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Population assessments of fish species often rely on data from surveys with different objectives, such as measuring biodiversity or community dynamics. These surveys often contain spatial-temporal dependencies that can greatly influence conclusions drawn from analyses. Pygmy whitefish (PWF, Prosopium coulterii) populations in Lake Superior were recently assessed as Threatened by the Committee on the Status of Endangered Species in Canada, which motivated a thorough analysis of available data to improve our understanding of its population status. The US Geological Survey conducts annual bottom trawl surveys in Lake Superior that commonly capture PWF. We used these data (1989-2018) to model temporal trends in PWF biomass density and make lake-wide population projections. We used a Bayesian approach, integrated nested Laplace approximation (INLA), and compared the impact of including different random structures on model fit. Inclusion of spatial structure improved model fit and conclusions differed from models omitting random effects. PWF populations have experienced periodic fluctuations in biomass density since 1989, though 2018 may represent the lowest density in the 30-year time series. Lake-wide biomass was estimated to be 71.51. Les evaluations de populations d'especes de poissons reposent souvent sur des donnees de releves aux objectifs varies, comme la mesure de la biodiversite ou de la dynamique des communautes. Ces releves contiennent souvent des dependances spatiotemporelles qui peuvent grandement influencer les conclusions tirees des analyses. Le Comite sur la situation des especes en peril au Canada a recemment etabli que les populations de menominis pygmees (Prosopium coulterii) dans le lac Superieur sont menacees, ce qui a motive une analyse exhaustive des donnees disponibles dans le but d'ameliorer la comprehension du statut des populations de ce poisson. Le U.S. Geological Survey effectue des releves annuels au chalut de fond dans le lac Superieur qui capturent generalement des menominis pygmees. Nous avons utilise ces donnees (1989-2018) pour modeliser les tendances dans le temps de la densite de biomasse de menominis pygmees et etablir des projections concernant les populations pour l'ensemble du lac. Nous avons utilise une approche bayesienne, l'approximation de Laplace emboitee integree (ALEI), et compare l'incidence de l'inclusion de differentes structures aleatoires sur le calage des modeles. L'inclusion d'une structure spatiale ameliore le calage et mene a des conclusions differentes de celles decoulant de modeles qui n'integrent pas d'effets aleatoires. Si la densite de la biomasse de populations de menominis pygmees a connu des fluctuations periodiques depuis 1989, l'annee 2018 pourrait etre caracterisee par la plus faible densite de la serie chronologique de 30 ans. La biomasse dans l'ensemble du lac est estimee a 71,5 t. [Traduit par la Redaction], Introduction Fish population assessments, whether for the purposes of conservation or fisheries management, must often rely on data from monitoring surveys designed to meet other objectives. For example, monitoring surveys [...]

