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Freshwater habitat restoration is a major conservation objective, motivating efforts to restore habitat complexity and quality for fishes. Restoration based on the engineering activities of beavers (Castor canadensis) increases fish habitat complexity, but how this affects fish habitat use and movement behaviours is not well known. We used a network of passive integrated transponder antennas to quantify small-scale movement and microhabitat use of 175 individual juvenile steelhead (Oncorhynchus mykiss) in a stream channel with a complex bathymetric profile resulting from a beaver impoundment and in a simplified channel devoid of beaver activity. Our results show that juvenile steelhead exploit microhabitat heterogeneity by employing a range of behaviours that maximizes available habitat via spatial and temporal partitioning among individuals. These results suggest spatial resource partitioning as a potential mechanism for the previously established positive correlations among steelhead density, survival, and production with beaver-based restoration within the study watershed. More broadly, our findings provide insight as to how populations can exploit habitat complexity through spatial partitioning that can be informative for planning restoration and management actions. La restauration des habitats d'eau douce constitue un important objectif de conservation a l'origine d'efforts pour retablir la complexite et la qualite d'habitats pour les poissons. Si la restauration reposant sur les activites de genie civil des castors (Castor canadensis) accroit la complexite des habitats de poissons, son incidence sur l'utilisation de l'habitat et les comportements de deplacement des poissons demeure meconnue. Nous avons utilise un reseau d'antennes a radio-etiquettes passives integrees pour quantifier les deplacements a petite echelle et l'utilisation de microhabitats par 175 truites arc-en-ciel (Oncorhynchus mykiss) juveniles dans le chenal d'un cours d'eau au profil bathymetrique complexe cause par une digue de castor, et dans un chenal simplifie exempt d'activite de castors. Nos resultats montrent que les truites arc-en-ciel juveniles exploitent l'heterogeneite des microhabitats en ayant recours a un eventail de comportements qui maximise l'habitat disponible grace au partage spatial et temporel de l'habitat entre individus. Ces resultats suggerent que le partage spatial des ressources est un mecanisme qui pourrait expliquer les correlations positives deja etablies entre la densite, la survie et la production de truites arc-en-ciel et la restauration reposant sur les castors dans le bassin versant etudie. Plus largement, nos constatations fournissent de l'information sur la maniere dont les populations peuvent exploiter la complexite de l'habitat grace au partage spatial de ce dernier, qui peut eclairer la planification d'interventions de restauration et d'amenagement., Introduction Habitat degradation is one of the principal threats to freshwater populations worldwide (Dudgeon et al. 2005), with over a third of the rivers in the United States designated as [...]

Lake sturgeon are arguably the largest and most unique freshwater fish in North America. Unfortunately their uniqueness includes many characteristics that make them especially vulnerable to anthropogenic impacts including overfishing, habitat fragmentation, and degradation. For approximately 100 years lake sturgeon populations across North America have either been in decline and (or) have experienced a sluggish recovery. While this is partly due to lake sturgeon life history, most researchers agree that habitat fragmentation and degradation are currently the highest risk to the species. Though most lake sturgeon populations are depressed, there are a few exceptions that offer a glimpse into what a stable population or recovery may look like. The following review highlights such instances as well as what is known and more importantly what is not known about this unique species. Specifically, we highlight the need for improved and organized sharing of raw data given the fact that many researchers do not have access to the plethora of information available to others (e.g., otoliths for aging). We examine the varying life history and diet choices of this plastic species offering hypotheses for differences in migration routes and distances as well the differing recovery rates found across their range. We highlight myths about the species providing evidence that they may not be as long lived and fecund as previously thought. We examine the lake sturgeon's current legal status across North America including the efforts of nonprofit groups that have had success in increasing population numbers. Most importantly, we highlight logistical problems faced by researchers and data gaps in the literature that must be filled to