Stream Residence Research Articles

Bipolar Membrane Capacitive Deionization for pH-Assisted Ionic Separations

Selective ionic separations represent an increasingly important technical area for the strategic interests of the U.S. economy─for example, securing critical minerals and materials and circular economy aspirations that include recovering organic acids from processed biomass. This work disseminates bipolar membrane (BPM) capacitive deionization for selective ionic separations from multicomponent, ionic species mixtures. The selective separations are guided by the Pourbaix diagram and acid–base equilibria principles. BPM capacitive deionization was demonstrated to generate alkaline or acidic process streams depending upon the location of the BPM in the electrochemical cell. The role of system operating parameters, such as the cell voltage, residence time, and feed concentration on effluent stream pH was studied. It was observed that the pH adjustment in BPM-CDI/MCDI (MCDI, membrane capacitive deionization) was more sensitive to the cell voltage when compared to the process stream residence time and salt feed concentration. The BPM-MCDI gave over 6 times higher percentage of copper(II) removal when compared to sodium ion removal from brine mixtures. Finally, BPM-MCDI demonstrated over 40% greater removal for copper ions from brine mixtures and fivefold higher removal for itaconic acid from brine mixtures when benchmarked against a traditional flow-by-MCDI setup.

Haor-Based Floodplain-Rich Freshwater Ichthyofauna in Sylhet Division, Bangladesh: Species Availability, Diversity, and Conservation Perspectives

Biodiversity assessment is important for evaluating community conservation status. The haor basin in Sylhet Division represents a transitional zone with high species availability, rare occurrences and endemism. As a result, this study aims to describe the haor-based freshwater fish composition, including habitat, trophic ecology, availability and conservation status. Semi-structured questionnaires were used to collect data on fish samples through focus group discussions, field surveys, and interviews with fisheries stakeholders on a monthly basis. We identified 188 morpho-species, of which 176 were finfish and 12 shellfish, distributed into 15 orders and 42 families where 29%, 42%, 15%, and 14% species were commonly available, moderately available, abundantly available, and rarely available, respectively. Cypriniformes was the dominant order in both total species and small indigenous species identified. Approximately 45.34% of species were riverine, 31.58% floodplain residents, 12.55% estuarine, 2.83% migratory, and 7.69% were exclusively hill stream residents. Carnivores and omnivores were the most dominant trophic groups. A total of 87.76% species were used as food, 12.23% as ornamental and 6.91% as sport fish. Approximately 50 species were threatened (7 critically endangered, 23 endangered and 20 vulnerable) at the national level, most of them belonging to Cypriniformes and Siluriformes. Based on endemism, 16 species were endemic of which Sygnathidae, Cobitidae, Olyridae, Cyprinidae and Balitoridae fell under the threatened category. Minimizing intense fishing efforts, banning indiscriminate fishing and destructive fishing gear, initiating fish sanctuaries and beel nurseries, and implementing eco-friendly modern fishing technology are suggested to conserve the threatened species. This study represents a guideline for assessing the availability and conservation of freshwater fish in the Sylhet belt and serves as a reference for decision-makers in order to allow for the sustainable exploitation of fisheries resources within an ecosystem-based framework.

Urban stream rehabilitation in a densely populated Brazilian metropolis

Environmental rehabilitation of urban streams has been widely applied in Global North countries, at least since the 1970s, but it is a recent approach in Global South countries. The objective of this paper is to evaluate whether the rehabilitation experience carried out since 2006 in three urban stream sites in the third-largest Brazilian metropolis (c. 5.5 million inhabitants) was and continues to be effective in terms of socio-environmental improvement after 10 years of interventions. These interventions included the rehabilitation of watercourses (e.g., improvement of water quality through the management of sewage and garbage, stabilization of riverbanks, revegetation of riparian zones, riverbed naturalization, removal of riverbank housing). We evaluated water quality, physical habitat structure, and benthic macroinvertebrate assemblages in three test sites in three sampling periods: pre-intervention (2004–2005), early post-intervention (2008–2011) and late post-intervention (2018–2019). Additionally, three reference-stream sites (2018–2019) were assessed to compare the conditions of the three tested sites versus the reference sites. We also assessed citizen perceptions concerning the interventions through questionnaires given to urban stream residents at the three tested sites in early and late post-rehabilitation (215 in 2008, 180 in 2019). The results of water quality monitoring showed a significant improvement in most parameters used to calculate the Water Quality Index (WQI) in the early intervention phase, and WQI scores have improved since. The physical habitat and macroinvertebrate indicators indicated moderate improvements. The residents indicated increased appreciation of the environmental improvements over 10 years. Given the results in Belo Horizonte, we believe that implementation and evaluation of similar projects and programs aimed at rehabilitating urban streams are technically viable using our approaches throughout the Global South.

