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Reference: Can.J. Fish.Aquat. Sci. 79(8): 1321-1334. https://doi. org/10.1139/cjfas-2021-0112. In Fig. 3 of the originally published article, sites BC1 and CC1 are highlighted in light grey, indicating they were part of [...]

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. Key words: spotted gar, Lepisosteus oculatus, critical habitat, submerged aquatic vegetation, habitat selection, coastal wetlands, Endangered, Species at Risk Act, Introduction Understanding the habitat requirements of fish species listed under Canada's Species at Risk Act (SARA) is fundamental for their protection and recovery. However, the habitats required by the early [...]

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 [+ or -] standard deviation) were 0.61 [+ or -] 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 [+ or -] 570 eggs) compared with age 1+ fish (576 [+ or -] 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. Key words: spawning, imperilled species, minnows, egg diameter, fecundity length relationship, silver shiner, Notropis photogenis La saison de reproduction est un élément clé du cycle biologique d'une espèce. L'estimation de la fécondité propre à l'espèce peut améliorer les modèles démographiques utilisés pour établir des cibles de rétablissement pour des espèces en péril. Nous présentons des estimations du diamètre des oeufs et de la fécondité et établissons une relation entre la longueur et la fécondité pour le méné-miroir, Notropis photogenis (Cope,1865), une espèce de petit poisson d'eau douce qui figure sur la liste des espèces menacées de la Loi sur les espèces en péril du Canada. Nous documentons en outre l'incidence d'un ver acanthocéphale parasite, Leptorhynchoides thecatus (Linton, 1891), dans le tube gastrointestinal de ménés-miroirs, ce qui constitue la première observation publiée du parasite chez cette espèce. Le diamètre moyen ([+ or -]écart-type) des oeufs de ménés-miroirs est de 0,61 [+ or -] 0,15 mm et la fourchette des valeurs va de 0,13 à 0,92 mm. La fécondité va de 311 à 2768 oeufs et est significativement plus grande chez les poissons de 2-3 ans et plus (1475 [+ or -] 570 oeufs) que chez les poissons d'un an et plus (576 [+ or -] 270 oeufs). Nous soulignons le fait que l'infection par le parasite a un impact négatif sur l'embonpoint des individus et que d'autres travaux sont nécessaires pour déterminer l'impact de l'infestation de parasites sur l'efficacité de la reproduction, le recrutement, la susceptibilité à la prédation et la survie chez le méné-miroir au Canada. Les estimations présentées de la fécondité et du diamètre des oeufs pour des ménés-miroirs canadiens peuvent être intégrées à la modélisation démographique future pour cette espèce menacée. [Traduit par la Rédaction] Mots-clés : frai, espèce en péril, ménés, diamètre des oeufs, relation entre fécondité et longueur, méné-miroir, Notropis photogenis, Introduction Reproduction is a critical component of life history (Winemiller and Rose 1992). Fecundity, in particular, has implications for population dynamics, species persistence, and estimates of minimum viable population size [...]

