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Understanding population dynamics of migratory birds requires baseline knowledge of nonbreeding distributions, migratory routes, and population-specific migratory connectivity. The Canada Warbler (Cardellina canadensis) is a declining Ncarctic-Ncotropical migratory songbird, but limited information exists describing its population-specific migration ecology. We aimed to understand how individuals from a central Appalachian breeding population were spatially distributed during the stationary nonbreeding period, infer the strength and pattern of migratory connectivity, and understand migratory route patterns. We deployed 32 geolocator tags on adult male birds in 2020 and 10 tags retrieved in 2021 provided usable data. Stationary nonbreeding season locations suggest moderate population connectivity, with birds clustered on the Andean slopes on each side of the Magdalena Valley in northern Colombia. Post-breeding (boreal fall) migration was largely overland through Mexico and Central America, and pre-breeding (boreal spring) migration routes were significantly farther cast based on the westernmost longitude recorded during migration (mean difference = 232 km), consistent with a pattern of counterclockwise loop migration. The evidence of counterclockwise loop migration is a novel finding in Canada Warblers and suggests the shorter duration of pre-breeding migration may be due to a time-minimizing strategy involving trans-Gulf flights. Our data additionally provide the first insight into the migratory ecology of a population of Canada Warblers breeding near the southern extent of their range and serve as a foundation for full annual cycle demographic modeling. Received 10 June 2023. Accepted 30 December 2023. Key words: annual cycle, Colombian Andes, loop migration, migratory connectivity, West Virginia. Entender las dinamicas de poblacion de las aves migratorias requiere conocimiento de linea base de sus distribuciones no reproductivas, rutas de migracion y conectividad migratoria especifica de la poblacion. La reinita Cardellina canadensis es un ave canora migratoria Neartica-Neotropical, pero existe informacion limitada que describa la ecologia migratoria especifica de sus poblaciones. Nuestro objetivo era entender como los individuos de la poblacion reproductiva de los Appalachian centrales estaba distribuida espacialmente durante el periodo estacionario no reproductivo, inferir la fuerza y el patron de conectividad migratoria y entender los patrones de rutas migratorias. Colocamos 32 marcas de geolocalizacion en aves masculinas adultas en el 2020 y recuperamos 10 marcas en el 2021 con datos utilizables. Las localizaciones estacionarias de la estacion no reproductiva sugieren una moderada conectividad de poblaciones, con aves agrupadas en las pendientes de los Andes en cada lado del Valle de Magdalena en el norte de Colombia. La migracion post reproductiva (otono boreal) fue mayormente sobre el continente a traves de Mexico y Centroamerica y las rutas pre reproductivas (primavera boreal) fueron significativamente mas hacia el este basadas en la longitud mas al oeste registrada durante la migracion (diferencia promedio = 232 km), lo que es consistente con un patron de migracion circular en direccion contra reloj. La evidencia de la migracion circular a contra reloj es un descubrimiento nuevo para las reinitas Cardellina canadensis y sugiere que la duracion menor de migracion pre reproductiva puede deberse a una estrategia de minimizar el tiempo que involucran los vuelos trans-Golfo. Nuestros datos adicionales dan un primer acercamiento a la ecologia migratoria de una poblacion de reinitas Cardellina canadensis que se reproducen cerca de la parte mas sureno de su rango y sirve como base para modelar de un ciclo anual demografico completo. Palabras clave: ciclo anual, Andes colombianos, migracion circular, conectividad migratoria, West Virginia., Migratory connectivity describes the strength of population cohesion throughout the full annual cycle (Webster et al. 2002). Processes during one period of the annual cycle may be shaped by carryover [...]

Ancient soils unearthed at Cahokia Mounds near St. Louis suggest that the largest precontact Indigenous settlement in North America, home to tens of thousands, did not die out due to [...]

Before collapsing, bay scallops (Argopecten irradians) supported commercial fisheries in Florida but, following decades of restoration efforts and management actions, still support a recreational fishery. Settlement was monitored along the west coast of Florida from 1992 through 2018, using collector traps. The primary environmental variables retained in the analyses included temperature, salinity, and red tide concentration (Karenia brevis). The settlement rate generally increased for the first days of trap deployment, then leveled off or declined. Settlement peaked when the average water temperatures were between 21[degrees]C and 23[degrees]C at four sites: St. Andrew Bay, St. Joseph Bay, West Coast, and Pine Island Sound, indicative of a fall peak in spawning. At the Tampa Bay and Sarasota Bay sites, settlement peaked when temperatures were around 16[degrees]C, indicative of winter spawning. At most sites, the highest peak in settlement occurred in association with declines in temperature of 10[degrees]C-15[degrees]C during the fall, with a smaller, secondary peak occurring with similar increases in temperature during the spring. Warming winter temperatures may already be negatively affecting the ability of the subpopulations to synchronously spawn, with unknown impacts to population dynamics. At all sites, settlement declined rapidly when salinity fell below 30 with little settlement occurring below 27, and approached zero when salinity fell below approximately 20. The occurrence of K. brevis exceeding 10,000 cells/L resulted in reduced settlement. In the core populations of West Coast and Steinhatchee, K. brevis was uncommon, and settlement resumed rapidly when blooms abated. For sites outside the core population, settlement was reduced for 2-4 y after red tides. Recovery of populations in these noncore sites probably relies on exogenous supply of larvae from the core. If blooms of K. brevis that penetrate the core region, as was observed in 2021, become more severe, more frequent, or have longer durations, the entire Florida scallop population could be endangered. KEY WORDS: environmental factors, estuary, Karenia brevis, long-term monitoring, Argopecten irradians, INTRODUCTION Bay scallops (Argopecten irradians) range from Nova Scotia to northern Mexico and possibly as far south as Columbia, inclusive of the northern Gulf of Mexico (Abbott, 1974), with no [...]

Population variability is a ubiquitous feature of all life--indeed, evolution is defined by variation. Over evolutionary and geologic time scales, variation is what enables species to survive and new species [...]

INTRODUCTION With nearly three thousand species across every part of the world, except the Antarctic, mosquito population numbers peak over all other animals except for ants and termites (Gates 2014). [...], In this study, a deterministic mathematical model for mosquito population dynamics is presented. The use of chemical insecticide to control population is incorporated into the model. It is assumed that there is insecticide sensitive (sensitive-type) and insecticide resistant (resistant-type) mosquitoes in the environment. Conditions for the existence and stability of four equilibria of the model have been established. Numerical simulations are carried out to confirm the analytical results and the implications, in terms of mosquito control in the environment, are discussed.

Reproduction and early life history are central to understanding the biology and ecology of organisms, however such information is limited for solitary corals. Here, we compared the reproductive traits of the solitary coral Heliofungia actiniformis from different latitudinal locations (Singapore, 1°N and the Philippines, 16°N) and examined their early life development, settlement competency, and juvenile growth and survival. A total of 32 corals from Pulau Hantu reefs in Singapore and 102 corals from Bolinao and Anda reefs in the Philippines were studied between 2019 and 2022. Heliofungia actiniformis broadcasts spawned gametes during several nights, generally between 22:00 and 01:00, before and after full moon, from February to May in Singapore and from March to June in the Philippines. Spawning within a month occurred for up to 16 nights in Singapore and 10 nights in the Philippines. Sex change in two individuals between years was observed in the Philippines. The average egg size was smaller in Singapore than that in the Philippines. We determined that eggs were fertilized within 2 h after sperm addition, and developed into swimming larvae within 64 h, which began to settle after 24 h. Larval survival after three mo of culture was 1.72 ± 1.0% and juvenile diameter ranged from 0.33 to 1.30 mm. Asexual buds were first observed in 15 mo old juveniles that were at least 8 mm in diameter. 24 mo old juveniles were observed to detach from their stalk and the empty stalk regenerated polyps. Our results highlight the latitudinal variability in the reproductive traits of solitary corals, serve as a baseline for their early life history, and advance our understanding of their population dynamics., Author(s): Sherry Lyn G. Sayco [sup.1] [sup.2] , Rian Prasetia [sup.3] [sup.4] , Peter A. Todd [sup.3] , Yossi Loya [sup.5] , Brian Valencia [sup.1] , Lala Grace Calle [sup.1] [...]

