, numerous research gaps exist, in part owing to the need for specialized research methods. The Canadian Freshwater Species at Risk Research Network (SARNET) was formed and identified or implemented approaches to address current research gaps, including (1) captive experimental research populations, (2) nonlethal methods for estimating abundance and distribution, (3) nonlethal field methods to measure life-history parameters, (4) species distribution models informed by co-occurring species, (5) conservation physiology to inform habitat and threat science, (6) evidence syntheses to evaluate threats and recovery measures, (7) disease-transmission models to understand mussel-host relationships, (8) experimental mesocosms and manipulative experiments to evaluate key habitat stressors, (9) threat and hazard models for predictive applications, and (10) rigorous evaluation of surrogate species. Over a dozen threat- and recovery-focused SARNET research applications are summarized, demonstrating the value of a coordinated research program between academics and government to advance scientific research on, and to support the recovery of, imperilled freshwater species. Des mesures de retablissement reposant sur des travaux de recherche scientifique rigoureux sont necessaires a une conservation efficace. Pour les especes de poissons d'eau douce et mulettes en peril au Canada, il existe de nombreuses lacunes dans la recherche, dues partiellement a la necessite de methodes de recherche specialisees. Le reseau canadien de recherche sur les especes d'eau douce en peril (SARNET) a ete cree et il a cerne ou applique differentes approches visant a combler ces lacunes, dont les suivantes : (1) des populations experimentales captives de recherche, (2) des methodes non letales d'estimation de l'abondance et de la repartition, (3) des methodes de terrain non letales de mesure de parametres du cycle biologique, (4) des modeles de repartition des especes integrant des donnees sur les especes cooccurrentes, (5) la physiologie de la conservation pour soutenir les travaux scientifiques sur les habitats et les menaces, (6) des syntheses de donnees probantes pour evaluer les menaces et measures de retablissement, (7) des modeles de transmission des maladies pour comprendre les relations mulettes-hotes, (8) des mesocosmes experimentaux et des experiences de manipulation pour evaluer des facteurs de stress cles des habitats, (9) des modeles de menaces et de dangers pour des applications predictives et (10) Revaluation rigoureuse d'especes substitutives. Un resume de plus d'une douzaine d'applications des travaux de recherche du SARNET axees sur les menaces et le retablissement est presente, qui demontre l'utilite d'un programme de recherche au sein duquel les travaux de chercheurs universitaires et gouvernementaux sont coordonnes afin de faire avancer la recherche scientifique sur les especes d'eau douce en peril et soutenir leur retablissement. [Traduit par la Redaction], Introduction An important goal of conservation biology is to prevent species extinctions caused by human activity (Soule 1985). When populations decline and become imperilled, various recovery measures are often enacted [...]

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 (C[T.sub.max]) among three lineages (western, central, eastern) of imperilled redside dace (Clinostomus elongatus). C[T.sub.max] of eastern adults was 3-4[degrees]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 C[T.sub.max] 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. Si la reintroduction est un outil de conservation de plus en plus utilise pour soutenir le retablissement de populations d'especes menacees, il faut, pour assurer son succes, que le phenotype des animaux introduits convienne a leur nouvel habitat. Pour les poissons, la tolerance a la chaleur pourrait etre un caractere cle dans les habitats urbanises. Nous avons compare la tolerance a la chaleur (C[T.sub.max]) de trois lignees (de l'Ouest, centrale et de l'Est) de menes longs (Clinostomus elongatus), une espece menacee. La C[T.sub.max] d'adultes de l'Est est de 3-4[degrees]C plus basse que celle des autres lignees, mais les adultes des trois lignees presentent des reactions d'acclimatation thermique semblables. En revanche, une difference de ~80 % est relevee entre les reactions d'acclimatation des juveniles des lignees centrale et de l'Ouest. En utilisant ces donnees, nous predisons comment chacune des lignees repondrait a la reintroduction hypothetique dans des habitats urbanises relativement chauds. En raison des differences de reaction d'acclimatation des juveniles, les marges de securite thermique predites pour la lignee centrale sont deux fois plus grandes que les marges predites pour la lignee de l'Ouest. Globalement, nous suggerons que la C[T.sub.max] est un caractere important a incorporer au processus de selection de populations sources; toutefois, il existe un besoin urgent d'etablir des populations de recherche experimentale en captivite d'especes menacees pour etudier les sources d'incertitude qui demeurent. [Traduit par la Redaction], Introduction Fisheries management has a long history of using translocations (moving wild fish from one place to another) and captive breeding programs to augment and expand natural populations of commercially [...]