Human-driven environmental change underlies recent changes in water clarity in many of the world's great lakes, yet our understanding of the consequences of these changes on the fish and fisheries they support remains incomplete. Herein, we offer a framework to organize current knowledge, guide future research, and help fisheries managers understand how water clarity can affect their valued populations. Emphasizing Laurentian Great Lakes findings where possible, we describe how changing water clarity can directly affect fish populations and communities by altering exposure to ultraviolet radiation, foraging success, predation risk, reproductive behavior, or territoriality. We also discuss how changing water clarity can affect fisheries harvest and assessment through effects on fisher behavior and sampling efficiency (i.e., catchability). Finally, we discuss whether changing water clarity can affect understudied aspects of fishery performance, including economic and community benefits. We conclude by identifying generalized predictions and discuss their implications for priority research questions for the Laurentian Great Lakes. Even though the motivation for this work was regional, the breadth of the review and generality of the framework are readily transferable to other freshwater and marine habitats. Si des modifications de l'environnement causees par les humains sous-tendent les changements recents de la clarte de l'eau dans bon nombre des grands lacs de la planete, notre comprehension des consequences de ces changements sur les poissons et les peches qu'ils soutiennent demeure incomplete. Nous presentons un cadre pour organiser les connaissances actuelles, orienter la recherche future et aider les gestionnaires des peches a comprendre l'incidence possible de la clarte de l'eau sur les populations qu'ils gerent. En mettant l'accent, dans la mesure du possible, sur des constatations relatives aux Grands Lacs laurentiens, nous decrivons l'incidence directe que peuvent avoir les variations de la clarte de l'eau sur les populations et communautes de poissons en modifiant l'exposition au rayonnement ultraviolet, le succes d'approvisionnement, le risque de predation, le comportement de reproduction ou la territorialite. Nous abordons egalement l'incidence que peuvent avoir les modifications de la clarte de l'eau sur les prises et revaluation des peches par le biais d'effets sur le comportement des pecheurs et l'efficacite d'echantillonnage (c.-a-d., la capturabilite). Enfin, nous tentons d'etablir si les modifications de la clarte de l'eau peuvent avoir une incidence sur des aspects sous-etudies de la performance des peches, y compris les avantages economiques et pour les collectivites. Nous concluons en formulant des predictions generales et discutons des questions de recherche prioritaires qu'elles font ressortir pour les Grands Lacs laurentiens. Meme si l'intention a l'origine du present article etait regionale, la portee de la synthese et le caractere general du cadre font qu'ils peuvent etre transposes aisement a d'autres habitats marins et d'eau douce. [Traduit par la Redaction], Introduction Although scientists have increasingly documented changing water clarity in freshwater ecosystems worldwide, we do not fully understand its effects on aquatic food webs and the fisheries that they support. [...]

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 [...]

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 [...]

Alternative reproductive tactics (ARTs) can generate considerable within-species life history variation but are often overlooked. Here, we use the invasive round goby (Neogobius melanostomus) to address a number of ecological and evolutionary questions about ARTs. Making use of a 12-year, multisite Laurentian Great Lakes data set, we show that the guarder male tactic was twice as common as the sneaker male tactic but that nonreproductive males were the most common morph. The ratio of guarder to sneaker males did not vary spatially despite a wide range of resource densities across sites. Guarders and sneakers spanned similar age ranges, suggesting that the ARTs are nonsequentially expressed. Based on short-term (gut contents) diet analyses, both reproductive tactics consumed fewer types of food and tended to consume fewer items overall when compared with nonreproductive males. Long-term (isotope) diet analyses showed that guarder males fed at a higher trophic level (higher [[delta].sup.15]N) and had a broader isotopic niche. Our results show that ARTs are an important aspect of this invasive species' breeding system and should be accounted for when assessing and managing populations. Si differentes tactiques de reproduction peuvent se traduire par des variations considerables du cycle biologique au sein d'une meme espece, dans bien des cas, elles ne sont pas prises en consideration. Nous utilisons le gobie a taches noires (Neogobius melanostomus), une espece envahissante, pour examiner differentes questions relatives a l'ecologie et Revolution touchant aux differentes tactiques de reproduction. A la lumiere d'un ensemble de donnees de 12 ans couvrant de multiples sites dans la region des Grands Lacs laurentiens, nous demontrons que les males gardiens etaient deux fois plus repandus que les males furtifs, mais que les males non reproducteurs representaient la tactique la plus repandue. Le rapport des males gardiens et furtifs ne variait pas dans l'espace, malgre une grande fourchette de densite des ressources entre les sites. Les fourchettes d'age des males gardiens et furtifs etaient semblables, donnant a penser que les differentes tactiques de reproduction ne s'expriment pas sequentiellement. A la lumiere d'analyses des regimes alimentaires a court terme (contenus stomacaux), les individus adoptant les deux tactiques de reproduction consommaient moins de types d'aliments et avaient tendance a consommer moins d'articles en general que les males non reproducteurs. Des analyses des regimes alimentaires sur le long terme (isotopiques) montrent que les males gardiens s'alimentaient a un niveau trophique plus eleve ([[delta].sup.15]N plus grands) et occupaient une niche isotopique plus large. Nos resultats montrent que l'adoption de differentes tactiques de reproduction est un aspect important du systeme de reproduction de cette espece envahissante qui devrait etre integre a l'evaluation et la gestion des populations. [Traduit par la Redaction], Introduction The round goby (Neogobius melanostomus) is a highly successful invasive species that has established new populations in both Europe and North America (Corkum et al. 2004; Kornis et al. [...]