Freshwater biodiversity is declining from impacts associated with anthropogenic stressors. Here, we use carbon ([[delta].sup.13]C) and nitrogen ([[delta].sup.15]N) 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. La biodiversite d'eau douce est en baisse en raison d'impacts associes a des facteurs de stress d'origine humaine. Nous utilisons les isotopes stables du carbone ([[delta].sup.13]C) et de l'azote ([[delta].sup.15]N) pour evaluer les effets sur les reseaux trophiques a la suite d'un deversement issu d'une mine de charbon qui a deplace des organismes et modifie les caracteristiques biophysiques de cours d'eau. Nous comparons des parametres de la niche isotopique de macroinvertebres benthiques et la communaute de poissons, dont l'omble de fontaine (Salvelinus fontinalis), non indigene, et la truite arc-en-ciel (Oncorhynchus mykiss) de l'Athabasca, une espece menacee, afin d'inferer les variations spatiales d'utilisation des ressources dans differents sites le long d'un gradient de perturbation de l'habitat. La position trophique de macroinvertebres benthiques predateurs est rehaussee la ou les impacts du deversement sont les plus prononces. La contribution du carbone autochtone aux regimes alimentaires de consommateurs est la plus faible chez les organismes preleves du site ayant subi les plus grands impacts du deversement minier, menant a une expansion inattendue de la taille de la niche isotopique de la truite arc-en-ciel et de la communaute d'invertebres aquatiques. Collectivement, nos resultats indiqueraient la presence de variations de l'assimilation des ressources trophiques a differents niveaux du reseau trophique, mues par la voie energetique allochtone dans les sites de l'etude ou les impacts sont grands. Nous concluons que cela reflete une reaction biotique a la modification des ressources aquatiques basales dans la foulee d'une importante perturbation d'origine industrielle. [Traduit par la Redaction], 1. Introduction Multiple environmental stressors such as habitat degradation and invasive species can negatively impact freshwater biodiversity (Dudgeon et al. 2006; Fausch et al. 2010), though the interaction among stressors [...]

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. Si la comprehension des facteurs qui sous-tendent l'etablissement d'especes est d'importance cle pour la gestion de poissons envahissants, les roles de la pression de propagule et des facteurs environnementaux ne sont pas souvent quantifies dans les modeles conjoints. Nous estimons la probabilite d'etablissement de la carpe noire (Mylopharyngodon piceus), une espece envahissante, en examinant l'influence relative de la pression de propagule (taille a l'introduction et structure par age) et de facteurs environnementaux (survie hivernale des jeunes de l'annee modulee par la temperature, survie des adultes, age a la maturite et longevite). Des simulations demontrent que tant la pression de propagule que des facteurs environnementaux peuvent agir comme goulots d'etranglement non lineaires pour l'etablissement. Le modele applique a 12 affluents et secteurs littoraux des Grands Lacs montre que l'etablissement de la carpe noire est probable quand il y a assez de propagules et dans la plupart des conditions environnementales (p median = 0,21-0,73, 0,70-1,00 et 0,46-0,97 pour 100 paires de poissons de 4, 9 et 16 ans, respectivement), sauf pour les jeunes de l'annee (p < 0,01). Notre analyse est une des rares etudes a examiner le role relatif de la pression de propagule et des conditions environnementales sur l'etablissement et elle indique que ces deux facteurs peuvent mener a l'echec de l'etablissement, independamment ou en parallele, dans un ecosysteme donne. [Traduit par la Redaction], Introduction Invasive species continue to pose staggering impacts on ecosystem structure and function (Mollot et al. 2017), raising questions about the circumstances that result in successful invasions. The number of [...]

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 [...]

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. Des programmes de reproduction en captivite sont largement utilises par les specialistes de la conservation comme moyen de conservation, de reintroduction et de supplementation de populations menacees de poissons d'eau douce et de mulettes. Nous avons realise une cartographie systematique pour dresser un portrait du corpus documentaire existant sur l'efficacite des programmes de reproduction en captivite et de lacher. Une des constatations cles est le fait que revaluation de l'efficacite des trois etapes de tels programmes (c.-a-d., prelevement de geniteurs, methodes d'elevage/de lacher et surveillance apres le lacher) est limitee. Nous avons cerne des groupements de donnees probantes pour les evaluations de la supplementation associees aux methodes d'elevage/de lacher pour des parametres relies a la croissance et la survie des poissons, et l'etape de surveillance pour des parametres relies a la diversite genetique, la croissance et la survie des poissons, axes principalement sur les salmonides. Le schema experimental de nombreuses etudes est toutefois inadequat (c.-a-d., absence de comparateur). Globalement, les etudes sur l'efficacite des programmes de reproduction en captivite pour les mulettes menacees sont rares, soulignant la necessite d'assurer une large disponibilite de ce type d'information quand de telles etudes sont realisees. Les extrants de cette cartographie systematique (c.-a-d., la base de donnees en decoulant et les cartes de densite) font ressortir la necessite d'une evaluation systematique plus poussee de l'efficacite de programmes de reproduction en captivite et de lacher. [Traduit par la Redaction], Introduction Global freshwater biodiversity has declined by over 80% since the 1970s, to the point where it is clearly in crisis (Harrison et al. 2018). Freshwater fishes have some of [...]