An adaptation-focused evaluation of Canada’s first competency-based medical education implementation in radiology

ObjectivesSystematic program evaluation of the Queen's University diagnostic radiology residency program following transition to a competency-based medical education (CBME) curriculum. MethodsRapid Evaluation methodology and the Core Components Framework were utilized to measure CBME implementation. A combination of interviews and focus groups were held with program leaders (n = 6), faculty (n = 10), both CBME stream and traditional stream residents (n = 6), and program staff (n = 2). Interviews and focus groups were transcribed and analyzed abductively. Study team met with program leaders to review common themes and plan potential adaptations. ResultsStrengths of CBME implementation included more frequent and timely feedback as well as the role of the Academic Advisor. However, frontline faculty felt insufficiently supported with regards to the theory and practical implementation of the new curriculum and found assessment tools unintuitive. The circumstances surrounding the curricular implementation also resulted in some negative sentiment. Additional faculty and resident education workshops were identified as areas for improvement as well as changes to assessment tools for increased clarity. Residents overall viewed the changes favorably, with traditional stream residents indicating that they also had a desire for increased feedback. ConclusionsRapid Evaluation is an effective method for program assessment following curricular change in diagnostic radiology. A departmental champion driving enthusiasm for change from within may be valuable. Adequate resident and faculty education is key to maximize change and smooth the transition. Advances in knowledge: This study provides insights for other radiology training programs transitioning to a CBME framework and provides a structure for programmatic assessment.

Influence of Steelhead Trout Stocking Size and Location on Emigration and Adult Returns

AbstractEffective stocking programs are an essential part of maintaining most high‐quality tributary steelhead Oncorhynchus mykiss fisheries in the Great Lakes, requiring sufficient numbers of stocked fish to survive, imprint, and return as adults. New York’s Lake Erie tributaries have long supported popular and economically important recreational steelhead fisheries, attracting anglers from across the country. Recent research has illustrated New York’s dependence on “stray” steelhead from other jurisdictions, making New York fisheries vulnerable to other agencies’ management decisions. We hypothesized that the limited contribution by New York‐stocked steelhead was attributable to poor poststocking survival and imprinting due to the smaller stocking size relative to other Lake Erie jurisdictions. We took an experimental approach to describe how the combination of stocking size and within‐stream stocking location interact to influence emigration and adult returns and identify mechanisms that may be driving these relationships, with the goal of identifying stocking strategies that improve adult returns. Stocked steelhead >150 mm total length emigrated from the stream by the end of May; small‐size steelhead tended to remain in the stream and exhibited upstream migration. The residual population of steelhead lost body condition and likely experienced high mortality. Adult returns from large‐size fish that were stocked 6.4 km upstream were 4.1 times greater than small‐size fish stocked upstream and six times greater than fish stocked near the lake confluence (0.8 km upstream). We conclude that many of the steelhead stocked by New York are too small to imprint and emigrate, instead remaining as stream residents that experience poor survival and ultimately make minimal contributions to the adult fishery. Increases in the stocking size of New York steelhead coupled with stocking well upstream of the lake confluence would result in increased adult returns of New York‐stocked fish to their streams of origin and improved fishery performance and resiliency.

