Geology topics

Michael H. Meeuwig

Publications and source records attributed to Michael H. Meeuwig.

6 recordsLinked to original sources

USGS2023

A comprehensive multi-state conditional occupancy model for evaluating interactions of non-native and native species

A major challenge in ecology is disentangling interactions of non-native, potentially invasive species on native species. Conditional two-species occupancy models examine the effects of dominant species (e.g., non-native) on subordinate species (e.g., native) while considering the possibility that occupancy of one species may affect occupancy and/ or detection of the other. Although conditional two-species models are useful for evaluating the influence of one species on presence of another, it is possible that species interactions are density dependent. Therefore, we developed a novel two-species occupancy model that incorporates multiple abundance states (i.e., absent, present, abundant) of the native species. We showcase the utility of this model with a case study that incorporates random effects and covariates on both occupancy and detection to help disentangle species interactions given varying occupancy and detection in different abundance states. We use snorkel survey data from the Umpqua basin, Oregon, where it is hypothesized that smallmouth bass Micropterus dolomieu , a non-native piscivore, exclude Umpqua chub Oregonichthys kalawatseti , a small endemic minnow. From our two-species multi-state (2SMS) model, we concluded that average occupancy was low for both fishes, and that when non-native bass were present, overall native chub occupancy in the present (0.18 ± 0.05 SD) and abundant (0.19 ± 0.03) states was higher than when non-natives were absent (0.14 ± 0.02/ 0.08 ± 0.02), indicating the non-native was not excluding the native species. By incorporating a species interaction factor, we found a positive association (6.75 ± 5.54 SD) between native chub and non-native bass. The covariates strongly related to occupancy were elevation, algae, and land cover type (urban and shrub). Detection probability for both species (0.21–0.82) was most strongly related to the covariates day of year, water temperature, gravel substrate, and stream order/ magnitude. Incorporation of detection probability and covariates enabled interpretation of interactions between the two species that may have been missed without their inclusion in the modeling process. Our new 2SMS occupancy model can be used by scientists and managers with a broad range of survey and covariate data to disentangle species interactions problems to help them inform management decisions.

Frontiers in Ecology and Evolution↗

USGS2022

Engaging stakeholders to develop a decision support model of conservation risk and management capacity to prioritize investments in Bull Trout recovery

Rarely are sufficient resources available to support the full suite of management actions to promote recovery of a species across their entire distribution. Decision support models are a tool that can inform natural resource management decisions with consideration of the perspectives from a variety of stakeholders who work across large geographic and jurisdictional extents. We offer an example of a decision support model that was developed by several Federal and State natural resource agencies to rank Bull Trout Salvelinus confluentus core areas for prioritizing conservation investment within Oregon, USA. We engaged State level decision makers to identify parameters believed to be influential in determining funding allocations for Bull Trout core areas. Parameters were linked in a model framework that was further refined with input from local Bull Trout experts with knowledge specific to the various core areas. The model produces a relative priority value that is a combination of the conservation risk to the species and the management capacity to address threats. A series of sensitivity analyses suggests that Bull Trout persistence and threat score are most influential in determining the relative priority of a core area, and life-history and genetic diversity are least influential. One of the more powerful products from this work is an interactive web-based application ( https://das.ecosphere.fws.gov/public/obts/ ) that anyone can use to explore how their beliefs in parameter values will affect the relative priority of Bull Trout core areas across Oregon. Our modeling effort is an example of engaging stakeholders with different roles in species recovery and across a large geographic area to create a clearer path forward in allocating limited resources for species recovery. This approach can be employed to address a number of natural resource management situations across species and habitats.

Oregon↗

USGS2017

A comparison of two mobile electrode arrays for increasing mortality of Lake Trout embryos

Conservation of sport fisheries and populations of several native fishes in the western United States is dependent on sustained success of removal programs targeting invasive Lake Trout Salvelinus namaycush . Gill-netting of spawning adults is one strategy used to decrease spawning success; however, additional complementary methods are needed to disrupt Lake Trout reproduction where bycatch in gill nets is unacceptable. We developed and tested two portable electrode arrays designed to increase Lake Trout embryo mortality in known spawning areas. Both arrays were powered by existing commercial electrofishing equipment. However, one array was moved across the substrate to simulate being towed behind a boat (i.e., towed array), while the other array was lowered from a boat and energized when sedentary (i.e., sedentary array). The arrays were tested on embryos placed within substrates of known spawning areas. Both arrays increased mortality of embryos (>90%) at the surface of substrates, but only the sedentary array was able to increase mortality to >90% at deeper burial depths. In contrast, embryos at increasingly deeper depths exhibited progressively lower mortality when exposed to the towed array. Mortality of embryos placed under 20 cm of substrate and exposed to the towed array was not significantly different from that of unexposed embryos in a control group. We suggest that the sedentary array could be used as a viable approach for increasing mortality of Lake Trout embryos buried to 20 cm and that it could be modified to be effective at deeper depths.