Scyphozoan medusae are critical components of marine ecosystems; however, our knowledge on their population dynamics and life history needed to understand their role on ecosystem functioning is relatively scarce. We used data from fish-stock assessment cruises (1993-2013), artisanal fisheries and stranding events (2006-2007), to assess spatio-temporal variation in biomass, growth and reproduction, of a large and abundant scyphomedusae (Lychnorhiza lucerna) in a productive estuarine ecosystem (Río de la Plata Estuary, RLPE) (35°S-57°W) from the Southwestern Atlantic Ocean. Medusae consisted of sexually mature individuals only, occurring consistently during austral summer. Medusae biomass displayed a patchy distribution, concentrating mainly in two geographically different hot-spots associated to a frontal feature (turbidity front) of the RLPE. Individual size, relative fecundity, and degree of gonad development varied significantly between hot-spots. Biomass varied greatly among years. Bell diameter, wet weight, and percentage of fully developed oocytes increased during the first half of the summer but decreased during the second half of it. Our results suggest high predictability of the period of occurrence and the distribution of L. lucerna in the RLPE. Physical mechanisms of medusa aggregation, potential effects of medusae on zooplankton dynamics, fisheries production, and conservation of sea turtles, as well as their potential for the development of a local jellyfish fishery, are here discussed. This work provides novel information on patterns of distribution, growth and development of L. lucerna medusae, which can help to enhance our understanding of the role of large medusae on ecosystem functioning of marine ecosystems worldwide., Author(s): F. A. Puente-Tapia [sup.1] [sup.2] , L. M. Chiaverano [sup.1] [sup.2] , L. Sobrero [sup.1] [sup.2] , L. Allega [sup.1] , J. Burla [sup.1] , M. S. Dutto [sup.2] [...]

The European eel (Anguilla anguilla) is endangered due to its peculiar life-history cycle, fishing pressure and difficulty in global population management. To improve our understanding of the population dynamics and refine conservation policies, an extended mark and recapture experiment and glass eel stocking were conducted in the River Rhone Delta (France) over 8 years. Around 1100 yellow eels were PIT-tagged and released in 2007, 2.5 kg of glass eels were released each year from 2008 to 2012, and the population was monitored using fishing between 2007 and 2015. After capture or recapture, the body parameters, sex and maturity were assessed. Age was estimated from otolith growth rings. At the end of the experiment, silver eels were between 352 and 875 mm long (age 17 to 185 months) and yellow eels between 170 and 868 mm long (age 12 to 123 months). Age estimates were validated using mark and recapture and showed 16% age underestimates and 5% inaccurate ages. The growth rates were extremely variable with lengths ranged by 2-fold at a given age. These results highlight the difficulty of eel population management, at least in the Mediterranean area. L'anguille europeenne (Anguilla anguilla) est menacee en raison de son cycle biologique singulier, de la pression de peche et de la difficulte que presente la gestion de sa population. Pour une meilleure comprehension de la dynamique de sa population et de la politique de conservation, une vaste experience de marquage-recapture et le deversement de civelles a ete realisee dans le delta du Rhone (France) sur une periode de huit ans. Quelques 1100 anguilles jaunes ont ete marquees avec des PIT-tags et relachees en 2007, 2,5 kg de civelles ont ete relaches chaque annee de 2008 a 2012, et la population a fait l'objet d'une surveillance par peche de 2007 a 2015. Apres capture ou recapture, les parametres corporels, le sexe et la maturite ont ete enregistres. L'age a ete estime a partir d'anneaux de croissance des otolites. A la fin de l'experience, les anguilles argentees faisaient de 352 a 875 mm de long (leurs ages allant de 17 a 185 mois) et les anguilles jaunes, de 170 a 868 mm de long (12 a 123 mois). La validation des ages estimes par marquage et recapture a revele que 16 % des ages etaient sous-estimes et 5 % etaient inexacts. Les taux de croissance etaient extremement variables, les longueurs pouvant varier du simple au double pour un age donne. Ces resultats soulignent le defi que represente la gestion de populations d'anguilles, du moins dans la region mediterraneenne. [Traduit par la Redaction], Introduction In the 1980s, the European eel (Anguilla anguilla) was considered to be pest species in France, but, nowadays, it is listed as a critically endangered species by the IUCN [...]

When estimating mortality from disease with fish population models, common disease surveillance data such as infection prevalence are not always informative, especially for fast-acting diseases that may go unobserved in infrequently sampled populations. In these cases, seroprevalence--the proportion of fish with measurable antibody levels in their blood--may be more informative. In cases of life-long immunity, seroprevalence data require less frequent sampling intervals than infection prevalence data and can reflect the cumulative exposure history of fish. We simulation tested the usefulness of seroprevalence data in an age-structured fish stock assessment model using viral hemorrhagic septicemia virus (VHSV) in Pacific herring (Clupea pallasii) as a case study. We developed a novel epidemiological model to simulate population dynamics and seroprevalence data and fitted to these data in an integrated catch-at-age model with equations that estimate age- and time-varying mortality from disease. We found that simulated seroprevalence data can provide accurate estimates of infection history and disease-associated mortality. Importantly, even models that misspecified nonstationary processes in background or disease-associated mortality, but included seroprevalence data, accurately estimated annual infection and population abundance. Les donnees courantes de surveillance des maladies, par exemple sur la prevalence d'infections, n'offrent pas toujours de l'information utile pour l'estimation de la mortalite par maladie a l'aide de modeles de populations de poissons, particulierement pour des maladies a action rapide qui pourraient passer inapercues dans des populations echantillonnees peu frequemment. Dans ces cas, la seroprevalence, soit la proportion de poissons presentant des concentrations mesurables d'anticorps dans le sang, peut fournir de l'information utile. Dans les cas d'immunite durable, les donnees de seroprevalence requierent un echantillonnage moins frequent que les donnees de prevalence d'infections et peuvent refleter les antecedents d'exposition cumulatifs des poissons. Nous avons verifie par simulation l'utilite de donnees de seroprevalence dans un modele devaluation de stock de poissons structure par age en utilisant le virus de la septicemie hemorragique virale (VSHV) chez des harengs du Pacifique (Clupea pallasii) comme etude de cas. Nous avons developpe un nouveau modele epidemiologique pour simuler la dynamique de la population et les donnees de seroprevalence et avons cale ces donnees sur un modele integre de prises en fonction de l'age avec des equations qui estiment la mortalite par la maladie selon l'age et variable dans le temps. Nous constatons que les donnees de seroprevalence simulees peuvent fournir des estimations exactes des antecedents d'infection et de la mortalite associee a la maladie. Fait a noter, meme les modeles qui integrent erronement des processus non stationnaires a la mortalite de reference ou associee a la maladie, mais qui incluent des donnees de seroprevalence estiment avec exactitude le taux d'infection annuel et l'abondance de la population. [Traduit par la Redaction], Introduction Infectious and parasitic diseases can rapidly alter the biomass, abundance, and demographics of fish populations (Ford and Haskin 1982; Gaughan et al. 2000). These alterations arise from direct or [...]

