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Lake sturgeon (Acipenser fulvescens) exhibit a complex life-history strategy where behaviour, including habitat selection, depends on ontogenetic stage. Protection or recovery efforts for one stage may not impact other stages. Stage-structured models have been used to explore the sensitivity of the population to changes in vital rates of individual stages. Recent research demonstrates that juvenile mortality may be lower than estimated in prior modelling efforts and density-dependent. We constructed a Lefkovitch matrix model to reflect an updated understanding of the prerecruitment stages of the lake sturgeon. We then compared the model to a population of lake sturgeon on the Ontario--Minnesota border. Our model predicts that population growth rate, time to equilibrium, and final population size were most sensitive to changes to the survival of early adults, followed by subadults and juveniles. Sensitivity to changes in age-0 survival was very low in contrast to earlier modelling efforts, while sensitivities to juvenile (ages 1-7 years) and subadult (ages 8-23 years) were higher than previously reported values. Key words: population structure, statistical analysis, matrix models, lake sturgeon, protected species Les esturgeons jaunes (Acipenserfulvescens) emploient une strategie de cycle biologique complexe dans laquelle les comportements, dont la selection d'habitats, dependent de l'etape de l'ontogenese. Les efforts de protection ou de retablissement pour une etape pourraient ne pas avoir d'incidence sur les autres etapes. Des modeles structures selon l'etape ont ete utilises pour explorer la sensibilite de la population a des variations de taux vitaux de differentes etapes. Des travaux recents demontrent que la mortalite des juveniles pourrait etre plus faible que les estimations issues d'efforts de modelisation passes et pourrait dependre de la densite. Nous avons construit un modele matriciel de Lefkovitch refletant une comprehension a jour des etapes pre-recrutement du cycle de vie de l'esturgeon jaune. Nous avons ensuite compare le modele a une population d'esturgeons jaunes chevauchant la frontiere de l'Ontario et du Minnesota. Notre modele predit que le taux de croissance de la population, le temps pour atteindre l'equilibre et la taille finale de la population sont les variables les plus sensibles aux variations de la survie des adultes precoces, suivis des subadultes et des juveniles. La sensibilite aux variations de la survie d'individus de moins d'un an est tres faible comparativement aux resultats d'efforts de modelisation anterieurs, alors que les sensibilites des juveniles (1-7 ans) et des subadultes (8-23 ans) sont plus elevees que les valeurs rapportees precedemment. [Traduit par la Redaction] Mots-cles : structure de la population, analyse statistique, modeles matriciels, esturgeon jaune, espece protegee, Introduction Restoring populations of lake sturgeon (Acipenser fulvescens) requires habitat protection and restoration across the species' North American range. Mathematical models are often employed in estimating recovery potential and determining [...]

From observations of Caribou (Rangifer tarandus) during 1974-2017 on the Lake Superior archipelago that makes up Slate Islands Provincial Park, we infer direct and indirect effects of the arrival of Gray Wolves (Canis lupus) in the winters of 1993-1994, 2002-2003, and 2013-2014. Arrivals consisted of wolf pairs in the first and third cases, and, in each instance, wolves survived at least one additional winter. Wolves created conditions that led to behavioural changes in Caribou consistent with avoiding predators. Caribou did not frequent calving locations near shoreline areas, nor did they use water to escape from wolves. Wolves occupied a Red Fox (Vulpes vulpes) den, and its general location, at one time frequented by Caribou, became the most common area to find Caribou carcasses and was avoided by Caribou when wolves were present. Caribou were functionally extirpated by wolves, with just two to four males remaining in 2017. Wolves also appear to have caused extirpation of American Beaver (Castor canadensis) and Red Fox from the archipelago, while Snowshoe Hare (Lepus americanus) populations were unaffected by wolves. [ABSTRACT FROM AUTHOR]

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