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. Il importe de comprendre les exigences d'habitat au niveau de la population pour la conservation efficace d'especes en peril, en particulier celles dont les aires de repartition sont fragmentees. L'etude se penche sur la repartition a echelle fine d'une espece menacee, le mene camus (Notropis anogenus), dans le cours superieur du fleuve Saint-Laurent en Ontario (Canada). La modelisation de l'occupation, des analyses multivariees et la modelisation de la cooccurrence ont ete utilisees pour cerner les variables environnementales correlees a la repartition et aux associations d'especes des menes camus dans une echancrure, la baie de Thompson. L'abondance de menes camus est la plus elevee dans des sites de la partie externe de la baie, ou l'eau est plus froide, moins turbide et de pH plus eleve et ou la vegetation aquatique immergee est plus abondante que dans les sites de l'interieur de la baie. La probabilite d'occupation par des menes camus augmente avec la distance par rapport a l'interieur de la baie et avec la presence de Chara vulgaris, et diminue quand la conductivite augmente. L'etude revele une cooccurrence positive de menes camus avec sept especes, dont le menton noir et le museau noir, et une cooccurrence negative avec le crapet arlequin. Des especes de centrarchides sont dominantes a la grandeur de la baie de Thompson, une observation importante pour la conservation puisque l'abondance de certains predateurs centrarchides indigenes connait une augmentation coincidant avec les changements climatiques, ce qui pourrait menacer la persistance des cyprinides rares et en peril comme le mene camus. [Traduit par la Redaction], Introduction Understanding distribution and habitat use across multiple scales is essential for the conservation of imperilled species (Purvis et al. 2005; Razgour et al. 2011). This is, in part, because [...]

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. La quantification des reactions d'especes vulnerables rares a des agents de stress ambiants presente des defis particuliers. L'objectif de l'etude etait de comprendre les reactions de poissons vulnerables designes en vertu de la Loi sur les especes en peril a des agents de stress ambiants dans des lacs, cours d'eau et milieux humides du bassin des Grands Lacs canadiens. Nous avons utilise un modele de repartition conjointe d'especes (MRCE) afin d'ameliorer les estimations des reactions d'especes vulnerables a des agents de stress ambiants et les effets de caracteres fonctionnels sur ces reactions, en << empruntant de l'information >> sur des especes abondantes pour lesquelles la quantite d'information est plus grande. Nous avons mesure l'abondance, des caracteres fonctionnels et des relations taxonomiques pour 115 especes de poissons d'eau douce, dont 12 especes vulnerables, ainsi que des elements du milieu ambiant dans 1972 sites. Le MRCE produit des estimations plus precises de reactions que des modeles a espece unique cales sur les donnees de chaque espece vulnerable. Les associations d'habitat inferees a partir des resultats du MRCE montrent un important chevauchement avec les associations fournies par les rapports de situation du COSEPAC. Les reactions derivees du modele a des agents de stress ambiants peuvent constituer une base utile aux gestionnaires pour la classification d'especes selon leur tolerance a differentes formes de changement ambiant et complementer les criteres qualitatifs concernant les exigences en matiere d'habitat actuellement utilises dans les evaluations de la vulnerabilite d'especes. [Traduit par la Redaction], Introduction Anthropogenic changes to the environment are a major threat to aquatic species worldwide (Darwall and Freyhof 2016; Myers et al. 2017; Reid et al. 2019). In the Canadian Great [...]

