Estimating westslope cutthroat trout (Oncorhynchus clarkii lewisi) movements in a river network using strontium isoscapes

This paper is not subject to U.S. copyright. The definitive version was published in Canadian Journal of Fisheries and Aquatic Sciences 69 (2012): 906-915, doi:10.1139/f2012-033.We used natural variation in the strontium concentration (Sr:Ca) and isotope composition (87Sr:86Sr) of stream waters and corresponding values recorded in otoliths of westslope cutthroat trout (Oncorhynchus clarkii lewisi) to examine movements during their life history in a large river network. We found significant spatial differences in Sr:Ca and 87Sr:86Sr values (strontium isoscapes) within and among numerous spawning and rearing streams that remained relatively constant seasonally. Both Sr:Ca and 87Sr:86Sr values in the otoliths of juveniles collected from nine natal streams were highly correlated with those values in the ambient water. Strontium isoscapes measured along the axis of otolith growth revealed that almost half of the juveniles had moved at least some distance from their natal streams. Finally, otolith Sr profiles from three spawning adults confirmed homing to natal streams and use of nonoverlapping habitats over their migratory lifetimes. Our study demonstrates that otolith geochemistry records movements of cutthroat trout through Sr isoscapes and therefore provides a method that complements and extends the utility of conventional tagging techniques in understanding life history strategies and conservation needs of freshwater fishes in river networks.Bonneville Power Administration, Montana Fish, Wildlife & Parks, and the US Geological Survey funded this work. Partial support was provided by NSF grants OCE-0134998 and OCE-0215905 to SRT

Combining demographic and genetic factors to assess population vulnerability in stream species

Accelerating climate change and other cumulative stressors create an urgent need to understand the influence of environmental variation and landscape features on the connectivity and vulnerability of freshwater species. Here, we introduce a novel modeling framework for aquatic systems that integrates spatially explicit, individual-based, demographic and genetic (demogenetic) assessments with environmental variables. To show its potential utility, we simulated a hypothetical network of 19 migratory riverine populations (e.g., salmonids) using a riverscape connectivity and demogenetic model (CDFISH). We assessed how stream resistance to movement (a function of water temperature, fluvial distance, and physical barriers) might influence demogenetic connectivity, and hence, population vulnerability. We present demographic metrics (abundance, immigration, and change in abundance) and genetic metrics (diversity, differentiation, and change in differentiation), and combine them into a single vulnerability index for identifying populations at risk of extirpation. We considered four realistic scenarios that illustrate the relative sensitivity of these metrics for early detection of reduced connectivity: (1) maximum resistance due to high water temperatures throughout the network, (2) minimum resistance due to low water temperatures throughout the network, (3) increased resistance at a tributary junction caused by a partial barrier, and (4) complete isolation of a tributary, leaving resident individuals only. We then applied this demogenetic framework using empirical data for a bull trout (Salvelinus confluentus) metapopulation in the upper Flathead River system, Canada and USA, to assess how current and predicted future stream warming may influence population vulnerability. Results suggest that warmer water temperatures and associated barriers to movement (e.g., low flows, dewatering) are predicted to fragment suitable habitat for migratory salmonids, resulting in the loss of genetic diversity and reduced numbers in certain vulnerable populations. This demogenetic simulation framework, which is illustrated in a web-based interactive mapping prototype, should be useful for evaluating population vulnerability in a wide variety of dendritic and fragment

Climate change vulnerability of Arctic char across Scandinavia

Climate change is anticipated to cause species to shift their ranges upward and poleward, yet space for tracking suitable habitat conditions may be limited for range-restricted species at the highest elevations and latitudes of the globe. Consequently, range-restricted species inhabiting Arctic freshwater ecosystems, where global warming is most pronounced, face the challenge of coping with changing abiotic and biotic conditions or risk extinction. Here, we use an extensive fish community and environmental dataset for 1762 lakes sampled across Scandinavia (mid-1990s) to evaluate the climate vulnerability of Arctic char (Salvelinus alpinus), the world's most cold-adapted and northernly distributed freshwater fish. Machine learning models show that abiotic and biotic factors strongly predict the occurrence of Arctic char across the region with an overall accuracy of 89 percent. Arctic char is less likely to occur in lakes with warm summer temperatures, high dissolved organic carbon levels (i.e., browning), and presence of northern pike (Esox lucius). Importantly, climate warming impacts are moderated by habitat (i.e., lake area) and amplified by the presence of competitors and/or predators (i.e., northern pike). Climate warming projections under the RCP8.5 emission scenario indicate that 81% of extant populations are at high risk of extirpation by 2080. Highly vulnerable populations occur across their range, particularly near the southern range limit and at lower elevations, with potential refugia found in some mountainous and coastal regions. Our findings highlight that range shifts may give way to range contractions for this cold-water specialist, indicating the need for pro-active conservation and mitigation efforts to avoid the loss of Arctic freshwater biodiversity.publishedVersio

Challenges in Columbia River Fisheries Conservation: A Response to Duda et al.

The salmonid fisheries of the Columbia River Basin (CRB) have enormous socioeconomic, cultural, and ecological importance to numerous diverse stakeholders (eg state, federal, tribal, nonprofit), and there are a wide array of opinions and perspectives on how these fisheries should be managed. Although we appreciate Duda et al.\u27s commentary, it offers only one perspective of many in this context. The objective of our paper (Hand et al. 2018) was to provide justification for “the importance of social–ecological perspectives when communicating conservation values and goals, and the role of independent science in guiding management policy and practice for salmonids in the CRB”. However, we did not intend to strictly advocate for a single course of action, and the available space within our paper\u27s Panel 1 limited us from engaging in a thorough ecological debate

Prenatal hypoxia induces increased cardiac contractility on a background of decreased capillary density.