Growth, Condition, and Trophic Relations of Stocked Trout in Southern Appalachian Mountain Streams

AbstractStream trout fisheries are among the most popular and valuable in the United States, but many are dependent on hatcheries to sustain fishing and harvest. Thus, understanding the ecology of hatchery‐reared trout stocked in natural environments is fundamental to management. We evaluated the growth, condition, and trophic relations of Brook Trout Salvelinus fontinalis, Brown Trout Salmo trutta, and Rainbow Trout Oncorhynchus mykiss that were stocked in southern Appalachian Mountain streams in western North Carolina. Stocked and wild (naturalized) trout were sampled over time (monthly; September 2012–June 2013) to compare condition and diet composition and to evaluate temporal dynamics of trophic position with stable isotope analysis. Relative weights (Wr) of stocked trout were inversely associated with their stream residence time but were consistently higher than those of wild trout. Weight loss of harvested stocked trout was similar among species and sizes, but fish stocked earlier lost more weight. Overall, 40% of 141 stomachs from stocked trout were empty compared to 15% of wild trout stomachs (N = 26). We identified a much higher rate of piscivory in wild trout (18 times that of stocked trout), and wild trout were 4.3 times more likely to consume gastropods relative to stocked trout. Hatchery‐reared trout were isotopically similar to co‐occurring wild fish for both δ13C and δ15N values but were less variable than wild trout. Differences in sulfur isotope ratios (δ34S) between wild and hatchery‐reared trout indicated that the diets of wild fish were enriched in δ34S relative to the diets of hatchery‐reared fish. Although hatchery‐reared trout consumed prey items similar to those of wild fish, differences in consumption or behavior (e.g., reduced feeding) may have resulted in lower condition and negative growth. These findings provide critical insight on the trophic dynamics of stocked trout and may assist in developing and enhancing stream trout fisheries.

Population connectivity of adfluvial and stream-resident Lahontan cutthroat trout: implications for resilience, management, and restoration

Population connectivity between resident and migratory cutthroat trout (Oncorhynchus clarkii ssp.) is understudied, but has implications for population viability and management. We examined evidence for stream residency, studied the spatial patterns of stream use by adfluvial and stream-resident trout, and measured migration rates with changing stream depth for Lahontan cutthroat trout (Oncorhynchus clarkii henshawi) in the Summit Lake Basin, Nevada (USA). Passive integrated transponder technology and a fry trap were used to track fish movements and identify the distribution of resident and adfluvial trout. Stream residents were distributed throughout the network. Adfluvial spawners concentrated in lower reaches, but also migrated up to 12.9 km. Adfluvial juveniles migrated to the lake from lower reaches and from upstream of adfluvial spawners. High stream depths coincided with more adfluvial juveniles migrating to the lake and more adfluvial spawners moving into the stream, which led to more accessing the upper watershed. This work shows that connectivity is central to adfluvial–resident Lahontan cutthrout trout population dynamics and may lead to increased probability of persistence — a characteristic of these isolated, threatened trout populations.

Hyporheic Exchange Controls Fate of Trace Organic Compounds in an Urban Stream.

First-order half-lives for 26 trace organic compounds (TrOCs) were determined in the hyporheic zone (HZ) and along a 3 km reach of a first-order stream in South Australia during both dry and wet seasons. Two salt tracer experiments were conducted and evaluated using a transient storage model to characterize seasonal differences in stream residence time and transient storage. Lagrangian and time-integrated surface water sampling were conducted to calculate half-lives in the surface water. Half-lives in the HZ were calculated using porewater samples obtained from a modified mini-point sampler and hyporheic residence times measured via active heat-pulse sensing. Half of the investigated TrOCs (e.g., oxazepam, olmesartan, candesartan) were not significantly removed along both the investigated river stretch and the sampled hyporheic flow paths. The remaining TrOCs (e.g., metformin, guanylurea, valsartan) were found to be significantly removed in the HZ and along the river stretch with relative removals in the HZ correlating to reach-scale relative removals. Using the modeled transport parameters, it was estimated that wet season reach-scale removal of TrOCs was predominately caused by removal in the HZ when the intensity of hyporheic exchange was also higher. Factors that increase HZ exchange are thus likely to promote in-stream reactivity of TrOCs.

