Wild Salmon Center

Abstract Climate change is threatening ecologically and culturally important species. For species with broad ranges and complex life cycles, such as migratory Pacific salmon ( Oncorhynchus spp.), climate exposure may vary across space and diverse life history strategies. Here, we quantify climate exposure and adaptive capacity across the North American range and remarkable phenological diversity of Chinook salmon ( O. tshawytscha ). We compiled data on adult freshwater migration timing and its environmental covariates for 295 populations of Chinook salmon spanning 29 degrees of latitude from California to Alaska. We linked this migration timing data to recent (1990s) and future (2040s) water temperatures to quantify thermal exposure during each population's timing of entrance to freshwater. At northern latitudes, Chinook migration timing was compressed to 3 months during the summer, while at southern latitudes, migration occurred across months before and after stressful peak summer water temperatures. Earlier migration timing was associated with longer migration distances and greater elevations gained. Thermal exposure was controlled by latitude and run‐timing, with lower latitude and summer and fall runs being most exposed to potentially harmful temperatures both now and into the future. However, potentially harmful climate exposure was predicted to increase the most in mid‐latitude populations (~45° to 55°) that have not yet adapted to migrate before and after peak summer temperatures. If Chinook salmon phenology were to keep pace with projected climate warming by the 2040s, the majority (75%) of populations would need to shift their migration timing earlier in the year, pulling their migration farther apart from their fall spawning phenology. Collectively, these findings showcase how latitude and life history diversity influence climate change risk and indicate the importance of preserving existing migration timing diversity and adaptive capacity across the broad range of a migratory species.

Abstract Recent advancements in the automatic re-identification of animal individuals from images have opened up new possibilities for studying wildlife through camera traps and citizen science projects. Existing methods leverage distinct and permanent visual body markings, such as fur patterns or scars, and typically employ one of two approaches: local features or end-to-end learning. The end-to-end learning-based methods outperform local feature-based methods given a sufficient amount of good-quality training data, but the challenge of gathering such datasets for wildlife animals means that local feature-based methods remain a more practical approach for many species. In this study, we aim to achieve two goals: (1) to obtain a better understanding of the impact of training-set size on animal re-identification, and (2) to explore ways to combine various methods to leverage the advantages of their approaches for re-identification. In the work, we conduct comprehensive experiments across six different methods and six animal species with various training set sizes. Furthermore, we propose a simple yet effective combination strategy and show that a properly selected method combinations outperform the individual methods with both small and large training sets up to 30%. Additionally, the proposed combination strategy offers a generalizable framework to improve accuracy across species and address the challenges posed by small datasets, which are common in ecological research. This work lays the foundation for more robust and accessible tools to support wildlife conservation, population monitoring, and behavioral studies.

Abstract Studies can only guide conservation if their findings are informative at the scales at which practitioners and policymakers operate. Yet, it is rarely tested whether large-scale studies reach similar conclusions to the smaller-scale studies on which conservation traditionally relies. We examine whether predictors of extinction risk are consistent across global, regional, and local scales, for 210 tropical forest mammal species (≥ 1 kg) that existed during the last 130,000 years, in 64 tropical forests, across three biogeographical realms. We found consistent predictors of extinction risk (body mass, generation length, diet, brain volume and scansoriality) when analyses differed only in their spatial resolution. However, predictors differed when analyses also varied in their temporal extent. Macroecological findings about extinction risk can, thus, inform conservation at smaller scales, but they risk misidentifying threatened species if differences in temporal extent are not recognised.

Reduced-representation sequencing methods, such as Restriction-site Associated DNA sequencing (RAD-seq), use restriction enzymes to achieve a cost-effective approach for generating genome-wide SNP data. However, a major limitation of these methods is

Sperm whales Physeter macrocephalus resident in the Gulf of Mexico are geographically isolated from other populations, making them vulnerable to the impacts of oil and gas exploration prevalent in the region. Despite long-standing research focused on sperm whales in the Gulf of Mexico, genetic structure within this population has not yet been investigated, nor has there been an assessment of the impacts of the 2010 Deepwater Horizon oil spill on population structure. Here, we investigated the spatial structure and temporal variation in mitochondrial DNA haplotype frequencies from 619 genetic samples collected from 377 individual sperm whales identified by microsatellite genotyping. This study uses samples collected over nearly 2 decades from 2000-2017 to support previous findings of genetic isolation of the Gulf of Mexico population from those in the Western North Atlantic (FST = 0.242, p < 0.001) and Caribbean (FST = 0.423, p < 0.001). In addition, we demonstrate significant changes in population structure within the Gulf of Mexico across both space and time. Most notably, the Central subregion, where the 2010 Deepwater Horizon oil spill originated, underwent a significant change in haplotype frequencies across time (FST = 0.141, p < 0.001), with implications for disruption of matrilineal population structure. Our findings of spatial and temporal structure within Gulf of Mexico sperm whales highlight the importance of regular monitoring and the establishment of baseline population data in the face of anthropogenic and environmental impacts.

Mongolian grayling is a large piscivorous grayling endemic to the endorheic basin of the Khovd and Zavkhan River systems in western Mongolia. Ongoing large‐scale hydropower development in the Khovd River has raised concerns about potential impacts on the Mongolian grayling populations in the area. Very little is known about the behavior and biology of Mongolian grayling, which makes it difficult to predict the impacts of damming and to plan for conservation and management mitigation actions. In this study, we used acoustic telemetry to track migration and survival of Mongolian grayling in the Khovd River system before the onset of hydropower construction. We found that the Mongolian grayling in the Khovd River conduct extensive seasonal migrations (> 170 km) to reach overwintering and spawning habitat and that migration routes pass through the Shijigtiin Canyon which is currently being developed for hydropower. We also found that Mongolian grayling in the downstream Khar Lake predominantly reside in the lake and only use lotic habitat during the spawning season, including the dammed Chono‐Kharaikh River. Based on our results, we argue that the ongoing hydropower development of the Khovd River will have severe impacts on the grayling population by disrupting the annual migration cycle, prohibiting access to spawning and overwintering habitat, and altering flow regimes on downstream spawning grounds.

