Population viability of Arctic grayling (Thymallus arcticus) in the Gibbon River, Yellowstone National Park

摘要: The fluvial Arctic grayling Thymallus arcticus is restricted to less than 5% of its native range in the contiguous United States and was listed as Category 3 under Endangered Species Act (ESA) until a 2007 ruling removed protection. Fluvial were thought be Big Hole River, Montana, where abundances declining. Although lower Gibbon Yellowstone National Park (YNP) considered extirpated by 1935, anglers frequently reported catching throughout river since 1980. My goal determine if viable population persisted or fish caught downstream emigrants from lacustrine populations headwater lakes. I developed three objectives address this goal: 1) 2) source River detected lakes (occupied populations), 3) are successfully spawning River. In 2005 2006, estimated ranged 0 95 109, respectively. Larger resulted when Chapman modification incorporated into electrofishing estimates, increasing ranges vary 421 506 However, both methods estimation accompanied large standard errors reflecting few river. Relatively comparison other systems. Genetic analyses indicated that system likely belonged same population, most notably supported very low genetic differentiation (FST = 0.0021 ± 0.002) between lake fish. Lengths at ages similar among all successful not documented below Little Falls (the first barrier upstream movement lakes). Few adults no fry implying reproducing does exist. These findings may affect future ESA considerations while providing data for management within outside YNP.