Balancing Water Demand Needs with Protection of River Water Quality by Minimising Stream Residence Time: an Example from the Thames, UK

Freshwater resources in the River Thames basin in southern UK are faced with combined pressures of future population growth and climate change. River basin managers are seeking increasingly innovative methods to meet water demand whilst at the same time maintaining ecological status. Using a river network hydrochemical model modified to account for possible future climate and population, the paper assesses the impact on downstream water quality of changing the location of a major point of abstraction serving the city of Oxford. The rationale behind the hypothetical change, although entailing an increase in energy costs and capital expenditure, was that flows would be maintained along a sensitive stretch of river. Model results at a location a further 23 km downstream suggested that better water quality would arise from this change. The predicted improvements included a decrease in the annual frequency of low DO concentrations (<6 mg L−1) from 8–9 days to 2–3 days and a decrease in 90th percentile (summer) temperatures of 0.6 °C. It is believed these improvements would primarily be attributable to shortening of river residence time which curtails accelerated phytoplankton growth. The overall conclusion, of relevance both for the Thames basin and elsewhere, is that water quality in a river network can be surprisingly sensitive to the location of abstractions. Changing the location of abstractions should be considered as part of a suite of measures available to river basin managers when making plans to meet future water demand.

Oxidative stress and partial migration in brown trout (Salmo trutta)

During migration, animals are typically limited by their endogenous energetic resources that must be allocated to the physiological costs associated with locomotion, as well as avoiding and (or) compensating for oxidative stress. To date, there have been few attempts to understand the role of oxidative status in migration biology, particularly in fish. Semi-anadromous brown trout (Salmo trutta L., 1758) exhibit partial migration, where some individuals smoltify and migrate to sea, and others become stream residents, providing us with an excellent model to investigate the link between oxidative stress and migration. Using the brown trout, we obtained blood samples from juveniles from a coastal stream in Denmark in the fall prior to peak seaward migration that occurs in the spring, and assayed for antioxidant capacity (oxygen radical absorbance capacity) and oxidative stress levels (ratio of oxidized to reduced glutathione). We found that individuals that migrated had higher antioxidant capacity than residents and that future migration date was negatively correlated with both antioxidant capacity and body length in the fall. This study provides the first evidence that oxidative status is associated with migration strategy and timing, months in advance of the actual migration, and provides insight into the role of oxidative status in animal migration.

The Relationship Between Academic Motivation and Lifelong Learning During Residency: A Study of Psychiatry Residents.

To examine the relationship between lifelong learning (LLL) and academic motivation for residents in a psychiatry residency program, trainee factors that influence LLL, and psychiatry residents' LLL practices. Between December 2014 and February 2015, 105 of 173 (61%) eligible psychiatry residents from the Department of Psychiatry, University of Toronto, completed a questionnaire with three study instruments: an LLL needs assessment survey, the Jefferson Scale of Physician Lifelong Learning (JeffSPLL), and the Academic Motivation Scale (AMS). The AMS included a relative autonomy motivation score (AMS-RAM) measuring the overall level of intrinsic motivation (IM). A significant correlation was observed between JeffSPLL and AMS-RAM scores (r = 0.39, P < .001). Although there was no significant difference in JeffSPLL and AMS-RAM scores based on respondents' level of training (senior vs. junior resident), gender, or age, analysis of AMS subdomains showed that junior residents had a significantly higher score on the extrinsic motivation identification domain (mean difference [M] = 0.38; 95% confidence interval [CI] [0.01, 0.75]; P = .045; d = 0.44) compared with senior residents. Clinician scientist stream (CSS) residents had significantly higher JeffSPLL scores compared with non-CSS residents (M = 3.15; 95% CI [0.52, 5.78]; P = .020; d = 0.57). The use of rigorous measures to study LLL and academic motivation confirmed prior research documenting the positive association between IM and LLL. The results suggest that postgraduate curricula aimed at enhancing IM, for example, through support for learning autonomously, could be beneficial to cultivating LLL in learners.

Effect of stocking sub-yearling Atlantic salmon on the habitat use of sub-yearling rainbow trout

Abstract Atlantic salmon ( Salmo salar ) restoration in the Lake Ontario watershed may depend on the species' ability to compete with naturalized non-native salmonids, including rainbow trout ( Oncorhynchus mykiss ) in Lake Ontario tributaries. This study examined interspecific habitat associations between sub-yearling Atlantic salmon and rainbow trout as well as the effect of salmon stocking on trout habitat in two streams in the Lake Ontario watershed. In sympatry, Atlantic salmon occupied significantly faster velocities and deeper areas than rainbow trout. However, when examining the habitat use of rainbow trout at all allopatric and sympatric sites in both streams, trout habitat use was more diverse at the sympatric sites with an orientation for increased cover and larger substrate. In Grout Brook, where available habitat remained constant, there was evidence suggesting that trout may have shifted to slower and shallower water in the presence of salmon. The ability of sub-yearling Atlantic salmon to affect a habitat shift in rainbow trout may be due to their larger body size and/or larger pectoral fin size. Future studies examining competitive interactions between these species during their first year of stream residence should consider the size advantage that earlier emerging Atlantic salmon will have over rainbow trout.

