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Similar to many freshwater ecosystems, the Laurentian Great Lakes of North America have undergone numerous anthropogenic stressors resulting in considerable loss of biodiversity and habitat. Among Great Lakes fishes, the coregonine sub-family has endured the most extensive declines, including extinction of several species (Coregonus johannae, C. alpenae, and C. kiyi orientalis) and at least 10 instances of local extirpations of other species (C. nigripinnis, C. reighardi, C. zenithicus, C. hoyi, and C. artedi) across all 5 lakes, much of which occurred prior to the 1960s owing to overfishing, interactions with non-indigenous species, and habitat loss. Despite these declines, no federal-, provincial-, or state-mandated actions were ever implemented to conserve coregonine diversity, potentially because so much of the coregonine declines occurred prior to the enactment of federal conservation legislation. Possible explanations for inaction since enactment of that legislation include insufficient data on biological vulnerability or threats, unresolved taxonomy, and limited support from the fishery management agencies and their stakeholders prior to the 2000s. In recent decades, however, several fishery management agencies have undertaken efforts to re-introduce coregonine diversity. These efforts helped lead to development of a science-based framework to restore coregonines that was universally endorsed by fishery managers representing eight U.S. states, four U.S. tribal organizations, and the province of ON, Canada, in May 2018. The basin-wide framework is based on principles of conservation biology and adaptive management. We describe details of its key steps, including planning, restoring, and evaluating, while also describing recent implementation efforts to develop methods, improve available resources, and enhance coordination across the basin. Although our paper describes a regional effort to restore native coregonines, our adaptive-management approach could be used by other multi-agency stakeholders seeking to conserve or restore native fishes. [ABSTRACT FROM AUTHOR]

Canadian coastal waters of the Pacific Ocean and the Atlantic Ocean as well as inland freshwater habitats in Ontario were sampled for centrohelid heliozoans (free-living heterotrophic single-celled organisms) over a period of nearly five decades. More than 60 species and subspecies were revealed, including 1 Triangulopteris, 1 Raphidocystis, 2 Pseudoraphidocystis, 3 Raineriophrys, 4 Pseudoraphidiophrys, 12 Choanocystis, 15 Pterocystis, and 25 Acanthocystis taxa. Of these, 22 were officially named and described as new to science based primarily on the morphology of the siliceous scales that cover the cell. New species were compared with images and/or descriptions of close "relatives" to validate their new species assignments. New data on five species of Acanthocystis and one species of Choanocystis required revisions of their descriptive taxonomy that in some cases resulted in the splitting off of separate species or subspecies. Very little can be concluded about global distribution of centrohelid heliozoans, owing to the paucity of records. For many of the taxa reported here, previous records consist of just one or two findings from other parts of the world. One example is Choanocystis antarctica Tikhonenkov and Mylnikov, 2011 that was previously known only from Antarctic seawater, but is reported here from an Ontario softwater lake. [ABSTRACT FROM AUTHOR]

Globally, many freshwater species are depleting and require population-level assessments. Many species distribution modelling frameworks are available for such assessments, but comparisons are needed to understand their predictive performance under different settings. K-fold cross-validation techniques were employed to compare the performance of three commonly used frameworks: machine learning, spatiotemporal modelling, and Gaussian process (GP) modelling. Through application to New Zealand populations of longfin eel (Anguilla dieffenbachii) and shortfin eel (Anguilla australis), area under the receiver operating characteristic curve (AUC) and true skill statistic (TSS) model performance metrics were estimated. All modelling frameworks produced approximately consistent distribution maps but differed in predictive performance. AUC and TSS results indicated that model predictions from the spatiotemporal modelling framework were the most accurate, followed by GP modelling. However, all modelling frameworks performed similarly when training and test data were spatially independent. In addition to having the best predictive performance, the spatiotemporal modelling framework showed the greatest promise for advancement in population-level assessment and is therefore recommended. The results are useful for freshwater ecologists and resource managers to make informed decisions on the appropriateness of a modelling framework for their research objective. [ABSTRACT FROM AUTHOR]