Hypoxia (dissolved oxygen < 2 mg l-1) has long been a prevalent feature of the central basin of Lake Erie. Studies of the sublethal impacts of hypoxia on fishes have focused on individual species feeding rates, behavior and spatial distributions over short time periods, but the long-term effects on the fish community and its foodweb are poorly known. Sublethal effects of hypoxia on fish include: interrupting their vertical migration, displacing them from bottom habitats either up into the water column or away from the hypoxic zones, altering predator-prey relationships by segregation or aggregation of predators and their prey, and increasing fishing mortality by concentrating fish at the edge of hypoxic zones. We used the Ecopath with Ecosim foodweb model to investigate the singular and combined effects of nutrient concentration and hypoxia on the foodweb structure in Lake Erie's central basin. Our model tracked predator-prey interactions and population biomass of 33 model groups. We balanced the model in Ecopath and calibrated it against biomass time series data from 1996 up to 2020. Model simulations were run with varied nutrients (from 20 to 220% of the previous nutrient loading target level) and hypoxia (none, average summer value from 1996 to 2017, historical high) as forcing variables on the foodweb. Model results suggested that nutrients had positive, non-linear effects on foodweb biomass, while hypoxia decreased biomass of benthos, benthivorous fishes, and some omnivores, but increased biomass of plankton and planktivorous fishes. Nutrient effects were greater than hypoxia effects on the foodweb. Results of the foodweb model analysis may inform water quality and fisheries management strategies for Lake Erie's central basin. [ABSTRACT FROM AUTHOR]

Asian carp (bighead carp, Hypophthalmichthys nobilis; grass carp, Ctenopharyngodon idella and silver carp, H. molitrix) are a group of invasive species that are predicted to cause ecological effects if they invade the Great Lakes basin. Although Asian carp age at maturity is known to be an important factor in the risk of establishing a population, there is relatively little maturity data for North America. We found that air temperature can be used to predict the age at maturity of Asian carp. Nonlinear regressions using mean annual air temperature and annual degree days to predict age at maturity explain 60% and 62% of the variation respectively. These models predict that maturation is possible in locations that were previously excluded from Asian carp spawning range based on data from the Amur River. As expected, we find faster maturation in more southern areas of North America, although there are relatively large errors predicting age at maturity in the Mississippi River population. We conclude that due to the effect of faster maturation on population growth rates, southern Great Lakes locations (e.g. Lake Erie) may be at greater risk of faster population establishment. [ABSTRACT FROM AUTHOR]

