Publications
2026
- Thermal bottlenecks constrain early-life survival of native fish in regulated riversPublished in: Science Advances, 12(34), eaeg3586
Climate change is reshaping thermal regimes worldwide, threatening species whose early development depends on narrow temperature ranges. Yet directly linking warming to reproductive failure in wild populations remains intractable, particularly in aquatic ecosystems. We developed an empirical framework integrating stable isotope thermometry of archival tissues, landscape-scale temperature modeling, and field surveys to identify when and where successful reproduction occurs. Applying this approach to endangered winter-run Chinook salmon confined below a large dam, we revealed a narrow “critical thermal window” during early development. Surviving juveniles experienced temperatures below 12.5°C within ∼15 days of fertilization, and modest warming during this period sharply reduced survival. In warm years, dam-released cold-water overlapped only briefly with this window, restricting successful reproduction to a small fraction of the total spawning season. These results show how climate warming and river regulation interact to constrain population persistence and provide a framework to guide research on assessing climate vulnerability in temperature-sensitive species.
- Mass mortality of aquatic organisms in the San Francisco Estuary – using community science to document the impacts of a severe harmful algal bloomPublished in: Frontiers in Marine Science, 13, 1893110
In July 2022, a harmful algal bloom of
Heterosigma akashiwo
originated in a man-made lagoon and expanded to more than 4,500 km² of open-water habitat in the San Francisco Estuary, triggering a widespread mass mortality event involving bony fishes, sharks, rays, crustaceans, mollusks, polychaetes, and jellyfish. Notably, the event affected the southernmost spawning populations of White Sturgeon (
Acipenser transmontanus
) and federally threatened Green Sturgeon (
Acipenser medirostris
). Because the bloom arose rapidly and without precedent, coordinated response efforts by resource managers began only after the event was well underway, limiting documentation of its early impacts. However, members of the public and local conservation groups submitted numerous observations through platforms such as iNaturalist, non-profit reporting portals, and agency hotlines. To reconstruct the progression and consequences of the HAB, we synthesized information from these community-science platforms together with available agency observations. In total, 401 distinct community reports and 14 scientific reports documented mortality spanning 25 families, including 18 identified fish species. A total of 691 sturgeon carcasses were reported, many of which were mature White Sturgeon. Although severe hypoxia developed for five days near the end of the bloom, most mortality occurred prior to this period, indicating that toxic effects of
H. akashiwo
were likely the primary driver of sturgeon deaths. Our findings underscore the value of community engagement, community science, and social-media reporting for documenting stochastic disturbances such as harmful algal-bloom-induced mass mortality events, and highlight the need for improved planning, monitoring, and rapid response capacity among local, state, and federal agencies to address future harmful algal-bloom-induced mortality events. - Widespread high prevalence of vaterite in pink salmon (Oncorhynchus gorbuscha) otolithsPublished in: Canadian Journal of Fisheries and Aquatic Sciences, cjfas-2026-0064
Pacific salmonids rely on precise sensory mechanisms, including the sagittal otolith, to support long-distance migrations. Vaterite replacement of otolith aragonite can impair sensory function, and compromise otolith-based reconstructions of environmental history. Otoliths from 1,116 native and invasive pink salmon across the Pacific and Atlantic Oceans were examined for vaterite prevalence, extent, and timing of formation. Visual assessment proved to be a reliable and efficient method for identifying otolith mineralogy, based on validation using X-ray diffraction. We document exceptionally high vaterite prevalence in pink salmon from both Atlantic (97%) and Pacific (94-96%) populations, with minimal geographic variation and no differences among native and invasive or wild and hatchery populations. Vaterite levels far exceeded those reported for other salmonids, including hatchery-reared populations. Our results indicate that vaterite formation can occur at any life stage, beginning as early as the juvenile freshwater stage and peaking early in the marine phase. Overall, our findings support an association between the unusually high prevalence of vaterite in pink salmon and a life-history strategy characterized by rapid growth.
- Listening to the Past to Help California’s Salmon in the FuturePublished in: Frontiers for Young Minds, 14, 1619598
Chinook salmon have long been an important food source and central part of many Indigenous cultures along the Pacific Ocean. Salmon are also nature’s bridge between the ocean and the land because they carry nutrients from the sea to rivers and forests, feeding many animals and plants. But today, salmon are in trouble. Dams, habitat loss, overfishing, and climate change have caused their numbers to drop sharply. To protect salmon, scientists need to understand how they lived long ago. By studying ancient salmon bones, such as tiny ear stones (called otoliths) and backbones (called vertebrae), found at old Indigenous village sites, researchers can discover where salmon lived, how old they were, and how their environment has changed. These clues from the past help us make better choices to care for salmon, the ecosystem, and all the people that depend on them.
- A dendritic strontium river isoscape for fisheries applications in the Sacramento River basin, California, USAPublished in: North American Journal of Fisheries Management, vqag027
Abstract
Objective
Understanding the origins and movements of fish is fundamental to effective conservation and fisheries management. Strontium isotope ratios (87Sr/86Sr) in otoliths provide a powerful tracer of natal origin and migratory pathways. However, existing 87Sr/86Sr isoscapes for the Sacramento River basin, an ecosystem that supports ecologically and economically important salmon populations, rely on discrete classification approaches that overlook unsampled habitats and do not incorporate spatial uncertainty. Our objective was to develop a continuous, network-explicit 87Sr/86Sr isoscape with quantified uncertainty to fill in data gaps and enable probabilistic assignments of fish origin and movement.
Methods
We used river water 87Sr/86Sr data from 106 sites (1997–2021) to develop spatial stream network models that use dendritic connectivity and watershed characteristics (lithology, bedrock age, and land cover) to predict river water 87Sr/86Sr throughout the basin. Models were fitted using maximum and restricted likelihood and were evaluated via Akaike’s information criterion and leave-one-out cross validation. We produced both historical (pre-dam) and present-day (below-dam) isoscapes, delineated uncertainty-informed isotopic ranges using k-means clustering, and applied a proof-of-concept Bayesian assignment to estimate natal origins and early rearing habitats for two endangered winter-run Chinook Salmon Oncorhynchus tshawytscha.
Results
Cross validation indicated strong performance of the 87Sr/86Sr model (leave-one-out cross validation: R2 = 0.91; root mean square error = 0.0005). Uncertainty-informed clustering identified 19 isotopic “suites” (reaches with indistinguishable 87Sr/86Sr values) in present-day anadromous habitats and 25 suites in the historical network. Example natal and early rearing assignments included predictions that challenged expectations for juvenile salmon migration based on predicted river 87Sr/86Sr compositions.
