Geology topics

Vincent S. D'Angelo

Publications and source records attributed to Vincent S. D'Angelo.

4 recordsLinked to original sources

USGS2017

Suppression of invasive lake trout in an isolated backcountry lake in Glacier National Park

Fisheries managers have implemented suppression programmes to control non-native lake trout, Salvelinus namaycush (Walbaum), in several lakes throughout the western United States. This study determined the feasibility of experimentally suppressing lake trout using gillnets in an isolated backcountry lake in Glacier National Park, Montana, USA, for the conservation of threatened bull trout, Salvelinus confluentus (Suckley). The demographics of the lake trout population during suppression (2009–2013) were described, and those data were used to assess the effects of suppression scenarios on population growth rate ( λ ) using an age-structured population model. Model simulations indicated that the population was growing exponentially ( λ = 1.23, 95% CI: 1.16–1.28) prior to suppression. However, suppression resulted in declining λ (0.61–0.79) for lake trout, which was concomitant with stable bull trout adult abundances. Continued suppression at or above observed exploitation levels is needed to ensure continued population declines.

Fisheries Management and Ecology↗

USGS2016

Genetic status and conservation of Westslope Cutthroat Trout in Glacier National Park

Invasive hybridization is one of the greatest threats to the persistence of Westslope Cutthroat Trout Oncorhynchus clarkii lewisi . Large protected areas, where nonhybridized populations are interconnected and express historical life history and genetic diversity, provide some of the last ecological and evolutionary strongholds for conserving this species. Here, we describe the genetic status and distribution of Westslope Cutthroat Trout throughout Glacier National Park, Montana. Admixture between Westslope Cutthroat Trout and introduced Rainbow Trout O. mykiss and Yellowstone Cutthroat Trout O. clarkii bouvieri was estimated by genotyping 1,622 fish collected at 115 sites distributed throughout the Columbia, Missouri, and South Saskatchewan River drainages. Currently, Westslope Cutthroat Trout occupy an estimated 1,465 km of stream habitat and 45 lakes (9,218 ha) in Glacier National Park. There was no evidence of introgression in samples from 32 sites along 587 km of stream length (40% of the stream kilometers currently occupied) and 17 lakes (2,555 ha; 46% of the lake area currently occupied). However, nearly all (97%) of the streams and lakes that were occupied by nonhybridized populations occurred in the Columbia River basin. Based on genetic status (nonnative genetic admixture ≤ 10%), 36 Westslope Cutthroat Trout populations occupying 821 km of stream and 5,482 ha of lakes were identified as “conservation populations.” Most of the conservation populations ( N = 27; 736 km of stream habitat) occurred in the Columbia River basin, whereas only a few geographically restricted populations were found in the South Saskatchewan River ( N = 7; 55 km) and Missouri River ( N = 2; 30 km) basins. Westslope Cutthroat Trout appear to be at imminent risk of genomic extinction in the South Saskatchewan and Missouri River basins, whereas populations in the Columbia River basin are widely distributed and conservation efforts are actively addressing threats from hybridization and other stressors. A diverse set of pro-active management approaches will be required to conserve, protect, and restore Westslope Cutthroat Trout populations in Glacier National Park throughout the 21st century.

Glacier National Park↗

USGS2013

Factors influencing the distribution of native bull trout and westslope cutthroat trout in western Glacier National Park, Montana

The widespread declines of native bull trout ( Salvelinus confluentus ) and westslope cutthroat trout ( Oncorhynchus clarkii lewisi ) populations prompted researchers to investigate factors influencing their distribution and status in western Glacier National Park, Montana. We evaluated the association of a suite of abiotic factors (stream width, elevation, gradient, large woody debris density, pool density, August mean stream temperature, reach surface area) with the occurrence (presence or absence) of bull trout and westslope cutthroat trout in 79 stream reaches in five sub-drainages containing glacial lakes. We modeled the occurrence of each species using logistic regression and evaluated competing models using an information theoretic approach. Westslope cutthroat trout were widely distributed (47 of 79 reaches), and there appeared to be no restrictions on their distribution other than physical barriers. Westslope cutthroat trout were most commonly found in relatively warm reaches downstream of lakes and in headwater reaches with large amounts of large woody debris and abundant pools. By contrast, bull trout were infrequently detected (10 of 79 reaches), with 7 of the 10 (70%) detections in sub-drainages that have not been compromised by non-native lake trout ( S. namaycush ). Bull trout were most often found in cold, low-gradient reaches upstream of glacial lakes. Our results indicate that complex stream habitats in sub-drainages free of non-native species are important to the persistence of native salmonids in western Glacier National Park. Results from this study may help managers monitor and protect important habitats and populations, inform conservation and recovery programs, and guide non-native species suppression efforts in Glacier National Park and elsewhere.

Montana↗

USGS2012

A fine-scale assessment of using barriers to conserve native stream salmonids: a case study in Akokala Creek, Glacier National Park, USA

Biologists are often faced with the difficult decision in managing native salmonids of where and when to install barriers as a conservation action to prevent upstream invasion of nonnative fishes. However, fine-scale approaches to assess long-term persistence of populations within streams and watersheds chosen for isolation management are often lacking. We employed a spatially-explicit approach to evaluate stream habitat conditions, relative abundance, and genetic diversity of native westslope cutthroat trout (Oncorhynchus clarkii lewisi) within the Akokala Creek watershed in Glacier National Park- a population threatened by introgressive hybridization with nonnative rainbow trout (O. mykiss) from nearby sources. The systematic survey of 24 stream reaches showed broad overlap in fish population and suitable habitat characteristics among reaches and no natural barriers to fish migration were found. Analysis of population structure using 16 microsatellite loci showed modest amounts of genetic diversity among reaches, and that fish from Long Bow Creek were the only moderately distinct genetic group. We then used this information to assess the potential impacts of three barrier placement scenarios on long-term population persistence and genetic diversity. The two barrier placement scenarios in headwater areas generally failed to meet general persistence criteria for minimum population size (2,500 individuals, Ne = 500), maintenance of long-term genetic diversity (He), and no population subdivision. Conversely, placing a barrier near the stream mouth and selectively passing non-hybridized, migratory spawners entering Akokala Creek met all persistence criteria and may offer the best option to conserve native trout populations and life history diversity. Systematic, fine-scale stream habitat, fish distribution, and genetic assessments in streams chosen for barrier installation are needed in conjunction with broader scale assessments to understand the potential impacts of using barriers for conservation of native salmonid populations threatened by nonnative fish invasions.

Open Fish Science Journal↗