Geology topics

Ron Pierce

Publications and source records attributed to Ron Pierce.

4 recordsLinked to original sources

USGS2016

Conservation of native Pacific trout diversity in western North America

Pacific trout Oncorhynchus spp. in western North America are strongly valued in ecological, socioeconomic, and cultural views, and have been the subject of substantial research and conservation efforts. Despite this, the understanding of their evolutionary histories, overall diversity, and challenges to their conservation is incomplete. We review the state of knowledge on these important issues, focusing on Pacific trout in the genus Oncorhynchus. Although most research on salmonid fishes emphasizes Pacific salmon, we focus on Pacific trout because they share a common evolutionary history, and many taxa in western North America have not been formally described, particularly in the southern extent of their ranges. Research in recent decades has led to the revision of many hypotheses concerning the origin and diversification of Pacific trout throughout their range. Although there has been significant success at addressing past threats to Pacific trout, contemporary and future threats represented by nonnative species, land and water use activities, and climate change pose challenges and uncertainties. Ultimately, conservation of Pacific trout depends on how well these issues are understood and addressed, and on solutions that allow these species to coexist with a growing scope of human influences.

Fisheries↗

USGS2016

Are brown trout replacing or displacing bull trout populations in a changing climate?

Understanding how climate change may facilitate species turnover is an important step in identifying potential conservation strategies. We used data from 33 sites in western Montana to quantify climate associations with native bull trout (Salvelinus confluentus) and non-native brown trout (Salmo trutta) abundance and population growth rates (λ). We estimated λ using exponential growth state space models and delineated study sites based on bull trout use for either Spawning and Rearing (SR) or Foraging, Migrating, and Overwintering (FMO) habitat. Bull trout abundance was negatively associated with mean August stream temperatures within SR habitat (r = -0.75). Brown trout abundance was generally highest at temperatures between 12 and 14°C. We found bull trout λ were generally stable at sites with mean August temperature below 10°C but significantly decreasing, rare, or extirpated at 58% of the sites with temperatures exceeding 10°C. Brown trout λ were highest in SR and sites with temperatures exceeding 12°C. Declining bull trout λs at sites where brown trout were absent suggests brown trout are likely replacing bull trout in a warming climate.

Idaho, Montana↗

USGS2015

Long term changes in trout numbers following channel reconstruction, instream wood placement, and livestock removal from a spring creek in the Blackfoot Basin, Montana

To restore habitat for wild trout, Kleinschmidt Creek, a low-gradient, groundwater-dominated stream in the Blackfoot Basin, Montana, was reconstructed using natural channel design principles. Reconstruction increased stream sinuosity from a ratio of 1.1 to 1.6, decreased mean channel width from 14.5 to 2.8 m, and increased sediment transport capacity to reduce accumulations of fine instream sediment. To further improve trout habitat, coarse woody debris (CWD) was variably placed within the new channel and livestock were excluded to promote the vegetative recovery of the riparian area. To evaluate the response of wild trout (92% Brown Trout Salmo trutta ) to channel restoration, the abundance (number of trout per linear meter) and biomass (g/linear m) of age 1+ trout were monitored for 15 years (1998–2012) in a reach with low density CWD (1.3 stems/100 m) and compared with regional (reference) trends. Posttreatment (2002–2012) trout numbers in the low-density CWD reach were also compared with those in a reach with high-density CWD (18.2 stems/100 m). Long-term trends for the reference reaches showed a significant negative trend in trout abundance and no significant trend for biomass. Long-term trends for the low-density CWD reach showed a significant positive trend in abundance, as well as a significant trend in biomass. Trout abundance and biomass increased over the posttreatment period in the low-density CWD reach. However, in the high density CWD reach, while posttreatment abundance increased significantly, there was no significant trend in biomass. These results demonstrated that channel restoration increased wild trout populations in a deep, narrow, vegetated stream and that instream wood provided primarily short-term benefits during the early phase of habitat recovery.

Montana↗

USGS2014

Instream habitat restoration and stream temperature reduction in a whirling disease-positive Spring Creek in the Blackfoot River Basin, Montana

Anthropogenic warming of stream temperature and the presence of exotic diseases such as whirling disease are both contemporary threats to coldwater salmonids across western North America. We examined stream temperature reduction over a 15-year prerestoration and postrestoration period and the severity of Myxobolus cerebralis infection (agent of whirling disease) over a 7-year prerestoration and postrestoration period in Kleinschmidt Creek, a fully reconstructed spring creek in the Blackfoot River basin of western Montana. Stream restoration increased channel length by 36% and reduced the wetted surface area by 69% by narrowing and renaturalizing the channel. Following channel restoration, average maximum daily summer stream temperatures decreased from 15.7°C to 12.5°C, average daily temperature decreased from 11.2°C to 10.0°C, and the range of daily temperatures narrowed by 3.3°C. Despite large changes in channel morphology and reductions in summer stream temperature, the prevalence and severity of M. cerebralis infection for hatchery Rainbow Trout Oncorhynchus mykiss remained high (98–100% test fish with grade > 3 infection) versus minimal for hatchery Brown Trout Salmo trutta (2% of test fish with grade-1 infection). This study shows channel renaturalization can reduce summer stream temperatures in small low-elevation, groundwater-dominated streams in the Blackfoot basin to levels more suitable to native trout. However, because of continuous high infections associated with groundwater-dominated systems , the restoration of Kleinschmidt Creek favors brown trout Salmo trutta given their innate resistance to the parasite and the higher relative susceptibility of other salmonids.

Montana↗