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 [...]

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. Si l'utilisation de deplacements pour retablir des populations necessite un nombre suffisamment grand d'individus de populations sources, le retrait de trop d'individus peut mener a l'effondrement de ces populations. Pour comprendre le compromis entre les probabilites de disparition de populations sources et le succes du deplacement, des modeles demographiques matriciels qui integrent des effets Allee, la dependance a la densite et une stochasticite demographique et environnementale ont ete combines a un modele qui simule des retraits de populations sources. Nous appliquons ces modeles a des scenarios de deplacement de dards de sable (Ammocrypta pellucida; etat de la Loi sur les especes en peril: menaces) au Canada. Les resultats donnent a penser que les deplacements necessitent le plus souvent des populations sources de plus de 20 000 individus, puisque la probabilite de disparition d'une population source augmente parallelement au nombre et a la frequence des retraits. La mortalite liee au transport ou les pertes immediatement apres l'introduction ont egalement une incidence sur le succes du deplacement. L'incertitude entourant des parametres du cycle biologique et la force d'effets Allee accroissent l'incertitude associee a la taille requise des populations sources. Bien que des processus stochastiques aient une incidence sur la probabilite de succes du deplacement, des facteurs comme la densite et la frequence d'ensemencement peuvent etre controles, de sorte que le deplacement pourrait etre une strategie viable pour le retablissement du dard de sable, meme si des seuils prudents sont appliques pour contrer l'effet de l'incertitude. [Traduit par la Redaction], Introduction The number of species that are currently at heightened risk of extinction continues to rise (Chapin et al. 2000; Rockstrom et al. 2009). Reversing this trend requires rigorous evaluation [...]

In data-poor regions, modeled river temperatures are essential for predicting potential stressors for species at risk. With limited data from the Grand, Thames, and Sydenham rivers in southern Ontario, Canada, we evaluated simple mixed-effect regression models to predict water temperature using air temperature from nearby weather stations. Model performance was assessed for periods relevant to the fitness of the black redhorse (Moxostoma duquesni): June to August, when heat events may be likely; and May, when spawning occurs. All of the models performed better when trained on data from these periods, compared with using data from the entire growing season. The best model was a linear regression using 5 days of lagged air temperature. This model had a root mean square error for summer means of 1.5[degrees]C. The differences in prediction error at different times of year highlight the importance of considering species ecology in model interpretation. However, the improvement in model fit when using only data from the relevant time of year suggests that relatively simple models can be used effectively in a management arena when applied appropriately. Dans les regions pour lesquelles peu de donnees sont disponibles, les temperatures modelisees des rivieres sont d'importance fondamentale pour la prediction de facteurs de stress potentiels pour les especes en peril. A partir de donnees limitees pour les rivieres Grand, Thames et Sydenham, dans le sud de l'Ontario (Canada), nous avons evalue des modeles de regression a effets mixtes simples pour la prediction des temperatures de l'eau a partir de temperatures de l'air mesurees a des stations meteorologiques a proximite. La performance des modeles a ete evaluee pour des periodes importantes pour l'aptitude du chevalier noir (Moxostoma duquesnii), soit de juin a aout, quand des episodes de chaleur sont probables, et en mai, quand le frai a lieu. Tous les modeles ont donne de meilleurs resultats quand ils etaient prealablement entraines avec des donnees pour ces periodes que lorsque des donnees pour toute la saison de croissance etaient utilisees. Le meilleur modele est une regression lineaire integrant cinq jours de donnees de temperatures de l'air decalees (ecart-type moyen estival 1,5[degrees]C). Les differentes erreurs de prevision a differents moments de l'annee soulignent l'importance de tenir compte de l'ecologie de l'espece pour l'interpretation des modeles. L'amelioration du calage sur les modeles que produit l'utilisation de donnees seulement pour les periodes importantes de l'annee donne cependant a penser que, s'ils sont bien appliques, des modeles relativement simples peuvent etre utilises efficacement en gestion. [Traduit par la Redaction], Introduction Water temperature is one of the primary factors that determine the survival, growth, and reproduction of aquatic organisms in flowing systems (Wismer and Christie 1987; Caissie 2006; Hasnain et [...]

