New Zealand Journal of Marine and Freshwater Research abstracts
Short communication
Comparison of coded abundance and fixed count rapid assessment techniques
for biomonitoring in New Zealand streams
Ian C. Duggan
Mike R. Scarsbrook*
John M. Quinn
National Institute of Water and Atmospheric
Research Limited
P.O. Box 11 115
Hamilton, New Zealand
*Author for correspondence.
Abstract We compared the performance of fixed count
subsampling (100, 200, and 300 individuals) and coded abundance (rare, common,
abundant, very abundant, very very abundant) with full count sampling for
rapid assessment biomonitoring. Examining change in the Quantitative Macroinvertebrate
Community Index (QMCI) and % Ephemeroptera, Plecoptera, and Trichoptera (EPT)
values between sites upstream and downstream of pollution inputs, we found
c. 1:1 relationships between assessments made using both rapid assessment
methods and full counts. However, variability was greater using coded abundance,
and to a degree that is likely to lead to incorrect assessments on occasion.
The loss of information content in the data set, defined as Bray-Curtis distances
based on community composition between the two rapid assessment methods and
those of full counts, was significantly greater using coded abundance than
fixed counts. Assessment of stream invertebrate community composition using
fixed counts, even as low as 100 animals, provided superior results to coded
abundance in the two independent data sets tested.
Keywords biomonitoring; methods; coded abundance; fixed
counts; invertebrates
M01088 Received 6 December 2001; accepted 17 September 2002; Published
20 March 2003
New Zealand Journal of Marine and Freshwater Research, 2003, Vol. 37:
23-29
0028-8330/03/3701-0023 $7.00 © The Royal Society of New Zealand
2003
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