Many anguillid eel species display facultative catadromy. Some eel spend their entire life cycle in marine coastal areas, but the geographical extent of this, especially at the extremes of their distributional ranges, is unknown. We analysed otolith Sr:Ca and Ba:Ca from yellow-stage European eel (Anguilla anguilla) sampled along the coast of Norway and in several freshwater lakes (58°N–63°N), to infer their initial settlement and later life movement patterns with regards to habitat salinity. Most eel (80%) sampled in marine habitats (n = 371) had settled and remained in marine water, but 20% had moved between marine and freshwater habitats and were hence classified as inter-habitat shifters. Among freshwater sampled eel (n = 99), 80% had settled and remained in fresh water, but 20% were classified as inter-habitat shifters. The average growth rates for marine water residents, inter-habitat shifters, and freshwater residents were 35, 27, and 17 mm·year–1, respectively. Northern European shallow marine habitats may serve as important yellow eel growth habitats and may be critical to buffer the European eel population against the general decrease in continental recruitment. [ABSTRACT FROM AUTHOR]

Trichomycetes are a group of fungi and protists living in the guts of immature aquatic insects and other arthropods. The nature of this relationship is poorly understood but it is mostly described as obligately commensalistic, with the microbes exploiting a unique microhabitat. Collections of trichomycetes were made from freshwater insects in aquatic habitats near Castlegar in the Columbia Mountains, part of the Rocky Mountain Range in southeastern British Columbia. The collection sites were at altitudes ranging from 435 to 935 m and were made in July 2006. A total of 32 species were recorded including four new species, Harpella filispora sp. nov., Orphella columbiensis sp. nov., Smittium nodiradicatum sp. nov., and Smitium basiangustatum sp. nov. described here. These are the first records from Western Canada and two, Austrosmittium patagonicum and Glotzia distorta are new continental records. These findings are compared to reports from the western edge of the Rocky Mountain range near the Boise Mountains in Idaho and the Southern Rockies in Colorado. [ABSTRACT FROM AUTHOR]

Although human fragmentation of freshwater habitats is ubiquitous, the genetic consequences of isolation and a roadmap to address them are poorly documented for most fishes. This is unfortunate, because translocation for genetic rescue could help mitigate problems. We used genetic data (32 SNPs) from 203 populations of westslope cutthroat trout (Oncorhynchus clarkii lewisi) to (1) document the effect of fragmentation on genetic variation and population structure, (2) identify candidate populations for genetic rescue, and (3) quantify the potential benefits of strategic translocation efforts. Human-isolated populations had substantially lower genetic variation and elevated genetic differentiation, indicating that many populations are strongly influenced by random genetic drift. Based on simple criteria, 23 populations were candidates for genetic rescue, which represented a majority (51%) of suitable populations in one major region (Missouri drainage). Population genetic theory suggests that translocation of a small number of individuals (∼5 adults) from nearby populations could dramatically increase heterozygosity by up to 58% (average across populations). This effort provides a clear template for future conservation of westslope cutthroat trout, while simultaneously highlighting the potential need for similar efforts in many freshwater species. [ABSTRACT FROM AUTHOR]

Diadromous species act as nutrient vectors between their marine and freshwater habitats. Few valuations of this regulating service exist and none at the scale of species distribution ranges. This large-scale approach seems particularly relevant for species moving and exchanging individuals across borders and territories as these populations may strongly depend upon each other in terms of population viability and provision of ecosystem services. The development of a new nutrient routine within an existing mechanistic species distribution model provided estimates of the "maximum potential" of the anadromous allis shad (Alosa alosa) to provide nitrogen and phosphorous subsidies throughout western Europe. During their seasonal reproductive migration, shad provided low amounts of nutrient subsidies when compared to North American anadromous species and annual riverine nutrient loads. However, these subsidies are delivered as pulses concentrated in space and time, suggesting that more work is needed to figure out the significance of these shad-derived nutrients in terms of riverine ecosystem functioning. The evidence of a substantial flow of strayers delivering nutrient subsidies in several rivers confirmed the need for large-scale management of migratory species to ensure a sustainable provision of ecosystem services. [ABSTRACT FROM AUTHOR]

We quantified the population dynamics and life history diversity of seven brood years of coho salmon (Oncorhynchus kisutch) using a life-cycle approach. Four life history patterns, composed of fry, fry–nomad, parr, and yearling migrants indicated the importance of connectivity and access to a full range of freshwater and estuarine rearing environments through the year. Survival of each life history type varied annually with the yearling migrants contributing an average of 70% to the spawners in all but one return year. Fifty-eight percent of the spawners of the 2013 return year had an estuarine rearing strategy, primarily parr migrants that overwintered in the estuary. Fry migrants, thought to be surplus production, were consistently observed in the estuary and represented in the returning spawners. The annual contribution of alternative rearing strategies to the spawners may support the resilience and viability of the population. We recommend that life cycle models of coho salmon account for the contribution of estuary migrants to the productivity and persistence of coho salmon in support of management and restoration of populations. [ABSTRACT FROM AUTHOR]