Understanding the diurnal cycle in fluvial dissolved organic carbon – The interplay of in-stream residence time, day length and organic matter turnover

There is increasing interest in characterising the diurnal fluctuation of stream solute concentrations because observed data series derived from spot samples may be highly subjective if such diurnal fluctuations are large. This can therefore lead to large uncertainties, bias or systematic errors in calculation of fluvial solute fluxes, depending upon the particular sampling regime. A simplistic approach would be to assume diurnal fluctuations are constant throughout the water year, but this study proposes diurnal cycles in stream water quality can only be interpreted in the context of stream residence time and changing day length. Three years of hourly dissolved organic carbon (DOC) concentration and flow data from the River Dee catchment (1674 km2) were analysed, and statistical analysis of the entire record shows there is no consistent diurnal cycle in the record. From the 3-year record (1095 days) there were only 96 diurnal cycles could be analysed. Cycles were quantified in terms of their: relative and absolute amplitude; duration; time to maximum concentration; asymmetry; percentile flow and in-stream residence time. The median diurnal cycle showed an amplitude that was 9.2% of the starting concentration; it was not significantly asymmetric; and occurred at the 19th percentile flow. The median DOC removal rate was 0.07 mg C/l/hr with an inter-quartile range of 0.052–0.100 mg C/l/hr. Results were interpreted as controlled by two, separate, zero-order kinetic rate laws, one for the day and one for the night. There was no single diurnal cycle present across the record, rather a number of different cycles controlled by the combination of in-stream residence time and exposure to contrasting light conditions. Over the 3-year period the average in-stream loss of DOC was 32%. The diurnal cycles evident in high resolution DOC data are interpretable, but require contextual information for their influence on in-stream processes to be understood or for them to be utilised.

Sexual maturation in stream residents from migratory populations of brook trout inhabiting Lake Superior tributaries

There is mounting evidence that populations of brook trout (Salvelinus fontinalis) inhabiting bays and tributaries along the north shore of Lake Superior exhibit partial migration. In this system some fish originate in tributaries and move into the lake for much of the year, grow large and migrate back into tributaries to spawn, whilst other smaller fish reside in tributaries and grow slowly. This study determined whether the stream dwelling brook trout reach sexual maturity in the stream habitats, a criterion needed to distinguish partial migration from other forms of migration that could maintain divergent forms and life histories of brook trout. Maturational development was determined for fish collected in July and August. Sampling these populations during fall spawning was not permitted due to conservation concerns. Male and females sampled from tributaries displayed δ13C signatures and growth histories characteristic of stream residency. Assessment of maturational development suggested that 33% of females would have been expected to spawn in the fall of that year. Our findings demonstrate that a portion of fish residing in tributaries reach sexual maturity without adopting summer residency in the lake providing evidence for partial migration over other forms of migration. Improved understanding of the variation in migratory behaviour in these brook trout populations will contribute to their conservation and management in the face of lake-wide declines of the migrant fish.

Do natural history data predict the movement ecology of fishes in Lake Ontario streams?

Little is known about the movements of most stream fishes, so fisheries managers often rely on natural history data from the literature to make management decisions. Observations of over 15 000 individuals from 37 species across 3 years were used to evaluate four aspects of the reliability of literature data for predicting the movement behaviour of stream fishes: (i) water temperature when fish enter streams; (ii) reasons for moving into the streams; (iii) stream residence times of migrants; and (iv) relative use of lake and stream habitats. Comparisons of our data for arrival times in the streams, water temperature at arrival, and time spent in the streams were highly correlated with literature data, whereas relative use of the lake was not. Further, our detailed data revealed two novel findings: (1) in many species juveniles were also moving into streams, even in those species where adults were clearly spawning in the streams; and (2) adult-sized individuals were moving into streams for nonreproductive purposes. Our results suggest that fishery managers can confidently use natural history information to gain general insights into the movement ecology of fishes, but should also recognize that this information remains incomplete in important ways.