We developed a spatially explicit simulation model of poaching behaviour to quantify the relative influence of the intensity, frequency, and spatial distribution of poaching on metapopulation viability. We integrated our model of poaching with a stochastic, habitat-based, spatially explicit population model, applied it to examine the impact of poaching on northern abalone (Haliotis kamtschatkana) metapopulation dynamics in Barkley Sound, British Columbia, Canada, and quantified model sensitivity to input parameters. While demographic parameters remained important in predicting extinction probabilities for northern abalone, our simulations indicate that the odds of extinction are twice as high when populations are subjected to poaching. Viability was influenced by poaching variables that affect the total number of individuals removed. Of these, poaching mortality was the most influential in predicting metapopulation viability, with each 0.1 increase in mortality rate resulting in 22.6% increase in the odds of extinction. By contrast, the location and spatial correlation of events were less important predictors of viability. When data are limited, simulation models of poaching combined with sensitivity analyses can be useful in informing management strategies and future research directions. Nous avons developpe un modele de simulation spatialement explicite du comportement de braconnage pour quantifier l'influence relative de l'intensite, de la frequence et de la repartition spatiale du braconnage sur la viabilite de metapopulations. Nous avons integre notre modele de braconnage a un modele de population stochastique spatialement explicite base sur l'habitat, l'avons applique pour examiner l'incidence du braconnage (Haliotis kamtschatkana) sur la dynamique de metapopulations d'ormeaux nordiques dans la baie Barkley (Colombie-Britannique, Canada) et avons quantifie la sensibilite du modele aux parametres de depart. Si les parametres demographiques demeurent importants pour la prevision des probabilites de disparition pour l'ormeau nordique, nos simulations indiquent que les chances de disparition sont deux fois plus grandes quand les populations font l'objet de braconnage. La viabilite est influencee par des variables associees au braconnage qui ont une incidence sur le nombre total d'individus retires. De ces variables, la mortalite par braconnage est celle qui influence le plus la prediction de la viabilite de metapopulations, chaque augmentation de 0,1 du taux de mortalite se traduisant par une hausse de 22,6% de la probabilite de disparition. En revanche, l'emplacement et la correlation spatiale des evenements sont des variables moins importantes pour ce qui est de predire la viabilite. Quand les donnees sont limitees, les modeles de simulation du braconnage combines a des analyses de la sensibilite peuvent etre utiles pour eclairer les strategies de gestion et orienter les travaux de recherche futurs. [Traduit par la Redaction], Introduction Considered to be one of the primary threats to biodiversity, overexploitation has led to the decline and disappearance of many species worldwide (Wilcove et al. 1998; Venter et al. [...]

Habitat loss represents the greatest threat to freshwater biodiversity. The potential for life history attributes to correlate with the risks associated with habitat loss represents a possible mechanism for more effective and rapid assessments, especially in data-limited situations. Body size correlates with many other life history attributes and is a good starting point for investigating correlates with habitat loss. Here, we use a generic stage-based matrix population model, parameterized using length-based allometries, to investigate if such a mechanism exists. Our analysis revealed that small species (shorter maximum body length) were initially more sensitive to the loss of habitat. Moreover, distinct stage-based patterns exist showing an increased sensitivity of population growth rate for small species to both habitat loss and vital rate perturbations of pre-adult stages. This indicates that the pre-adult period represents a critical stage for the continued production of small species and increased importance of the conservation of habitat used by young-of-the-year and juvenile fishes. La disparition d'habitat represente la plus grande menace pour la biodiversite des milieux d'eau douce. La possibilite que des attributs du cycle biologique soient correles aux risques associes a la disparition d'habitat constitue un mecanisme possible pour des evaluations plus efficaces et rapides, particulierement dans des situations oU les donnees sont limitees. La taille du corps est correlee a de nombreux autres attributs du cycle biologique et represente un bon point de depart pour l'etude des correlats de la disparition d'habitat. Nous utilisons un modele matriciel generique base sur les stades dont les parametres sont etablis en utilisant des allometries axees sur la longueur pour verifier si un tel mecanisme existe. Notre analyse revele que les petites especes (longueur du corps maximum plus courte) sont initialement plus sensibles a la disparition d'habitat. En outre, il existe des motifs distincts selon les stades qui indiquent une sensibilite accrue des taux de croissance des populations de petites especes tant a la disparition d'habitat qu'aux perturbations des rythmes vitaux des stades pre-adultes. Cela indique que la periode pre-adulte constitue une etape critique pour la production continue des petites especes et souligne l'importance de la conservation des habitats utilises par les jeunes de l'annee et les poissons juveniles. [Traduit par la Redaction], Introduction Freshwater ecosystems are vulnerable to anthropogenic disturbance due to landscape influences on habitat and fishes (e.g., Chu et al. 2014; Kaufmann et al. 2014; Tanentzap et al. 2014). Fishes [...]