Effective management of freshwater fish habitat is essential to supporting healthy aquatic ecosystems and sustainable fisheries. In Canada, recent changes to the Fisheries Act enhanced the protection of fish habitat, but application of those provisions relies on sound scientific evidence. We employed collaborative research prioritization methods to identify scientific research questions that, if addressed, would significantly advance the management of freshwater fish habitat in Canada. This list was generated by a diverse group of freshwater fish experts, including substantial contributions from practitioners who administer provisions of the Fisheries Act. The research questions generated in this study identify priority topics for future research, while highlighting issues that could be addressed with different funding models. As a result, this study should support evidence-based management of Canada's aquatic resources by identifying scientific knowledge gaps faced by practitioners, and suggesting mechanisms to address them. Given the important contribution of Canadian freshwater systems to global ecosystem values, and the similar scientific challenges facing fish habitat managers in other jurisdictions, this study is likely to have broad applicability. [ABSTRACT FROM AUTHOR]

This review provides a Canadian perspective on freshwater zooplankton diversity and ecology across scales and systems. It aims at describing how zooplankton are diverse in forms and functions, and constitute a key component of plankton food webs, a model for ecological theories and a sentinel for monitoring ecological integrity and function in lakes facing environmental changes and anthropogenic stressors. These objectives are addressed across a continuum of scales (continental, regional and local) and systems (reservoirs, lakes and ponds). This perspective shows that the environmental control of zooplankton biodiversity, community structure and function in Canada is complex and variable. Zooplankton communities demonstrated a wide range of responses to anthropogenic disturbances across scales and systems due to interactions with watershed biogeochemistry and climate. This review supports the Multiple Forces hypothesis where forcing by abiotic factors (climate, nutrients, morphometry and chemistry) has a fundamental role at continental scale over Canadian ecoregions, and at regional scale in the Boreal ecozones. In contrast, forcing by biotic factors (algal resources and predators) is relatively more influential at local scale, in resort and urban regions. The challenge for future research will be to combine all new concepts and approaches in a global perspective to better understand the responses of freshwater zooplankton to multiple environmental changes and anthropogenic stressors in Canada. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Two primary goals in fisheries research are to (i) understand how habitat and environmental conditions influence the distribution of fishes across the landscape and (ii) make predictions about how fish communities will respond to environmental and anthropogenic change. In inland, freshwater ecosystems, quantitative approaches traditionally used to accomplish these goals largely ignore the effects of species interactions (competition, predation, mutualism) on shaping community structure, potentially leading to erroneous conclusions regarding habitat associations and unrealistic predictions about species distributions. Using two contrasting case studies, we highlight how joint species distribution models (JSDMs) can address the aforementioned deficiencies by simultaneously quantifying the effects of abiotic habitat variables and species dependencies. In particular, we show that conditional predictions of species occurrence from JSDMs can better predict species presence or absence compared with predictions that ignore species dependencies. JSDMs also allow for the estimation of site-specific probabilities of species co-occurrence, which can be informative for generating hypotheses about species interactions. JSDMs provide a flexible framework that can be used to address a variety of questions in fisheries science and management. [ABSTRACT FROM AUTHOR]

This study examined the migratory patterns of introduced rainbow trout (Oncorhynchus mykiss) in three rivers in Prince Edward Island, Canada, using acoustic telemetry and otolith microchemistry. Only 6% of acoustically tagged fish in three river systems left coastal embayments. A cohort of rainbow trout in all three rivers entered saline waters. Habitat use differed among migrants in the three rivers, as Montague River fish occupied estuary habitat (mean 20.79 PSU) more often than West River and Dunk River fish that tended to occupy both riverine tidal (mean 1.27 and 4.29 PSU, respectively) and freshwater habitats (<0.5 PSU), particularly during summer months (July and August). A second cohort of rainbow trout remained exclusively in fresh water. Migratory individuals were more likely to arise from anadromous mothers, but freshwater mothers produced migratory offspring in all sites. Migratory individuals were significantly larger than nonmigratory freshwater residents. This study suggests that partial residency was the primary strategy, with prominent tidal occupation, while secondary marine and freshwater contingents were included in the full range of successful migratory strategies. [ABSTRACT FROM AUTHOR]