Conclusions
This study developed a continuous, network-explicit 87Sr/86Sr isoscape that integrates existing river data to predict 87Sr/86Sr in unsampled reaches and the likely achievable range and resolution of otolith-based origin and life history inference. The resulting river isoscape provides a valuable tool to predict salmon movements and identify habitats supporting their survival and growth that otherwise might remain undetected. Coupling these predictions with complementary approaches that ground-truth juvenile presence (e.g., targeted fish surveys) represents an important step toward science-informed restoration and management of critical habitats throughout the Sacramento River basin. - Workshop on emerging methods and technologies for the automated analysis of calcified structures (WKETAC)Published in: ICES Scientific Reports, 3072847 Bytes, 32
Calcified structures (otoliths, scales, etc) are essential to the management of commercial species. Every year, more than one million pieces are collected and analysed across the world to provide data essential to fishery management, such as age estimations and stock identification. Recent years have seen significant advances in the analysis and use of calcified structures for extracting biological information, and the development of new technologies related to image processing and analysis has shown a strong potential for automation and standardization. This workshop aimed to bring together institutes and experts across the world to provide an exhaustive review of the developments in this field, outline areas and stocks of highest interest, and develop an international framework for collaboration. More than 70 European and non-European researchers participated. The first day was devoted to presentations of projects, methods and case studies, which were discussed with all participants. It provided an opportunity to present different emerging methods, such as AI-driven image analysis and spectroscopic data. In the case of deep learning approaches, the workshop was useful in reviewing and discussing the acquisition of two-dimensional and three-dimensional images, their standardization, and the algorithms to be developed. Discussions also touched upon the advances and limitations of these new technologies and approaches. The second day was mainly devoted to discussions around the optimization of the automated analysis of calcified structures for fish population monitoring and how to develop a collaborative framework for data exchange and standardization. Among the outputs of those discussions was the creation of a dynamic repository of expertise listing for different approaches, the associated institute, the list of species and stocks of primary interest, sample availability and current limitations and challenges. Additionally, the group began discussing pilot studies to successfully implement these automated methods, which will be further developed within an international project proposal to create and support a digital twin of physical archives in which large image repositories could be curated and exchanged to assist the development of automated methods and operational tools for monitoring commercial species.
- Global compilation of bioavailable strontium isotope dataPublished in: Scientific Data
Abstract
Bioavailable strontium isotope ratios (
87
Sr/
86
Sr) have broad applications for geolocation and movement reconstructions in ecology, paleontology, archaeology, forensics, and environmental and food sciences. These applications require a comprehensive
87
Sr/
86
Sr reference dataset to identify isotopically distinct areas. Bioavailable
87
Sr/
86
Sr reference datasets have been created for many regions world-wide and are based on a large range of different sample materials including soil, water, flora, and fauna. Here we compiled and harmonized 28,347 published bioavailable
87
Sr/
86
Sr data from over 150 countries representing decades of work by hundreds of researchers to provide a global dataset as a basis for reference and isoscape development. These data provide researchers across many different disciplines with a common reference dataset to use as a foundation for their research projects. Metadata and method details are provided to allow for the individual assessment of the data. The dataset is available at two community data repositories dedicated to stable isotope data, IsoArcH and IsoBank. - Early marine growth and spawning body size vary by year and region in invasive pink salmon (Oncorhynchus gorbuscha)Published in: Aquatic Sciences, 88(3), 77
Abstract
Non-native pink salmon (
Oncorhynchus gorbuscha
) have increased rapidly in Norwegian rivers since 2017, yet their marine ecology remains poorly understood. To assess variation in marine growth, we analysed scales from 476 individuals returning to northern (Barents Sea region) and central (Atlantic region) Norway in 2019 and 2021. Clear differences in growth and body size emerged between regions and years, with fish returning in 2019 experiencing the poorest growth and reaching the smallest adult size. Differences in growth histories indicate that pink salmon captured in the two regions may have experienced distinct marine feeding resource conditions, possibly because they followed different migratory pathways, beginning in the first weeks at sea. Approximately one-third of individuals experienced distinct periods of depressed growth during their first spring and summer at sea, and these events were more common among fish returning to central Norway. Mid- to late-season growth during the first year at sea strongly influenced adult size, highlighting the importance of favourable conditions during this period. At the same time, it was shown that growth after the winter could more than compensate for poor growth up until then. The pronounced variability in growth performance suggests that environmental conditions during the marine phase strongly shape adult size and may influence the future invasion potential of pink salmon in the North Atlantic. As this invasive species continues to expand, continued monitoring of growth and improved understanding of their marine ecology and environmental drivers of growth will be essential for anticipating invasion dynamics and impacts on native ecosystems. - A Modern Ghost Story: Increased Selective Mortality of Salmon Under Climate ExtremesPublished in: Global Change Biology, 32(4), e70854
ABSTRACT
Hydroclimate volatility poses a growing threat to species' persistence, particularly when combined with widespread habitat loss and other stressors. Although the negative impacts of drought on aquatic species are well documented, wet conditions are generally assumed to enhance recruitment of migratory species during freshwater life stages. Life‐history theory predicts that species with multiple migratory strategies should be more resilient to climate extremes by spreading risk across time and space. Testing these assumptions requires tracking both survivors and ‘ghosts’ across life stages and broad spatial scales. For many Pacific salmonids, a substantial fraction of the population disperses downstream soon after emergence (‘early migrants’), rearing in downstream habitats before entering the ocean. The extent to which hydroclimatic conditions influence selection against this phenotype and its lifetime success is poorly understood. To address this data gap, we tracked nine cohorts of Chinook salmon (
Oncorhynchus tshawytscha
) at sequential points through their life cycle, using otolith and eye lens isotopes to identify habitats and conditions associated with the highest losses of early migrants. Comparisons of juvenile (
n
= 2197) and adult (
n
= 3937) samples revealed large spatiotemporal variation in the strength of selective mortality. Early migrants became progressively rarer at each consecutive sampling point, including among adult returns, indicating carryover effects from freshwater into the ocean. At the southern edge of the species range—where water scarcity is an intensifying issue—we had predicted positive relationships between river flow, growth and survival. Instead, trends were consistently quadratic, suggesting that both drought and extreme high flows can reduce rearing opportunities and cohort strength. Ultimately, all phenotypes contributed to reproduction in all years, underscoring the importance of maintaining diverse life history portfolios and implementing climate‐ready restoration strategies that provide refugia and growth opportunities across the full spectrum of flow conditions. - Advancing provenance assignment using machine learning and time series analysis of chemical chronologies in archival tissuesPublished in: Ecological Informatics, 103604
- Combining kinship analysis and otolith geochemistry to investigate homing and straying of invasive pink salmon (Oncorhynchus gorbuscha)Published in: Boreal Environment Research
2025
- Population Structure and Movement Dynamics of Redband Trout in the Kootenai River BasinPublished in: River Research and Applications, rra.70027
ABSTRACT
Redband Trout
Oncorhynchus mykiss gairdneri
is a species of high conservation concern in the Kootenai River basin, United States and Canada. However, identifying the specific mechanisms influencing Redband Trout is difficult as its life history structure is largely unknown. Using otolith microchemistry analysis, we found that 18.5% (
n
= 66) of the fish sampled (
n
= 329) were a product of mainstem Kootenai River spawning. The remainder were fish (
n