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 (C[T.sub.max]), while the agitation temperature ([T.sub.ag]) was 3.4[degrees]C lower than the C[T.sub.max]. 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. C[T.sub.max] was lower when measured under 40% for normoxia-acclimated fish but not for hypoxia-acclimated fish. Hypoxia-acclimated fish had higher [T.sub.ag] 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. Pour les poissons d'eau douce, des temperatures elevees de l'eau associees au rechauffement climatique et l'hypoxie peuvent se produire simultanement et sont susceptibles d'interagir, puisque les deux phenomenes ont une incidence sur le metabolisme oxydatif. Nous avons quantifie les effets de l'acclimatation a des temperatures elevees et a l'hypoxie sur la tolerance thermique du mene camus (Notropis anogenus), un cyprinide menace dans son aire de repartition canadienne. Dans une experience, des menes camus ont ete assujettis a des acclimatations sequentielles de deux semaines a six temperatures de plus en plus elevees. La temperature maximum critique (C[T.sub.max]) des poissons acclimates a des eaux plus chaudes a augmente, alors que la temperature d'agitation ([T.sub.ag]) etait de 3,4[degrees]C inferieure a la C[T.sub.max]. Dans une autre experience, des poissons ont ete acclimates a trois traitements d'oxygene dissous (saturations en air de >95, ~56 ou ~40 %) pendant deux semaines, puis evalues dans des conditions de saturation en air de >95 % et 40 %. La C[T.sub.max] mesuree a une saturation en air de 40 % etait plus faible pour les poissons acclimates a la normoxie, mais non pour les poissons acclimates a l'hypoxie. Ces derniers presentaient une [T.sub.ag] plus elevee et des fenetres d'agitation plus petites que les poissons acclimates a la normoxie, donnant a penser que l'acclimatation a l'hypoxie ameliore certains aspects de la tolerance thermique. Nous examinons la plasticite de la tolerance thermique des menes camus et demontrons qu'ils pourraient etre plus vulnerables aux temperatures elevees que d'autres especes de Notropis non en peril. [Traduit par la Redaction], Introduction Freshwater organisms face multiple threats associated with land conversion, influx of pollutants and contaminants, hypoxia, overharvesting, and species invasions (Dudgeon et al. 2006; Strayer and Dudgeon 2010; Hermoso 2017). [...]

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. Plus de 15 annees se sont ecoulees depuis la promulgation de la Loi sur les especes en peril du Canada. Afin d'evaluer les avancees scientifiques a l'appui de la loi, nous avons recense les realisations en recherche jusqu'en 2017 touchant aux especes aquatiques menacees dans le bassin des Grands Lacs et du fleuve Saint-Laurent a la lumiere de documents concernant le retablissement et d'un sondage aupres de specialistes qui couvrent 1182 activites portant sur 68 sujets de recherche visant 45 especes de poissons et de moules. Les plus grandes avancees sont observees dans les domaines de l'ecologie des populations (38 % des activites presentant des avancees majeures) et de la science des habitats (28 %), relativement moins d'avancees etant observees dans les domaines des menaces (mecanismes et impacts, 19 %) et du retablissement (attenuation des menaces et reintroduction, 21 %). Au vu du retard au plan des avancees, les themes des menaces et de la reintroduction ont ete priorises pour un reseau canadien de recherche sur les especes d'eau douce en peril (SARNET, 2017-2020), dont les travaux ont mis l'accent sur d'importantes lacunes dans les connaissances offrant de nouvelles applications. Le present numero special offre un aperqu des projets du SARNET, qui portent sur un eventail d'activites analytiques, de terrain et de laboratoire originales. Un investissement soutenu en recherche sur des approches nouvelles et existantes est necessaire a la poursuite d'avancees scientifiques concernant les poissons et les moules, a l'appui de la Loi sur les especes en peril au Canada. [Traduit par la Redaction], Introduction The United Nations Convention on Biological Diversity (CBD) was established in 1992 to recognize the profound value of protecting biodiversity. The global response to the CBD was substantial, with [...]

