This thesis focuses on fisheries managers’ efforts to restore native cutthroats to northern Nevada’s Pyramid Lake for recreation, and the Paiutes’ battle to preserve them as a means of livelihood. Their efforts to reconstruct the fishery revealed the implausibility of environmental restoration, but more importantly underlined the motivations necessary to attempt it. Chapter 2 describes how the Pyramid Lake Lahontan cutthroat— historically an important subsistence resource for Northern Paiutes— were initially exploited for profit in the late 1800s and early 1900s, and gradually destroyed as agricultural interests diverted the Truckee River’s water and industrial pollution contaminated the trout’s aquatic habitat. Fisheries managers in Nevada turned to artificial propagation to meet the demands of fishermen and replace the native fish industrialization destroyed. The Nevada Fish and Game Commission experimented with non-native introductions and like most of the West became proponents of rainbow trout and their recreational potential. Chapter 3 narrates a history of the Nevada Fish and Game Commission’s project to restore trout to Pyramid Lake in the 1950s and 1960s after its native cutthroat became extinct in the early 1940s. For the Commission, restoring Pyramid Lake meant establishing trout and salmon populations— native or not— to feed the growing outdoor tourism industry. While the Commission made plans to restore natural spawning runs, these were unsuccessful, and the Commission relied on stocking the lake to maintain the fishery. However, these experiments failed and eventually cutthroats from other lakes in Nevada proved better occupants of the lake. Chapter 4 describes the native cutthroat’s role in the water debate carried out in government agencies and in the courts in the 1970s and 1980s to decide whether or not water diverted from the Truckee for agriculture should be returned to the Paiutes to support their shrinking lake and dwindling fishery. Environmentalist groups like the Sierra Club joined the Paiutes in their effort to gain water that would allow for the native fishery’s restoration. Their vision clashed with that of agriculturists who feared losing water they depended on for their crops. However, after a lengthy struggle, the Paiutes won an important victory toward preserving their lake.

Through a myriad of practices, anthropogenic land and water use has caused the localized extirpation or complete elimination of many native fishes throughout North America. Specifically, native salmonids have seen substantial declines in population sizes and geographic distributions due to a number of factors, including habitat loss or degradation, overharvest, or the introduction of non-native competitors and predators. Among those affected, the 14 subspecies of cutthroat trout found across western North America have been subject to two extinctions and five listings as Threatened as per the Endangered Species Act. Lahontan cutthroat trout Oncorhynchus clarkii henshawi have experienced marked reductions throughout their native range in the western Great Basin, U.S. In Pyramid Lake, Nevada, where they were once locally extirpated due to overfishing, water loss, and degraded spawning habitat, Lahontan cutthroat trout have been successfully stocked and managed, though they do not routinely reach their pre-extirpation sizes. With little research to determine the factors influencing Lahontan cutthroat trout in Pyramid Lake, I used a suite of modeling tools and empirical data to elucidate the influence of the current surrounding environment on Lahontan cutthroat trout in Pyramid Lake. To identify important food web interactions that may affect the availability of food to Lahontan cutthroat trout, I used diet composition and stable isotope analyses of carbon and nitrogen to understand dietary trends. Large Lahontan cutthroat trout (>400 mm TL), along with non-native Sacramento perch Ambloplites interruptus, relied most heavily on fish prey, yet neither species showed signs of cannibalism or preying on the other species. Diet composition and stable isotope analyses also indicated that Lahontan cutthroat trout rely mostly on tui chub Gila bicolor and other fish for food. I also used results from bioenergetic and hydroacoustic analyses to compare the number of tui chub consumed by trout to the number of tui chub in the lake, during the time of this study. Results from these analyses suggest that trout consume well below the number of tui chub available in the lake, indicating that trout are not limited by the availability of tui chub. Lastly, I used a number of biotic and abiotic predictors to determine which factors influence the distribution, and subsequently abundance, of trout in Pyramid Lake and found that biotic factors were very weak predictors of trout distribution, further indicating that trout are not limited by food resources in Pyramid Lake.

