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Summary Lake Sturgeon is a potamodromous, fluvial‐dependent species from the family Acipenseridae, and one of the largest freshwater fishes within its North American range extending to the Great lakes, Mississippi River, and Hudson Bay drainages. Like almost all other sturgeon species, Lake Sturgeon populations throughout its range suffered mass declines or extirpation in the late 1800s into the early 1900s, due to extensive overexploitation and habitat loss and alteration. However, Lake Sturgeon are still present in low to high densities throughout their native range due primarily to factors including: the species long life span and resiliency, the remote location of many northern populations, long‐term pro‐active management programs effectively controlling exploitation, improved habitat and water‐quality conditions, and recovery programs that have been in effect since the late 1970s. Recovery programs initiated in the late 1970s are now just beginning to show signs of natural recruitment from populations re‐built with stocked fish. Large sustainable recreational Lake Sturgeon fisheries with annual harvests of up to 45 000 kg and a commercial fishery with an annual harvest of up to 80 000 kg still exist and are maintained for Lake Sturgeon due primarily to rigid regulations, harvest controls, enforcement, and user involvement. The prognosis for the species is generally good, although habitat loss and maintaining public interest in the species management and recovery continue to be the greatest threats to local and regional populations. Hydropower development, especially in the northern part of the species’ range, is especially challenging due to the potential negative impact this type of development can have on a long migrating fish like Lake Sturgeon. Advances in understanding Lake Sturgeon life history, habitat requirements, and distribution within and among water systems has strongly indicated that dams and Lake Sturgeon can co‐exist, if the correct planning and necessary mitigative techniques are employed at each site on a case‐by‐case basis.

Summary Lake sturgeon are considered imperilled across much of their range where rehabilitation efforts have been employed to enhance recovery. Habitat requirements are not known for all life stages of lake sturgeon, especially the juvenile stage. Juvenile lake sturgeon can be important in assessing effectiveness of rehabilitation efforts and therefore life history requirements for this stage is important. The objectives of this study were to determine if juvenile lake sturgeon within the Ottawa River, Canada has a depth preference; if so, to determine if depth selectivity was a function of body length; and finally, to determine if spatial structuring exists for juvenile lake sturgeon within reach type (i.e. impounded vs unimpounded reaches). A depth stratified, index netting program selective to juvenile lake sturgeon was conducted in the Ottawa River, Canada from 2008–2010. Overall, a total of 192 juvenile lake sturgeon were sampled. A Bayesian approach was used to analyze the data including logistic regression, Poisson regression and generalized linear model. The probability of capturing a juvenile lake sturgeon in a net and their relative abundance was greatest as the 12–20 m depth stratum and lowest at 35–50 m depth stratum in both impounded and unimpounded river reaches. Lake sturgeon mean total length was smallest at shallowest depth stratum (1–3 m) and greatest in the deepest depth stratum (50–75 m). For spatial segregation, mean total length of lake sturgeon was significantly smaller in the lower reach of the three contiguous, unimpounded reaches whereas the trend was opposite in impounded reaches where the smallest lake sturgeon were sampled in the upper third of the river reach. This study therefore identified areas where the probability of capturing a juvenile lake sturgeon is the greatest and where to best expend efforts through a stratified random sample study design when conducting effectiveness monitoring of any restoration or management actions.

Summary Sturgeon and paddlefish were historically the dominant large fishes in all major Northern American Rivers. All ten species have been affected the past 150 years from anthropogenic stressors such that they are considered imperiled by various jurisdictions. Status papers have been presented for each species as part of a special publication on North American Acipenseriformes. The objective of this paper is to provide a summary of the similarities and differences in life history, habitat requirements, and stressors among the species. Optimistically, this would facilitate better management of the order as a whole if management actions for one species can inform another, especially in situations where populations are too low to obtain pertinent information.