= 264) that originated from one of 31 tributaries throughout the basin. Redband Trout were captured between 0 and 153 km from their assigned natal tributaries. Most migratory fish originated from tributaries in the uppermost portion of the study area and had migratory mothers. However, a diversity of life history types (e.g., multi‐year resident, migratory) was observed in the population. Redband Trout were estimated to outmigrate from natal habitats at a variety of ages (0–3 years) and lengths (12–430 mm). Our results highlight diversity in the population structure of Redband Trout and provide information valuable to conservation efforts in the Kootenai River system. Interestingly, several tributaries identified as natal habitats of Redband Trout contain substantial obstacles originally considered barriers to upstream fish passage. In addition, some streams in the lower portion of the Kootenai River basin with degraded habitat that were not expected to contribute Redband Trout had natal assignments. These observations indicate previously unknown sources of Redband Trout and support the notion that improved fish passage in disconnected and degraded streams could increase production of Redband Trout throughout the Kootenai River basin. Restoration efforts in the mainstem that include considerations for spawning and natal habitat may also aid in conservation efforts for Redband Trout. Our research demonstrates the value of microchemistry in planning and evaluating habitat restoration to recover fishes in large rivers. - Archaeological evidence across four millennia indicates recent erosion of Chinook salmon age structure in CaliforniaPublished in: Marine Ecology Progress Series
- Otolith-based comparisons of wild versus hatchery-origin delta smeltPublished in: Endangered Species Research, 57, 467-480
The rapid decline of California’s endangered delta smelt
Hypomesus transpacificus
has called for immediate and effective conservation actions. Since 2021, up to 92000 cultured delta smelt have been released annually into the Sacramento-San Joaquin River Delta, with ecological field surveys capturing both hatchery-produced (‘cultured’) and wild-spawned (‘wild’) individuals. Cultured fish now constitute the bulk of the catch, highlighting their critical role in conserving the species. Questions remain, however, regarding differences between cultured and wild individuals, their relative health, and how to accurately classify individuals collected in the field. We applied otolith-based tools to contrast the health and environmental histories of wild and cultured delta smelt collected
in situ
from 2019-2023. Specifically, we quantified differences in otolith development, otolith-somatic proportionality, ontogenetic growth, and otolith strontium isotope (
87
Sr/
86
Sr) geochemistry. We then developed mixture discriminant analysis models to identify cultured and wild individuals based on their geochemical profiles. Cultured and wild fish exhibited similar otolith-somatic proportionality, whereas cultured fish exhibited higher frequencies of abnormal (vateritic) otolith development. Growth varied ontogenetically in both groups; however, growth rates were highest in wild fish during the early life history and higher in cultured fish during later life stages. Geochemical profiles were distinct between groups, resulting in >95% classification success. Together, these results highlight the utility of otolith-based approaches for identifying wild and cultured delta smelt and quantifying differences in their health and environmental histories. Such data are key to understanding population dynamics and for informing the management and conservation of imperiled species. - Reconstructing Salmon growth trajectories through biochronologies across a highly variable growthscapePublished in: Canadian Journal of Fisheries and Aquatic Sciences, cjfas-2024-0139
Measuring the growth of migratory fish across habitats is difficult because field observations only provide a snapshot into their life; yet, understanding which habitats provide better growth opportunities is crucial for their conservation. We experimentally enclosed individually tagged juvenile Chinook Salmon (Oncorhynchus tshawytscha) in habitats with known differences in growth potentials to evaluate four different models (Dahl-Lea, Fraser-Lee, Biological Intercept, Modified Fry) used to back-calculated size-at-age from otoliths. We found that otolith-derived fish size reconstructions were most accurate using the Biological Intercept or Modified Fry model, though bias remains for slow-growing fish. This tool was then used in a case study to reconstruct the mosaic of inter- and intra-habitat growth opportunities available to fishes, providing a useful framework for assessing and monitoring fish responses to habitat restoration and a changing environment.
- Identifying escaped farmed salmon from fish scales using deep learningPublished in: Biology Methods and Protocols, 10(1), bpaf078
Abstract
Escaped farmed salmon are a major concern for wild Atlantic salmon (Salmo salar) stocks in Norway. Fish scale analysis is a well-established method for distinguishing farmed from wild fish, but the process is labor and time intensive. Deep learning has recently been shown to automate this task with high accuracy, though typically on relatively small and geographically limited datasets. Here we train and validate a new convolutional neural network on nearly 90 000 scale images from two national archives, encompassing heterogeneous imaging protocols, hundreds of rivers, and time series extending back to the 1930s. The model achieved an F1 score of 0.95 on a large, independent test set, with predictions closely matching both genetic reference samples and known farmed-origin scales. By developing and testing this new model on a large and diverse dataset, we demonstrate that deep learning generalizes robustly across ecological and methodological contexts, supporting its use as a validated, large-scale tool for monitoring escaped farmed salmon. - Multi-isotope analysis of mammalian fauna from the Middle Pleistocene (MIS6) Lazaret Cave: palaeoecological, palaeoenvironmental and archaeological implicationsPublished in: Journal of Archaeological Science: Reports, 68, 105456
- Inter-method differences (SIMS vs. IRMS) in oxygen isotope fractionation: insights from Chinook salmon otolithsPublished in: Geochimica et Cosmochimica Acta, S0016703725005903
- Environmental sampling to capture bioavailable strontium isotope distributions on CorsicaPublished in: Applied Geochemistry, 190, 106511
- Early evidence for establishment of a Chinook salmon population in a restored watershedPublished in: Ecosphere, 16(3), e70207
Abstract
As fish populations face compounding pressures under climate change, highly modified rivers are receiving increasing research and conservation attention as important sites for restoration. Across the North Pacific Ocean, Chinook salmon (
Oncorhynchus tshawytscha
) have experienced unprecedented declines and extirpations because of habitat loss and fragmentation and climate variability. Here, we studied a rare example of a novel salmon population developing in Putah Creek, California, a dam‐controlled stream flowing through an area of intensive agriculture where salmon were unlikely to occur prior to the rehabilitation of a more natural flow regime. We used otoliths from adult Chinook salmon carcasses recovered from Putah Creek to determine river or hatchery of origin for five spawning year classes. Our results provide evidence of successful salmon reproduction, outmigration survival, and natal homing of individuals back to Putah Creek in recent years. Although hatchery‐origin fish that strayed to Putah Creek to spawn dominated returns each year, this study documents life‐cycle completion required for the potential development of a self‐sustaining salmon population. This study demonstrates that targeted restoration and flow rehabilitation efforts can generate viable new salmon spawning habitat in dam‐controlled river systems, which could help mitigate habitat lost to dams and developments. Further, successful anadromous life‐cycle completion can occur in new spawning habitat within the first several generations, which will help inform efforts to restore or reintroduce salmon in other altered river systems. - Validating estuarine movements from otoliths for an imperiled fishPublished in: Aquatic Biology
2024
- An evaluation of fin ray microchemistry to describe movement of White Sturgeon in the Kootenai River basin: insights and limitationsPublished in: Frontiers in Freshwater Science, 2, 1475115
Introduction
White Sturgeon
Acipenser transmontanus
in the Kootenai River basin is listed as endangered in the United States and Canada. Declines have been mainly attributed to poor recruitment exacerbated by the environmental effects of Libby Dam in Montana. Reduced primary production downstream of Libby Dam has been identified as one factor limiting growth of White Sturgeon, thereby limiting natural reproduction through delayed sexual maturity. However, estimating changes in growth over time without knowledge of fish location (i.e., Kootenai River vs. Kootenay Lake) is difficult. The objective of this project was to use microchemistry analysis to describe the movement of White Sturgeon within the Kootenai River basin.
Methods
Water samples (
n
= 27) and White Sturgeon fin rays (
n
= 162) collected in the Kootenai River basin were measured for strontium isotope (
87
Sr:
86
Sr) ratios using laser ablation multicollector inductively coupled plasma mass spectrometry. All water samples and a subset of fin rays (
n
= 8) were also analyzed for trace elements (e.g., Sr, Ba, Mg). Fin ray annuli were measured and tested using knowledge of known age; known locations from physical capture events were assigned to age at capture.
Results
Strontium isotope analysis was unable to detect differences in the Kootenai River and Kootenay Lake using water or fin ray samples. The Kootenai River and Kootenay Lake were distinguishable using trace element data from water samples, but not fin rays. The discrepancy with trace elements appears to be associated with the physiology of fin ray growth.
