Initial Analyses of Change Detection Capabilities and Data Redundancies in the Long Term Resource Monitoring Program
Dates
Publication Date
2001-09
Summary
Evaluations of Long Term Resource Monitoring Program sampling designs for water quality, fish, aquatic vegetation, and macroinvertebrates were initiated in 1999 by analyzing data collected since 1992 in six trend analysis areas. Initial emphasis was placed on evaluating statistical power to detect change from one year or sampling interval to the next, and on determining what spatial, methodological, or target variable redundancies existed in the data sets. Power to detect change was evaluated at halved, present, and doubled levels of effort. Power to detect change for different variables varied widely and was greatly influenced by sample size and for species by their frequency of occurrence. Power for detecting annual and seasonal [...]
Summary
Evaluations of Long Term Resource Monitoring Program sampling designs for water quality, fish, aquatic
vegetation, and macroinvertebrates were initiated in 1999 by analyzing data collected since 1992 in six trend analysis
areas. Initial emphasis was placed on evaluating statistical power to detect change from one year or sampling interval
to the next, and on determining what spatial, methodological, or target variable redundancies existed in the data sets.
Power to detect change was evaluated at halved, present, and doubled levels of effort. Power to detect change for
different variables varied widely and was greatly influenced by sample size and for species by their frequency of
occurrence. Power for detecting annual and seasonal changes in most water-quality variables seems adequate. A
doubling of effort would provide little increase in power, and some reduction or redistribution of effort may be
possible. For fish, we could detect a 20% change (at α = 0.05 and power of 0.7) in annual mean catch-per-unit-effort
for 41 species in at least one trend analysis area. Doubling effort would not appreciably enhance power for rare
species. Power for detecting change in aquatic vegetation seemed adequate. However, power for detecting change in
macroinvertebrates was low, especially in Navigation Pool 26, the Open River, and La Grange Pool. Results of these
analyses should provide useful information for evaluating the effects of potential changes to sampling designs.