I studied population densities of forest bird communities in the Mariana Islands of Saipan, Aguiguan and Sarigan in order to evaluate hypotheses concerning seasonal shifts in populations, habitat effects on densities, inter-island differences in densities, social group size and underlying reasons for community structuring. With the exception of one species, I found no evidence to support the hypothesis that seasonal shifts occur in populations. Hence, this island system differs in this regard from mainland tropical forests. I also found, contrary to theory, no evidence that the presence of altered habitat permits populations to be greater than they would be in their absence, as disturbed habitat had far lower densities of most species than native forest. Furthermore, I found no support for the hypothesis that social group size differs seasonally as a consequence of differential breeding activity, which is again contrary to findings for mainland tropical forests. A high density of nectar resources on two islands appeared responsible for high population densities of the Micronesian Myzomela on them. Inter-island density comparisons showed strong evidence for there being unfilled niches on Sarigan, thereby making the island a favorable site for species translocations. Examination of the prehistoric composition of Marianas forest bird communities indicated that they once resembled in density structure those of the comparatively pristine Palau Islands. Removing ecologically similar but now absent species from the original Mariana communities likely resulted in reduced competition for resources in ways that increased niche breadth and, thus, populations. The wholesale loss of species in the Marianas has led to communities in which three ecologically versatile species now account for the vast majority of individuals in the community. Keywords: bird community, community structure, community dynamics, population density, Pacific island, native forest, disturbed habitat, THE AVIFAUNA OF THE MARIANA ISLANDS is among the most endangered on Earth. The southernmost island of Guam has, since the 1980s, lost virtually all of its native birds to [...]

Forest understory herbs exhibit a large range of variation in morphology and life history. Here, we expand the reported range of variation by describing the belowground structures of two very different species, Xerophyllum tenax (Pursh) Nutt. and Chimaphila umbellata (L.) Nutt. We excavated individuals in forests of the Cascade Mountains in the Pacific Northwest of the United States. Xerophyllum tenax has short rhizomes but an extensive root system that is exceptionally large among forest understory species. The roots reach 4 m in length and may occupy an area 50 times that of the aboveground canopy. In contrast, C. umbellata has very small roots but an extensive rhizome system. The largest plant we excavated had 57 m of connected rhizomes and still had a seedling source. Both species have long-lived individuals but differ in response to disturbance. On the basis of monitoring 151 permanent 1 [m.sup.2] plots in an old-growth forest, X. tenax increased only minimally in density over 40 years following tephra deposition from the 1980 eruption of Mount St. Helens, whereas the density of C. umbellata increased substantially. The very different morphology of these two species highlights the large range of variation found among forest herbs, which needs to be considered when examining the forest understory. Key words: Chimaphila umbellata, forest herbs, forest understory plants, Mount St. Helens, rhizomes, root systems, volcanic tephra, Xerophyllum tenax. Les herbes de sous-bois présentent une grande variabilité en matière de morphologie et de cycle biologique. Les auteurs élargissent ici la variabilité rapportée en décrivant les structures souterraines de deux espèces très différentes, Xerophyllum tenax (Pursh) Nutt. et Chimaphila umbellata (L.) Nutt. Ils ont excavé des individus dans les forêts de la chaîne des Cascades, sur la côte nord-ouest du Pacifique, aux Etats-Unis. Xerophyllum tenax possède des rhizomes courts, mais un système racinaire étendu qui est exceptionnellement grand parmi les espèces de sous-bois. Les racines atteignent 4 m de long et peuvent occuper une surface 50 fois supérieure à celle de la canopée aérienne. En revanche, C. umbellata a de très petites racines, mais un système de rhizomes étendu. La plus grande plante excavée avait 57 m de rhizomes connectés et avait encore une source de semis. Les deux espèces ont des individus à longue durée de vie, mais diffèrent dans leur réponse aux perturbations. D'après le suivi de 151 parcelles permanentes de 1 [m.sup.2] dans une forêt ancienne, la densité de X. tenax n'a augmenté que de façon minime au cours des 40 années qui ont suivi le dépôt de téphra de léruption du mont St Helens en 1980, alors que la densité de C. umbellata a augmenté de façon substantielle. La morphologie très différente de ces deux espèces met en évidence la grande variabilité que lon trouve parmi les herbes forestières, qui doit être pris en compte lors de l'examen du sous-étage forestier. [Traduit par la Rédaction] Mots-clés : Chimaphila umbellata, herbes forestières, plantes de sous-bois, mont Saint Helens, rhizomes, systèmes racinaires, téphra volcanique, Xerophyllum tenax., Introduction Understory herbs areanimportant componentofmany forest ecosystems and often make up the majority of the vascular species in temperate forests (Bierzychudek 1982; Whigham 2004; Gilliam 2007). These species constitute a [...]

In sea turtles, somatic growth rates and Age at Sexual Maturity (ASM) are important parameters for investigating population dynamics. Moreover, ASM informs on the time lag needed to observe the effects of past environmental variables, threats and conservation measures acting at nesting beaches on future numbers of clutches or nesting females, that are the most monitored indices. Assessing ASM of mixed populations that share the same foraging areas is difficult, as in the case of the Mediterranean Sea that is frequented by turtles originating from both the Mediterranean and the Atlantic. Here we investigated growth rates of loggerhead sea turtles (Caretta caretta) foraging in the Adriatic Sea, known to be frequented only by individuals of Mediterranean origin. Capture-mark-recapture records of 79 turtles provided growth rates ranging from - 1.1 to 9.6 cm yr.sup.-1 which were analyzed through Generalized Additive Models. When integrated with previous data on growth rates in the first years of life, results indicate a non-monotonic growth curve, likely due to an ontogenetic shift from oceanic to neritic areas. Using an integration equation, we estimated mean ASM to be 29.5 or 25.0 year based on mean nester size in Greece (83.4 cm curved carapace length, CCL) or across the Mediterranean (79.7 cm CCL), respectively. Growth rates and size-at-age are similar to the Atlantic population, but Mediterranean turtles mature earlier at a smaller size. The heterogenous growth rates and ASM reported so far in the Mediterranean are probably due, at least in part, to different foraging areas., Author(s): Giulia Baldi [sup.1] , Giovanni Furii [sup.2] , Massimo Del Vecchio [sup.2] , Pasquale Salvemini [sup.3] , Carola Vallini [sup.4] , Valeria Angelini [sup.5] , Sauro Pari [sup.5] , [...]