Can the heterogeneity in stream dissolved organic carbon be explained by contributing landscape elements?

Abstract. The controls on stream dissolved organic carbon (DOC) concentrations were investigated in a 68 km2 catchment by applying a landscape-mixing model to test if downstream concentrations could be predicted from contributing landscape elements. The landscape-mixing model reproduced the DOC concentration well throughout the stream network during times of high and intermediate discharge. The landscape-mixing model approach is conceptually simple and easy to apply, requiring relatively few field measurements and minimal parameterisation. Our interpretation is that the higher degree of hydrological connectivity during high flows, combined with shorter stream residence times, increased the predictive power of this whole watershed-based mixing model. The model was also useful for providing a baseline for residual analysis, which highlighted areas for further conceptual model development. The residual analysis indicated areas of the stream network that were not well represented by simple mixing of headwaters, as well as flow conditions during which simple mixing based on headwater watershed characteristics did not apply. Specifically, we found that during periods of baseflow the larger valley streams had much lower DOC concentrations than would be predicted by simple mixing. Longer stream residence times during baseflow and changing hydrological flow paths were suggested as potential reasons for this pattern. This study highlights how a simple landscape-mixing model can be used for predictions as well as providing a baseline for residual analysis, which suggest potential mechanisms to be further explored using more focused field and process-based modelling studies.

Interspecific Aggressive Behaviour of Invasive Pumpkinseed Lepomis gibbosus in Iberian Fresh Waters

Pumpkinseed Lepomis gibbosus (L.) are successful invaders in Europe, where this species exerts multiple ecological effects, mainly through trophic interactions. Behavioural interference represents a potential impact for native fauna and this is of particular conservation concern in the Iberian Peninsula because of the highly valuable endemic fauna inhabiting streams of this region. However, aggressive interactions have not previously been examined under natural conditions in Iberian fresh waters. To address this gap in knowledge, the aim of the present study was to assess the effect of pumpkinseed aggression on endemic fauna of an Iberian stream, the River Bullaque (central Spain). In September 2009, we analysed the aggression and environmental contexts of these behavioural interactions by snorkelling: aggressor size, aggression type, shoal size, previous activity to aggression, recipient species, response to aggression, microhabitat structure and prey availability. Small pumpkinseed displayed more threat and fewer pursuit behaviours relative to medium and large individuals, reflecting an ontogenetic behavioural shift from low to high aggression intensity. Small aggressors came from large shoals, with bottom feeding being the most frequently observed activity prior to an aggressive interaction; whereas large pumpkinseed were less gregarious and they were mostly ambulating within the water column prior to aggression. Recipient species of aggression included non-native crayfish and fishes, and more importantly, endemic fishes and frogs. Retreat was the most common response to aggression, irrespective of aggressor size. Small pumpkinseed displayed aggressive behaviours over coarse substrata containing elevated macrobenthos biomass; whereas aggression by large individuals was observed in deeper waters. These findings suggest that small and large pumpkinseed exert a high impact on other stream residents through aggression in competition for food and territory defence, respectively. This study highlights the usefulness of direct observations in the wild for assessing the effects of behavioural interference of invasive fishes on Iberian aquatic communities.