Management and conservation of freshwater habitat requires fine spatial resolution and watershed-scale and life-stage-specific methods due to complex linkages among land, climate, water uses, and aquatic organism necessities. In this study, we present a valley-scale microhabitat resolution, process-based bioenergetics approach that combines high-resolution topobathymetric LiDAR survey with two-dimensional hydrodynamic and bioenergetics modeling. We applied the model to investigate the role of lateral habitat, stream morphological complexity, water use, and temperature regimes on aquatic habitat quality distribution of juvenile Chinook salmon (Oncorhynchus tshawytscha) within the Lemhi River (eastern Idaho, USA). Modeling results showed two key aspects: (i) a reduction in diverted flows is not sufficient to improve habitat quality potentially because of a legacy of morphological simplification (directly due to straightening and wood removal and indirectly due to low in-channel flows) and (ii) morphological complexity and connectivity with side channels and margin areas, which are key and vital elements to support suitable habitats that meet or exceed energetic needs to sustain or promote growth of individuals and populations. [ABSTRACT FROM AUTHOR]

It is hypothesized that in diadromous fish, migrations may occur because of differences in the availability of food in marine and freshwater habitats. The benefits of migration to sea may be increased growth opportunities and reproductive output, while the costs may be increased mortality and increased energy use. Here we examine mortality rates of anadromous Arctic char (Salvelinus alpinus) and brown trout (Salmo trutta) in fresh water and at sea over a 25-year period to test these hypotheses. Daily mortality rates were 5–15 times higher at sea than in fresh water, with highest rates for first-time migrants, inferring a clear trade-off between increased mass gain and mortality risk during the sea migration. Descending smolts were caught in a trap at the outlet of the river, individually tagged, and thereafter recorded each time they passed through the trap on their annual migration between the river and the sea. Brown trout females seemed to benefit to a higher degree from migrating to sea than did female Arctic char, probably because of the higher growth rate at sea, and hence higher reproductive output. [ABSTRACT FROM AUTHOR]

Trichomycetes are fungi and protists living in the guts of arthropods. Herbivorous insects in freshwater habitats commonly house these microbes, and there are over 300 species described. One very common group of aquatic insects occurring in most freshwater systems is caddisflies, belonging to the Order Trichoptera. Although these are potentially good hosts for trichomycetes, there has been little published on trichomycetes in this host and none have been described from caddisflies. We collected and dissected caddisfly larvae from multiple sites in Canada from 2001 to 2018 and describe five new species of trichomycetes from trichopteran larvae. Data are presented on the prevalence and seasonal variation of trichomycetes in caddisfly larvae at one site in Nova Scotia where multi-year collections were made. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Body size is one of the most perceptible traits of organisms and is an important fitness proxy in evolutionary studies. Oceanic threespine stickleback ( Gasterosteus aculeatus L., 1758) have colonized and adapted to numerous freshwater habitats throughout the Holarctic since the most recent glacial retreat, giving us natural 'replicates' of both convergent and divergent evolution. I observed considerable body-size variation among 22 threespine stickleback populations within a small region surrounding Cook Inlet, Alaska, USA. Larger bodied populations tended to have bimodal size-frequency distributions, whereas most smaller bodied populations had unimodal distributions. Bimodal distributions suggested the presence of at least two age classes within large-bodied populations. I used a Bayesian approach to infer mean size of presumed age-1 and age-2+ fish from bimodal size-frequency distributions; I found significant differences in size among populations within ages and sexes, suggesting significant divergence in growth rate among populations. I did not find significant correlations between growth rates (age-specific size) and geographic distances among populations, drainage affiliation, or distance to the sea. Thus, historical processes like isolation by distance, gene flow, or recent common ancestry did not explain differences in growth among populations, suggesting a role for local adaptation or phenotypic plasticity in size divergence. [ABSTRACT FROM AUTHOR]

Reduction of freshwater habitat quality due to land use change can have major impacts on diadromous fish. Partitioning this impact from other potential drivers, such as changing marine conditions and climate, is hampered by a lack of long-term data sets. Here, four decades of data were used to assess the impact of land use change on Salmo salar and anadromous Salmo trutta in the Burrishoole catchment, Ireland, one of the few index sites for diadromous fish in the North Atlantic. Land use change was found to have no significant impact on the freshwater survival of either salmon or trout. However, climate impacted significantly on the survival of salmon and trout in fresh water, with poor survival in years with wetter, warmer winters, coinciding with positive North Atlantic Oscillation values. Additionally, cold springs were associated with higher survival in trout. The addition of hatchery fish into the salmon spawning cohort coincided with low freshwater survival. Our results highlight the necessity for a broad ecosystem approach in any conservation effort of these species. [ABSTRACT FROM AUTHOR]

