Overview: Maryland Biological Stream Survey
Maryland and other state monitoring programs have determined that fish indicators
are ineffective in headwater streams, where stream salamanders may replace
fish as top predators. Because of their life history, physiology, abundance,
and ubiquity, stream salamanders are likely representative of biological integrity
in these streams. The goal of this study was to determine whether stream salamanders
are effective indicators of ecological conditions across biogeographic regions
and gradients of human disturbance. During the summers of 2001 and 2002, we
intensively surveyed for stream salamanders at 76 stream sites located west
of the Maryland Coastal Plain, that were also monitored by the Maryland Biological
Stream Survey (MBSS) and City of Gaithersburg. We found 1,584 stream salamanders,
including all eight species known in Maryland, using two 15x2-m transects
and two 4-m2 quadrats that spanned both stream bank and channel. 
We
performed removal sampling on transects to estimate salamander species detection
probabilities, which ranged from 0.71-0.85. Stepwise regressions identified
15 of 52 non-salamander variables, representing water quality, physical habitat,
land use, and biological conditions, that best predicted salamander metrics.
Indicator development involved (1) identifying reference (non-degraded) and
degraded sites (using percent forest, shading, riparian buffer width, aesthetic
rating, and benthic macroinvertebrate and fish indices of biotic integrity);
(2) testing 17 candidate salamander metrics (representing species richness
and composition, abundance, species tolerance, reproductive function, and
trophic function) for their ability to distinguish reference from degraded
sites; and (3) combining metrics into an index that effectively discriminated
sites according to known stream conditions. Final indices for Highlands, Piedmont,
and non-Coastal Plain regions were comprised of four metrics: number of species,
number of salamanders, percentage of intolerant salamanders, and number of
adult salamanders, producing classification efficiencies between 80% and 90%.
Partial validation of these indices was obtained when a test of the number-of-salamanders
metric produced an 82% correct classification of 618 MBSS sites surveyed in
1995-97. This study supports the use of stream salamander monitoring and a
composite stream salamander index of biotic integrity (SS-IBI) to determine
stream quality in Maryland.
Contact
Please contact Dr. Mark Southerland (southerlandmar@versar.com) for more information.