Discussion
Although this study did not meet its original objective of describing the movement of White Sturgeon in the Kootenai River basin from fin ray microchemistry, our results provide insight into the potential influence of physiology on microchemistry analysis. In particular, fin ray microchemistry of slow-growing fishes may be possible in freshwater systems with further investigation into the physiological processes associated with growth and the incorporation of elements into calcified structures. - Integrating otolith and genetic tools to reveal intraspecific biodiversity in a highly impacted salmon populationPublished in: Journal of Fish Biology, jfb.15847
Abstract
Intraspecific biodiversity is vital for species persistence in an increasingly volatile world. By embracing methods that integrate information at different spatiotemporal scales, we can directly monitor and reconstruct changes in intraspecific biodiversity. Here we combined genetics and otolith biochronologies to describe the genotypic and phenotypic diversity of Chinook salmon (
Oncorhynchus tshawytscha
) in the Yuba River, California, comparing cohorts that experienced a range of hydroclimatic conditions. Yuba River salmon have been heavily impacted by habitat loss and degradation, and large influxes of unmarked hatchery fish each year have led to concern about introgression and uncertainty around the viability of its wild populations, particularly the rarer spring‐run salmon. Otolith strontium isotopes showed that Yuba River origin fish represented, on average, 42% (range 7%–73%) of spawners across six return years (2009–2011, 2018–2020), with large interannual variability. The remainder of adult Chinook salmon in the river were primarily strays from the nearby Feather River hatchery, and since 2018 from the Mokelumne River hatchery. Among the Yuba‐origin spawners, on average, 30% (range 14%–50%) exhibited the spring‐run genotype. The Yuba‐origin fish also displayed a variety of outmigration phenotypes that differed in the timing and size at which they left the Yuba river. Early‐migrating fry dominated the returns (mean 59%, range 33%–89%), and their contribution rates were negatively correlated with freshwater flows. It is unlikely that fry survival rates are elevated during droughts, suggesting that this trend reflects disproportionately low survival of larger later migrating parr, smolts, and yearlings along the migratory corridor in drier years. Otolith daily increments indicated generally faster growth rates in non‐natal habitats, emphasizing the importance of continuing upstream restoration efforts to improve in‐river growing conditions. Together, these findings show that, despite a long history of habitat degradation and hatchery introgression, the Yuba River maintains intraspecific biodiversity that should be taken into account in future management, restoration, and reintroduction plans. The finding that genotypic spring‐run are reproducing, surviving, and returning to the Yuba River every year suggests that re‐establishment of an independent population is possible, although hatchery‐wild interactions would need to be carefully considered. Integrating methods is critical to monitor changes in key genetic, physiological, and behavioral traits to assess population viability and resilience. - Forensic geochemistry identifies the illegal introduction of Walleye into Lake Cascade, IdahoPublished in: North American Journal of Fisheries Management, nafm.10985
Abstract
Objective
The illegal introduction of fish species can disrupt ecosystems, collapse food webs, and undermine recreational fishing opportunities. Determining whether introduced fish are locally reproducing is important for resource managers. Here, we used the geochemical analysis of otoliths to investigate the potential illegal introduction of a Walleye
Sander vitreus
caught in 2022, in Lake Cascade, Idaho. Lake Cascade is known for its recreational Yellow Perch
Perca flavescens
fishery and has no documented resident population of Walleye.
Methods
To determine if the Walleye was spawned in Lake Cascade or introduced from elsewhere, we analyzed otoliths for strontium isotopes (
87
Sr/
86
Sr) and compared them to local water samples and three locally caught Yellow Perch.
Result
The Walleye otolith revealed a shift from higher
87
Sr/
86
Sr values (0.70878) in its early life to a period of intermediate value (0.70842) equal to Payette Lake water, then finally to a lower value (0.70807) comparable to the Lake Cascade water and resident Yellow Perch otoliths.
Conclusion
These results suggest that the Walleye was initially transplanted to the Payette Lake area from a currently unknown source in 2020, 2 years before its capture. It resided there briefly before migrating south into Lake Cascade. This study further highlights the benefit of geochemical analyses to identify the illegal introduction of fish and to provide resource managers with a powerful tool for early detection and prevention of the establishment of illegally introduced fish species.
,
Impact statement
Otolith geochemical analyses reveal that an invasive Walleye caught in Lake Cascade, Idaho, did not originate there but was instead illegally introduced. This showcases the potential of this tool to provide independent evidence of illegal introductions. - Remnant salmon life history diversity rediscovered in a highly compressed habitatPublished in: Evolutionary Applications, 17(7), e13741
Abstract
Chinook salmon (
Oncorhynchus tshawytscha
) display remarkable life history diversity, underpinning their ability to adapt to environmental change. Maintaining life history diversity is vital to the resilience and stability of Chinook salmon metapopulations, particularly under changing climates. However, the conditions that promote life history diversity are rapidly disappearing, as anthropogenic forces promote homogenization of habitats and genetic lineages. In this study, we use the highly modified Yuba River in California to understand if distinct genetic lineages and life histories still exist, despite reductions in spawning habitat and hatchery practices that have promoted introgression. There is currently a concerted effort to protect federally listed Central Valley spring‐run Chinook salmon populations, given that few wild populations still exist. Despite this, we lack a comprehensive understanding of the genetic and life history diversity of Chinook salmon present in the Yuba River. To understand this diversity, we collected migration timing data and GREB1L genotypes from hook‐and‐line, acoustic tagging, and carcass surveys of Chinook salmon in the Yuba River between 2009 and 2011. Variation in the GREB1L region of the genome is tightly linked with run timing in Chinook salmon throughout their range, but the relationship between this variation and entry on spawning grounds is little explored in California's Central Valley. We found that the date Chinook salmon crossed the lowest barrier to Yuba River spawning habitat (Daguerre Point Dam) was tightly correlated with their GREB1L genotype. Importantly, our study confirms that ESA‐listed spring‐run Chinook salmon are spawning in the Yuba River, promoting a portfolio of life history and genetic diversity, despite the highly compressed habitat. This work highlights the need to identify and protect this life history diversity, especially in heavily impacted systems, to maintain healthy Chinook salmon metapopulations. Without protection, we run the risk of losing the last vestiges of important genetic variation. - Restoring freshwater habitat mosaics to promote resilience of vulnerable salmon populationsPublished in: Ecosphere, 15(3), e4803
Abstract
Phenotypic diversity and abundance drive salmon resilience in the face of increasing environmental variability. But what happens when human activities fundamentally alter the habitat complexity that drives this diversity? And how can we restore habitats to recover both diversity and abundance to support salmon persistence in a warming climate? Here, we looked at the impact of a large watershed restoration effort on the abundance and climate resilience of the three remaining core natural spring‐run Chinook Salmon populations in the California Central Valley (Butte, Mill, and Deer Creek). Butte Creek fish, which have floodplain access, had higher overall productivity and faster juvenile growth compared with Mill and Deer Creek populations, and the proportion of floodplain inundation was positively correlated with Butte Creek adult abundance two years later. While Butte Creek exhibited significant increases in abundance post‐restoration (~2000%), it generally exhibited lower phenotypic diversity and only a marginal increase in population stability after restoration based on the coefficient of variation (CV). In particular, Butte Creek salmon tended to exhibit larger drops in escapement following dry years (e.g., return years 2010, 2017) compared with Mill and Deer Creek populations, presumably due to limited inundation of its downstream floodplain. The late‐migrating juvenile strategy (i.e., yearling), which disproportionately supported Mill and Deer Creek populations during droughts, was uncommon among Butte Creek adults (averaging 60% of returns for Mill and Deer Creek vs. 0.3% for Butte Creek). Increased spring‐run stock complex stability was found, post‐restoration, when combining the three spring‐run populations (i.e., lower aggregate CV). However, among‐river pairwise correlations also suggested increased synchronization in population abundances post‐restoration, potentially due to increasing frequency and severity of extreme climatic events (e.g., droughts and ocean warming). This study underscores the importance of restoring a connected mosaic of aquatic habitats across modified landscapes, such as cold water refugia and floodplains, to preserve multiple (across‐population) life history pathways for increasing salmon stock complex stability and abundance. These landscape‐scale process‐based habitat restoration efforts are likely to be crucial for the successful long‐term recovery of vulnerable species in a rapidly changing climate. - Otolith microchemistry combined with genetics reveal patterns of straying and population connectivity in anadromous brown trout ( <i>Salmo trutta</i> )Published in: Ecology of Freshwater Fish, eff.12760
Abstract
Salmonids are well known for their natal homing behaviour, meaning they return to breed in the same area where they originated. However, not all individuals return to their natal breeding grounds—a behavioural trait known as straying. The prevalence of straying is difficult to explore and therefore quantitative estimates for straying are seldom reported. In this study, otolith microchemistry and genetics were combined to investigate patterns of straying over ecological and evolutionary time, respectively, between neighbouring rivers flowing into Mariager fjord, Denmark. Otolith microchemistry was used to determine the river of origin for sea trout (
Salmo trutta
) upon their return to freshwater and 288 SNP markers were used to determine genetic structure among the rivers in the fjord. In this system, where the distance between rivers is short, otolith microchemistry achieved 80% accuracy in assigning juvenile brown trout to their natal river, thus allowing us to determine that approximately 43% of the adult sea trout had returned to non‐natal rivers to spawn, with a similar proportion of strayers and natal homers in all of the rivers. Genetic analysis further supported that there was substantial gene flow among individuals originating from different rivers, indicating that sea trout in Mariager fjord make up one population. The findings obtained from otolith microchemistry and genetics complement each other and provide further evidence that sea trout in this system migrate to non‐natal rivers and spawn there, which consequently affects the genetic structure of the population.