Moving toward ecosystem-based fisheries management requires integration of biotic and abiotic factors into our understanding of population dynamics. Using blue crab (Callinectes sapidus) in the Chesapeake Bay as a model system, we applied Gaussian Graphical Models (GGMs) to understand the influence of climatic, water quality, and biotic variables on estimates of key indices of blue crab recruitment for 1990-2017. Variables included the North Atlantic Oscillation (NAO), Susquehanna River discharge, wind forcing, hypoxic volume, submerged aquatic vegetation, and the catch per unit effort of striped bass (Morone saxatilis). Direct effects of age-1+ crabs and summer salinity on recruitment were significant. Phase of the NAO in summer and spring, summer and winter discharge, and hypoxic volume indirectly affected the recruitment. A simulation study showed that GGM model selection achieved nominal coverage and outperformed structural equation modeling (SEM) and Multivariate Adaptive Regression Splines (MARS). GGMs have the potential to improve ecosystem-based management of blue crabs in Chesapeake Bay. Specifically, the approach can be used to examine ecosystem impacts on blue crab productivity and to improve forecasts of blue crab recruitment. Le passage a une gestion ecosystemique des peches necessite l'integration de facteurs biotiques et abiotiques a la comprehension de la dynamique des populations. En utilisant le crabe bleu (Callinectes sapidus) de la baie de Chesapeake comme systeme modele, nous avons applique des modeles graphiques gaussiens (MGGs) pour comprendre l'influence de variables climatiques, biotiques et relatives a la qualite de l'eau sur les estimations d'indices cles du recrutement de crabes bleus pour la periode de 1990 a 2017. Ces variables comprennent l'oscillation nord-atlantique (ONA), le debit du fleuve Susquehanna, le forcage eolien, le volume hypoxique, la vegetation aquatique immergee et les prises par unite d'effort de bars d'Amerique (Morone saxatilis). Les effets directs des crabes de plus d'un an et de la salinite estivale sur le recrutement sont significatifs. La phase de l'ONA en ete et au printemps, le debit estival et hivernal et le volume hypoxique ont des effets indirects sur le recrutement. Une etude de simulation montre que la selection de modeles MGG atteint la couverture nominale et donne de meilleurs resultats que les modeles d'equations structurales (MES) et la regression multivariee par splines adaptatives (MARS). Les MGG pourraient ameliorer la gestion ecosystemique des crabes bleus dans la baie de Chesapeake. L'approche peut notamment etre utilisee pour examiner les impacts ecosystemiques sur la productivite des crabes bleus et pour ameliorer les projections de recrutement de crabes bleus. [Traduit par la Redaction], Introduction The importance of conducting fisheries management within an ecosystem-based context is becoming increasingly clear (Link 2010). Often ecosystem-based approaches are motivated by a desire to account for the impacts [...]

Abstract: The avifauna of Saipan, Northern Marianas Islands, includes a variety of endemic and range-restricted species of conservation concern. Monitoring population dynamics, trends, and vital rates of these species can [...]

Prey diversity and energy density have been linked to each other and to population trends in many studies of bird and mammal diets. We re-examined these relationships in Steller sea lions (Eumetopias jubatus (Schreber, 1776)) using data collected from the Aleutian Islands, where there has been a strong longitudinal gradient in population trend. Diet diversity and energy density metrics were similar in the western Aleutians, where sea lion counts declined consistently, and in the easternmost Aleutian area, where population trends improved significantly. We compared traditional deterministic diet diversity metrics with diversity scores based on an occupancy model that accounts for differences in sample size and uncertainty in prey group detection. This analysis indicated that there was no significant change in diet diversity over the 23-year study period or any significant differences across the Aleutian Islands. These results are consistent with prey abundance data from nine groundfish bottom trawl surveys conducted over the same period. While diet studies detail what Steller sea lions eat and provide an estimate of their energy intake, they provide only limited information on the energy expended to obtain their food or the consequences of their diet and foraging ecology on individual or population fitness. Key words: Steller sea lion, Eumetopias jubatus, diet, diet diversity, diet energy density, population dynamics, Aleutian Islands. La diversite des proies et la densite energetique ont ete reliees l'une a l'autre et a des tendances demographiques dans de nombreuses etudes sur les regimes alimentaires d'oiseaux et de mammiferes. Nous avons reexamine ces relations chez les otaries de Steller (Eumetopias jubatus (Schreber, 1776)) en utilisant des donnees recueillies dans les lles Aleoutiennes, ou la tendance demographique definit un important gradient longitudinal. Les mesures de la diversite du regime alimentaire et de la densite energetique etaient similaires dans l'ouest des Aleoutiennes, ou le nombre d'otaries avait uniformement diminue, et dans l'extreme est de l'archipel, ou les tendances demographiques s'etaient significativement ameliorees. Nous avons compare des mesures deterministes traditionnelles de la diversite des regimes alimentaires a des notes de diversite reposant sur un modele d'occupation qui tient compte des variations de la taille des echantillons et de l'incertitude associee a la detection des groupes de proies. L'analyse indique qu'il n'y a pas eu de changement significatif de la diversite des regimes alimentaires au cours des 23 annees de l'etude, ou de variations spatiales significatives a l'echelle des lles Aleoutiennes. Ces resultats concordent avec des donnees sur l'abondance de proies de neuf evaluations des poissons demersaux au chalut de fond menees durant la meme periode. Si les etudes des regimes alimentaires decrivent ce que les otaries de Steller mangent et fournissent une estimation de leur apport energetique, elles ne fournissent qu'une information limitee sur l'energie qu'elles depensent pour obtenir leur nourriture ou les consequences de leur regime alimentaire et de l'ecologie de leur approvisionnement sur l'aptitude individuelle ou de la population. [Traduit par la Redaction] Mots-cles : otarie de Steller, Eumetopias jubatus, regime alimentaire, diversite des regimes alimentaires, densite energetique du regime alimentaire, dynamique des populations, iles Aleoutiennes., Introduction Diversity is a commonly calculated index in diet studies of free-ranging predators. It has been related to population performance in both negative and positive ways depending on the circumstances. [...]

Stock reproductive potential informs population dynamics and response to harvest. Indices of body condition, like relative weight ([W.sub.r]), may indicate individual energetic state and provide a mechanistic link between spawning stock traits and recruitment. We tested for relationships among [W.sub.r] of three female size classes (381-456, 457-557, and [greater than or equal to] 558 mm total length), reproductive traits, and age-0 recruitment using data from 92 walleye (Sander vitreus) populations in the Ceded Territory of Wisconsin during 1989-2015 and a lake-specific time series from Escanaba Lake, Wisconsin, during 1958-2014. In Escanaba Lake, [W.sub.r] was positively related to maturation in small females and was positively related to fecundity and gonadosomatic index in intermediate fish. Among and within populations, [W.sub.r] demonstrated compensatory density dependence and positive relationships with growing degree-days. Recruitment was positively related to large female [W.sub.r] variation across lakes and negatively related to small female [W.sub.r] variation in Escanaba Lake. Improving the condition of large female walleye may promote recruitment, and [W.sub.r] may serve as an accessible metric of reproductive potential in walleye stock-recruit analyses. Le potentiel reproducteur des stocks fournit de l'information sur la dynamique des populations et les reactions a la peche. Des indices d'embonpoint, comme l'indice de masse relative ([W.sub.r]), pourraient refleter l'etat energetique des individus et constituer un lien mecaniste entre des caracteres du stock reproducteur et le recrutement. Nous avons verifie la presence de liens entre le [W.sub.r] de trois classes de taille de femelles (longueur totale : 381-456, 457-557 et [greater than or equal to] 558 mm), des caracteres associes a la reproduction et le recrutement d'individus de moins d'un an en utilisant des donnees de 92 populations de dore jaune (Sander vitreus) dans le Territoire cede du Wisconsin recueillies de 1989 a 2015, ainsi qu'une serie chronologique pour le lac Escanaba (Wisconsin) allant de 1958 a 2014. Dans ce lac, le [W.sub.r] est positivement relie a la maturation chez les petites femelles et a la fecondite et l'indice gonadosomatique chez les poissons de taille intermediaire. Au sein de populations et entre elles, le [W.sub.r] presente une dependance compensatoire sur la densite et des relations positives avec le nombre de jours de croissance. Le recrutement est positivement relie aux variations du [W.sub.r] des grosses femelles dans tous les lacs et negativement relie aux variations du [W.sub.r] des petites femelles dans le lac Escanaba. L'amelioration de l'embonpoint de gros dores jaunes femelles pourrait favoriser le recrutement, et le [W.sub.r] pourrait constituer une mesure facilement accessible du potentiel reproducteur pour les analyses du recrutement au stock pour le dore jaune. [Traduit par la Redaction], Introduction Variation in the reproductive potential of fish stocks can have important influences on population growth, recruitment dynamics, and responses to environmental change (Marshall et al. 1999; Dorner et al. [...]