North American Journal of Fisheries Management↗

USGS2015

Spawning and rearing behavior of bull trout in a headwater lake ecosystem

Numerous life histories have been documented for bull trout Salvelinus confluentus . Lacustrine-adfluvial bull trout populations that occupy small, headwater lake ecosystems and migrate short distances to natal tributaries to spawn are likely common; however, much of the research on potamodromous bull trout has focused on describing the spawning and rearing characteristics of bull trout populations that occupy large rivers and lakes and make long distance spawning migrations to natal headwater streams. This study describes the spawning and rearing characteristics of lacustrine-adfluvial bull trout in the Quartz Lake drainage, Glacier National Park, USA, a small headwater lake ecosystem. Many spawning and rearing characteristics of bull trout in the Quartz Lake drainage are similar to potamodromous bull trout that migrate long distances. For example, subadult bull trout distribution was positively associated with slow-water habitat unit types and maximum wetted width, and negatively associated with increased stream gradient. Bull trout spawning also occurred when water temperatures were between 5 and 9 °C, and redds were generally located in stream segments with low stream gradient and abundant gravel and cobble substrates. However, this study also elucidated characteristics of bull trout biology that are not well documented in the literature, but may be relatively widespread and have important implications regarding general characteristics of bull trout ecology, use of available habitat by bull trout, and persistence of lacustrine-adfluvial bull trout in small headwater lake ecosystems.

Montana↗

USGS2011

Trophic relationships between a native and a nonnative predator in a system of natural lakes

Bull trout, a species of char listed as threatened under the US Endangered Species Act, have been displaced from portions of their historic range following the introduction of nonnative lake trout. It has been suggested that competitive exclusion as a result of trophic overlap between bull trout and lake trout may be the causal mechanism associated with displacement of bull trout. This study used stable isotope data to evaluate trophic relationships among native bull trout, nonnative lake trout and other fishes in seven lakes in Glacier National Park (GNP), Montana. Bull trout and lake trout had greater δ 15 N values relative to other fishes among lakes (δ 15 N ≥ 3.0‰). Lake trout had greater δ 15 N values relative to bull trout (δ 15 N = +1.0‰). Bull trout had greater δ 13 C values relative to lake trout in six of the seven lakes examined. Although both bull trout and lake trout had greater δ 15 N values relative to other fishes within lakes in GNP, differences in δ 15 N and δ 13 C between bull trout and lake trout suggest that they are consuming different prey species or similar prey species in different proportions. Therefore, displacement of bull trout as a direct result of complete overlap in food resource use is not anticipated unless diet shifts occur or food resources become limiting. Additionally, future studies should evaluate food habits to identify important prey species and sources of partial dietary overlap between bull trout and lake trout.

Montana↗

USGS2010

Use of cover habitat by bull trout, Salvelinus confluentus, and lake trout, Salvelinus namaycush, in a laboratory environment

Lacustrine-adfluvial bull trout, Salvelinus confluentus , migrate from spawning and rearing streams to lacustrine environments as early as age 0. Within lacustrine environments, cover habitat provides refuge from potential predators and is a resource that is competed for if limiting. Competitive interactions between bull trout and other species could result in bull trout being displaced from cover habitat, and bull trout may lack evolutionary adaptations to compete with introduced species, such as lake trout, Salvelinus namaycush . A laboratory experiment was performed to examine habitat use and interactions for cover by juvenile (i.e., <80 mm total length) bull trout and lake trout. Differences were observed between bull trout and lake trout in the proportion of time using cover ( F 1,22.6 = 20.08, P < 0.001) and bottom ( F 1,23.7 = 37.01, P < 0.001) habitat, with bull trout using cover and bottom habitats more than lake trout. Habitat selection ratios indicated that bull trout avoided water column habitat in the presence of lake trout and that lake trout avoided bottom habitat. Intraspecific and interspecific agonistic interactions were infrequent, but approximately 10 times greater for intraspecific interactions between lake trout. Results from this study provide little evidence that juvenile bull trout and lake trout compete for cover, and that species-specific differences in habitat use and selection likely result in habitat partitioning between these species.

Environmental Biology of Fishes↗