2023
- A needle in a haystack: Strontium isotopes (87Sr/86Sr) in otoliths identify origin of Largemouth Bass from a large Southwest reservoirPublished in: Canadian Journal of Fisheries and Aquatic Sciences, cjfas-2023-0148
Largemouth Bass Micropterus salmoides, a popular warm water sport fish, is routinely stocked in reservoirs throughout the USA to augment wild populations. Evaluating if these supplementations are successful requires distinguishing hatchery-sourced fish from their wild counterparts. From 2011 to 2019, over 467,000 Largemouth Bass fingerlings were stocked from multiple hatchery sources into a large southwestern reservoir (Elephant Butte Reservoir, New Mexico USA) to supplement the sportfish population. To identify hatchery-sourced Largemouth Bass, we measured strontium isotope ratios (87Sr/86Sr) and determined ages using otoliths and dorsal spines. Otolith analysis of 169 fish classified 92.9% (n = 159) to the reservoir with few fish of hatchery origin (2 from Arkansas, 1.2% and 1 from Montana, 0.6%). While stocking over 467,000 fingerlings across eight years appears to reflect negligible stocking success, it is likely that low and variable stocking densities (average 3.0, range 0.29–7.77 fish/ha) likely contributed to the low stocking success in Elephant Butte Reservoir. Dorsal fin spines did not yield accurate age reconstructions and their 87Sr/86Sr were affected by matrix interferences preventing source assignments.
- Laser ablation strontium isotopes and spatial assignment show seasonal mobility in red deer (Cervus elaphus) at Lazaret Cave, France (MIS 6)Published in: Frontiers in Ecology and Evolution, 11, 988837
Zooarchaeological analysis is a useful means of exploring faunal palaeoecology, paleoclimate and past human behaviours. The Middle Pleistocene archaeological site Lazaret Cave, located in modern-day Nice, France, features a vast assemblage of faunal remains pertinent to the understanding of early Neanderthal subsistence behaviours as well as red deer (
Cervus elaphus
) ecology during MIS 6. This pilot study examines materials from archaeological layer UA25, a short-term occupation layer at Lazaret dating to ~150,000 years ka, which has revealed 28 early Neanderthal remains as well as thousands of faunal bones, of which red deer and ibex (
Capra ibex
) are most abundant. Molars from three red deer mandibles and a single ibex were analysed for strontium (
87
Sr/
86
Sr) isotopic analysis using laser ablation mass spectrometry to determine animal movements during tooth formation, combined with intra-tooth oxygen (
δ
18
O) isotope analysis to determine seasonality. The isotope data was modelled within a local
87
Sr/
86
Sr isoscape and computational spatial assignment was undertaken to reconstruct potential summer and winter ranges of red deer. Results from this pilot study show seasonal mobility within 20 km of Lazaret, identifying two possible summer and winter ranges for the red deer excavated from UA25. Both possible summer ranges are located at higher elevations further from Lazaret while winter ranges have been assigned to lower elevations closer to the coastline and closer to Lazaret. The ibex shows no
87
Sr/
86
Sr variation throughout the first, second and third molar and the spatial assignment indicates it lived proximal to the site during the period of tooth formation. In addition to providing the first evidence of red deer spatial ecology in southern France during MIS 6, we also infer from the faunal isotope data that hominins at Lazaret Cave were likely hunting red deer in autumn and winter when they were closer to the cave site, while hunting in summer would have required up to 20 km of travel. - Reading the biomineralized book of life: expanding otolith biogeochemical research and applications for fisheries and ecosystem-based managementPublished in: Reviews in Fish Biology and Fisheries
Chemical analysis of calcified structures continues to flourish, as analytical and technological advances enable researchers to tap into trace elements and isotopes taken up in otoliths and other archival tissues at ever greater resolution. Increasingly, these tracers are applied to refine age estimation and interpretation, and to chronicle responses to environmental stressors, linking these to ecological, physiological, and life-history processes. Here, we review emerging approaches and innovative research directions in otolith chemistry, as well as in the chemistry of other archival tissues, outlining their value for fisheries and ecosystem-based management, turning the spotlight on areas where such biomarkers can support decision making. We summarise recent milestones and the challenges that lie ahead to using otoliths and archival tissues as biomarkers, grouped into seven, rapidly expanding and application-oriented research areas that apply chemical analysis in a variety of contexts, namely: (1) supporting fish age estimation; (2) evaluating environmental stress, ecophysiology and individual performance; (3) confirming seafood provenance; (4) resolving connectivity and movement pathways; (5) characterising food webs and trophic interactions; (6) reconstructing reproductive life histories; and (7) tracing stock enhancement efforts. Emerging research directions that apply hard part chemistry to combat seafood fraud, quantify past food webs, as well as to reconcile growth, movement, thermal, metabolic, stress and reproductive life-histories provide opportunities to examine how harvesting and global change impact fish health and fisheries productivity. Ultimately, improved appreciation of the many practical benefits of archival tissue chemistry to fisheries and ecosystem-based management will support their increased implementation into routine monitoring.