Lake sediments contain the remains of midge communities that may be used as biological proxies for inferring past environmental changes. Freshwater midges, including Chironomidae and Chaoboridae, from two alpine tarns (Pyramid Lake and Bullwinkle Lake) in the Cassiar Mountains of northern British Columbia were used to estimate Holocene palaeotemperature changes, and more specifically, to test for the presence of the Milankovitch thermal maximum, an early Holocene warm interval coinciding with peak Holocene summer solar insolation. Mean July air temperatures were reconstructed using midge-inference models developed via weighted averaging-partial least squares (WA-PLS) regression. Cold-tolerant midge taxa dominate the stratigraphies from both Pyramid and Bullwinkle Lakes; however, warm-adapted species are more common in Bullwinkle Lake. Early Holocene warming is apparent at both lakes, however it is unclear whether this is indicative of the Milankovitch thermal maximum. A decrease in temperature occurs from 8,700-7,900 cal. yr BP at Pyramid Lake, around the same time that the 8,200 cal. yr BP cooling event occurred in the northern hemisphere. During the middle Holocene, records from Pyramid Lake indicate an overall decrease in temperature, with a short period of warmer temperatures that peak at 5,100 cal. yr BP. Temperatures fluctuate little during this time at Bullwinkle Lake. A short warming phase is apparent at both lakes during the late Holocene. July temperatures are highest at 2,000 cal. yr BP (10.5°C) in Pyramid Lake and at 1,200 cal. yr BP (13°C) in Bullwinkle Lake. Thereafter, temperatures return to what they were before the warming occurred, and at Bullwinkle Lake, vary little throughout the remainder of the Holocene.

Lake sediments contain the remains of midge communities that may be used as biological proxies for inferring past environmental changes. Freshwater midges, including Chironomidae and Chaoboridae, from two alpine tarns (Pyramid Lake and Bullwinkle Lake) in the Cassiar Mountains of northern British Columbia were used to estimate Holocene palaeotemperature changes, and more specifically, to test for the presence of the Milankovitch thermal maximum, an early Holocene warm interval coinciding with peak Holocene summer solar insolation. Mean July air temperatures were reconstructed using midge-inference models developed via weighted averaging-partial least squares (WA-PLS) regression. Cold-tolerant midge taxa dominate the stratigraphies from both Pyramid and Bullwinkle Lakes; however, warm-adapted species are more common in Bullwinkle Lake. Early Holocene warming is apparent at both lakes, however it is unclear whether this is indicative of the Milankovitch thermal maximum. A decrease in temperature occurs from 8,700-7,900 cal. yr BP at Pyramid Lake, around the same time that the 8,200 cal. yr BP cooling event occurred in the northern hemisphere. During the middle Holocene, records from Pyramid Lake indicate an overall decrease in temperature, with a short period of warmer temperatures that peak at 5,100 cal. yr BP. Temperatures fluctuate little during this time at Bullwinkle Lake. A short warming phase is apparent at both lakes during the late Holocene. July temperatures are highest at 2,000 cal. yr BP (10.5°C) in Pyramid Lake and at 1,200 cal. yr BP (13°C) in Bullwinkle Lake. Thereafter, temperatures return to what they were before the warming occurred, and at Bullwinkle Lake, vary little throughout the remainder of the Holocene.

Lake sediments contain the remains of midge communities that may be used as biological proxies for inferring past environmental changes. Freshwater midges, including Chironomidae and Chaoboridae, from two alpine tarns (Pyramid Lake and Bullwinkle Lake) in the Cassiar Mountains of northern British Columbia were used to estimate Holocene palaeotemperature changes, and more specifically, to test for the presence of the Milankovitch thermal maximum, an early Holocene warm interval coinciding with peak Holocene summer solar insolation. Mean July air temperatures were reconstructed using midge-inference models developed via weighted averaging-partial least squares (WA-PLS) regression. Cold-tolerant midge taxa dominate the stratigraphies from both Pyramid and Bullwinkle Lakes; however, warm-adapted species are more common in Bullwinkle Lake. Early Holocene warming is apparent at both lakes, however it is unclear whether this is indicative of the Milankovitch thermal maximum. A decrease in temperature occurs from 8,700-7,900 cal. yr BP at Pyramid Lake, around the same time that the 8,200 cal. yr BP cooling event occurred in the northern hemisphere. During the middle Holocene, records from Pyramid Lake indicate an overall decrease in temperature, with a short period of warmer temperatures that peak at 5,100 cal. yr BP. Temperatures fluctuate little during this time at Bullwinkle Lake. A short warming phase is apparent at both lakes during the late Holocene. July temperatures are highest at 2,000 cal. yr BP (10.5°C) in Pyramid Lake and at 1,200 cal. yr BP (13°C) in Bullwinkle Lake. Thereafter, temperatures return to what they were before the warming occurred, and at Bullwinkle Lake, vary little throughout the remainder of the Holocene. / Irving K. Barber School of Arts and Sciences (Okanagan) / Earth and Environmental Sciences, Department of (Okanagan) / Graduate