Background: Chronic hypoxia in utero (CHU) is one of the most common insults to fetal development and may be associated with poor cardiac recovery from ischaemia-reperfusion injury,yet the effects on normal cardiac mechanical performance are poorly understood. Methods: Pregnant female wistar rats were exposed to hypoxia (12% oxygen, balance nitrogen)for days 10–20 of pregnancy. Pups were born into normal room air and weaned normally. At 10 weeks of age, hearts were excised under anaesthesia and underwent retrograde 'Langendorff' perfusion. Mechanical performance was measured at constant filling pressure (100 cm H2O) with intraventricular balloon. Left ventricular free wall was dissected away and capillary density estimated following alkaline phosphatase staining. Expression of SERCA2a and Nitric Oxide Synthases (NOS) proteins were estimated by immunoblotting. Results: CHU significantly increased body mass (P < 0.001) compared with age-matched control rats but was without effect on relative cardiac mass. For incremental increases in left ventricular balloon volume, diastolic pressure was preserved. However, systolic pressure was significantly greater following CHU for balloon volume = 50 μl (P < 0.01) and up to 200 μl (P < 0.05). For higher balloon volumes systolic pressure was not significantly different from control. Developed pressures were correspondingly increased relative to controls for balloon volumes up to 250 μl (P < 0.05).Left ventricular free wall capillary density was significantly decreased in both epicardium (18%; P <0.05) and endocardium (11%; P < 0.05) despite preserved coronary flow. Western blot analysis revealed no change to the expression of SERCA2a or nNOS but immuno-detectable eNOS protein was significantly decreased (P < 0.001) in cardiac tissue following chronic hypoxia in utero. Conclusion: These data offer potential mechanisms for poor recovery following ischaemia, including decreased coronary flow reserve and impaired angiogenesis with subsequent detrimental effects of post-natal cardiac performance

Enhanced Proliferation of Monolayer Cultures of Embryonic Stem (ES) Cell-Derived Cardiomyocytes Following Acute Loss of Retinoblastoma

Background: Cardiomyocyte (CM) cell cycle analysis has been impeded because of a reliance on primary neonatal cultures of poorly proliferating cells or chronic transgenic animal models with innate compensatory mechanisms. Methodology/Principal Findings: We describe an in vitro model consisting of monolayer cultures of highly proliferative embryonic stem (ES) cell-derived CM. Following induction with ascorbate and selection with puromycin, early CM cultures are.98 % pure, and at least 85 % of the cells actively proliferate. During the proliferative stage, cells express high levels of E2F3a, B-Myb and phosphorylated forms of retinoblastoma (Rb), but with continued cultivation, cells stop dividing and mature functionally. This developmental transition is characterized by a switch from slow skeletal to cardiac TnI, an increase in binucleation, cardiac calsequestrin and hypophosphorylated Rb, a decrease in E2F3, B-Myb and atrial natriuretic factor, and the establishment of a more negative resting membrane potential. Although previous publications suggested that Rb was not necessary for cell cycle control in heart, we find following acute knockdown of Rb that this factor actively regulates progression through the G1 checkpoint and that its loss promotes proliferation at the expense of CM maturation. Conclusions/Significance: We have established a unique model system for studying cardiac cell cycle progression, and show in contrast to previous reports that Rb actively regulates both cell cycle progression through the G1 checkpoint an

Angiogenesis gene expression in murine endothelial cells during post-pneumonectomy lung growth

Although blood vessel growth occurs readily in the systemic bronchial circulation, angiogenesis in the pulmonary circulation is rare. Compensatory lung growth after pneumonectomy is an experimental model with presumed alveolar capillary angiogenesis. To investigate the genes participating in murine neoalveolarization, we studied the expression of angiogenesis genes in lung endothelial cells. After left pneumonectomy, the remaining right lung was examined on days 3, 6, 14 and 21days after surgery and compared to both no surgery and sham thoracotomy controls. The lungs were enzymatically digested and CD31+ endothelial cells were isolated using flow cytometry cell sorting. The transcriptional profile of the CD31+ endothelial cells was assessed using quantitative real-time polymerase chain reaction (PCR) arrays. Focusing on 84 angiogenesis-associated genes, we identified 22 genes with greater than 4-fold regulation and significantly enhanced transcription (p <.05) within 21 days of pneumonectomy. Cluster analysis of the 22 genes indicated that changes in gene expression did not occur in a single phase, but in at least four waves of gene expression: a wave demonstrating decreased gene expression more than 3 days after pneumonectomy and 3 sequential waves of increased expression on days 6, 14, and 21 after pneumonectomy. These findings indicate that a network of gene interactions contributes to angiogenesis during compensatory lung growth

Distribution and movement of domestic rainbow trout, Oncorhynchus mykiss, during pulsed flows in the South Fork American River, California

We tracked the movements of ten small (SL = 25.5–31.0 cm) and ten large (SL = 32.0–38.5 cm) radio-tagged domestic rainbow trout (Oncorhynchus mykiss) in response to frequent pulsed releases of water in the South Fork American River (California) from July to October 2005. In week one all the small trout moved less than 1 km upstream or downstream of their release sites. Four small trout moved 1–3 km upstream or downstream of their release sites in the following 8 weeks. Seven out of ten large trout moved downstream after their release. In subsequent weeks most large trout showed smaller upstream and downstream movements, and were observed between 1 km upstream and 8 km downstream of their release sites. Our results suggest that domestic rainbow trout with SL &gt; 25 cm are not forced downstream by daily pulsed flow increases from 5 to over 40 m3s−1