Catchability plays a central role in fisheries stock assessment. Since catchability often varies with time depending on population density, environmental factors, and anthropogenic effects, assuming constant catchability in population models can lead to biased abundance estimates. Here we present a novel way to simultaneously estimate time-varying catchability and abundance by integrating a short-term (month-based) removal method and a long-term (year-based) age-structured population dynamics model. We applied this approach to commercial fishery data for a Japanese pufferfish (Takifugu rubripes) population and found that the models with time-varying catchability greatly outperformed the models with constant catchability in terms of predictive ability and model consistency. The temporal variation in catchability was parsimoniously predicted by fishing effort and population size, indicating the existence of effort- and density-dependent catchability. Our approach, integrating population dynamics at different timescales, will help avoid inadvertent overexploitation and contribute to sustainable harvesting by enhancing the estimation accuracy of time-varying catchability and abundance. La capturabilite joue un role cle dans l'evaluation des stocks de peche. Comme elle varie souvent dans le temps en fonction de la densite de population, de facteurs ambiants et d'effets d'origine humaine, l'hypothese d'une capturabilite constante dans les modeles de populations peut mener a des estimations biaisees de l'abondance. Nous presentons une nouvelle approche pour estimer simultanement la capturabilite variable dans le temps et l'abondance en integrant une methode de retrait a court terme (mensuel) et un modele de dynamique des populations structure par age a long terme (annuel). Nous appliquons cette approche a des donnees de peche commerciale pour une population de poissons-globes japonais (Takifugu rubripes) et constatons que les modeles integrant la capturabilite variable dans le temps donnent de bien meilleurs resultats que les modeles a capturabilite constante en ce qui concerne la valeur predictive et la coherence des modeles. La variation temporelle de la capturabilite est parcimonieusement predite par l'effort de peche et la taille de la population, ce qui indique l'existence d'une capturabilite dependant de l'effort et de la densite. Notre approche, qui integre la dynamique de la population a differentes echelles temporelles, aidera a eviter la surexploitation par inadvertance et favorisera des peches durables en rehaussant l'exactitude des estimations de la capturabilite variable dans le temps et de l'abondance. [Traduit par la Redaction], Introduction Fisheries scientists often must conduct stock assessments of fish populations using only commercial fisheries data. However, such data can be problematic because they are collected without proper sampling design [...]

Anthropogenic disturbance can negatively impact animal populations and alter the behaviour of individuals. Disturbance associated with the energy sector has been increasing in the boreal forest of northern Alberta. Disturbances associated with the oil and gas industry vary in the infrastructure present and sensory stimuli generated. Two common types are compressor stations and roads. It is important to assess population consequences of disturbance on small mammals because they serve as prey, predators, and seed-spore dispersers in the terrestrial ecosystems that they inhabit. To test the effects of disturbance from the energy sector on the abundance and activity of small mammals, we used mark-recapture methods and live-trapped in forested areas with one side adjacent to a clearing with industrial infrastructure present (road or compressor station) or absent (control sites). We found no difference in abundance or activity of deer mice (Peromyscus maniculatus (Wagner, 1845)) and southern red-backed voles (Myodes gapperi (Vigors, 1830)) between sites and did not detect an edge effect on abundance within sites, regardless of the presence of industrial infrastructure. Our results suggest minimal effects of industrial disturbance on the abundance and activity of these species, and the infrastructure and sensory stimuli generated are unlikely to be key drivers of their population dynamics or behaviour. Key words: boreal forest, compressor station, deer mouse, Peromyscus maniculatus, energy sector, live-trapping, roads, southern red-backed vole, Myodes gapperi. Les perturbations d'origine humaine peuvent avoir une incidence négative sur les populations animales et modifier le comportement des individus. Les perturbations associées au secteur énergétique sont en croissance dans la forêt boréale du nord de l'Alberta. Les perturbations associées à l'industrie pétrolière et gazière varient selon les infrastructures présentes et les stimuli sensoriels produits. Les stations de compression et les routes en sont des types répandus. Il importe d'évaluer les conséquences démographiques de perturbations sur les petits mammifères parce que ces derniers jouent des rôles de proies, prédateurs et agents de dispersion de graines ou spores dans les écosystèmes terrestres dans lesquels ils vivent. Pour vérifier les effets de perturbations par le secteur énergétique sur l'abondance et l'activité de petits mammifères, nous avons employé des méthodes de marquage-recapture et capturé des spécimens vivants dans des secteurs boisés ayant un côté attenant à une zone déboisée où des infrastructures industrielles (route ou station de compression) sont présentes ou absentes (sites témoins). Nous n'avons relevé aucune différence sur le plan de l'abondance ou de l'activité des souris sylvestres (Peromyscus maniculatus (Wagner, 1845)) et des campagnols de Gapper (Myodes gapperi (Vigors, 1830)) entre les sites, ni décelé d'effet de bordure sur l'abondance à l'intérieur des sites, que des infrastructures industrielles soient ou non présentes. Nos résultats indiqueraient donc des effets minimes des perturbations industrielles sur l'abondance et l'activité de ces espèces, et il est peu probable que les infrastructures et les stimuli sensoriels produits exercent une importante influence sur la dynamique de leurs populations ou sur leurs comportements. [Traduit par la Rédaction] Mots-clés : forêt boréale, station de compression, souris sylvestre, Peromyscus maniculatus, secteur énergétique, capture de spécimens vivants, routes, campagnol de Gapper, Myodes gapperi., Introduction Exploration and production of hydrocarbons have resulted in considerable alteration and fragmentation of vegetation conditions throughout North America (Allred et al. 2015) and specifically in the boreal forest of [...]

Understanding how environmental conditions influence habitat selection and suitability of free-ranging animals is critical, as the outcome may have implications for individual fitness and population dynamics. Density and snow are among the most influential environmental conditions driving habitat-selection patterns of northern ungulates. We used two decades of census data from high Arctic Greenland to quantify inter- and intra-annual variations in muskox (Ovibos moschatus (Zimmermann, 1780)) habitat selection and suitability during the Arctic summer (July through October). Across years, habitat selection varied considerably, and the strength of habitat selection appeared negatively related to both muskox density and spring snow cover. In early summer, habitat suitability was high and spatially rather uniform. Towards the autumn, suitable habitats contracted to just the lower elevations, when muskoxen exhibited increasingly stronger habitat selection towards low elevations and dense vegetation. This selection strategy clearly reflects the need to build up fat reserves for the upcoming winter, highlighting the energetic importance of the Arctic summer. Extreme climatic events such as freezing rainin autumn are increasing in frequency in Greenland and limit muskox access to high-quality forage in fens. Such events may therefore negatively affect the energy acquisition process of muskox with potential cascading consequences on population dynamics. Key words: Arctic, ecological-niche factor analysis, ENFA, ideal-free distribution, Mahalanobis distance, muskox, Ovibos moschatus. La compréhension de l'influence des conditions environnementales sur la sélection et la qualité des habitats d'animaux en liberté est d'importance capitale puisque cette influence peut avoir des conséquences sur l'aptitude des individus et la dynamique des populations. La densité et la neige figurent parmi les conditions environnementales qui exercent la plus grande influence sur les motifs de sélection d'habitats des ongulés septentrionaux. Nous utilisons deux décennies de données de recensement dans l'Extrême Arctique groenlandais pour quantifier les variations inter- et intra-annuelles de la sélection et de la qualité de l'habitat du boeuf musqué (Ovibos moschatus (Zimmermann, 1780)) durant l'été arctique (de juillet à octobre). D'une année à l'autre, la sélection de l'habitat varie considérablement, et la force de la sélection de l'habitat semble présenter une relation négative avec la densité de boeufs musqués et la couverture de neige printanière. Au début de l'été, la qualité de l'habitat est élevée et assez uniforme dans l'espace. À l'approche de l'automne, les habitats de qualité diminuent pour se limiter aux faibles altitudes, alors que les boeufs musqués présentent une sélection de l'habitat de plus en plus forte et ciblant les faibles altitudes et la végétation dense. Cette stratégie de sélection reflète clairement la nécessité d'accumuler des réserves de graisse pour l'hiver à venir, soulignant l'importance énergétique de l'été arctique. Les phénomènes climatiques extrêmes comme de la pluie verglaçante en automne sont de plus en plus fréquents au Groenland et limitent l'accès des boeufs musqués à de la nourriture de haute qualité dans les tourbières basses. De tels phénomènes peuvent donc avoir une incidence négative sur le processus d'acquisition d'énergie des boeufs musqués et une cascade d'effets possibles sur la dynamique des populations. [Traduit par la Rédaction] Mots-clés : Arctique, analyse factorielle de la niche écologique, ENFA, répartition libre idéale, distance de Mahalanobis, boeuf musqué, Ovibos moschatus., Introduction Understanding where and how animals select for habitat and resources therein is a crucial component of ecological research because the outcome of this process can have implications for individual [...]

