Geology topics

Christine E. Verhille

Publications and source records attributed to Christine E. Verhille.

4 recordsLinked to original sources

USGS2025

Native Yellowstone cutthroat trout Oncorhynchus virginalis bouvieri growth and survival in a headwater stream primarily driven by warming stream temperatures, with non-native brown trout Salmo trutta posing an additional threat to survival

Warming rivers and interactions with non-native species impact salmonid species globally. Understanding how hydroclimatic conditions synergistically and independently interact with non-native species is critical for effectively managing salmonids into the future. We used a 10-year mark–recapture dataset to assess how native Yellowstone cutthroat trout (YCT) Oncorhynchus virginalis bouvieri and non-native brown trout Salmo trutta growth rates and apparent survival were affected by hydroclimatic conditions and (for YCT) the presence of brown trout in a tributary. Growth (YCT) and survival (both species across size classes) were negatively related to warming stream temperatures. Brown trout growth was positively related to increasing daily streamflow variability (a proxy for streamflow), but this variable was not included in the top YCT growth model. Density-dependent effects appeared to be non-existent (growth) or weakly positive (survival). When sympatric with brown trout, YCT displayed worse survival than allopatric YCT across environmental conditions. Broadly, we found native and non-native trout respond to different hydroclimatic conditions that shift with changing climatic conditions, and brown trout represent an additional threat to YCT survival.

Montana↗

USGS2022

The importance of phenology and thermal exposure to early life history success of nonnative Smallmouth Bass in the Yellowstone River

Knowledge of potential spread by introduced species is critical to effective management and conservation. The Smallmouth Bass Micropterus dolomieu is an example of a fish that has been introduced globally, often spreads after introduction, and has substantial predatory impacts on fish assemblages. Nonnative Smallmouth Bass in the free-flowing Yellowstone River, Montana, have expanded from warmer, downstream sections of river into colder, upstream sections containing socio-economically valuable trout fisheries. We sought insight into mechanisms controlling upstream spread by evaluating whether progressively colder upstream climates physiologically constrained successful recruitment by limiting age-0 growth and preventing overwinter survival (i.e., population establishment). We documented the phenology, growth, and overwinter survival of age-0 Smallmouth Bass across a temperature gradient leading to their upstream extent in the Yellowstone River. The upstream extent of population establishment did not appear limited by water temperature alone. Age-0 body size at the onset of winter did not differ significantly between colder, upstream reaches and warmer, downstream reaches. Instead, the earlier hatch timing exhibited by some age-0 individuals in upstream sections allowed them to experience longer growing seasons than many individuals in downstream sections. This counter-intuitive hatching phenology mediated much of the expected decreases in growth in colder, upstream climates. Furthermore, evidence of successful overwinter survival and simulations of age-0 starvation mortality indicated that age-0 individuals at the upstream extent of their distribution successfully recruited to the age-1 year-class during four consecutive years. However, age-0 individuals were rare or absent throughout the uppermost upstream distribution of adults, suggesting that something other than temperature limits or discourages reproduction farther upstream. Taken together, our results suggest that Smallmouth Bass have not yet reached the thermal limit of their upstream distribution in the Yellowstone River and that future spread may challenge fisheries managers tasked with management of coldwater trout fisheries in this river.

Montana, Wyoming↗

USGS2020

Inter-population differences in salinity tolerance of adult wild Sacramento splittail: osmoregulatory and metabolic responses to salinity

The Sacramento splittail ( Pogonichthys macrolepidotus ) is composed of two genetically distinct populations endemic to the San Francisco Estuary (SFE). The allopatric upstream spawning habitat of the Central Valley (CV) population connects with the sympatric rearing grounds via relatively low salinity waters, whereas the San Pablo (SP) population must pass through the relatively high-salinity Upper SFE to reach its allopatric downstream spawning habitat. We hypothesize that if migration through SFE salinities to SP spawning grounds is more challenging for adult CV than SP splittail, then salinity tolerance, osmoregulatory capacity, and metabolic responses to salinity will differ between populations. Osmoregulatory disturbances, assessed by measuring plasma osmolality and ions, muscle moisture and Na + -K + -ATPase activity after 168 to 336 h at 11‰ salinity, showed evidence for a more robust osmoregulatory capacity in adult SP relative to CV splittail. While both resting and maximum metabolic rates were elevated in SP splittail in response to increased salinity, CV splittail metabolic rates were unaffected by salinity. Further, the calculated difference between resting and maximum metabolic values, aerobic scope, did not differ significantly between populations. Therefore, improved osmoregulation came at a metabolic cost for SP splittail but was not associated with negative impacts on scope for aerobic metabolism. These results suggest that SP splittail may be physiologically adjusted to allow for migration through higher-salinity waters. The trends in interpopulation variation in osmoregulatory and metabolic responses to salinity exposures support our hypothesis of greater salinity-related challenges to adult CV than SP splittail migration and are consistent with our previous findings for juvenile splittail populations, further supporting our recommendation of population-specific management.

California↗

USGS2016

Inter-population differences in salinity tolerance and osmoregulation of juvenile wild and hatchery-born Sacramento splittail

The Sacramento splittail ( Pogonichthys macrolepidotus ) is a minnow endemic to the highly modified San Francisco Estuary of California, USA and its associated rivers and tributaries. This species is composed of two genetically distinct populations, which, according to field observations and otolith strontium signatures, show largely allopatric distribution patterns as recently hatched juveniles. Juvenile Central Valley splittail are found primarily in the nearly fresh waters of the Sacramento and San Joaquin rivers and their tributaries, whereas San Pablo juveniles are found in the typically higher-salinity waters (i.e. up to 10‰) of the Napa and Petaluma Rivers. As the large salinity differences between young-of-year habitats may indicate population-specific differences in salinity tolerance, we hypothesized that juvenile San Pablo and Central Valley splittail populations differ in their response to salinity. In hatchery-born and wild-caught juvenile San Pablo splittail, we found upper salinity tolerances, where mortalities occurred within 336 h of exposure to 16‰ or higher, which was higher than the upper salinity tolerance of 14‰ for wild-caught juvenile Central Valley splittail. This, in conjunction with slower recovery of plasma osmolality, but not ion levels, muscle moisture or gill Na + ,K + -ATPase activity, in Central Valley relative to San Pablo splittail during osmoregulatory disturbance provides some support for our hypothesis of inter-population variation in salinity tolerance and osmoregulation. The modestly improved salinity tolerance of San Pablo splittail is consistent with its use of higher-salinity habitats. Although confirmation of the putative adaptive difference through further studies is recommended, this may highlight the need for population-specific management considerations.

California↗