In several groups of anadromous fishes, but especially the salmonids, some populations migrate from the ocean to fresh water many months prior to spawning. This 'premature migration' reduces growth opportunities at sea, compels them to occupy much less productive freshwater habitats, and exposes them to extremes of flow and temperature, disease, and predation. We first review migration in salmonids and find great variation in timing patterns among and within species, relative to the timing of reproduction. Premature migration is widely distributed among species but not in all populations, and we propose two hypotheses to explain it. First, the fish may be making 'the best of a bad situation' by entering early because access to suitable breeding sites is constrained seasonally by flow or temperature regimes, so they sacrifice growing opportunities at sea. Alternatively or additionally, some populations may be 'balancing risks and benefits' as they trade off the benefits of growth at sea against the risk of mortality there. In this model, the reduced risk of mortality at sea must be balanced against the risk of mortality in freshwater habitats from thermal stress, disease, and predators. Premature migration may be favored where temperatures and flows are moderate or where lakes provide safety from predators and reduce energetic expenditure. Consistent with this hypothesis, early return is characteristic of larger, older salmonids (that would benefit less from additional time at sea to grow than would smaller fish). Finally, we consider the vulnerability of premature migrants to climate change and selective fisheries. Migration timing is an important part of the portfolio of phenotypic diversity that conveys resilience to species, population complexes, and the fisheries that depend on them. The premature migrants are often especially valued in fisheries and also often of particular conservation concern, and the phenomenon merits further research. [ABSTRACT FROM AUTHOR]

Determining the diets of threatened Spectacled Eiders ( Somateria fischeri (Brandt, 1847)) in relation to life-history stages will provide information to help identify and characterize their critical habitats. Quantitative fatty acid signature analysis (QFASA) is a novel tool that estimates the proportion of diet items in consumers from their fat depots. We conducted feeding experiments to validate the use of QFASA to estimate the mixed diets of captive female Spectacled Eiders using egg yolk fatty acids (FA) collected in 2008 and 2009. Calibration coefficients (CCs) for individual FA were developed to account for FA modification (due to eider lipid metabolism) from diets of eiders into egg yolk. We also compared the FA profiles between fertile and infertile eggs. Egg yolk FA profiles did not differ significantly between infertile and fertile eggs collected in either year. Using the CCs developed from eggs collected in 2008, QFASA closely estimated the 2009 diet composition of eiders. We conclude that using infertile eggs has the potential to provide a noninvasive method to elucidate diets of breeding female Spectacled Eiders and possibly other avian species, and to provide insight into understanding the sources (i.e., marine wintering or freshwater breeding habitat) and timing (i.e., prebreeding or breeding) of nutrient acquisition during reproduction. [ABSTRACT FROM AUTHOR]

Juvenile Oncorhynchus mykiss maternity was determined from otolith strontium:calcium ratios to investigate the degree of anadromy in eight freshwater streams draining to a common fjord. The percentages of O. mykiss parr produced by anadromous females ranged from an annual average of 41.3% (Hamma Hamma River) to 100% (Dewatto River). The proportion of stream habitat available to resident O. mykiss upstream of barriers to anadromous migration explained a significant portion of the variability in maternal life history below barrier falls and was included in each of the five logistic regression models with the lowest AIC scores. Transitional hydrologic profiles, low mean annual temperatures and high mean annual stream flow, common to Olympic Peninsula streams, were each associated with greater proportions of offspring from resident females. Only 2 out of 234 parr from the lowland, rain-driven, low-flow streams of the Kitsap Peninsula were produced by resident females. Thus, large-scale habitat features, and primarily the presence or absence of resident populations above natural barriers to anadromous migration, appeared to shape the degree of anadromy among populations. [ABSTRACT FROM AUTHOR]

Washington harbor seals ( Phoca vitulina richardii (Gray, 1864)) are currently managed as two stocks: Washington Coastal Stock and Washington Inland Waters Stock. Previous analysis of mitochondrial DNA (mtDNA) in Washington harbor seals showed four geographically and genetically distinct populations. In this study of biparentally inherited nuclear DNA, we analyzed nine microsatellite loci on 482 samples of unweaned pups from nine locations in Washington State and the US-Canadian transboundary waters to determine if there were differences in gene flow between males and females. We found the same four genetically and geographically distinct populations as the analysis of maternally inherited mtDNA: Washington Coast, north Inland Waters, Hood Canal, and south Puget Sound. We recommend that the coastal stock remain as is, but the harbor seals in the Washington Inland Waters should be managed as three distinct populations rather than one. [ABSTRACT FROM AUTHOR]

