|SREL Reprint #1998|
Path analysis of collective properties and habitat relationships of fish assemblages in coastal plain streams
Andrew L. Sheldon and Gary K. Meffe
Abstract: Collective properties of fish assemblages at 44 sites in low-gradient
streams (orders 1-3) on the upper coastal plain of South Carolina, U.S.A., were
highly variable among sites: richness, 2-17 species per site; density, 0.2-9.5
individuals-m 2 ; mean individual mass,-22.2 g per individual; and biomass,
0.1-42.1 g-m - 20.4 . Principal components analysis reduced 15 habitat
parameters to four interpretable components that were used as orthogonal
predictive variables in path analysis. Path analysis, with a directional model
containing intermediate steps and multiple dependent variables, was used as an
alternative to multiple regression. Two principal components, associated with
velocity (and its covariates) and depth (and its covariates), were the primary
correlates of biomass (R 2 = 49%), richness (44%), mean size (36%), and density
(20%), with cover variables contributing relatively little to any R2 value. Velocity
effects were negative and depth effects positive for all collective properties.
Habitat effects on biomass were mediated by effects on individual fish size rather
than numbers. Correlations of collective properties at sites sampled in 2 years
were similar to those from the single year, habitat-based path model, implying that
the path model was adequate and inclusive, and accurately reflected collective
properties of these communities.
SREL Reprint #1998
Sheldon, A.L. and G.K. Meffe. 1995. Path analysis of collective properties and habitat relationships of fish assemblages in coastal plain streams. Canadian Journal of Fisheries and Aquatic Sciences 52:23-33.