Theses and Dissertations at Montana State University (MSU)
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Item Reproductive and juvenile ecology of mountain whitefish in the upper Green River, Wyoming(Montana State University - Bozeman, College of Letters & Science, 2022) Brown, Colter Davis; Chairperson, Graduate Committee: Christopher S. GuyMountain Whitefish Prosopium williamsoni are a salmonid native to the northern Rocky Mountains that has experienced declines in population abundance in rivers throughout Idaho, Colorado, Wyoming, and Montana. Problems with recruitment are suspected, but often the specific mechanisms causing population declines are unknown. Our approach to better understand the mechanisms that influence Mountain Whitefish population dynamics was to compare population characteristics between the Green River, Wyoming and the Madison River, Montana populations. Boyer et al. (2017a) conducted an extensive study on the movement and reproductive ecology of Mountain Whitefish in the Madison River, and we used this study as a template to make direct comparisons between the populations. Our primary research questions were 1) what is the age and length at first maturity, spawning periodicity, fecundity, and age structure of Mountain Whitefish, 2) what is the spatial and temporal distribution of Mountain Whitefish through their spawning period, and what influence do abiotic factors have on spawning and movement, and 3) what is the spatial distribution and habitat use of age-0 Mountain Whitefish? We collected otoliths and gonadal samples from 127 Mountain Whitefish in the Green River, implanted 100 fish with radio transmitters and tracked them from September 1 to early November in 2019 and 2020, determined spawning period and locations using egg mats, kick netting, and angling, and sampled age-0 Mountain Whitefish using a beach seine in slow-water habitats. The geographic separation and difference in hydrogeomorphic conditions between the systems allowed us to form generalizations about Mountain Whitefish in the Intermountain West. We found Mountain Whitefish in both systems mature between ages 2 and 4, primarily spawn annually, have a similar relative fecundity, spawning movements vary, males begin movement prior to females, and age-0 fish drift downstream of spawning locations and use slow-water silt-laden habitats after hatching. The main disparities between systems were that in the Green River water temperature was more suitable for embryo development, and age structure was more uniform and older. This research enhanced our understanding of Mountain Whitefish reproductive and juvenile ecology and provided evidence for factors that may influence recruitment of Mountain Whitefish.Item Spatial and temporal variability in movements and vital rates of sympatric salmonids in an unfragmented, inland watershed(Montana State University - Bozeman, College of Letters & Science, 2019) Lance, Michael James; Chairperson, Graduate Committee: Alexander V. ZaleThe life history patterns and vital rates of stream dwelling fish can differ across biological, spatial, and temporal scales. We determined the movement patterns and vital rates of three abundant salmonids--brown trout (Salmo trutta), mountain whitefish (Prosopium williamsoni), and rainbow trout (Oncorhynchus mykiss)--in the Smith River watershed of Montana, a system with three distinct geomorphic regions: the headwaters, semi-wilderness canyon, and prairie. We marked 7,172 fish with passive integrated transponder (PIT) tags, monitored their watershed-scale movements past 15 stationary PIT arrays over four years, and relocated fish between arrays by conducting mobile surveys along the Smith River and major tributaries. Fish movement patterns and survival probabilities varied seasonally, among species, and among locations within the watershed. Volume of movement and diversity of movers were both greatest in the canyon region and in lower portions of tributaries. Fish rarely left the canyon, but movement into the canyon from other regions was common among some groups of fish. Mountain whitefish were most likely to move and brown trout were least likely to move. The stream lengths traversed by fish followed a leptokurtic distribution with most fish travelling < 10 km and decreasing numbers of fish travelling farther. Distinct life history patterns were not evident as judged by the stream lengths traversed by tagged fish; rather, a continuous spectrum of distances traversed was apparent. Species-specific spawning periods were associated with increased frequency of movement by mountain whitefish and rainbow trout. Increases in the frequency of watershed-scale movements of all three species were associated mean daily water temperatures of 11.7-15.3°C, compared to periods when water temperatures were cooler or warmer. Annual probabilities of survival were highest among mountain whitefish (0.38-0.54) and lower among brown trout (0.16-0.38) and rainbow trout (0.08-0.39). Survival of rainbow trout and mountain whitefish was highest in the canyon. Survival of mountain whitefish was also high in the headwaters but was lowest in the prairie. Movements of fish in the Smith River watershed were diverse, allowed movement among habitats with different probabilities of survival, and probably contributed to meta-population function, population resiliency, and species diversity.Item A hematological study on the mountain whitefish, Prosopium williamsoni(Montana State University - Bozeman, College of Agriculture, 1962) Hubbard, Ida M.Item Studies on the behavior and life history of the mountain whitefish (Prosopium williamsoni Girard)(Montana State University - Bozeman, College of Agriculture, 1970) Liebelt, James Edward