Summary An increased electrofishing sampling effort will increase detection probabilities of riverine fishes. In this study, a repeat‐sampling approach was used in small to medium‐sized Ontario (Canada) rivers to estimate: (i) species‐specific detection probabilities of freshwater fishes, (ii) the number of sampling events required to confidently detect species, and (iii) the power of timed‐search surveys to detect future distribution (or occupancy) declines. Wadeable habitats at 36 sites were sampled with a backpack electrofisher on four separate dates during the summer low‐flow period in 2013 and 2014. Forty‐two species were collected, including three species of conservation concern (American eel Anguilla rostrata Lacépède, 1802, channel darter Percina copelandi Jordan, 1877, northern sunfish Lepomis peltastes Cope, 1870), and two recreationally important species (largemouth bass Micropterus salmoides Lacépède, 1802 and smallmouth bass Micropterus dolomieu Lacépède, 1802). A hierarchical Bayesian modelling approach was used to estimate detection probabilities and site occupancy for 18 species at four levels of effort: 250, 500, 750 and 1,000 s. In all cases, species detection was imperfect. Search effort had a positive effect on estimates of detection probability and site occupancy and the power to detect declines in future distribution. Detection probabilities ranged from 0.11 to 0.66 with an effort of 250 s, and 0.27 to 0.92 with an effort of 1,000 s. For 13 species, detection and power to detect changes in distribution were significantly improved by increasing sampling effort from 250 to 750 s or 1,000 s. For the channel darter and northern sunfish, three replicate sampling visits (of 750 or 1,000 s duration) are recommended for confident detection.

Summary Historical abundance and biomasss of lake sturgeon (Acipenser fulvescens Rafinesque, 1817) in the Great Lakes were estimated from historical commercial harvest data from 1879 to 1920 using two modeling techniques: a surplus production model with a Bayesian approach, and a depletion model. In addition, theoretical sustainable levels of exploitation and temporal recovery periods were estimated based on the surplus production model. The historical biomass of Lake Sturgeon in the Great Lakes during the period from 1879 to 1885 varied for each model and ranged from 313 900 to 6 473 000 kg (0.5–16.7 kg ha−1) using the surplus production model to 968 000 to 25 414 000 kg (2.4–31.7 kg ha−1) using the depletion model. The intrinsic population growth rate as determined from the surplus production model ranged from 0.079 to 0.123, and the theoretical sustainable exploitation rate ranged from 2.0 to 3.1%. The predicted recovery period for the overexploited populations was in excess of 60 years given recruitment assuming all other impediments to population recovery were removed.

Summary The objectives of this study were to (i) assess the variation in relative abundance of lake sturgeon (Acipenser fulvescens Rafinesque, 1817) subjected to various man‐induced stresses and physical characteristics at a landscape scale across Ontario; and (ii) ascertain the factors that explain the variability observed among rivers using a multivariate approach. A standardized index netting program targeting juvenile and adult Lake Sturgeon was conducted over two field seasons at 22 river sites across Ontario. Each river had unique or different human‐induced stresses and physical characteristics. Relative abundance of Lake Sturgeon varied in river across the Ontario landscape. A principal component analysis was conducted using site physical characteristics with the associated anthropogenic stressors. The catch‐per‐unit‐effort (CPUE) for juvenile and adult Lake Sturgeon were then regressed with the scores of principal components having eigenvalues >1. The variation observed was best explained by the negative relationship observed between CPUE and the presence of hydroelectric generating stations. Historical commercial fisheries also had an effect on Lake Sturgeon abundance whereas subsistence fisheries seemed to focus on rivers that were not regulated and where Lake Sturgeon numbers were greater. Research and recovery efforts should focus on minimizing the impact of hydroelectric generation on Lake Sturgeon while achieving socioeconomic goals.