Burbot Early Life History Strategies in the Great Lakes

AbstractBurbot Lota lota exhibit four previously known reproductive strategies in the Great Lakes region. In this paper we review those strategies and provide evidence for a fifth one—delayed deepwater spawning. The four known, shallow‐water strategies are as follows: (1) spawning by self‐sustaining, landlocked populations, (2) spawning in tributaries in winter and the exit of larvae to a Great Lake, (3) spawning by residents in a spawning stream with access to a Great Lake, and (4) spawning on unconsolidated and rocky areas in shallow water in winter in the lake proper. Resident, landlocked populations exist in some Michigan and Wisconsin rivers (e.g., the Muskegon River in Michigan). The evidence for winter tributary spawning is the appearance of newly hatched Burbot in the St. Marys and Bark rivers during April–June. Evidence for Burbot juveniles leaving spawning streams is U.S. Fish and Wildlife Service tributory mouth trap data. The evidence for winter nearshore spawning comes from power plant monthly entrainment studies (Mansfield et al. 1983). Our proposed fifth strategy is spring and summer spawning at deep reefs, where there is probably cobble or boulder habitat. Our evidence comes from midlake reefs in Lake Michigan and offshore areas of Lake Huron: (1) we collected adult Burbot at midlake reefs in Lake Michigan, (2) we collected many Burbot larvae (many of which were newly hatched) from Lakes Michigan and Huron in June–August, and (3) we collected a Burbot egg in a PONAR grab in mid‐July from 73 m in southern Lake Huron. An important question remains, namely, which life history strategy provides the highest recruitment success for this species. It may be that adaptability ensures the survival of this important, top‐predator fish during periods of crisis (e.g., encounters with dams, Sea Lamprey Petromyzon marinus predation).

Variation of δ18O and δD in precipitation and stream waters across the Kashmir Himalaya (India) to distinguish and estimate the seasonal sources of stream flow

Summary The spatial and temporal distribution of δ 18 O and δD measurements of precipitation and stream waters were used to distinguish various sources and components of stream flow and to estimate their residence times in snow dominated mountainous catchments of Kashmir Himalaya. A marked spatial and seasonal variability of stable isotopes of oxygen and hydrogen was observed in precipitation with δ 18 O and δD varied from −12.98‰ to −0.58‰ and −74.5‰ to −11.1‰, respectively during the period from November 2007 to January 2009. The seasonal changes in stable isotopes of precipitation with depleted and enriched 18 O and 2 H in January/March/May and July/September/November, respectively at each site are attributed to the seasonal changes in ambient temperature, precipitation, source of moisture and airmass trajectory. The mean altitude effect of −0.23‰ and −1.2‰ per 100 m change in elevation for δ 18 O and δD, respectively, was observed based on amount weighted mean precipitation isotopic composition data. Unlike precipitation, less variability of stable isotopes of streams was found with δ 18 O and δD ranging from −11.56‰ to −6.26‰ and −65.4‰ to −36.4‰, respectively, the depleted values being observed in the headwaters of the streams/tributaries and enriched values at lower elevations of the watersheds. The LMWL established for the Kashmir Himalayas, based on amount weighted monthly samples is δD = 7.59 (± 0.32) × δ 18 O + 11.79 (± 2.07) ( r 2 = 0.96) with lower slope and intercept than GMWL, is very close to the LMWL for the western Himalayas. The seasonal regression lines suggest the effect of evaporation with lower slopes and intercepts except in winter. The results suggest that the winter precipitation (snow) dominantly contributes the annual stream flow with average snowmelt contribution of about 29% in early spring, 66% in late spring, 61% in summer while the baseflow contribution is found in the order of 40% in autumn season. The mean stream residence times (MRTs) varied from 6 to 12.4 months. The longer MRT of the Liddar catchment is attributed to its complex topography and larger area.

Genetic relationships and gene flow between resident and migratory brook trout in the Salmon Trout River

Genetic differentiation among brook trout (Salvelinus fontinalis) of different life history forms and populations can result from reproductive isolation imposed by natural or anthropogenically derived barriers to gene flow, behavioral incompatibilities, or differential exposure to environmental cues. We used multi-locus microsatellite genotypes and likelihood and Bayesian-based analyses to characterize the degree of genetic differentiation and evidence of introgression among stream resident brook trout above a natural barrier, and putative stream residents and adfluvial (coaster) brook trout from below the barrier in the Salmon Trout River (STR); the sole tributary along the southern shore of Lake Superior known to be inhabited by a viable remnant population of coaster brook trout. Two genetically differentiated populations were identified, generally associated with individuals inhabiting sections of the STR above and below the falls. No evidence of differentiation was found between a priori classified resident and coaster brook trout from below the falls. Gene flow from individuals above the falls was detected based on evidence of interbreeding between upper river individuals and coasters below the falls. We collected only a relatively small number of individuals that we a priori classified as being stream residents below the falls, and these individuals had a high probability of having ancestry originating from the population above the barrier, which suggests that the stream-resident life history may be exceptionally rare or absent in the lower Salmon Trout River.