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assessed Purple Wartyback (PWB, Cyclonaias tuberculata) as Threatened in Canada. Here population modelling is presented to assess the impacts of harm, determine abundance and habitat recovery targets, and conduct long-term projections of population recovery in support of a recovery potential assessment (RPA). The model incorporated parameter uncertainty, environmental stochasticity, and density-dependence into population projections. The analysis demonstrated that PWB populations were most sensitive to perturbations to adult survival under most circumstances. As population growth rate (λ) increased the sensitivity of juvenile survival to perturbation increased and surpassed adult survival sensitivity when λ > 1.2. Estimates of the level of harm that would reduce population growth rate to 1 were estimated for populations in the Sydenham and Thames rivers. Population viability analysis was used to identify potential recovery targets. Demographic sustainability, (i.e., a self-sustaining population over 250 years) can be achieved with population sizes of ~2,800 (CI: 1,900-4,000) adults. It was estimated that populations of minimum viable population (MVP) size would require 623.3 m² (CI: 251.9-1,396.9) and 2,900 m² (CI: 301.5-17,166.3) in the Sydenham and Thames rivers respectively. Therefore, there is sufficient habitat to support PWB populations in both systems. [ABSTRACT FROM AUTHOR]

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) has assessed Lake Chubsucker (Erimyzon sucetta) in Canada as Endangered. Population modelling is presented to assess the impacts of harm and determine abundance and habitat recovery targets in support of a recovery potential assessment (RPA). This analysis demonstrated that Lake Chubsucker were most sensitive to perturbations to adult survival. Population viability analysis was used to identify potential recovery targets. Demographic sustainability (i.e., a selfsustaining population over the long term) can be achieved with population sizes of ~ 33,600 individuals of age-1 and older with a catastrophe frequency of 15% per generation and desired persistence probability of 99% over 100 years. Such a population would require 0.41 km2 of lacustrine habitat or 0.12 km² of riverine habitat. [ABSTRACT FROM AUTHOR]

Recent food-web changes in the Laurentian Great Lakes are affecting energy and nutrient allocation to lake whitefish (Coregonus clupeaformis) with potential downstream effects on egg condition and recruitment. We tested whether egg condition was conserved or varied with maternal condition in eight stocks from Lakes Erie, Michigan, and Superior. Egg condition was conserved across stocks based on (i) a lack of correlation between females and eggs for total lipid, DHA, and other essential fatty acids; (ii) higher levels of energy and long-chain polyunsaturated fatty acids (LC-PUFA) in eggs compared with females; and (iii) no among-stock differences for those same variables in eggs. Females from northern Lake Michigan generally made the greatest trade-offs between egg size and fecundity. Highly fecund females provisioned less lipid, but more n-3 LC-PUFA to their eggs. A lack of stock-level patterns in energy and nutrient allocation suggests that trade-offs occur at the level of individual females and that females in poor condition make greater trade-offs among egg size and fecundity, total lipids, and n-3 LC-PUFA than females in good condition. Resume: Des modifications recentes des reseaux trophiques dans les Grands Lacs laurentiens ont une incidence sur l'allocation d'energie et de nutriments chez les grands coregones (Coregonus clupeaformis), incluant des effets en aval potentiels sur l'etat des reufs et le recrutement. Nous avons tente d'etablir si l'etat des reufs etait conserve ou variait selon l'etat d'embonpoint maternel au sein de huit stocks des lacs Erie, Michigan et Superieur. L'etat des reufs etait conserve dans tous les stocks a la lumiere (i) de l'absence de correlation entre les femelles et les reufs sur le plan des lipides totaux, de l'ADH et d'autres acides gras essentiels, (ii) de niveaux plus eleves d'energie et d'acides gras polyinsatures a longue chaine (AGPLC) dans les reufs que chez les femelles et (iii) de l'absence de variation au sein des stocks en ce qui concerne ces memes variables dans les reufs. Les femelles de la partie nord du lac Michigan sont celles qui presentaient les compromis les plus importants entre la taille des reufs et la fecondite. Les femelles tres fecondes transferaient moins de lipides, mais plus d'AGPLC n-3 a leurs reufs. L'absence de tendance en matiere d'allocation d'energie et de nutriments a l'echelle des stocks donne a penser que les compromis s'exercent a l'echelle individuelle chez les femelles et que les femelles en mauvais etat d'embonpoint font de plus grands compromis entre la taille des reufs et la fecondite, les lipides totaux et les AGPLC n-3 que les femelles en bon etat. [Traduit par la Redaction], Introduction Lake whitefish (Coregonus clupeaformis) support important commercial, recreational, and aboriginal subsistence fisheries throughout the Laurentian Great Lakes. From 1995 to 2005, lake whitefish growth and body condition declined precipitously [...]