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 [...]

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. Nous faisons des projections sur les effets de la combinaison de l'evolution de la population humaine (de 2018 a 2046) et des cas d'etablissement d'espece aquatique envahissante (EAE) de carpes a grosse tete (Hypophthalmichthys spp.) et d'amours blancs (Ctenopharyngodon idella) sur l'activite de peche sportive canadienne pour les Grands Lacs laurentiens. Il est predit que l'evolution de la population humaine aura une plus grande incidence sur le nombre total d'excursions de peche (augmentation d'environ 143 000 excursions ou 11,4 %) que n'importe quel etablissement d'EAE (diminution maximum d'environ 44 000 excursions ou 3,5 %). Cependant, l'augmentation projetee de 11,4 % du nombre d'excursions de peche decoulant de l'evolution de la population humaine ne suit pas l'augmentation projetee de 38 % de la population de l'Ontario (Canada) de 2018 a 2046. L'urbanisation accrue et le vieillissement de la population, qui sont associes a des baisses des taux de participation a la peche, expliquent cet ecart. Les effets combines de l'evolution de la population humaine et de l'etablissement d'EAE illustrent l'importance de tenir compte de l'evolution de la population humaine, puisqu'elle inverse les conclusions et se traduit en une augmentation nette projetee de l'ordre de 92 000 a 125 000 du nombre d'excursions de peche. Le modele combine permet aussi de cerner des secteurs de croissance potentielle de la peche, comme la peche a terre par des citadins dans la partie ouest du lac Ontario. [Traduit par la Redaction], Introduction Recreational fisheries are defined and influenced by aquatic resources and people. While researchers frequently examine how changes to aquatic resources affect outcomes for recreational fisheries, much less attention is [...]

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]

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. Les ecosystemes d'eau douce figurent parmi les milieux les plus menaces sur terre. Les perturbations dans le paysage terrestre sont amplifiees dans les ecosystemes d'eau douce et, combinees a des facteurs de stress d'ampleur planetaire comme les changements climatiques et les especes envahissantes, creent une situation complexe pour le retablissement d'especes de poissons menacees. Au vu du declin dramatique des poissons d'eau douce a l'echelle planetaire, leur conservation et leur retablissement necessitent des efforts tout aussi extremes, et le rapatriement constitue une approche possible. Le rapatriement designe l'action de relacher une espece dans des regions dont elle a ete extirpee. Paradoxalement, les introductions de poissons a des fins recreatives existent depuis longtemps, mais les exemples de rapatriement d'especes de poissons en peril sont relativement rares comparativement a celui d'especes terrestres. A la lumiere de la documentation sur la restauration et l'introduction d'especes, nous cernons cinq themes ecologiques a examiner dans l'evaluation du potentiel de rapatriement de poissons d'eau douce et suggerons que le rapatriement constitue l'approche << extreme >> necessaire pour atteindre des objectifs de conservation significatifs. [Traduit par la Redaction], Introduction Species repatriation involves the intentional return or release of a species within its native range at locations where it has previously been extirpated and therefore represents one of several [...]

