Data from: Contemporary land change alters fish communities in a San Francisco Bay drainage, California, U.S.A.

Urbanization is one of the leading threats to freshwater biodiversity, and
urban regions continue to expand globally. Here we examined the
relationship between recent urbanization and shifts in stream fish
communities. We sampled fishes at 32 sites in the Alameda Creek Watershed,
near San Francisco, California, in 1993–1994 and again in 2009, and we
quantified univariate and multivariate changes in fish communities between
the sampling periods. Sampling sites were classified into those downstream
of a rapidly urbanizing area (“urbanized sites”), and those found in less
impacted areas (“low-impacted sites”). We calculated the change from
non-urban to urban land cover between 1993 and 2009 at two scales for each
site (the total watershed and a 3km buffer zone immediately upstream of
each site). Neither the mean relative abundance of native fish nor
nonnative species richness changed significantly between the survey
periods. However, we observed significant changes in fish community
composition (as measured by Bray-Curtis dissimilarity) and a decrease in
native species richness between the sampling periods at urbanized sites,
but not at low-impacted sites. Moreover, the relative abundance of one
native cyprinid (Lavinia symmetricus) decreased at the urbanized sites but
not at low-impacted sites. Increased urbanization was associated with
changes in the fish community, and this relationship was strongest at the
smaller (3km buffer) scale. Our results suggest that ongoing land change
alters fish communities and that contemporary resurveys are an important
tool for examining how freshwater taxa are responding to recent
environmental change.