WWRC 91-03
Field Comparison of Three Devices Used to Sample Substrate in Small Streams
Abstract
We conducted a field study to compare the composition of substrate samples collected
from small streams with three types of samplers: an excavated-core sampler, a single-probe freeze-core
sampler, and a shovel. Large particles (>50 mm in diameter) occurred most frequently in
excavated-core samples (76%) and least frequently in freeze-core samples (52%), but they had the
greatest influence on overall sample composition when they occurred in freeze-core samples. Excavated-core
and shoveled samples did not differ significantly in composition, but freeze-core
samples differed significantly from both excavated-core and shoveled samples for some particle
sizes. When freeze-core samples were divided into halves, the lower portion contained significantly
more fine particles than the upper portion. We concluded that the freeze-core sampler does not
produce samples similar to excavated-core samples and is too expensive and cumbersome for
routine management applications. Conversely, the shovel produces substrate samples similar to
those obtained with an excavated-core sampler, and it is the least expensive and least cumbersome
of the samplers. Field biologists should consider the shovel a viable alternative to an excavated-core
sampler when sampling streams similar to the ones we studied.
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