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. Key words: stable isotopes, endangered species, species conservation, niche overlap, trophic niche, eastern sand darter, Ammocrypta pellucida. Si la specificite des niches peut predisposer des populations de certaines especes a diminuer durant des periodes de restriction des ressources, la specificite des niches trophiques de nombreux petits poissons d'eau douce demeure meconnue. Nous employons une approche a deux volets comprenant l'analyse des contenus stomacaux et l'analyse d'isotopes stables pour examiner le regime alimentaire et la niche trophique du dard de sables (Ammocrypta pellucida (Putnam, 1863)), une espece menacee, et de poissons cooccurrents dans la riviere Thames, en Ontario (Canada). A l'instar d'etudes anterieures, l'analyse des contenus stomacaux revele que le dard de sables consomme une gamme variee d'organismes benthiques, dont des chironomides, cladoceres, ostracodes, oligochetes et ephemeropteres; cependant, la contribution relative de differents groupes de proies, etablie a la lumiere de l'analyse d'isotopes stables, n'est pas la meme, faisant ressortir la possibilite de variations saisonnieres de la consommation de proies. Malgre des indices d'une strategie generaliste, l'analyse d'isotopes stables indique que le dard de sables a une niche trophique relativement etroite comparativement a celles de poissons cooccurrents. Le chevauchement des niches trophiques est relativement faible entre le dard de sables et des poissons s'alimentant a la derive (mene bleu (Cyprinella spiloptera (Cope, 1867)), mene emeraude (Notropis atherinoides Rafinesque, 1818) et buffalos (genre Ictiobus Rafinesque, 1820)), mais plus evident entre le dard de sables et des poissons benthiques et benthopelagiques (raseux-de-terre noir (Etheostoma nigrum Rafinesque, 1820) et dard noir (Percina maculata (Girard, 1859))), ce qui indique une plus grande probabilite de concurrence avec ces especes durant des periodes de rarete des proies. [Traduit par la Redaction] Mots-cles : isotopes stables, espece en voie de disparition, conservation des especes, chevauchement de niches, niche trophique, dard de sables, Ammocrypta pellucida., Introduction Species diversity is influenced at local scales by factors such as habitat disturbance, resource availability, and competitive and predatory interactions, which interact to dictate the long-term trajectory of individual [...]

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. Pendant plus de deux decennies, la Commission des pecheries des Grands Lacs tente de cerner des approches pour complementer et potentiellement remplacer l'utilisation de barrieres et de lampricides pour lutter contre les lamproies (Petromyzon marinus) dans les Grands Lacs, mais sans succes a ce jour. L'article se penche sur le potentiel des technologies genetiques modernes pour la suppression de ces populations envahissantes. Nous avons cerne six options de recombinaison dont la faisabilite semble moderee a grande, dont un panel d'experts a estime que la plupart presentaient un risque extremement faible a faible, et pour lesquelles la recherche et developpement est largement appuyee par des parties prenantes. Les deux options qui combineraient le mieux une haute efficacite et de faibles risques sont une approche mendelienne de manipulation du rapport de masculinite et la modification genetique d'une espece proie combinee a l'elimination ou la sterilisation des lamproies qui s'en nourrissent. Les principaux enjeux concernant l'utilisation de mesures de lutte genetiques dans les Grands Lacs comprennent des problemes techniques associes au maintien d'une lignee de lamproies reproductrices, des connaissances manquantes sur la plupart des options, l'ampleur du soutien au sein du grand public et l'etendue et la nature des consultations nationales et internationales necessaires a la prise de decisions concernant les options de lutte antiparasitaire., Introduction The sea lamprey (Petromyzon marinus) is one of the world's most destructive environmental species. After invading the upper Laurentian Great Lakes (GL) in the 1930s, the sea lamprey destroyed [...]

Redside dace (Clinostomus elongatus) captured in a Lake Huron (Canada) tributary. Redside dace was recently listed as Endangered under Canada's Species at Risk Act (photo credit: Robin Gaspardy, Fisheries and [...]

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]