A robust assessment of the American eel (Anguilla rostrata) stock, required to guide conservation efforts, is challenged by the species' vast range, high variability in demographic parameters and data inadequacies. Novel ideas and underutilised resources that may assist both analytic assessments and spatially oriented modelling include (1) species and environmental databases; (2) mining of data from scattered sources; (3) infilling of data gaps by spatial analysis; (4) age estimation from measurements of DNA methylation; evaluation of eel abundance by (5) larval, (6) glass‐bottom boat, (7) net enclosure and (8) eDNA surveys; (9) accounting for dam‐induced habitat increases in eel watercourse modelling; (10) spatially oriented modelling with and without temporal components; (11) geographically nested modelling of glass eel recruitment; (12) spawner per recruit modelling and (13) life cycle modelling to examine larval allocation effects. Eel biologists are too few to gather the required assessment data across all of the species' range. Public posting of electrofishing and eDNA metabarcoding data sets and the use of machine learning techniques to comprehensively inventory small dams will help meet some data needs. These approaches address only a small proportion of the assessment challenges that face American eels. Worldwide collaboration amongst Anguilla scientists is a key enabler of progress towards stock assessment goals. [ABSTRACT FROM AUTHOR]

Numerous researchers have attempted to find suitable proxies for the lipid content of fishes. Owing to the high carbon content of lipids, C:N ratios have been used as a predictor of lipid content both for the purposes of quantifying condition and for stable isotope analyses. Here we examine the utility of C:N ratios for predicting the lipid content within and among populations, and to validate commonly used published percent lipid--C:N ratio models. No common percent lipid--C:N ratio model was found to apply; instead, population-specific influences on lipid content were observed. Published lipid prediction models significantly underestimated lipid content, and often had worse prediction error than the error obtained by using measured mean lipids as the prediction for all samples. Maximum prediction error by population ranged from a low of 50.7% to a high of 65.0%. Our results provide no support for the idea that there is a predictable relationship between bulk C:N ratios and lipid content. We recommend that sample-specific relationships be developed in situations where lipid prediction is needed, rather than relying on published models. De nombreux chercheurs ont essaye de trouver des variables de remplacement adeequates pour le contenu lipidique des poissons. A cause du fort contenu en carbone des lipides, les rapports C :N ont servi a predire le contenu lipidique, tant pour la mesure de la condition que pour les analyses d'isotopes stables. Nous examinons ici l'utilitei des rapports C :N pour la prediction du contenu lipidique au sein des populations et entre les populations afin de valider les modeles % de lipides--rapport C :N les plus communeement utilises dans la litteerature. Aucun des modeles communs % de lipides--rapport C :N n'est applicable; au contraire, on observe des influences specifiques aux populations sur le contenu lipidique. Les modeles de prediction des lipides dans la litteerature sous-estiment significativement le contenu lipidique et souvent ils ont une erreur de prediction plus importante que celle obtenue en utilisant la mesure des lipides moyens comme base de prediction pour tous les eechantillons. L'erreur de prediction maximale par population varie d'un minimum de 50,7 % a un maximum de 65,0 %. Nos resultats n'appuient en aucune facon la proposition qu'il existe une relation predictive entre les rapports globaux de C :N et le contenu lipidique. Nous recommandons d'etablir des relations specifiques aux echantillons pour obtenir des predictions des lipides plutot que de se fier aux modeles publies. [Traduit par la Redaction], Introduction Fish condition is a commonly used metric of fish health (Brown and Murphy 1991; Pangle and Sutton 2005; Hartman and Margraf 2006). Some of the factors that contribute to [...]