increase the odds of a successful recovery. Alongside the data gaps, the recovery of this species is fraught with political and industrial road blocks that are as varied as its current recovery. Subsequently, as is the case with many species, its survival will come down to solid scientific knowledge and the value placed on it by society. Key words: lake sturgeon, conservation, species at risk. L'esturgeon de lac constitue sans aucun doute l'unique et plus gros poisson d'eau douce en Amerique du Nord. Malheureusement, son unicite inclut plusieurs caracteristiques le rendant vulnerable aux impacts anthropogenes, incluant la surpeche ainsi que la fragmentation de l'habitat et sa degradation. Pendant environ 100 ans, les populations d'esturgeon de lac sur l'ensemble de l'Amerique du Nord ont connu un declin et/ou une lente recuperation. Alors que ceci est du en partie au cycle vital de l'esturgeon, la plupart des recherches s'accordent pour dire que la fragmentation de l'habitat et sa degradation constituent presentement le plus fort risque pour cette espece. Bien que la plupart des populations d'esturgeon de lac soient deprimees, il existe quelques exceptions offrant une idee de ce que represente une population stable ou en recuperation. Cette revue souligne de tels cas ainsi que ce que l'on connait au sujet de cette espece unique. Specifiquement, les auteurs insistent sur la necessite d'ameliorer et d'organiser le partage des donnees brutes, compte tenu du fait que plusieurs chercheurs n'ont pas acces a la plethore d'informations disponibles pour d'autres chercheurs (p. ex. otolithes pour mesurer l'age). On examine les variations du cycle biologique et les choix de diete chez cette espece plastique, en offrant diverses hypotheses pour expliquer les differences dans les routes de migration et leurs distances ainsi que les differents taux de recuperation observes sur l'ensemble de l'aire. On souligne les mythes au sujet de cette espece en fournissant la preuve qu'ils ne sauraient etre aussi viables et feconds qu'on le pensait jadis. Les auteurs examinent egalement le statut legal actuel sur l'ensemble de l'Amerique du Nord, incluant les efforts de groupes a but non lucratif qui ont reussi a augmenter les nombres de populations. Et ce qui est tres important, on souligne les problemes logistiques auxquels font face les chercheurs sur les donnees manquantes de la litterature, lesquelles doivent etre comblees pour augmenter les chances de reussir la recuperation. En plus de ces donnees manquantes, la recuperation de cette espece rencontre sur sa route des difficultes d'origine politique et industrielle aussi variees que sa recuperation actuelle. Subsequemment, comme c'est le cas avec de nombreuses especes, sa survie depend d'une connaissance scientifique solide et de la valeur accordee par la societe. [Traduit par le Redaction] Mots-cles : esturgeon de lac, conservation, espece a risque., Introduction Natural history Lake sturgeon (Acipenser fulvescens) are a relatively large, cartilaginous, benthic fish, endemic to many large rivers and lakes of North America (Peterson et al. 2007). Once prevalent [...]

Sleep deprivation (SD) can suppress cell proliferation in the hippocampal dentate gyrus of adult male rodents, suggesting that sleep may contribute to hippocampal functions by promoting neurogenesis. However, suppression of cell proliferation in rats by the platform-over-water SD method has been attributed to elevated corticosterone (Cort), a potent inhibitor of cell proliferation and nonspecific correlate of this procedure. We report here results that do not support this conclusion. Intact and adrenalectomized (ADX) male rats were subjected to a 96-h SD using multiple- and single-platform methods. New cells were identified by immunoreactivity for 5-bromo-2'-deoxyuridine (BrdU) or Ki67 and new neurons by immunoreactivity for BrdU and doublecortin. EEG recordings confirmed a 95% deprivation of rapid eye movement (REM) sleep and a 40% decrease of non-REM sleep. Cell proliferation in the dentate gyrus was suppressed by up to 50% in sleep-deprived rats relative to apparatus control or home cage control rats. This effect was also observed in ADX rats receiving continuous low-dose Cort replacement via subcutaneous minipumps but not in ADX rats receiving Cort replacement via drinking water. In these latter rats, Cort intake via water was reduced by 60% during SD; upregulation of cell proliferation by reduced Cort intake may obscure inhibitory effects of sleep loss on cell proliferation. SD had no effect on the percentage of new cells expressing a neuronal phenotype. These results demonstrate that the Cort replacement method is critical for detecting an effect of SD on cell proliferation and support a significant role for sleep in adult neurogenesis. cell proliferation; hippocampus; rapid eye movement sleep; stress; corticosterone