2022
- Visual, spectral, and microchemical quantification of crystalline anomalies in otoliths of wild and cultured delta smeltPublished in: Scientific Reports, 12(1), 20751
Abstract
Developmental abnormalities in otoliths can impact growth and survival in teleost fishes. Here, we quantified the frequency and severity of developmental anomalies in otoliths of delta smelt (
Hypomesus transpacificus
), a critically endangered estuarine fish that is endemic to the San Francisco Estuary. Left–right asymmetry and anomalous crystalline polymorphs (i.e., vaterite) were quantified and compared between wild and cultured populations using digital image analysis. Visual estimates of vaterite were validated using X-ray diffraction, Raman spectroscopy, laser ablation ICPMS, and electron probe microanalysis. Results indicated that cultured delta smelt were 80 times more likely to contain a vateritic otolith and 18 times more likely to contain relatively large (≥ 15%) amounts of vaterite. Similarly, cultured fish exhibited 30% greater asymmetry than wild fish. These results indicate that cultured delta smelt exhibit a significantly higher frequency of vestibular abnormalities which are known to reduce fitness and survival. Such hatchery effects on otolith development could have important implications for captive culture practices and the supplementation of wild fish populations with cultured individuals. - Strontium isotopes in otoliths reveal a diversity of natal origins for Tarek (Alburnus tarichi) in Lake Van, TurkeyPublished in: Fisheries Research, 255(May), 106441
- A large-scale environmental strontium isotope baseline map of Portugal for archaeological and paleoecological provenance studiesPublished in: Journal of Archaeological Science, 142(April), 105595
- Polygenic Discrimination of Migratory Phenotypes in an Estuarine Forage FishPublished in: G3 Genes|Genomes|Genetics
Migration is a complex phenotypic trait with some species containing migratory and non-migratory individuals. Such life history variation may be attributed in part to plasticity, epigenetics, or genetics. Although considered semi-anadromous, recent studies using otolith geochemistry have revealed life history variation within the critically endangered Delta Smelt. Broadly categorizable as migratory or freshwater residents, we examined RADseq data to test for a relationship between genetic variation and migratory behaviors. As previously shown, we found no evidence for neutral population genetic structure within Delta Smelt; however, we found significant evidence for associations between genetic variants and life history phenotypes. Furthermore, Discriminant Analysis of Principal Components, hierarchical clustering, and machine learning resulted in accurate assignment of fish into the freshwater resident or migratory classes based on their genotypes. These results suggest the presence of adaptive genetic variants relating to life history variation within a panmictic population. Mechanisms that may lead to this observation are genotype dependent habitat choice and spatially variable selection, both of which could operate each generation and are not exclusive. Given that the population of cultured Delta Smelt are being used as a refugial population for conservation, as a supply for wild population supplementation, and currently represent the majority of all living individuals of this species, we recommend that the hatchery management strategy consider the frequencies of life history-associated alleles and how to maintain this important aspect of Delta Smelt biological variation while under captive propagation.
- The Secrets in our TeethPublished in: Frontiers for Young Minds, 10
Your dentist can tell a lot about your health and daily habits just by looking at your teeth. But did you know that archaeological scientists have discovered that there is a lot more information hidden in teeth? We can study the chemical composition of teeth and can find out what types of food a person ate, and even where that food was growing. When we find teeth in archaeological sites, a method called isotope analysis can be used to reconstruct the movements and diets of people, even when no written records are available. In this article, we will discuss what our teeth are made of and how isotope analysis can be used to learn more about ancient people. We will then look at an archaeological site in France, where children discovered bones and teeth on the playground behind their kindergarten.
- Diversity in Habitat Use by White Sturgeon Revealed Using Fin Ray GeochemistryPublished in: Frontiers in Marine Science, 9(March), 1-18
Understanding life-history diversity in a population is imperative to developing effective fisheries management and conservation practices, particularly in degraded environments with high environmental variability. Here, we examined variation in habitat use and migration patterns of White Sturgeon ( Acipenser transmontanus ), a long-lived migratory fish that is native to the San Francisco Estuary, CA, United States. Annual increment profiles were combined with respective geochemical ( 87 Sr/ 86 Sr) profiles in sturgeon fin rays to reconstruct annual salinity chronologies for 112 individuals from 5 to 30 years old. Results indicated a complex and diverse amphidromous life history across individuals, characterized largely by estuarine residence, a general ontogenetic trend toward higher-salinity brackish habitats, and high variability in habitat use across all age groups. Hierarchical clustering based on fin ray geochemistry during the first 10 years of life, prior to sexual maturation, indicated at least four distinct migratory phenotypes which differed largely in the timing and duration of juvenile to subadult movements between fresh- and brackish-water habitats. This study provides information regarding habitat use and migration in sub-adult fish that was previously lacking. Different migratory phenotypes vary in exposure to stressors across time and space and populations. Understanding White Sturgeon habitat distributions through space and time at different life stages can help identify areas where habitat restoration would be most effective and develop management actions to reduce stressors associated with specific areas where White Sturgeon are present.
- Spatial Heterogeneity in Prey Availability, Feeding Success, and Dietary Selectivity for the Threatened Longfin SmeltPublished in: Estuaries and Coasts
Food availability is a key determinant of the nursery value of a given habitat for larval and juvenile fishes. Growth, survival, and recruitment success are often inter-correlated and influenced by prey availability and associated feeding success. This is likely true for the threatened population of Longfin Smelt ( Spirinchus thaleichthys ) in the San Francisco Estuary (SFE) which has collapsed in recent decades along with its preferred prey. In years with high precipitation and freshwater outflow, larval Longfin Smelt are found in shallow wetland habitats throughout the SFE, but variation in the availability of food and feeding success in these habitats remains unexplored. To examine spatial variation in the trophic value of different rearing habitats, we quantified variation in prey availability, feeding success, and prey selection for larval and juvenile Longfin Smelt captured in restored tidal marshes, sloughs, and open-water habitats in the northern and southern SFE. Prey abundance varied spatially, with densities approximately tenfold greater in southern sloughs and restored tidal ponds relative to northern and open-water habitats. Feeding success of larval Longfin Smelt was positively correlated with both fish length and prey density. Larval Longfin Smelt fed selectively on the copepod Eurytemora affinis , with larger individuals (> 25 mm total length) exhibiting an ontogenetic diet shift to larger mysid shrimps. Our results suggest that wetland habitats across the SFE vary greatly in their trophic value, with previously unexplored habitats exhibiting the highest densities of prey and the highest foraging success for larval Longfin Smelt.
2021
- Experimental validation of otolith-based age and growth reconstructions across multiple life stages of a critically endangered estuarine fishPublished in: PeerJ, 9, e12280
- The Clever Strategies That Fishes Use to Survive in San Francisco’s Dynamic EstuaryPublished in: Frontiers for Young Minds, 9
Estuaries are places where fresh water from rivers mixes with salty water from the ocean. Why does this matter? This mixing creates dynamic, ever-changing conditions that fishes must navigate in order to survive. Environmental conditions can change yearly, seasonally, daily, and even hourly. Fishes use many different strategies to adjust to this wild variation. Some are picky and only use certain habitats. Others use many different kinds of habitats and move between them at different times of the year. Adults and juveniles might even live away from each other in different parts of the estuary. In this article, we describe some of the clever strategies that fishes use to survive in estuaries. We also consider how scientists uncover these clever strategies and what each of us can do to help protect the fishes of the San Francisco Estuary and elsewhere.
- Geologic variability of conodont strontium isotopic composition quantified by laser ablation multiple collection inductively coupled plasma mass spectrometryPublished in: Palaeogeography, Palaeoclimatology, Palaeoecology, 568, 110308
- Geochemical Tools Identify the Origins of Chinook Salmon Returning to a Restored CreekPublished in: Fisheries, 46(1), 22-32
- Otolith-based approaches indicate strong effects of environmental variation on growth of a Critically Endangered estuarine fishPublished in: Marine Ecology Progress Series, 676, 37-56
In estuaries, fluctuating environmental conditions exact strenuous physiological demands on the fishes that inhabit these oft-impacted areas, including the Critically Endangered delta smelt Hypomesus transpacificus in California (USA). Using an archive of otoliths spanning 2011-2019, we examined how growth rates of wild subadult delta smelt vary ontogenetically, regionally, and in relation to variation in the physical environment during late-summer and fall in the upper San Francisco Estuary. Recent growth rates were quantified using otolith increment analysis and modeled as functions of both intrinsic (age) and extrinsic (temperature, salinity, clarity, and region) factors using a suite of generalized additive models. Age explained 60% of the variation in log 10 -transformed growth rates, which peaked at 50-80 d post hatch. Overall, age-adjusted growth rates declined at temperatures >20°C, increased with practical salinity values of 0-4, and exhibited interactive patterns with water clarity. Growth rates appeared highest in the West and Central Delta, and lowest in the North Delta, also corresponding with patterns in environmental conditions. Here, we provide new evidence for how vital rates of wild delta smelt vary spatially and in relation to abiotic environmental variation. Such otolith-based growth reconstructions often provide the first direct look at how the vital rates of wild fish respond to environmental variation in situ , and how future changes are likely to affect the dynamics of wild populations.