The integration of invasive species into native communities may result in the destabilization of food webs through predation of native prey and competition with native predators. These negative effects are likely to be exacerbated by climate change, increasing the frequency of heat waves, droughts, and high-flow events. Invasive Round Goby (Neogobius melanostomus) and native White Sucker (Catostomus commersonii) were collected from the wild and acclimated to a range of temperatures expected to capture increases in temperature under climate change. In the laboratory, we measured the effects of temperature (19, 22, 25, and 28°C) and velocity gradients (0, 0.15, 0.3, 0.6 m/s at 22 and 25°C) on the prey consumption and foraging behavior of each species. We found that the prey consumption and number of attacks (lunges at prey) of both species increased with temperature but were consistently higher in Round Goby. Velocity had an interactive effect with temperature for prey consumption and foraging behavior, where generally, velocity tolerance for both species was higher at 22°C than at 25°C. White Sucker tolerance to velocity was higher than Round Goby, suggesting that systems with higher velocities may provide a competitive advantage in high-flow environments. Our results stress the importance of interactive experiments when examining the impact of invasive species on native competitors under shifting climatic conditions. [ABSTRACT FROM AUTHOR]

Intraspecific functional variation is critical for adaptation to rapidly changing environments. For visual opsins, functional variation can be characterized in vitro and often reflects a species' ecological niche but is rarely considered in the context of intraspecific variation or the impact of recent environmental changes on species of cultural or commercial significance. Investigation of adaptation in postglacial lakes can provide key insight into how rapid environmental changes impact functional evolution. Here, we report evidence for molecular adaptation in vision in 2 lineages of Nearctic fishes that are deep lake specialists: ciscoes and deepwater sculpin. We found depth-related variation in the dim-light visual pigment rhodopsin that evolved convergently in these 2 lineages. In vitro characterization of spectral sensitivity of the convergent deepwater rhodopsin alleles revealed blue-shifts compared with other more widely distributed alleles. These blue-shifted rhodopsin alleles were only observed in deep clear postglacial lakes with underwater visual environments enriched in blue light. This provides evidence of remarkably rapid and convergent visual adaptation and intraspecific functional variation in rhodopsin. Intraspecific functional variation has important implications for conservation, and these fishes are of conservation concern and great cultural, commercial, and nutritional importance to Indigenous communities. We collaborated with the Saugeen Ojibway Nation to develop and test a metabarcoding approach that we show is efficient and accurate in recovering the ecological distribution of functionally relevant variation in rhodopsin. Our approach bridges experimental analyses of protein function and genetics-based tools used in large-scale surveys to better understand the ecological extent of adaptive functional variation. [ABSTRACT FROM AUTHOR]

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]

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]

Invasive grass carp (Ctenopharyngodon idella) are known to spawn in the Sandusky River, Ohio, USA, within the Great Lakes Basin, and are threatening to expand throughout the Great Lakes. Successful spawning is thought to require that eggs remain in suspension until hatching, which depends on river hydrodynamics and temperature-dependent egg development. Previous modelling efforts used one-dimensional hydrodynamic models that simplify egg movement by not simulating low- velocity zones within the river. To examine the effect of low-velocity zones on egg transit times and hatching rates, we developed a novel coupling of a biophysical Lagrangian particle tracker and three-dimensional hydrodynamic model on the Sandusky River during a high-flow event. The model successfully predicted egg-capture data for a range of developmental stages and revealed a mechanism that resuspends eggs trapped in low-velocity zones. The resuspension mechanism increases the residence time of grass carp eggs in spawning tributaries and can lead to successful hatching occurring in shorter distances than previously estimated. Grass carp potentially spawning in shorter tributary lengths has widespread implications for efforts preventing establishment in the Great Lakes Basin. Il est etabli que l'amour blanc (Ctenopharyngodon idella), une espece envahissante, fraye dans la riviere Sandusky (Ohio, Etats-Unis), dans le bassin des Grands Lacs, menaqant de s'etendre a la grandeur des Grands Lacs. La reussite du frai necessiterait que les reufs demeurent en suspension jusqu'a l'eclosion, ce qui depend de l'hydrodynamique de la riviere et du developpement dependant de la temperature des reufs. Des efforts de modelisation passes ont utilise des modeles hydrodynamiques unidimensionnels pour simplifier les deplacements des reufs, ne simulant pas les zones de faible vitesse du courant dans la riviere. Pour examiner l'effet des zones de faible vitesse sur le temps de transit et les taux d'eclosion des reufs, le jumelage novateur d'un dispositif biophysique de poursuite de particules lagrangien et un modele hydrodynamique tridimensionnel a ete mis au point pour examiner la riviere Sandusky durant un episode de crue. Le modele a predit avec succes les donnees de capture d'reufs pour differentes etapes du developpement et a revele un mecanisme de remise en suspension des reufs pieges dans des zones de faible vitesse. Ce mecanisme accroit le temps de residence des reufs d'amour blanc dans les affluents de frai et peut se traduire par une eclosion reussie sur de plus courtes distances que ce qui etait estime auparavant. La possibilite que des amours blancs puissent frayer avec succes dans de plus courts tronqons d'affluent a d'importantes consequences pour les efforts visant a prevenir l'etablissement de cette espece dans le bassin des Grands Lacs. [Traduit par la Redaction], Introduction Grass carp (Ctenopharyngodon idella) are an invasive species that could substantially affect the Laurentian Great Lakes, both ecologically and economically (Cudmore et al. 2017; Hayder 2019). Native to eastern [...]

