Modeling Stream Fish Habitat Limitations from Wedge-Shaped Patterns of Variation in Standing Stock

Autor: Jeanette Carpenter, Jay M. Thompson, Brian S. Cade, James W. Terrell
Rok vydání: 1996
Předmět:
Zdroj: Transactions of the American Fisheries Society. 125:104-117
ISSN: 1548-8659
0002-8487
DOI: 10.1577/1548-8659(1996)125<0104:msfhlf>2.3.co;2
Popis: A wedge-shaped pattern of variation in stream fish standing stock estimates relative to a habitat variable, in which range of standing stocks increases as a function of the variable, is consistent with the concept that the habitat variable is a limiting factor for fish populations. This pattern of variation complicates interpretation of parameter estimates and significance of ordinary least-squares (OLS) regression models of conditional mean standing stock; slopes of these regression models may have little or no relation to slopes of models describing standing stock limits. We modeled standing stock limits by testing for homoscedastic error distributions, screening plots of coordinate pairs for evidence of a wedge-shaped pattern of data, and estimating 90th regression quantiles for simple linear models. Application of this technique to data sets supporting 35 previously published OLS regression models of stream fish standing stocks led to rejection of homoscedasticity (P < 0.10) in 13 of the 35 d...
Databáze: OpenAIRE
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