Skip to Main Content
U.S. Forest Service
Caring for the land and serving people

United States Department of Agriculture

Home > Search > Publication Information

  1. Share via EmailShare on FacebookShare on LinkedInShare on Twitter
    Dislike this pubLike this pub
    Author(s): Ryan McManamay; Donald J. Orth; Charles A. Dolloff; David C. Mathews
    Date: 2015
    Source: Canadian Journal of Fisheries and Aquatic Sciences
    Publication Series: Scientific Journal (JRNL)
    Station: Southern Research Station
    PDF: Download Publication  (1.0 MB)


    Unregulated river systems are organized in a hierarchy in which large scale factors (i.e. landscape and segment scales) influence local habitats (i.e. reach, meso- and microhabitat scales), and both differentially exert selective pressures on biota. Dams, however, create discontinua in these processes and change the hierarchical structure. We examined the relative roles of hydrology and other instream factors, within a hierarchical landscape context, in organizing fish communities in regulated and unregulated tributaries to the Upper Tennessee River, USA. We used multivariate regression trees to identify factors that partition fish assemblages based on trait similarities, irrespective of spatial scale. We then used classical path analysis and structural equation modeling to evaluate the most plausible hierarchical causal structure of specific trait-based community components, given the data. Both statistical approaches suggested that river regulation affects stream fishes through a variety of reach-scale variables, not always through hydrology itself. Although we observed different changes in flow, temperature, and biotic responses according to regulation types, the most predominant path in which dam regulation affected biota was via temperature alterations. Diversion dams had the strongest effects on fish assemblages. Diversion dams reduced flow magnitudes leading to declines in fish richness, but increased temperatures leading to lower abundances in equilibrium species and nest-guarders. Peaking and run-of-river dams increased flow variability, leading to lower abundances in nest-guarding fishes. Flow displayed direct relationships with biotic responses; however, results indicated that changes in temperature and substrate had equal, if not stronger, effects on fish assemblage composition. The strength and nature of relationships depended on whether flow metrics were standardized for river size. We suggest that restoration efforts in regulated rivers focus on improving flow conditions in conjunction with temperature and substrate restoration.

    Publication Notes

    • You may send email to to request a hard copy of this publication.
    • (Please specify exactly which publication you are requesting and your mailing address.)
    • We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
    • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.


    McManamay, Ryan, A., Peoples, Brandon K.; Orth, Donald J.; Dolloff, Charles A.; Mathews, David C. 2015. Isolating causal pathways between flow and fish in the regulated river hierarchy. Canadian Journal of Fisheries and Aquatic Sciences. 72: 1731-1748  18 p. 10.1139/cjfas-2015-0227


    Google Scholar


    dams, fish assemblages, hydrology, fish life history, temperature, substrate

    Related Search

    XML: View XML
Show More
Show Fewer
Jump to Top of Page