Theses and Dissertations at Montana State University (MSU)
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Item Entrainment losses of westslope cutthroat trout into screened and unscreened irrigation canals on Skalkaho Creek, Montana(Montana State University - Bozeman, College of Letters & Science, 2005) Gale, Steven Burton; Chairperson, Graduate Committee: Alexander V. ZaleIrrigation canals are known to entrain anadromous and potamodromous salmonids of all life stages during their annual migrations. Fish screens may reduce or eliminate entrainment, but few studies exist on their benefits and these have evaluated effects on anadromous populations only. Prior to my study, none existed on the benefits of fish screens for non-anadromous salmonids. Large numbers of post-spawn adult and downstream migrant juvenile westslope cutthroat trout (Oncorhynchus clarkii lewisi) are potentially entrained into the seven irrigation canals on Skalkaho Creek, a tributary of the Bitterroot River. I quantified entrainment rates into the canals using telemetry and trapping before (2003) and after (2004) installation of three fish screens. I also examined the efficacy of the screens in returning downstream migrants to the stream. No telemetered adults were entrained in 2003, but most were residents and therefore did not migrate past the canals. In 2004, 79% of the telemetered adult migratory fish were entrained at either screened or unscreened canals, but all adults entrained in screened canals were successfully bypassed back to Skalkaho Creek. Only eight of 117 telemetered age-1 juveniles were entrained, whereas the others were residents and did not migrate. Only one of three age-1 juveniles entrained in 2004 was bypassed. The low number of migratory adult fish and age-1 juveniles I was able to telemeter suggests that the non-migratory, resident life history is now being selected for in this system, but screens should reverse this process. Downstream movement of age-0 westslope cutthroat trout in Skalkaho Creek increased their risk of entrainment. The Highline Canal entrained about 71% of age-0 westslope cutthroat trout moving downstream in 2003. If not for the screen to bypass them in 2004, 38% would have been entrained in the Highline Canal. A total of 6,049 age-0 westslope cutthroat trout were bypassed by all three screens. Most age-0 westslope cutthroat trout entrained at screened canals were successfully bypassed, whereas those entrained at unscreened canals were lost to the population. Fish screens were an effective management tool to reduce or eliminate entrainment at Skalkaho Creek and may be useful elsewhere to eliminate entrainment of inland salmonids.Item An assessment of losses of native fish to irrigation diversions on selected tributaries of the Bitterroot River, Montana(Montana State University - Bozeman, College of Letters & Science, 2007) Bahn, Leslie; Chairperson, Graduate Committee: Alexander V. ZaleWithdrawals of surface water for irrigation and stock water leave the Bitterroot River and its tributaries chronically dewatered during the irrigation season. These water withdrawals affect local trout populations by entraining migratory trout into irrigation diversion canals at multiple life stages, and through the loss and degradation of available habitat for aquatic species. Irrigation losses may be responsible in part for the low abundances and restricted distributions of migratory native westslope cutthroat trout Onchorhyncus clarkii lewisi and bull trout Salvelinus confluentus in this system. My objectives were to quantify entrainment of fish into irrigation diversions on Lost Horse and Tin Cup Creeks, two tributaries of the Bitterroot River used by migratory adult westslope cutthroat trout for spawning, and to identify characteristics of these diversions that correlate with entrainment. I sampled fish species by snorkeling, electrofishing, fry trapping, and reconnaissance at 60 sites in 2005 and 54 sites in 2006. Annual entrainment estimates for age-0 salmonids were 18,061 and 8,972 in 2005 and 2006 in Lost Horse Creek diversions. Concurrent entrainment estimates for Tin Cup Creek were 2,995 and 2,312. Annual entrainment estimates for juvenile and adult trout (>40 mm TL) were 7,947 and 7,877 in 2005 and 2006 in Lost Horse Creek diversions.Item Fish screen efficiency and effects of screened and unscreened irrigation canals on the downstream movement of westslope cutthroat trout juveniles in Skalkaho Creek, Montana(Montana State University - Bozeman, College of Letters & Science, 2007) Harnish, Ryan Alexander; Chairperson, Graduate Committee: Alexander V. ZaleFish screens were installed in three of seven irrigation canals that divert water from Skalkaho Creek, a tributary of the Bitterroot River, in 2003 to prevent the loss of fluvial-adfluvial westslope cutthroat trout to irrigation canal entrainment. A study conducted in 2003 and 2004 established that fish screens were effective at reducing the loss of adult and age-0 westslope cutthroat trout. The efficiency of fish screens at preventing the loss of age 1-4 juveniles, the effect of screening on age-0 westslope cutthroat trout downstream movements, and the magnitude of entrainment at unscreened canals remained unclear after this initial study. The goal of my study was to address these information gaps. Fish screens prevented the loss of about 82% of entrained juvenile westslope cutthroat trout and bull trout. About 69% of entrained juveniles exited the screened canals through the headgates, 14% were bypassed, 12% remained in the canals, and the fate of 5% remained unknown. Entrained fish took about 7 days to exit the screened canals. Fish screen efficiency, the route used by fish to exit, and the amount of time taken by fish to exit varied by canal.