Theses and Dissertations at Montana State University (MSU)
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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 The spawning and rearing habitats of rainbow trout and brown trout in two rivers in Montana(Montana State University - Bozeman, College of Letters & Science, 1981) Sando, Steven KentItem Responses of rainbow (Oncorhynchus mykiss) and brown trout (Salmo trutta) to creation of access into a spawning tributary(Montana State University - Bozeman, College of Letters & Science, 1996) Snelson, Scott IrvenItem Potential impacts of altering discharge pattern from Hauser Dam, Missouri River, on young-of-the-year brown trout and rainbow trout(Montana State University - Bozeman, College of Letters & Science, 1985) Carty, Daniel GregoryDaily flow fluctuations would occur in the Missouri River between Hauser Dam and Holter Reservoir if Hauser Dam were converted to a hydroelectric peaking facility. To address potential impacts of fluctuating flows on free-swimming young-of-the-year (YOY) brown trout (Salmo trutta) and rainbow trout (S. gairdneri) emergence, growth, abundance, distribtion, movement, and habitat use were investigated. During reduced-flow tests stranding, isolation, displacement, and habitat changes were evaluated. Hydraulic modeling was used to predict changes in the quantity of usable habitat at different discharges. Recruitment from a tributary into the river was also monitored. Field data were collected between April 1982 and November 1983. Young-of-the-year brown trout were first observed in early April while YOY rainbow trout were first found in mid-June. Both species used relatively shallow, low-velocity water near shore where cover was abundant. Reduced-flow tests in August of each year revealed little stranding or isolation, and YOY trout were not permanently displaced from temporarily dewatered habitat. Hydraulic modeling predicted an increase in the quantity of habitat as discharge decreased, but field observations indicated a reduction in habitat quality. The tributary was found to be a relatively important source of recruitment to the river rainbow trout fishery but rather unimportant to the river brown trout fishery.Item Effects of gas supersaturated water on juvenile brown and rainbow trout(Montana State University - Bozeman, College of Letters & Science, 1988) Connor, William PaulSix bioassays were conducted at the Bozeman Fish Technology Center using juvenile brown trout (Salmo trutta) and rainbow trout (Salmo gairdneri) to determine the influence of fish size and species to gas supersaturated water. Juveniles of both species were exposed for 30-d to 104 + 1.2% (control), 112 ± 1.0% (medium treatment), and 125 + 0.7% (high treatment) atmospheric gas supersaturated water. No significant mortality occurred in the 112% treatment except during two tests when percent total gas pressure exceeded 113%, indicating that a critical threshold exists above this pressure. As fish grew they became more susceptible to 125% gas supersaturation. Total mortality and mortality rate were less when fish were small. The frequency at which emphysema occurred by body region also varied with fish size and smaller fish died with different external symptoms than larger fish. Larger fish were more likely to die faster than smaller fish and with no external symptoms. Daily mortality of brown trout exposed to 125% gas supersaturation was always significantly greater than for rainbow trout of similar size. Juvenile brown trout that survived exposure to 112% supersaturation showed greater incidence of external symptoms of GBT than juvenile rainbow trout of similar size. Juvenile rainbow and brown trout were exposed to supersaturations from 112% -118% total gas pressure to test for recovery. Recovery varied according to external symptom severity. Fish that did not recover usually had severe exopthalmia. Juvenile brown trout, repeatedly exposed to 118% gas supersaturated water, given 30-d to recover between exposures, developed more severe symptoms with each exposure. Sublethal effects of exposure to gas supersaturated water on growth, predation, and microbial infection were tested using fish exposed to supersaturations from 112 - 118% total gas pressure. Surviving fish developed new symptoms more often than recurring symptoms. Growth of survivors of 30-d exposure to 112% total gas pressure was not different from control fish. There was no difference in vulnerability to predation in circular tanks between juvenile brown and rainbow trout caused by exposure to gas super-saturation. Predation tests conducted in an artificial stream suggested some difference in susceptibility may be present, but data were not conclusive. Bacterial challenges indicated that juvenile brown trout exposed to 118% gas supersaturated water for 5-d were more susceptible to infection by Aeromonas hvdrophila than non-exposed fish.Item Habitat use by adult brown trout and rainbow trout in response to gas supersaturation downstream of the Yellowtail Afterbay Dam, Bighorn River, Montana(Montana State University - Bozeman, College of Letters & Science, 1990) Williams, Thomas HerbertItem Behavior and microhabitat competition of brown trout and greenback cutthroat trout in an artificial stream(Montana State University - Bozeman, College of Letters & Science, 1989) Wang, LizhuItem Some environmental influences on egg production in brown trout (Salmo trutta) from Montana streams(Montana State University - Bozeman, College of Letters & Science, 1974) Lockard, Lawrence L.Item Reproductive biology of brown and rainbow trout below Hauser Dam, Missouri River, with reference to proposed hydroelectric peaking(Montana State University - Bozeman, College of Letters & Science, 1985) Spoon, Ronald L.Item Effects of stream temperature on angling success for rainbow and brown trout(Montana State University - Bozeman, College of Letters & Science, 1989) McMichael, Geoffrey Aaron