The population size has far-reaching effects on the fitness of a population that in turn influences the population extinction or persistence. Understanding the density- and age-dependent factors will facilitate more accurate predictions about the population dynamics and its asymptotic behavior. In this paper, we develop a rigorous mathematical analysis of the study of positive and negative effects of the increased population density in the classical nonlinear age-structured population model. One of the main results expresses the global stability of the system in terms of the newborn function only. We establish the existence of a threshold population size implying the population extinction, which is well known in the population dynamics as the Allee effect. Bibliography: 18 titles. Illustrations: 1 figure. Dedicated to N. N. Uraltseva on the occasion of her 85th birthday, 1 Introduction In biological populations, the density-dependent regulation represents a change in individual fitness caused by changes in the population size or density. The negative density- dependence, often explained by [...]

Environmental drivers of population vital rates, such as temperature and precipitation, often vary at short time scales, and these fluctuations can have important impacts on population dynamics. However, relationships between survival and environmental conditions are typically modeled at coarse temporal scales, ignoring the role of daily environmental variation in survival. Our goal was to determine the importance of fine-scale temporal variation in survival to population dynamics of stream salmonids. We extended the Cormack-Jolly-Seber model to estimate daily survival rates from seasonal samples of individually marked brook trout (Salvelinus fontinalis) in a stream network. Daily variation in temperature and flow were strongly associated with survival, but relationships varied between juvenile and adult trout and among streams. In all streams, juveniles had higher mortality in warm, low-flow conditions, but in the two larger streams, cold, high-flow conditions also reduced juvenile survival. Adult survival decreased during low flows, particularly in the fall spawning period. Differing survival responses among stream network components to short-term environmental events created shifts in optimal location for maximum survival across life stages, seasons, and years. Les facteurs environnementaux qui influencent les indices vitaux dans les populations, comme la temperature et les precipitations, varient souvent a de courtes echelles temporelles, et ces fluctuations peuvent avoir des effets importants sur la dynamique des populations. Cependant, les relations entre la survie et les conditions environnementales sont souvent modelisees a des echelles temporelles grossieres, evacuant du coup le role des variations environnementales journalieres sur la survie. Notre objectif etait de determiner l'importance de variations temporelles de courte duree de la survie pour la dynamique de populations de salmonides de cours d'eau. Nous avons elargi le modele de Cormack-Jolly-Seber pour estimer les taux de survie journaliers a partir d'echantillons saisonniers d'ombles de fontaine (Salvelinus fontinalis) etiquetes individuellement dans un reseau hydrographique. Les variations journalieres de temperature et de debit etaient fortement associees a la survie, mais les relations etaient differentes entre les juveniles et les adultes et d'un cours d'eau a l'autre. Dans tous les cours d'eau, les juveniles presentaient un taux de mortalite plus eleve dans des conditions chaudes et de faible debit, mais dans les deux cours d'eau plus grands, des conditions froides et de debit fort reduisaient egalement la survie des juveniles. La survie des adultes diminuait durant de faibles debits, particulierement durant la saison de frai automnale. Des reactions differentes de la survie dans differentes composantes d'un reseau hydrographique a des episodes environnementaux de courte duree modifiaient l'emplacement optimal pour une survie maximum pour les differentes etapes de cycle de vie et les differentes saisons et annees. [Traduit par la Redaction], Introduction Drivers of population vital rates, such as temperature and stream-flow, often vary at short time scales, and these fluctuations can have important impacts on population dynamics. However, studies of [...]

The grasslands conversion to forests is occurring globally and modifying the population dynamics of species. Here, we characterized the population dynamics of Podocarpus lambertii Klotzsch ex Endl. over four years in southern Brazilian forest-grassland mosaics. We asked (i) if the studied P. lambertii population would decrease or increase over time and (ii) what the role of forest patches is in the growth and recruitment of a P. lambertii population. Thus, we studied forest-grassland mosaics, stratified the population into four demographic classes, evaluated the population dynamics, and estimated the correlation between canopy cover and average number of individuals. All individuals of P. Lambertii occurred in forest patches. Density was high but decreased from seedlings to the reproductive stage. The population growth rate was [lambda] = 1.025, and the recruitment of individuals was high and variable among years. The transition and mortality rates showed a pattern of reduction from seedlings to the reproductive stage. Mortality rate for seedlings and juveniles was low and concentrated at the smaller heights. The correlations between canopy cover and the average number of individuals were positive and significant. The ecological characteristics of this species and specific conditions provided by forest patches allow population growth and species conservation in the southern Brazilian forest-grassland mosaics. Key words: canopy cover, conifers, forest patches, matrix population model, invasion of grasslands. La conversion des prairies en forets se poursuit globalement et modifie la dynamique de population des especes. Dans cet article, nous avons caracterise la dynamique de population de Podocarpus lambertii Klotzsch ex Endl. sur une periode de quatre ans dans les mosaiques de foret et de prairie du sud du Bresil. Nous nous demandons (i) si la population de P. lambertii a l'etude diminue ou augmente avec le temps et (ii) quel role jouent les parcelles de foret dans la croissance et le recrutement de la population de P. lambertii. Nous avons donc etudie les mosaiques de foret et de prairie, stratifie la population en quatre classes demographiques, evalue la dynamique de population et estime la correlation entre l'etendue du couvert forestier et le nombre moyen d'individus. Tous les individus de l'espece ont ete retrouves a l'interieur des parcelles de foret. La densite etait elevee mais diminuait du stade de semis au stade de reproduction. Le taux de croissance de la population etait [lambda] = 1,025 et le recrutement des individus etait eleve et variable selon les annees. Les taux de transition et de mortalite diminuaient du stade de semis au stade de reproduction. Le taux de mortalite chez les semis et les individus du stade juvenile etait faible et la mortalite etait concentree parmi les tiges les moins hautes. Les correlations entre l'etendue du couvert forestier et le nombre moyen d'individus etaient positives et significatives. Les caracteristiques ecologiques de cette espece et les conditions specifiques associees aux parcelles de foret permettent la croissance de la population et la conservation de l'espece dans les mosaiques de foret et de prairie du sud du Bresil. [Traduit par la Redaction] Mots-cles : etendue du couvert forestier, coniferes, parcelles de foret, modele matriciel de population, invasion des prairies., Introduction The structure of plant populations may be shaped by local biotic and abiotic conditions and can be characterized in terms of age, size, and form of the individuals that [...]