The dataset Future Flows Hydrology was developed as part of the project \"Future Flows and Groundwater Levels'' to provide a consistent set of transient daily river flow and monthly groundwater level projections across England, Wales and Scotland to enable the investigation of the role of climate variability on river flow and groundwater levels nationally and how this may change in the future. Future Flows Hydrology is derived from Future Flows Climate, a national ensemble projection derived from the Hadley Centre's ensemble projection HadRM3-PPE to provide a consistent set of climate change projections for the whole of Great Britain at both space and time resolutions appropriate for hydrological applications. Three hydrological models and one groundwater level model were used to derive Future Flows Hydrology, with 30 river sites simulated by two hydrological models to enable assessment of hydrological modelling uncertainty in studying the impact of climate change on the hydrology. Future Flows Hydrology contains an 11-member ensemble of transient projections from January 1951 to December 2098, each associated with a single realisation from a different variant of HadRM3 and a single hydrological model. Daily river flows are provided for 281 river catchments and monthly groundwater levels at 24 boreholes as .csv files containing all 11 ensemble members. When separate simulations are done with two hydrological models, two separate .csv files are provided. Because of potential biases in the climate–hydrology modelling chain, catchment fact sheets are associated with each ensemble. These contain information on the uncertainty associated with the hydrological modelling when driven using observed climate and Future Flows Climate for a period representative of the reference time slice 1961–1990 as described by key hydrological statistics. Graphs of projected changes for selected hydrological indicators are also provided for the 2050s time slice. Limitations associated with the dataset are provided, along with practical recommendation of use. Future Flows Hydrology is freely available for non-commercial use under certain licensing conditions. For each study site, catchment averages of daily precipitation and monthly potential evapotranspiration, used to drive the hydrological models, are made available, so that hydrological modelling uncertainty under climate change conditions can be explored further. doi:10.5285/f3723162-4fed-4d9d-92c6-dd17412fa37b

Summary Fragmentation of formerly continuous habitats can have significant consequences on subpopulations in isolated fragments. This study examined the temporal genetic consequences of historical river fragmentation by hydroelectric dams on lake sturgeon (Acipenser fulvescens Rafinesque, 1817), using temporal samples from two Ontario river systems. Temporal genetic analyses of samples from the Ottawa (dammed) and Kenogami (unregulated) river systems were used to (1) compare changes in genetic structure and diversity within and between free‐flowing and regulated systems; (2) assess how impoundments have influenced the spatial and temporal genetic structure and diversity within these contrasting systems; and (3) estimate effective population sizes (Ne) in both rivers using temporal genetic estimators. Levels of genetic diversity did not differ between impounded and free‐flowing rivers, nor did genetic diversity differ through time within a river system. Levels of genetic divergence over time were similarly minimal. We did, however, detect a 65% decline in effective population size in the impounded Ottawa River over two generations. Moreover, over the same time period the Ottawa River had substantially lower Ne estimates for Lake Sturgeon than the free‐flowing Kenogami River system. This study represents one of the first to observe genetic consequences of fragmentation on Lake Sturgeon. As such, this work reinforces the importance of maintaining or restoring habitat connectivity and availability for this migratory species, and mitigating other demographic threats that could compound, or be compounded by the effect of reduced genetic variation.

Summary The potential of sturgeon species and populations to adapt to current challenges and changing conditions will depend on their adaptive resources and capacity, which can be inferred from their genetic effective population size (Ne). Existing microsatellite genetic data from published studies were used to estimate Ne of lake sturgeon (Acipenser fulvescens) across hierarchical spatial and temporal scales. Previous analysis of mitochondrial DNA data suggested that the species has an evolutionary female effective population size (Nef) of ~8000, substantially lower than other North American freshwater fish species with similar distributions. Phylogeographic data were used to reconstruct the genetic makeup and diversity of phylogeographic lineages, and compare the genetic diversity and Ne of contemporary Canadian populations to their ancestral founding populations. A similar approach was used to estimate ancestral Ne for fragmented populations in formerly continuous habitats. On the finest spatiotemporal scale, point estimates of Ne for sturgeon populations in contiguous river fragments were compared against Ne values from reconstructed ancestral (pre‐fragmentation historical) populations to assess changes in Ne since fragmentation occurred. These results illustrate the versatility of genetic data for estimating historical demographics of sturgeon, as well as providing information on their adaptive potential and long‐term sustainability if given the ecological opportunity.