- Biogeochemical processes create distinct isotopic fingerprints to track floodplain rearing of juvenile salmonPublished in: Plos One, 16(10), e0257444
Floodplains represent critical nursery habitats for a variety of fish species due to their highly productive food webs, yet few tools exist to quantify the extent to which these habitats contribute to ecosystem-level production. Here we conducted a large-scale field experiment to characterize differences in food web composition and stable isotopes (δ¹³C, δ¹⁵N, δ³⁴S) for salmon rearing on a large floodplain and adjacent river in the Central Valley, California, USA. The study covered variable hydrologic conditions including flooding (1999, 2017), average (2016), and drought (2012–2015). In addition, we determined incorporation rates and tissue fractionation between prey and muscle from fish held in enclosed locations (experimental fields, cages) at weekly intervals. Finally, we measured δ³⁴S in otoliths to test if these archival biominerals could be used to reconstruct floodplain use. Floodplain-reared salmon had a different diet composition and lower δ 13 C and δ³⁴S (δ¹³C = -33.02±2.66‰, δ³⁴S = -3.47±2.28‰; mean±1SD) compared to fish in the adjacent river (δ¹³C = -28.37±1.84‰, δ³⁴S = +2.23±2.25‰). These isotopic differences between habitats persisted across years of extreme droughts and floods. Despite the different diet composition, δ¹⁵N values from prey items on the floodplain (δ¹⁵N = 7.19±1.22‰) and river (δ¹⁵N = 7.25±1.46‰) were similar, suggesting similar trophic levels. The food web differences in δ 13 C and δ³⁴S between habitats were also reflected in salmon muscle tissue, reaching equilibrium between 24–30 days (2014, δ¹³C = -30.74±0.73‰, δ³⁴S = -4.6±0.68‰; 2016, δ¹³C = -34.74 ±0.49‰, δ³⁴S = -5.18±0.46‰). δ³⁴S measured in sequential growth bands in otoliths recorded a weekly time-series of shifting diet inputs, with the outermost layers recording time spent on the floodplain (δ³⁴S = -5.60±0.16‰) and river (δ³⁴S = 3.73±0.98‰). Our results suggest that δ¹³C and δ³⁴S can be used to differentiate floodplain and river rearing habitats used by native fishes, such as Chinook Salmon, across different hydrologic conditions and tissues. Together these stable isotope analyses provide a toolset to quantify the role of floodplains as fish habitats.
2020
- Ontogenetic patterns in the calcification and element incorporation in fin rays of age-0 White SturgeonPublished in: Environmental Biology of Fishes
- Bioavailable Soil and Rock Strontium Isotope Data from IsraelPublished in: Earth System Science Data Discussions, 1-16
- Sampling Plants and Malacofauna in 87Sr/86Sr Bioavailability Studies: Implications for Isoscape Mapping and Reconstructing of Past Mobility PatternsPublished in: Frontiers in Ecology and Evolution, 8(December), 1-16
2019
- Complex life histories discovered in a critically endangered fishPublished in: Scientific Reports, 9(1), 16772
- Newly discovered spawning and recruitment of threatened Longfin Smelt in restored and under‐explored tidal wetlandsPublished in: Ecology, ecy.2868
- Calibrating temperature reconstructions from fish otolith oxygen isotope analysis for California's critically endangered Delta SmeltPublished in: Rapid Communications in Mass Spectrometry, 33(14), 1207-1220
Rationale: Oxygen isotope ratios (δ18O values) of fish otoliths (ear bones) are valuable geochemical tracers of water conditions and thermal life history. Delta Smelt (Hypomesus transpacificus) are osmerid forage fish endemic to the San Francisco Estuary, California, USA, that are on the verge of extinction. These fish exhibit a complex life history that allows them to survive in a dynamic estuarine environment; however, a rapidly warming climate threatens this thermally sensitive species. Here we quantify the accuracy and precision of using δ18O values in otoliths to reconstruct the thermal life histories of Delta Smelt. Methods: Delta Smelt were reared for 360 days using three different water sources with different ambient δ18Owater values (−8.75‰, −5.28‰, and −4.06‰) and different water temperatures (16.4°C, 16.7°C, 18.7°C, and 20.5°C). Samples were collected after 170 days (n = 28) and 360 days (n = 14) post-hatch. In situ δ18O values were measured from the core of the otolith to the dorsal edge using secondary ion mass spectrometry (SIMS) to reconstruct temporally resolved thermal life histories. Results: The δ18Ootolith values for Delta Smelt varied as a linear inverse function of water temperature: 1000 ln α = 18.39 (±0.43, 1SE)(103TK−1) − 34.56 (±1.49, 1SE) and δ18Ootolith(VPDB) − δ18Owater (VPDB) = 31.34(±0.09, 1SE) − 0.19(±0.01, 1SE) × T ° C. When the ambient δ18Owater value is known, this species-specific temperature-dependent oxygen isotope fractionation model facilitated the accurate (0.25°C) and precise (±0.37°C, 2σ) reconstruction of the water temperature experienced by the fish. In contrast, the use of existing general fractionation equations resulted in inaccurate temperature reconstructions. Conclusions: The species-specific δ18Ootolith fractionation equation allowed for accurate and precise reconstructions of water temperatures experienced by Delta Smelt. Characterization of ambient δ18Owater values remains a critical next step for reconstructing thermal life histories of wild Delta Smelt. This tool will provide new insights into habitat utilization, potential thermal refugia, and resilience to future warming for this critically endangered fish.
- Rocks, teeth, and tools: New insights into early Neanderthal mobility strategies in South-Eastern France from lithic reconstructions and strontium isotope analysisPublished in: PLOS ONE, 14(4), e0214925
- Who's been using my burial mound? Radiocarbon dating and isotopic tracing of human diet and mobility at the collective burial site, Le Tumulus des Sables, southwest FrancePublished in: Journal of Archaeological Science: Reports, 24(March), 955-966
- A strontium isoscape of north-east Australia for human provenance and repatriationPublished in: Geoarchaeology
2018
- Fishery collapse, recovery, and the cryptic decline of wild salmon on a major California riverPublished in: Canadian Journal of Fisheries and Aquatic Sciences, 75(11), 1836-1848
- IsoFishR: An application for reproducible data reduction and analysis of strontium isotope ratios (87Sr/86Sr) obtained via laser-ablation MC-ICP-MSPublished in: PLOS ONE, 13(9), e0204519
- A bioavailable strontium isoscape for Western Europe: A machine learning approachPublished in: PLOS ONE, 13(5), e0197386
- Mapping of bioavailable strontium isotope ratios in France for archaeological provenance studiesPublished in: Applied Geochemistry, 90, 75-86
2017
- Validating Fin Ray Microchemistry as a Tool to Reconstruct the Migratory History of White SturgeonPublished in: Transactions of the American Fisheries Society, 146(5), 844-857
- New Insights into Mesolithic Human Diet in the Mediterranean from Stable Isotope Analysis: The Sites of Campu Stefanu and Torre d'Aquila, CorsicaPublished in: International Journal of Osteoarchaeology, 27(4), 707-714
2016
- 87Sr/86Sr isotope ratio analysis by laser ablation MC-ICP-MS in scales, spines, and fin rays as a nonlethal alternative to otoliths for reconstructing fish life historyPublished in: Canadian Journal of Fisheries and Aquatic Sciences, 73(12), 1852-1860
Strontium isotope ratios (87Sr/86Sr) in otoliths are a well-established tool to determine origins and movement patterns of fish. However, otolith extraction requires sacrificing fish, and when working with protected or endangered species, the use of nonlethal samples such as scales, spines, and fin rays is preferred. Unlike otoliths that are predominantly aragonite, these tissues are composed of biological apatite. Laser ablation multicollector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) analysis of biological apatite can induce significant interference on mass 87, causing inaccurate 87Sr/86Sr measurements. To quantify this interference, we applied LA-MC-ICP-MS to three marine samples (white seabass (Atractoscion nobilis) otolith; green sturgeon (Acipenser medirostris) pectoral fin ray; salmon shark (Lamna ditropis) tooth), and freshwater walleye (Sander vitreus) otoliths, scales, and spines). Instrument conditions that maximize signal intensity resulted in elevated 87Sr/86Sr isotope ratios in the bioapatite samples, related to a polyatomic interference (40Ca31P16O, 40Ar31P16O). Retuning instrument conditions to reduce oxide levels removed this interference, resulting in accurate 87Sr/86Sr ratios across all tissue samples. This method provides a novel, nonlethal alternative to otolith analysis to reconstruct fish life histories.