The (Saussure) complex includes numerous amphipod cryptic species in freshwater habitats in America as revealed by DNA barcoding surveys. Two ecomorphs (small and large) have evolved numerous times in this complex. Few phenotypic criteria have been found to differentiate between the numerous species of this complex. The present study aims to explore genome size differences between some species of the H. azteca complex co-occurring in a Canadian boreal lake using flow cytometry. Nuclear DNA content was estimated for 50 individuals belonging to six COI haplotypes corresponding to four provisional species of the H. azteca complex. Species from the large ecomorph had C-values significantly larger than species from the small ecomorph, whereas slight differences were found among species of the small ecomorph. These differences in genome sizes might be linked to ecological and physiological differences among species of the H. azteca complex. [ABSTRACT FROM AUTHOR]

We used reported commercial catch data and historical information regarding unreported catches to estimate the abundance of winter steelhead, Oncorhynchus mykiss, in Puget Sound rivers in 1895, the year in which the peak commercial catch of steelhead occurred. We employed a Bayesian analysis to address the uncertainties associated with the estimation process and report abundance estimates for four large northern Puget Sound rivers and for the remaining aggregate of rivers and streams in Puget Sound. The central 90% of the posterior distribution of total abundance ranged from 485 000 to 930 000, with a mode of 622 000. Compared with the 25-year average abundance for all of Puget Sound of 22 000 for the 1980-2004 period, our results show that current abundance is likely only 1%-4% of what it was prior to the turn of the 20th century. Loss of freshwater habitat alone can account for this reduction in abundance only if there was an extraordinary decline in productivity. Our estimates of historical abundance should better inform the development of recovery goals for Puget Sound steelhead. Nous utilisons les données des déclarations des pêches commerciales, ainsi que des informations historiques au sujet des récoltes non déclarées, pour estimer l'abondance de la truite arc-en-ciel anadrome, Oncorhynchus mykiss, d'hiver dans les rivières de Puget Sound en 1895, l'année durant laquelle s'est produite la pêche commerciale de truites arc-en-ciel anadromes la plus importante. Une analyse bayésienne nous a servi à tenir compte des incertitudes reliées au processus d'estimation et à évaluer l'abondance dans quatre grandes rivières du nord de Puget Sound et pour l'ensemble des autres rivières et ruisseaux de Puget Sound. Les 90 pour cent du centre de la distribution a posteriori de l'abondance totale varient de 485 000 à 930 000, avec un mode à 622 000. tant donné la moyenne sur 25 ans de l'abondance de 22 000 pour l'ensemble de Puget Sound pour la période 1980-2004, nos résultats montrent que l'abondance actuelle est vraisemblablement seulement de 1%-4% de ce qu'elle était à la fin du dix-neuvième siècle. La perte des habitats d'eau douce par elle-même peut expliquer cette réduction de l'abondance seulement s'il y a eu un déclin extraordinaire de la productivité. Nos estimations de l'abondance dans le passé devraient fournir une base plus solide pour la mise au point de cibles de récupération pour les truites arc-en-ciel anadromes de Puget Sound. [ABSTRACT FROM AUTHOR]

We examined the pupping phenology and genetic variation between the currently defined stocks of harbor seals, Phoca vitulina richardsi (Gray, 1864), in Washington’s coastal and inland waters and looked in detail at genetic variation within the inland waters of Washington. We analyzed mtDNA variation in 552 harbor seals from nine areas in Washington State and the Canada-US transboundary waters. A total of 73 haplotypes were detected; 37 individuals had unique haplotypes. Pupping phenology and levels of genetic variation between the outer coastal stock (WA Coastal Estuaries, WA North Coast) and the inland waters stock (British Columbia, Boundary Bay, San Juan Islands, Smith/Minor Islands, Dungeness Spit, Hood Canal, Gertrude Island) corroborated the appropriateness of the present stock boundary. However, within the inland waters stock, Hood Canal and Gertrude Island were significantly different from the coastal stock, from the rest of the inland waters stock, and from each other. This indicates a total of four genetically distinct groups in Washington State, suggesting that managing the inland waters as a single stock may be erroneous. [ABSTRACT FROM AUTHOR]