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INVESTIGATION OF SCALE-DEPENDENT RELATIONSHIPS BETWEEN ENVIRONMENTAL FACTORS AND YOUNG-OF-THE-YEAR BROOK TROUT DENSITY

Ecological factors that determine species distributions are often scale-dependent, yet for certain high priority species research has focused on predicting population parameters primarily at local scales. We examined how the relationship between environmental factors and young-of-the-year (YOY) brook trout (Salvelinus fontinalis) varies across four spatial scales (stream, HUC-12, HUC-10, and HUC-8). Environmental and YOY density data were collected from 644 streams by participants in Pennsylvania’s Unassessed Waters Initiative. Eight competing models consisting of different combinations of stream width, pH, alkalinity, specific conductivity, and land use (evergreen, deciduous, and agricultural cover) were compared at each spatial scale using Akaike information criterion (AIC). Surprisingly, model performance was similar across all four scales, and consistently the best model was stream width. We suspect the relatively strong performance of this model at large scales may be an artifact of stream survey priorities for individual watersheds (i.e., smaller headwaters were sampled in some watersheds than in others). While questions remain about these large scale patterns, our findings at the stream scale suggest streams more than four meters wide are less likely to hold high densities of YOY brook trout.

David Janetski ( Co-Presenter/Co-Author), Indiana University of Pennsylvania, janetski@iup.edu;


Lauren Prasko (Primary Presenter/Author), Indiana University of Pennsylvania, l.m.prasko@iup.edu;


Aiden Simpson ( Co-Presenter/Co-Author), Pennsylvania Fish and Boat Commission, c-asimpson@pa.gov;