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]

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. Key words: fish, biodiversity, freshwater, Cyprinidae, Centrarchidae, invasive species, climate change, land use. La perte de biodiversite constitue un enjeu important en ce qui concerne les poissons d'eau douce en climat tempéré, et plus d'information sur cette question est requise. Une étude a été menée afin d'évaluer les modifications des communautés de poissons dans la zone littorale de 22 lacs sur une période de 45 ans (entre les années 1969-1979 et l'année 2014). Pour comparer les communautés de poissons, les registres de pêche à la senne ont ete compilés pour 22 lacs intérieurs et comparés à des données modernes recueillies en utilisant le même protocole. Les données d'abondance des poissons analysées par une approche multivariée reflètent la transition de communautés où dominent les cyprinidés à des communautés où dominent les centrar-chidés entre les deux périodes. Si aucune donnée n'appuie la possibilité d'une forte influence d'espèces envahissantes sur ces communautés, des changements significatifs de la température et de l'utilisation des sols autour de ces lacs ont eu lieu depuis que les données historiques ont été recueillies. L'étude constitue une contribution importante à la comprehension des variations de la biodiversité dans les communautés de poissons d'eau douce d'Amérique du Nord qui pourrait influencer les approches futures de gestion des pêches. [Traduit par la Rédaction] Mots-clés: poisson, biodiversité, eau douce, cyprinidés, centrarchidés, espèces envahissantes, changement climatique, utilisation des sols., Introduction Freshwater ecosystems are among the most ecologically threatened on the planet (Abell et al. 2008). There is evidence that North America's freshwater species are disappearing at a faster rate [...]

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]

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]

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]

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. La tanche (Tinca tinca), un poisson envahissant a l'echelle planetaire, se propage dans le fleuve Saint-Laurent et presente une menace imminente d'envahissement pour les Grands Lacs. Dans la foulee de son lacher illegal dans un affluent du Saint-Laurent en 1991, la tanche s'est repandue a la grandeur du bras principal du fleuve au cours de la derniere decennie, et son abondance dans les prises accessoires de peches commerciales a connu une augmentation exponentielle. La tanche est un consommateur benthique generaliste dont les impacts ecologiques en Amerique du Nord demeurent largement non documentes. Des rapports provenant d'autres regions envahies indiquent qu'elle peut faire concurrence a d'autres poissons benthiques, est l'hote d'un assemblage varie de parasites et de pathogenes, cause la deterioration de la clarte de l'eau dans les lacs peu profonds, limite la croissance des macrophytes submerges, reduit les populations de gasteropodes et favorise la croissance d'algues benthiques par le biais d'effets descendants. Les evaluations du risque et les modeles climatiques indiquent que les Grands Lacs sont vulnerables a l'envahissement par la tanche et font ressortir la necessite de mettre rapidement en place des mesures exhaustives, dont l'elaboration et l'application de protocoles de surveillance et d'intervention rapide incluant la prevention ou le ralentissement de la dispersion naturelle a travers les canaux. [Traduit par la Redaction], Introduction The Great Lakes have been invaded by at least 188 non-native species (Ricciardi 2006; A. Ricciardi, unpublished data), including 28 fishes (Mandrak and Cudmore 2010). These introductions have affected [...]