We studied the consequences of a nonnative species introduction and changes in temperature on early mortality and recruitment of native rainbow smelt (Osmerus mordax) and nonnative alewife (Alosa pseudoharengus) in Lake Champlain using a simulation model. Distribution patterns of adults and young-of-the-year (YOY) fish were predicted using a model based on observed distribution of different age groups as a function of temperature and light profiles simulated on a daily basis. Mortality rates averaged over the growing season were calculated as a function of fish densities and overlap between adults and YOY. Survival of YOY rainbow smelt and alewife depended on which predator was most abundant. Rainbow smelt YOY mortality rates are highest when rainbow smelt adults are abundant, and alewife YOY mortality rates are highest when alewife adults are abundant, potentially allowing coexistence. August and September mortality rates were higher in the climate change scenario because of increased overlap of adults and YOY of both species. These results indicate that accounting for spatiotemporal fish distribution patterns can be important when forecasting the interacting effects of climate change and aquatic invasive species on fish recruitment. Nous avons etudie les consequences de l'introduction d'une espece non indigene et des changements de temperature sur la mortalite precoce et le recrutement d'eperlans arc-en-ciel (Osmerus mordax) indigenes et de gaspareaux (Alosapseudoharengus) non indigenes dans le lac Champlain en utilisant un modele de simulation. Les motifs de repartition de poissons adultes et jeunes de l'annee ont ete predits en utilisant un modele base sur la repartition observee de differents groupes d'age en fonction de la temperature et de profiles de lumiere simules sur une base quotidienne. Les taux de mortalite moyens pour la saison de croissance ont ete calcules en fonction des densites de poissons et du chevauchement des adultes et des jeunes de l'annee. La survie des eperlans arc-en-ciel et des gaspereaux jeunes de l'annee depend du predateur qui est le plus abondant. Les taux de mortalite des eperlans arc-en-ciel jeunes de l'annee sont les plus eleves quand les eperlans arc-en-ciel adultes sont abondants et les taux de mortalite des gaspareaux jeunes de l'annee sont les plus eleves quand les gaspareaux adultes sont abondants, permettant possiblement une coexistence. Les taux de mortalite en aout et septembre sont les plus eleves dans le scenario de changement climatique en raison du chevauchement accru d'adultes et de jeunes de l'annee des deux especes. Ces resultats indiquent que la prise en consideration des motifs de repartition spatiotemporelle des poissons peut etre importante pour la prediction des effets interactifs des changements climatiques et d'especes aquatiques envahissantes sur le recrutement de poissons. [Traduit par la Redaction], Introduction Environmental and biological mechanisms causing variable recruitment in fish populations have long been of interest to fisheries science (Cushing 1975; Wootton 1990; Diana 1995) and have received increased attention [...]

Understanding what drives variation in fish abundance at reference sites provides perspective for assessing the effects of human alterations to river flow and land use. We examined temporal variation in fish community abundance in a headwater tributary of a large river in the upper South Island (New Zealand) over 10 years. We were interested in the influence of natural flow variation and temperature on native fish abundance within the context of potential competition/predation pressure from juvenile introduced trout. Results from biannual sampling highlighted the dominating influence of floods on fish population dynamics, overriding biotic effects. We found no evidence for adverse effects of trout on native fish, and flow-related habitat performed more poorly in explaining variation in fish abundance than low- and median-flow statistics. Differences in temporal variation in abundance between species were largely consistent with life histories that provide resistance and (or) resilience to flood flows and relative insensitivity to low flows. Long-term data (>10 years) are needed for detecting meaningful trends and quantifying the effects of human activities on fish community abundance. La comprehension des facteurs qui modulent les variations de l'abondance de poissons dans des sites de reference fournit une perspective pour evaluer les effets des modifications d'origine humaine du debit de rivieres et de l'utilisation des sols. Nous avons examine les variations temporelles de l'abondance de la communaute de poissons dans un affluent d'amont d'une grande riviere dans la partie nord de l'ile du Sud (Nouvelle-Zelande) sur une periode de 10 ans. Nous cherchions a comprendre l'influence des variations naturelles du debit et de la temperature sur l'abondance des poissons indigenes dans le contexte d'une pression de concurrence/predation potentielle par des truites introduites juveniles. Les resultats d'un echantillonnage semestriel font ressortir l'influence dominante des crues sur la dynamique des populations de poissons, supplantant les effets biotiques. Nous n'avons trouve aucun indice d'effets adverses des truites sur les poissons indigenes, et les habitats associes a l'ecoulement expliquent moins bien les variations d'abondance des poissons que les statistiques concernant les debits faibles et medians. Les differences de variations temporelles d'abondance entre especes s'expliquent en bonne partie par des cycles biologiques qui assurent une resistance ouune resilience aux debits de crue et une insensibilite relative aux faibles debits. Des donnees a long terme (>10 ans) sont necessaries pour pouvoir detecter des tendances significatives et quantifier les effets de l'activite humaine sur l'abondance de communautes de poissons. [Traduit par la Redaction], Introduction Freshwater fish are an integral component of aquatic ecosystems, and they have significant conservation, cultural, recreational, and economic values. They are also declining globally (Closs et al. 2015; Piccolo [...]

We investigated patterns of grass pickerel (Esox americanus vermiculatus Lesueur, 1846) distribution in three watersheds in Ontario, Canada, using site- and reach-scale habitat variables and fish community assemblage data to determine why this species occurs sporadically throughout watersheds despite abundant seemingly suitable, but unoccupied, habitat. Habitat and fish community data were collected using conventional field sampling methods, and reach-scale habitat data were compiled with the aid of a geographic information system. We found that occupied sites had lower baseflow indices and reach slopes but higher conductivity and agricultural land uses than unoccupied sites. More grass pickerel were detected when conductivity, channel cover, and wetlands in the floodplain were highest and bank slopes lowest; this is consistent with habitat preferences described elsewhere in its range. Habitat features at the site scale appeared more important than reach-scale features suggesting that grass pickerel may be using small habitat patches. This study identifies habitat elements important to grass pickerel and offers insights into management implications. Key words: habitat, distribution, endangered, fish, Canada, grass pickerel, Esox americanus vermiculatus. Nous avons examiné les motifs de répartition du brochet vermiculé (Esox americanus vermiculatus Lesueur, 1846) dans trois bassins versants en Ontario (Canada) en utilisant des variables associées à l'habitat à l'échelle du site et du tronçon et des données sur les assemblages des communautés de poissons afin d'établir les causes de la présence sporadique de l'espace à la grandeur des bassins versants malgré des habitats en apparence abondants, mais inoccupés. Les données sur l'habitat et les communautés de poissons ont été recueillies par des méthodes classiques d'échantillonnage de terrain, et les données sur l'habitat à l'échelle du tronçon ont été compilées à l'aide d'un système d'information géographique. Nous avons constaté que les sites occupés présentaient des indices de débit de base et des pentes de tronçon plus faibles, mais une plus grande conductivité et plus d'utilisations agricoles des terres que les sites inoccupés. Plus de brochets vermiculés étaient détectés là où la conductivité était la plus élevée, où la couverture du chenal et les milieux humides dans la plaine inondable étaient les plus abondants et où les pentes des berges étaient les plus faibles, ce qui concorde avec les préférences en matière d'habitat décrites ailleurs dans l'aire de répartition de l'espèce. Les éléments de l'habitat à l'échelle du site semblent plus importants que les éléments à l'échelle du tronçon, ce qui donne à penser que le brochet vermiculé pourrait utiliser de petites parcelles d'habitat. L'étude cerne des éléments de l'habitat qui sont importants pour le brochet vermiculé et en éclaire les conséquences en ce qui concerne la gestion. [Traduit par la Rédaction] Mots-clés : habitat, répartition, en péril, poisson, Canada, brochet vermiculé, Esox americanus vermiculatus., Introduction Most imperiled freshwater fishes are spatially rare; they often occur over a small geographic range in infrequent patches (Sheldon 1988; Magurran and Henderson 2003; Fagan and Stephens 2006; Jelks [...]

