24 research outputs found

    Long-term impacts of invasive species on a native top predator in a large lake system

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    1. Declining abundances of forage fish and the introduction and establishment of non-indigenous species have the potential to substantially alter resource and habitat exploitation by top predators in large lakes. 2. We measured stable isotopes of carbon (δ13C) and nitrogen (δ15N) in field-collected and archived samples of Lake Ontario lake trout (Salvelinus namaycush) and five species of prey fish and compared current trophic relationships of this top predator with historical samples. 3. Relationships between δ15N and lake trout age were temporally consistent throughout Lake Ontario and confirmed the role of lake trout as a top predator in this food web. However, δ13C values for age classes of lake trout collected in 2008 ranged from 1.0 to 3.9‰ higher than those reported for the population sampled in 1992. 4. Isotope mixing models predicted that these changes in resource assimilation were owing to the replacement of rainbow smelt (Osmerus mordax) by round goby (Neogobius melanostomus) in lake trout diet and increased reliance on carbon resources derived from nearshore production. This contrasts with the historical situation in Lake Ontario where δ13C values of the lake trout population were dominated by a reliance on offshore carbon production. 5. These results indicate a reduced capacity of the Lake Ontario offshore food web to support the energetic requirements of lake trout and that this top predator has become increasingly reliant on prey resources that are derived from nearshore carbon pathways

    GUBERNATORIAL INFLUENCE AND STATE BUREAUCRACY

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    Previous research has concentrated on differences in gubernatorial power across states. Relatively little research attention has been devoted to the sources of gubernatorial influence over state agencies. Based on data collected from state administrators in 1978, this study examines the effects of four sets of factors on the perceived influence of the governor over the state administrative apparatus. These sets are: formal powers of the governor, characteristics of the agencies, characteristics of the positions held by administrators, and personal characteristics of these officials. Results show that these factors account for nearly one-fourth of the variance in the influence of the governor over state agencies, as reported by agency heads.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline

    State administrators' opinions on administrative change, federal aid, federal relationships

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    The ACIR Library is composed of publications that study the interactions between different levels of government. This document addresses state administrators' opinions on administrative change, federal aid, and federal relationships
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