Title: Influences of spatial and temporal variation on fish-habitat relationships defined by regression quantiles
Author: Dunham, Jason B.; Cade, Brian S.; Terrell, James W.;
Source: Transactions of the American Fisheries Society. 131(1): 86-98
Publication Series: Miscellaneous Publication
Description: We used regression quantiles to model potentially limiting relationships between the standing crop of cutthroat trout Oncorhynchus clarki and measures of stream channel morphology. Regression quantile models indicated that variation in fish density was inversely related to the width:depth ratio of streams but not to stream width or depth alone. The spatial and temporal stability of model predictions were examined across years and streams, respectively. Variation in fish density with width:depth ratio (10th–90th regression quantiles) modeled for streams sampled in 1993–1997 predicted the variation observed in 1998–1999, indicating similar habitat relationships across years. Both linear and nonlinear models described the limiting relationships well, the latter performing slightly better. Although estimated relationships were transferable in time, results were strongly dependent on the influence of spatial variation in fish density among streams. Density changes with width:depth ratio in a single stream were responsible for the significant (P < 0.10) negative slopes estimated for the higher quantiles (>80th). This suggests that stream-scale factors other than width:depth ratio play a more direct role in determining population density. Much of the variation in densities of cutthroat trout among streams was attributed to the occurrence of nonnative brook trout Salvelinus fontinalis (a possible competitor) or connectivity to migratory habitats. Regression quantiles can be useful for estimating the effects of limiting factors when ecological responses are highly variable, but our results indicate that spatiotemporal variability in the data should be explicitly considered. In this study, data from individual streams and stream-specific characteristics (e.g., the occurrence of nonnative species and habitat connectivity) strongly affected our interpretation of the relationship between width:depth ratio and fish density.
Keywords: Oncorhynchus clarki, Salvelinus fontinalis, trout, habitats, streams, geomorphology, population dynamics, spatial variation, temporal variation, regression analysis
- 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.
- You may send email to email@example.com to request a hard copy of this publication. (Please specify exactly which publication you are requesting and your mailing address.)
XML: View XML
Dunham, Jason B.; Cade, Brian S.; Terrell, James W. 2002. Influences of spatial and temporal variation on fish-habitat relationships defined by regression quantiles. Transactions of the American Fisheries Society. 131(1): 86-98
Get the latest version of the Adobe Acrobat reader or Acrobat Reader for Windows with Search and Accessibility