The International Maritime Organization has proposed ballast water discharge standards to reduce densities of taxa transported in ballast water. While reduced propagule pressure will almost certainly lower the risk of species introductions, we ask if the proposed standards will be effective against taxa capable of rapid population growth from small inocula, such as parthenogenetic taxa. We modified a diffusion approximation to calculate establishment probabilities as the probability of reaching a critical threshold density necessary to initiate sexual reproduction (and production of diapausing eggs for long-term persistence) before the onset of adverse environmental conditions. We parameterize our model for six Cladocera using growth rates measured during enclosure experiments conducted under favourable environmental conditions (i.e., using a precautionary approach). We then examine predicted establishment probabilities at different inoculum densities to determine the efficacy of the proposed ballast water discharge standards. Our results indicate that future technologies in compliance with the proposed standards could reduce establishment probabilities for some parthenogenetic zooplankton threefold; however, there is still a risk of establishment for some taxa. L'organisation maritime internationale a propose des normes concernant l'evacuation de l'eau de ballastage afin de reduire la densite des taxons transportes dans cette eau de ballastage. Bien qu'une pression reduite des propagules puisse diminuer presque certainement le risque d'introduction d'especes, nous nous demandons si les normes proposees seront efficaces contre les taxons capables d'une croissance rapide de population a partir de petits inoculums, comme les taxons parthenogenetiques. Nous avons modifie une approximation de la diffusion afin de calculer la probabilite d'etablissement definie comme etant la probabilite d'atteindre la densite seuil requise pour l'initiation de la reproduction sexuelle (et la production d'[SS]ufs de diapause pour la persistance a long terme) avant l'arrivee de conditions environnementales defavorables. Nous avons determine les parametres du modele pour six cladoceres en utilisant des taux de croissances mesures dans des experiences en enclos menees dans des conditions favorables de milieu (donc en utilisant une approche prudente). Nous avons ensuite examine les probabilites d'etablissement predites a diverses densites d'inoculum afin de determiner l'efficacite des normes proposees pour l'evacuation de l'eau de ballastage. Nos resultats indiquent que des technologies futures en accord avec les normes proposees pourraient reduire par un facteur de trois les probabilites d'etablissement de certains organismes parthenogenetiques du zooplancton; il demeure encore, neanmoins, un risque d'etablissement pour certains taxons. [Traduit par la Redaction], Introduction At least 1000 nonindigenous species have been reported from aquatic habitats globally (e.g., Leppakoski et al. 2002; Hayes and Sliwa 2003; Ricciardi 2006), with ballast water recognized as the [...]