A better understanding of how human activities affect biodiversity can be important for effective resource management. We tested how excavation (maintenance) of agricultural drains (ditches) altered fish assemblages. Uncertainty regarding the effects of drain maintenance on fish assemblages has been a source of tension between landowners, drain superintendents, and fishery managers. Fish assemblages in eight southwestern Ontario drains were sampled repeatedly from before to 2 years after drain maintenance using a replicated before-after, control-impact (BACI) design. Relative to reference sites, we found no evidence for short- or long-term decreases in the number of species and total abundance of fishes following drain maintenance, nor any consistent change in assemblage composition, despite clear changes in physical habitat. The fish assemblages in drains were resilient to drain maintenance and did not show changes expected to concern fishery managers. Our findings provide fishery managers with the information needed to manage drain maintenance more effectively under the Fish Protection Program of the Fisheries Act and to develop drain maintenance practices that balance the needs of agriculture with the protection of fish biodiversity. Une meilleure comprehension de l'incidence de l'activite humaine sur la biodiversite peut etre importante pour une gestion efficace des ressources. Nous avons verifie comment l'excavation (entretien) de drains agricoles (fosses) modifie les assemblages de poissons. L'incertitude quant aux effets de l'entretien des drains sur les assemblages de poissons constitue une source de tension entre les proprietaries fonciers, les gestionnaires des drains et les gestionnaires des peches. Les assemblages de poissons dans huit drains du sud de l'Ontario ont ete echantillonnes a repetition avant leur entretien et jusqu'a deux ans apres ce dernier selon un schema avant-apres, temoin-intervention (<>). Par rapport aux emplacements de reference, nous n'avons observe aucun indice de baisse a court ou long terme du nombre d'especes ou de l'abondance totale de poissons apres l'entretien des drains, ni aucun changement coherent de la composition des assemblages, malgre des modifications tres nettes de l'habitat physique. Les assemblages de poissons dans les drains etaient resilients a l'entretien de ces derniers et ne presentaient pas de changements susceptibles de preoccuper les gestionnaires des peches. Nos constatations fournissent a ces derniers des renseignements necessaries pour gerer l'entretien des drains plus efficacement dans le cadre du programme de protection des poissons de la Loi sur les peches et pour elaborer des pratiques d'entretien des drains qui visent un equilibre entre les besoins des agriculteurs et la protection de la biodiversite de poissons. [Traduit par la Redaction], Introduction Scientists are being pressed to provide information on the ability of ecosystems to resist and recover from change caused by human actions. Truly wild ecosystems are largely nonexistent, and [...]

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. Les milieux humides sont de plus en plus menaces en raison de l'activite humaine. Dans les Grands Lacs laurentiens, les milieux humides littoraux fournissent des habitats essentiels pour de nombreux poissons. Par consequent, des approches d'echantillonnage efficientes des poissons de milieux humides sont necessaires pour en assurer une gestion efficace. Nous avons employe une strategie d'echantillonnage repete a l'aide d'une seine pour prelever des poissons de sept milieux humides. L'ensemble de donnees a ete utilise pour formuler des conseils pour optimiser l'echantillonnage des poissons de milieux humides. Pour atteindre la richesse visee, plus l'intensite de l'echantillonnage est forte, plus le nombre requis de sites d'echantillonnage est faible; moitie moins de sites etaient requis quand trois traits de seine etaient realises par site plutot qu'un seul. En moyenne, 97 sites a un trait etaient necessaires pour detecter 90 % des especes, comparativement a seulement 47 sites a trois traits. Il est predit que l'effort d'echantillonnage doit etre plus grand dans les zones comptant plus d'especes et des milieux humides plus grands. Le nombre d'individus et de sites necessaires pour detecter 90 % des especes augmentait de maniere exponentielle quand la richesse specifique augmentait, et le nombre d'individus necessaires etait positivement relie a la superficie des milieux humides. L'utilisation de filets d'isolement n'ameliorait pas la detection d'especes ni n'avait d'incidence sur leur composition. [Traduit par la Redaction], Introduction Wetlands are valuable ecosystems because of provisions and services that they provide for humans, such as flood control, purifying and storing water, groundwater discharge, carbon sequestration, and recreational opportunities [...]