- A comprehensive chronology of the Neanderthal site Moula-Guercy, Ardèche, FrancePublished in: Journal of Archaeological Science: Reports, 9, 309-319
- Improvement of laser ablation in situ micro-analysis to identify diagenetic alteration and measure strontium isotope ratios in fossil human teethPublished in: Journal of Archaeological Science, 70, 102-116
2015
- The distribution of megablocks in the Ries crater, Germany: Remote sensing, field investigation, and statistical analysesPublished in: Meteoritics & Planetary Science, 50(1), 141-171
The Ries impact structure, located in Bavaria, southern Germany, has a diameter of 26 km. It is one of the best studied impact craters on the Earth and it is used as an archetype for complex craters across the solar system [e.g. 1, 2]. However its geologic structure still poses questions regarding crater formation mechanics and about the distribution of distinct morphologic units. Especially the hummocky terrain of the megablock zone, which is located between the so-called inner crystalline ring and outer rim of the crater, is not well understood [2]. On the one hand it consists of excavated allochthonous blocks of brecciated crystalline and sedimentary rocks that are embedded in Bunte Breccia (a polymict lithic breccia), on the other hand it is built up of sedimentary blocks that slumped into the crater cavity during crater collapse [2, 3]. Thus the megablock zone gives unique insights into processes of target damaging, fragmentation and excavation and interaction with collapse-induced slumping. Published geologic maps merely display megablocks that are exposed at the surface [4]. A preliminary analysis of the area utilizing Google Earth imagery (average resolution of 1m/pxl) additionally show abundant megablocks in the near subsurface covered by soil that were not yet recorded until now. They are clearly visible in fields with sparse or no vegetation and show a structure and morphology similar to megablock outcrops at the surface. The megablocks could not be observed in fields with dense vegetation and residential areas. Visibility of megablocks in the fields is likely due to differences in humidity in the top soil caused by the different underlying megablock material. Using a 1-3 m shallow drilling device (Pürckhauer) we were able to prove the existence of several megablock structures that are clearly visible in remote sensing images. Their top was reached at a depth of around 2-3 m. A field campaign using a percussion piston corer in combination with the analysis of new high-resolution remote sensing images from the HRSC-AX Camera (resolution 20 cm/pxl) is carried out to further investigate the distribution, composition, and size of megablocks in the subsurface of the Ries crater as a function of radial distance to the crater center. The remote sensing images allow for a detailed mapping of the megablock structures while the field campaign provides ground truth. This is especially important since this detection technique has not been used on recognition of megablock structures before. To compensate for the problems of megablock visibility due to different levels of vegetation we will use Google Earth and HRSC-AX images that have been taken at different times. With the proposed combination of datasets, we will significantly increase our chance to observe megablock structures, thereby increasing our knowledge. Extensive field work also allows for detailed composition and structural analysis of the megablocks at the surface. Combining existing geologic maps [4 and references therein] with our results will yield a comprehensive map of the megablock zone of the Ries crater. Detailed analysis will provide a more in-depth understanding of the Ries impact crater, its complex geologic history and the emplacement mechanism of megablock structures in complex craters. These results can then be compared to similar complex impact craters on the Earth and on other terrestrial bodies like the Moon and Mars. References [1] Stöffler, 1997, Geologica Bavarica, 75, 163-189; [2] Kenkmann and Ivanov, 2006, Earth and Planetary Science Letters, 252, 15-29; [3] Pohl et al., 1977, Impact and Explosion Cratering, Flagstaff, Arizona; [4] Hüttner and Schmidt-Kaler, 1999, Geologica Bavarica, 104, 7.76.
2014
- The IRHUM (Isotopic Reconstruction of Human Migration) database – bioavailable strontium isotope ratios for geochemical fingerprinting in FrancePublished in: Earth System Science Data, 6(1), 117-122
2013
- Laser ablation depth profiling of U-series and Sr isotopes in human fossilsPublished in: Journal of Archaeological Science, 40(40), 2991-3000
We have explored laser depth profiling to obtain data sets for U-series as well as Sr analyses. Laser probing with an 81μm spot size allows for the exploration of low uranium domains of up to 400μm below the outer surface in tooth enamel. These low U domains will contain Sr isotope compositions of the individual, that are least affected by diagenetic Sr overprints. The small holes drilled for U surveying are not visible to the naked eye. Using larger spot sizes of around 233μm, laser drilling can be used to obtain reliable U-series isotope data to a depth of approximately 1000μm in enamel and around 1300μm in bone. Furthermore, meaningful 87Sr/86Sr isotope data can also be obtained with this spot size. Using our sampling strategy, the overall damage to a human tooth is minute, as demonstrated on a Neanderthal tooth from Moula-Guercy. We expect that laser ablation depth profiling will become routine for gaining insights into the age of human fossils and the migrations of ancient humans. © 2013 Elsevier Ltd.
2012
- Surface age of the ice–dust mantle deposit in Malea Planum, MarsPublished in: Planetary and Space Science, 60(1), 199-206
The mid- and high-latitudes of Mars are covered by a smooth young mantle that is interpreted as an atmospherically derived air-fall deposit of ice and dust related to recent climate changes. In order to determine relative and absolute ages of this surface unit within the southern hemisphere, a systematic survey of all available HiRISE and CTX images in the Malea Planum region from 5560??S latitude and 5070??E longitude was performed and the distribution and the morphology of small impact craters on the mantle deposit were investigated. Using crater size-frequency measurements, we derived absolute model ages of ???35 Ma for the surface of the mantle, immediately south of the Hellas basin rim. Morphologic observations of the mantle, its fresh appearance, very low number of craters, and superposition on older units support this very young Amazonian age. Nearly all observed craters on the smooth mantle in Malea Planum are small and show signs of erosion, evidence for the ongoing modification of the ice-dust mantle. However, this modification has not been strong enough to reset the surface age. Compared to the ice-dust mantle at higher latitudes in the northern and southern hemisphere, the surface of the mantle in Malea Planum is older and thus has been relatively stable during obliquity changes in the last ???35 Ma. This is consistent with the hypothesis that the ice-dust mantle is a complex surface deposit of different layers, that shows a strong latitude dependence in morphology and has been deposited and degraded at different times in martian history. ?? 2011 Elsevier Ltd. All rights reserved.