Geology topics

Harry J. Crockett

Publications and source records attributed to Harry J. Crockett.

4 recordsLinked to original sources

USGS2024

Prioritizing imperiled native aquatic species for conservation propagation

Native aquatic species are in decline, and hatcheries can play an important role in stemming these losses until larger ecological issues are addressed. However, as more federal and state agencies face budget uncertainty and the number of imperiled species increases, it is necessary to develop a tool to prioritize species for conservation propagation. Our objective was to create prioritized lists of aquatic species that may benefit from conservation propagation for five states in the United States. Biologists developed an influence diagram and provided information for multiple attributes affecting prevalence of species. The influence diagram and information for each species was used in a Bayesian belief network to generate a score to prioritize propagation of a species and the feasibility of propagation. When all taxa were ranked together within a state, mussels, amphibians, and a crustacean were included among fishes in the top species that may benefit from propagation. We recognize that propagation is one tool for conservation of imperiled species and that additional factors will need to be addressed to ensure species persistence. Nevertheless, we contend our quantitative approach provides a useful framework for prioritizing conservation propagation.

Colorado, Kansas, North Dakota, South Dakota, Utah↗

USGS2023

Optimal management decisions are robust to unknown dynamics in an amphibian metapopulation plagued by disease

Identifying conservation actions to recover threatened species can be challenging due to many ecological uncertainties. For example, major threats to a species' conservation are commonly known or suspected, but the specific impacts on population or metapopulation dynamics can be uncertain. This is frequently the case with emerging infectious diseases, including chytridiomycosis, a global driver of amphibian population declines caused by the fungal pathogens Batrachochytrium dendrobatidis (Bd) and Batrachochytrium salamandrivorans . While these diseases are known to cause amphibian declines and extirpations, the mechanisms of their landscape-scale spread are still largely unknown. Such uncertainty can lead to inaction which may jeopardize timely recovery of a species. Decision analysis is a pragmatic approach to making transparent and defensible decisions while dealing with uncertainties. We investigated whether optimal actions aimed at recovering boreal toad ( Anaxyrus boreas boreas ) metapopulations in the southern Rocky Mountains are robust to the unknown dynamics of Bd spread using value of information and regret analyses. Value of information is a decision-analytic tool for calculating the value of new information in terms of performance on management objectives, while regret measures the cost of acting under incorrect information. We further conducted a stochastic sensitivity analysis to identify the relative effects of metapopulation parameters on system dynamics. We found optimal actions were robust to the unknown dynamics of Bd spread. While boreal toad breeding occurrence is highly sensitive to Bd distribution, the optimal decision is not. Resolving the unknown dynamics of Bd spread would lead to a minimal gain of less than one breeding toad subpopulation at the end of 50 years, given the currently available management actions. Applying a decision-analytic framework coupled with value of information and regret analyses can help frame how uncertainties affect decisions in a way that empowers decision makers.

Animal Conservation↗

USGS2017

Identifying species conservation strategies to reduce disease-associated declines

Emerging infectious diseases (EIDs) are a salient threat to many animal taxa, causing local and global extinctions, altering communities and ecosystem function. The EID chytridiomycosis is a prominent driver of amphibian declines, which is caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd). To guide conservation policy, we developed a predictive decision-analytic model that combines empirical knowledge of host-pathogen metapopulation dynamics with expert judgment regarding effects of management actions, to select from potential conservation strategies. We apply our approach to a boreal toad ( Anaxyrus boreas boreas ) and Bd system, identifying optimal strategies that balance tradeoffs in maximizing toad population persistence and landscape-level distribution, while considering costs. The most robust strategy is expected to reduce the decline of toad breeding sites from 53% to 21% over 50 years. Our findings are incorporated into management policy to guide conservation planning. Our online modeling application provides a template for managers of other systems challenged by EIDs.

Conservation Letters↗

USGS2013

Barriers impede upstream spawning migration of flathead chub

Many native cyprinids are declining throughout the North American Great Plains. Some of these species require long reaches of contiguous, flowing riverine habitat for drifting eggs or larvae to develop, and their declining populations have been attributed to habitat fragmentation or barriers (e.g., dams, dewatered channels, and reservoirs) that restrict fish movement. Upstream dispersal is also needed to maintain populations of species with passively drifting eggs or larvae, and prior researchers have suggested that these fishes migrate upstream to spawn. To test this hypothesis, we conducted a mark–recapture study of Flathead Chub Platygobio gracilis within a 91-km reach of continuous riverine habitat in Fountain Creek, Colorado. We measured CPUE, spawning readiness (percent of Flathead Chub expressing milt), and fish movement relative to a channel-spanning dam. Multiple lines of evidence indicate that Flathead Chub migrate upstream to spawn during summer. The CPUE was much higher at the base of the dam than at downstream sites; the seasonal increases in CPUE at the dam closely tracked seasonal increases in spawning readiness, and marked fish moved upstream as far as 33 km during the spawning run. The upstream migration was effectively blocked by the dam. The CPUE of Flathead Chub was much lower upstream of the OHDD than at downstream sites, and <0.2% of fish marked at the dam were recaptured upstream. This study provides the first direct evidence of spawning migration for Flathead Chub and supports the general hypothesis that barriers limit adult dispersal of these and other plains fishes.

Colorado↗