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Richard Zabel

Publications and source records attributed to Richard Zabel.

2 recordsLinked to original sources

Management opportunities and research priorities for Great Plains grasslands

The Great Plains Grassland Summit: Challenges and Opportunities from North to South was held April 10-11, 2018 in Denver, Colorado. The geographical focus for the summit was the entire Great Plains. The summit was designed to provide syntheses of information about key grassland topics of interest in the Great Plains; networking and learning channels for managers, researchers and stakeholders; and working sessions for sharing input and ideas about challenges and future research and management opportunities. The summit was convened to better understand Great Plains stressors and resource demands and how to manage them, and to discuss methods for improved collaboration among natural resource managers, scientists, and stakeholders. Over 200 stakeholders, who collectively were affiliated with all of the Great Plains states, attended the summit. Attendees included university researchers, government scientists, and individuals affiliated with federal and state agencies, tribes, the private sector, and non-governmental organizations (NGOs). Plenary speakers provided syntheses of current knowledge on key topics to help stage working sessions on working lands, native plants and pollinators, native wildlife and biological diversity, invasive species, wildland and prescribed fire, energy development, and weather, water, and climate. The summit steering committee designed one suite of questions that were asked of participants in each working session. This report is a digest of the input from those who attended the seven working sessions and responded to the structured questions.

Colorado, Illinois, Iowa, Kansas, Minnesota, Misso↗

Survival and selection of migrating salmon from capture-recapture models with individual traits

Capture–recapture studies are powerful tools for studying animal population dynamics, providing information on population abundance, survival rates, population growth rates, and selection for phenotypic traits. In these studies, the probability of observing a tagged individual reflects both the probability of the individual surviving to the time of recapture and the probability of recapturing an animal, given that it is alive. If both of these probabilities are related to the same phenotypic trait, it can be difficult to distinguish effects on survival probabilities from effects on recapture probabilities. However, when animals are individually tagged and have multiple opportunities for recapture, we can properly partition observed trait-related variability into survival and recapture components. We present an overview of capture–recapture models that incorporate individual variability and develop methods to incorporate results from these models into estimates of population survival and selection for phenotypic traits. We conducted a series of simulations to understand the performance of these estimators and to assess the consequences of ignoring individual variability when it exists. In addition, we analyzed a large data set of >153 000 juvenile chinook salmon (Oncorhynchus tshawytscha) and steelhead (O. mykiss) of known length that were PIT-tagged during their seaward migration. Both our simulations and the case study indicated that the ability to precisely estimate selection for phenotypic traits was greatly compromised when differential recapture probabilities were ignored. Estimates of population survival, however, were far more robust. In the chinook salmon and steelhead study, we consistently found that smaller fish had a greater probability of recapture. We also uncovered length-related survival relationships in over half of the release group/river segment combinations that we observed, but we found both positive and negative relationships between length and survival probability. These results have important implications for the management of salmonid populations.

Ecological Applications↗