Regulatory agencies and fisheries managers tasked with implementing recovery plans for endangered species must frequently make decisions based on limited data, while also considering general uncertainty associated with prediction. Population viability analysis (PVA) is a modelling tool that is particularly useful for long‐lived species and can be applied even in the absence of robust estimates of life history parameters. As empirical data are accumulated over time, PVA inputs, model structure, and parameter estimates can be refined to increase model realism and accuracy.Since the first iterations of lake sturgeon (Acipenser fulvescens) PVA were run, approximately 15 years ago, based on conservative inputs for Canadian population units, important empirical data have accumulated from a variety of river systems that the species inhabits. Erratic recruitment patterns have been revealed, juvenile survival has been determined to be higher than initially believed, and growth rates have been found to vary by habitat (river) type.Exploiting an improved biological understanding of the species, somatic growth models derived from three well‐studied lake sturgeon populations were used to examine the effects of recruitment variability and incremental levels of adult harvest (mortality) on the probability of population recovery and risk of population decline. A total of 110 PVA scenarios (with 1,000 replicates per scenario) were run for each of the three somatic growth models (slow, medium, and fast).The PVA results suggest that the recovery potential for lake sturgeon populations may be higher than previous models, based on conservative inputs, have indicated. A few scenarios resulted in recovery after 100 years, and nearly half of the scenarios resulted in recovery after 250 years. Similarly, the probability of decline for small populations was most sensitive to adult harvest, with little change in the number of scenarios resulting in decline at the time points of 100, 250, and 500 years. A worked example highlights how the targeted monitoring of both juvenile and adult life stages can be used to evaluate the recovery potential of more than one population and prioritize management initiatives, such as harvest reduction and stocking. [ABSTRACT FROM AUTHOR]

The Fish and Fish Habitat Protection Program (FFHPP) has requested science advice on the potential consequences and how to quantify impacts from works, undertakings or activities (WUAs), other than fishing, that cause the death of fish, and ways that the death of fish can be offset. To support this request, this document is organized into four main sections. First, the available metrics for quantifying impacts and offsets for fish mortality are reviewed. There are differences in the data requirements and equivalency objectives among metrics; total biomass lost is the recommended metric for most cases. Second, modelling approaches that could be used to evaluate the community or food web consequences of fish mortality are briefly reviewed. An example of simple community models is provided, demonstrating that the outcomes for fish communities from fish mortality events are likely to be more than the sum of single species responses. Third, an overview is provided of the considerations that should be included in management decisions about fish mortality, providing information on the components that could be included in a risk management framework for WUA-related residual mortality. An adaptation of a precautionary fisheries management framework is presented as an example of a risk management framework for decisions about fish mortality impacts and offsets. Finally, the literature on current practices for offsetting fish mortality events is reviewed. There is evidence that habitat creation, habitat restoration and enhancement, and biological and chemical manipulation can all provide approaches to offsetting fish mortality, but consideration of the specifics of the offset application and sufficient monitoring, including pre-impact assessment, are needed to effectively achieve an offset for fish mortality. [ABSTRACT FROM AUTHOR]

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

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

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) has assessed the Lake Opeongo species pair (DU 13 and 14) of Lake Whitefish (LWF, Coregonus clupeaformis) in Canada as Threatened. Population modelling is presented to assess the impacts of harm and determine abundance and habitat recovery targets in support of a recovery potential assessment (RPA). This analysis demonstrated that LWF populations of both DUs were most sensitive to perturbations to adult survival. Population viability analysis was used to identify potential recovery targets. Demographic sustainability (i.e., a self-sustaining population over the long term) can be achieved with adult female population sizes of ~450 to ~2,300 for the largebodied DU or ~1,300 to ~8,700 for the small-bodied DU depending on catastrophe frequency and desired persistence probability. Lake Opeongo has sufficient habitat for populations of both DUs. [ABSTRACT FROM AUTHOR]

The scrounger (S) tactics in social foraging groups are probably a risk-sensitive rather than a rate-maximizing foraging tactic. The use of S tactics increases as the food clump density increases. When the producer's competitive efficiency is low, there is a negligible increase in S. This is consistent with the predictions of a risk-sensitive model. The experiments, conducted on European Starlings (Sturnus vulgaris) in an indoor aviary, support the risk-sensitive model but fail to reject the rate-maximizing model.