Status and trends of adult Lost River (&lt;em&gt;Deltistes luxatus&lt;/em&gt;) and shortnose (&lt;em&gt;Chasmistes brevirostris&lt;/em&gt;) sucker populations in Upper Klamath Lake, Oregon, 2015

Hewitt, David A.; Janney, Eric C.; Hayes, Brian S.; Harris, Alta C.

doi:10.3133/ofr20171059

Cited by 2 publications

(8 citation statements)

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“…All scenarios shared the same underlying parameters (or draws from the same parameter distribution) for starting abundance and adult survival (Table 1), but scenarios varied in the mechanism and magnitude of recruitment. We took initial abundance from spawning population abundance estimates from a modified Bayesian Lincoln-Petersen estimator (E.C., unpublished data) using long-term markrecapture data (Hewitt et al 2017). The initial abundance of each replicate was randomly selected from the posterior distribution of abundance from the most recent year with available estimates, which was 2016 for the Lost River Sucker Williamson population and the Shortnose Sucker and 2017 for the Lost River Sucker springs population.…”

Section: Methodsmentioning

confidence: 99%

“…Table 1. Parameters used to intialize populations for each model run for the Lost River Sucker Deltistes luxatus Williamson River (Oregon) spawners, the Lost River Sucker spring spawners, and the Shortnose Sucker Chasmistes brevirostris populations that reside in Upper Klamath Lake, Oregon: mean initial population size (MIPS), the mean (MFS) and standard deviation (SDFS) of empirical data of female survival from 2002 to 2014 for Lost River Sucker and 2001 to 2014 for Shortnose Sucker (Hewitt et al 2017), the coefficient of determination (R 2 ) from a linear model fit to predict male survival from female surival for each species on the basis of the same empirical data, the pseudoextinction level (PEL), the pseudorecovery level (PRL), and the male-to-female ratio (MFR). After the establishment of the annual cohort in the model, we simulated annual survival rates stochastically.…”

Section: Methodsmentioning

confidence: 99%

“…After the establishment of the annual cohort in the model, we simulated annual survival rates stochastically. We assumed that annual female survival followed a normal distribution on the logit scale using populationspecific means and SDs derived from empirical estimates from long-term monitoring (12-14 y, depending on the population; Hewitt et al 2017). We utilized reported survival estimates for 2002-2014 for both Lost River Sucker populations and for 2001-2014 for Shortnose Sucker.…”

Section: Methodsmentioning

confidence: 99%

“…Eggs and larvae are produced each year, but there appears to be consistent cohort collapse within the first 2 y on the basis of juvenile catches that fall to 0 during that period (Burdick and Martin 2017). However, annual survival of adults is relatively high, often around 90% (Hewitt et al 2017), suggesting that reintroducing suckers that have been raised past the survival bottleneck could result in recruitment of new individuals to the adult spawning populations (Day et al 2017).…”

Section: Introductionmentioning

confidence: 99%

“…Even after the cause of mortality is identified, management actions addressing these issues are likely to take years or decades to yield benefits (Wherry and Wood 2018). Although Upper Klamath Lake is thought to harbor the most abundant populations of both species, its populations have declined by over 75% (Shortnose Sucker) or 50% (Lost River Sucker) since 2001 (Hewitt et al 2017). Thus, captive rearing is likely necessary to sustain populations until the causes of juvenile mortality are determined and addressed (Day et al 2017).…”

Section: Introductionmentioning

confidence: 99%

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Population Viability of Endangered Lost River Sucker and Shortnose Sucker and the Effects of Assisted Rearing

Rasmussen

Childress

2018

Journal of Fish and Wildlife Management

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The Lost River Sucker Deltistes luxatus and Shortnose Sucker Chasmistes brevirostris are two narrowly endemic fish species in the upper Klamath Basin of southern Oregon and northern California. Both species have been federally listed as endangered pursuant to the U.S. Endangered Species Act since 1988 because of dramatic declines in abundance and distribution. In Upper Klamath Lake, Oregon, both species have only recruited a single cohort to the adult populations since that time. Most individuals in this population are at or older than the expected life span of the species. Consequently, the U.S. Fish and Wildlife Service and the Klamath Tribes have initiated assisted rearing efforts to stabilize the population. However, it is unclear how quickly these populations might become extirpated and how assisted rearing might alter population trajectories. We modeled the potential for extinction and recovery of the populations of endangered Lost River Sucker and Shortnose Sucker in Upper Klamath Lake. We simulated population trajectories over the next 50 y with a stochastic population viability assessment approach. Projections indicate that if population trajectories do not change, the Shortnose Sucker population may decline by 78% to number < 5,000 in 10 y and become completely extirpated within the next 30 (18.6% probability) to 40 y (99% probability). The two Lost River Sucker populations have a greater likelihood to remain extant after 50 y, with only 1% probability of extinction given our scenarios and assumptions, but the populations are likely to number fewer than 1,000 individuals. Our results also suggest that rearing of Klamath Lake sucker species in a controlled environment for augmenting the natural population will be effective in reducing extirpation probabilities over the next 50 y if survival to recruitment can be achieved, but a long-term effort of at least 40 y will be required. The necessity of long-term augmentation to ensure population persistence in the absence of natural recruitment underscores the urgent need to determine and address the causes of recruitment failure in the wild.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%