Abstract
Summit Lake, Nevada (USA) is the last high-desert terminal lake to have a native self-sustaining population of threatened Lahontan cutthroat trout (Oncorhynchus clarkii henshawi). From spring 2015 to fall 2017, we quantified adult abundance and survival and the total annual spawning run. Abundance and survival were estimated with mark-recapture using PIT tags, and the annual spawning run was estimated with PIT tag detections and counts of spawners. Adult abundance fluctuated from 830 (95% CI 559–1248) to 1085 (95% CI 747–1614), with no overall temporal trend, as a decrease in male abundance was generally offset by an equal increase in female abundance. Estimated mean adult survival was 0.51 (95% CI 0.44–0.58). The spawning run increased from 645 (2015) to 868 (2016), but then decreased slightly to 824 (2017, mean = 789 ± 118). Female spawners increased in 2016 but decreased slightly in 2017, whereas male spawners decreased each year. In addition, the proportion of adults that spawned each year increased overall. Our study suggests that the adult population remained stable although most of the study period included the recent, severe regional drought in the western United States (2012–2016).
Highlights
Cutthroat trout (Oncorhynchus clarkii spp.) are salmonids native to the coastal and inland waters of western North America[10]
Lahontan cutthroat trout (Oncorhynchus clarkii henshawi, Lahontan cutthroat) was the top fish predator in ancient Lake Lahontan, the large inland sea during the Pleistocene that covered much of northwestern Nevada and small portions of northeastern California and southeastern Oregon
We addressed the following conservation questions about the population dynamics of the lake population: (1) what are the total, female and male adult abundances?, (2) what are the overall, female, and male adult survival rates?, and (3) what is the total number of spawners in the primary spawning tributary and what is their proportion of the adult population? We estimated abundance and survival with a robust design mark-recapture approach using passive integrated transponder (PIT) tags
Summary
Cutthroat trout (Oncorhynchus clarkii spp.) are salmonids native to the coastal and inland waters of western North America[10]. Little is known about the population dynamics of cutthroat trout in lakes across the western US, especially the desert terminal mountain lakes of the Great Basin. Lahontan cutthroat trout (Oncorhynchus clarkii henshawi, Lahontan cutthroat) was the top fish predator in ancient Lake Lahontan, the large inland sea during the Pleistocene that covered much of northwestern Nevada and small portions of northeastern California and southeastern Oregon. By the mid1800s, Lahontan cutthroat occupied 11 lakes, which ranged from the northwestern corner of Nevada to the middle portion of the Sierra Nevada Mountains in California, with six lakes in the Sierra Nevada Mountains and five lakes eastward in the high desert sagebrush steppe of the western Great Basin. The precipitous decline of the adfluvial populations was a major reason the US Fish and Wildlife Service added Lahontan cutthroat to the US endangered species list in 197026. The number of spawners was estimated by the detection of tagged individuals by a PIT antenna and the capture of tagged and non-tagged individuals in the spawning tributary during the spawning run
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