Monitoring of salmon in Pacific Canada has been declining for decades. Counts of spawning salmon enable researchers to quantify stressor impacts, identify where management interventions are required, and evaluate recovery effort efficacy. These data are critical now, as uniquely adapted populations underlie salmon resilience (e.g., to climate change), and fine-scale data informs sustainable fishing opportunities including revitalizing terminal fisheries. We revisit the state of Pacific salmon spawner data from the Yukon to southern BC. Almost two-thirds of historically monitored salmon populations have no reported estimates in 2014–2023—the worst decade for data since broadscale surveys began in the 1950s. We found positive associations between the number of populations monitored and landed value for three of the five Pacific salmon species, suggesting that monitoring is, in part, motivated by the information needs of commercial fisheries management. We recommend aligning objectives and strategic investments to improve monitoring outcomes for salmon, ecosystems, and communities depending on them. We emphasize data stewardship, as ensuring access to these baseline data are a cornerstone for rebuilding wild Pacific salmon.

Abstract This study aims to improve the accuracy of the pulling force estimation by establishing the variable friction model of the dry-lubricated split sleeve when cold working an aluminum 2024-T3 hole. The variable friction model was empirically obtained from the friction experimental setup simplified from the split-sleeve cold expansion process. The contact-pressure-dependent variable friction model was derived through a systematic design of experiments approach with three different normal stress conditions, namely low normal stress (220 MPa), medium normal stress (440 MPa), and high normal stress (660 MPa), to cover the range of normal stresses occurred in the cold expansion process. A full quadratic response surface model was drawn for the friction coefficient's nonlinear relationship between the mandrel and the lubricated sleeve, depending on the normal stresses. The variable friction model was verified with 3-dimensional friction test finite element (FE) simulations. This FE modeling validates the variable friction model to predict the pulling forces with a sound agreement between the estimated and experimentally obtained values. We conducted split-sleeve cold expansion experiments to obtain the pulling force profile. Two three-dimensional (3D) FE numerical analyses of the same split-sleeve cold expansion process were conducted using the variable friction model and a constant frictional coefficient of 0.05. The pulling force profiles from the FE modeling with the variable friction model closely align with those from the experiments to show the four distinct regions.

Marine heatwaves have altered ecosystems globally, including changing community composition and facilitating the spread of invasive species. In south Puget Sound, Washington (USA), non-native Pacific oysters (Magallana gigas) have been farmed extensively for almost a century and grown in enhancement sites, however, they have only recently recruited in the wild. This study explores how the appearance of Pacific oysters was related spatially (eight sites) and temporally (decade) to warmer summer water temperatures in south Puget Sound and compares oyster persistence across five sites where recruitment occurred. The largest recruitment event from 2012-2020 was in the summer of 2015, in the middle of the east Pacific Blob marine heatwave which led to warm water temperatures off the west coast of North America. Throughout the study period, the number of oyster recruits each year was positively correlated with warmer water temperatures. Oyster population densities differed across the five sites where recruitment occurred and generally declined after 2015, but showed no site by year interactions, which is consistent with spatially-variable recruitment and similar post-recruitment survival. Mean oyster shell heights also differed among sites, which could reflect different growth trajectories or recreational harvest patterns. This study supports the claim that warming sea surface temperatures may interact with species introductions to change modern biogeography.

We have previously reported that a water extract (CAW) of the Ayurvedic plant Centella asiatica administered in drinking water can improve cognitive deficits in mouse models of aging and neurodegenerative diseases. Here we compared the effects of CAW administered in drinking water or the diet on cognition, measures of anxiety and depression-like behavior in healthy aged mice. Three- and eighteen-month-old male and female C57BL6 mice were administered rodent AIN-93M diet containing CAW (0, 0.2, 0.5 or 1% w/w) to provide 0, 200 mg/kg/d, 500 mg/kg/d or 1000 mg/kg/d for a total of 5 weeks. An additional group of eighteen-month-old mice were treated with CAW (10 mg/mL) in their drinking water for a total of five weeks to deliver the same exposure of CAW as the highest dietary dose (1000 mg/kg/d). CAW doses delivered were calculated based on food and water consumption measured in previous experiments. In the fourth and fifth weeks, mice underwent behavioral testing of cognition, anxiety and depression (n=12 of each sex per treatment group in each test). Aged mice of both sexes showed cognitive deficits relative to young mice while only female aged mice showed increased anxiety compared to the young female mice and no differences in depression were observed between the different ages. CAW (1000 mg/kg/d) in the drinking water improved deficits in aged mice in learning, executive function and recognition memory in both sexes and attenuated the increased measures of anxiety observed in the aged female mice. However, CAW in the diet only improved executive function in aged mice at the highest dose (1000 mg/kg/d) in both sexes and did so less robustly than when given in the water. There were no effects of CAW on depression-like behavior in aged animals regardless of whether it was administered in the diet or the water. These results suggest that CAW can ameliorate age-related changes in measures of anxiety and cognition and that the mode of administration is important for the effects of CAW on resilience to these age-related changes.