Part of the western Atlantic population of leatherback turtles (Dermochelys coriacea (Vandelli, 1761)) forage in Canadian waters, where high-use areas have been identified using satellite telemetry and opportunistic sightings. Here, we use sightings of leatherback turtles and ocean sunfish (Mola mola (Linnaeus, 1758)) obtained during a systematic large-scale aerial survey, along with opportunistic turtle sightings, to examine the seasonal occurrence and distribution of leatherback turtles in eastern Canada. Using environmental correlates, we predict the spatial and seasonal development of potentially suitable habitats. All data sets confirmed the presence of leatherback turtles off Nova Scotia during summer. They also highlighted turtle occurrence off southern Newfoundland. Opportunistic sightings suggest a seasonal shift in main turtle concentrations from southwest to northeast, with use of southern Newfoundland waters extending into September. A generalized additive model linking environmental characteristics and turtle observations suggests adding the Grand Banks off Newfoundland and waters east of Anticosti Island in the Gulf of St. Lawrence to the potentially important habitat for leatherback turtles. Direct observations helped delineate habitat currently used by leatherback turtles. In the context of climate change, this modelling approach may improve our ability to forecast changes in turtle habitat suitability and the risks of entrapment or collision associated with potentially changing usage patterns. Key words: leatherback turtle, Dermochelys coriacea, habitat, western Atlantic population, ocean sunfish, Mola mola, aerial survey, opportunistic sightings, spatial analysis. Une partie de la population de tortues luths (Dermochelys coriacea (Vandelli, 1761)) de l'Atlantique Ouest se nourrit dans les eaux canadiennes, où plusieurs aires fortement utilisées ont été cernées à partir de télémétrie satellitaire et d'observations opportunistes. Nous utilisons des observations de tortues luths et de poissons-lunes (Mola mola (Linnaeus, 1758)) obtenues dans le cadre d'un inventaire aérien systématique à grande échelle, ainsi que des observations opportunistes pour examiner la présence saisonnière et la répartition des tortues luths dans l'est du Canada. En utilisant des variables environnementales associées aux observations, nous prédisons l'évolution spatiale et temporelle des habitats potentiellement convenables. Tous les ensembles de données confirment la présence des tortues luths au large de la Nouvelle-Écosse durant l'été. Ils mettent également en lumière la présence de tortues dans les eaux situées au sud de Terre-Neuve. Les observations opportunistes laissent croire à un déplacement saisonnier des principales concentrations de tortues luths du sud-ouest vers le nord-est, et à l'utilisation jusqu'en septembre des eaux au sud de Terre-Neuve. Un modèle additif généralisé reliant les caractéristiques environnementales aux observations de tortues luths donne à penser qu'il faut ajouter les Grands Bancs de Terre-Neuve et les eaux à l'est de l'île d'Anticosti dans le golfe du Saint-Laurent aux habitats potentiellement importants pour les tortues luths. Les observations directes aident à délimiter les habitats utilisés actuellement par les tortues luths. Dans un contexte de changements climatiques, cette approche de modélisation pourrait améliorer la capacité de prédire les modifications des habitats de la tortue luth et les risques de piégeage ou de collision associés au changement possible des motifs d'utilisation. Mots-clés : tortue luth, Dermochelys coriacea, habitat, population de l'Atlantique Ouest, poisson-lune, Mola mola, inventaire aérien, observations opportunistes, analyse spatiale., Introduction The leatherback turtle (Dermochelys coriacea (Vandelli, 1761)) is the world's most widely distributed marine reptile, migrating across the tropical and temperate waters of the Atlantic, Pacific, and Indian oceans [...]

Partial migration, the phenomenon in which animal populations are composed of both migratory and nonmigratory individuals, is widespread among migrating animals. The proportion of migrants in these populations has direct influences on population genetics and dynamics, ecosystem dynamics, mating systems, evolution, and responses to environmental change, yet there are very few studies that measure the proportion of migrants. This is because existing methods to estimate the proportion of migrants are time-consuming and expensive. In this paper, we demonstrate a new method for estimating the proportion of migrants in a population based on sex ratio measurements. Many partially migratory taxa exhibit sex-biased migration or residency, and in these cases, the sex ratios of migrants and nonmigrants are fundamentally related to the proportion of migrants in the population. We define this relationship quantitatively and show how it can be used to infer the proportion of migrants in a population through a process we term 'sex-ratio balancing'. We obtain Bayesian estimates of proportion of migrants and quantify the uncertainty in these estimates with highest posterior density intervals. Lastly, we validate the sex-ratio balancing approach with a Chinook salmon (Oncorhynchus tshawytscha Walbaum in Artedi, 1792) data set. Sex-ratio balancing holds promise as a tool for quantifying partial migration and filling a key data gap about partially migratory taxa. Key words: partial migration, sex-ratio balancing, sex ratio, female-biased migration, Chinook salmon, Oncorhynchus tshawytscha, life-history diversity. La migration partielle, le phenomene selon lequel des populations animales sont composees d'individus migrateurs et non migrateurs, est repandue chez les animaux migrateurs. Si la proportion de migrants dans ces populations influence directement la genetique et la dynamique de la population, la dynamique des ecosystemes, les systemes de reproduction, l'evolution et les reactions aux changements environnementaux, tres peu d'etudes mesurent la proportion de migrants. La raison en est que les methodes disponibles pour estimer la proportion de migrants demandent beaucoup de temps et d'argent. Nous faisons la demonstration d'une nouvelle methode pour estimer la proportion de migrants dans une population, qui repose sur des mesures du rapport de masculinite. Chez de nombreux taxons partiellement migrateurs, la migration ou la residence sont biaisees selon le sexe et, dans ces cas, les rapports de masculinite des migrants et non-migrants sont fondamentalement relies a la proportion de migrants dans la population. Nous definissons quantitativement cette relation et montrons comment elle peut etre utilisee pour inferer la proportion de migrants dans une population par un processus que nous appelons 'equilibrage du rapport de masculinite' (<< sex-ratio balancing >>). Nous obtenons des estimations bayesiennes de la proportion de migrants et quantifions l'incertitude de ces estimations avec des intervalles de densite posterieure les plus eleves. Enfin, nous validons l'approche d'equilibrage du rapport de masculinite en utilisant un ensemble de donnees sur le saumon chinook (Oncorhynchus tshawytscha (Walbaum in Artedi, 1792)). L'equilibrage du rapport de masculinite est un outil prometteur pour quantifier la migration partielle et combler une importante lacune dans les donnees sur les taxons partiellement migrateurs. [Traduit par la Redaction] Mots-cles : migration partielle, equilibrage du rapport de masculinite, rapport de masculinite, migration biaisee en faveur des femelles, saumon chinook, Oncorhynchus tshawytscha, diversite des cycles biologiques., Introduction Life-history diversity is recognized as an important mechanism for population persistence, stability, and resilience (Kerr et al. 2010; Schindler et al. 2010). One particularly dramatic form of life-history diversity [...]