A review of aquatic plant monitoring and assessment methods

Aquatic plant management has become increasingly scrutinized by federal and state regulatory agencies, including the recent implementation of a National Pollutant Discharge Elimination System permitting program in each state. Many states require documentation of nuisance acres, and an evaluation of management success. Despite this need, no widely accepted "standard methods" for quantifying nuisance plants has been published. We review the most commonly used quantitative methods for monitoring plant distribution, species composition, and abundance, and make general recommendations to support management activities in monitoring plant populations and assessing management efficacy. It is important to choose an appropriate method to meet the goals and objectives of a given program, and to be willing to change methods as the needs and objectives of the program change. It is unlikely that the same monitoring and assessment method will be used throughout a program, especially a long-term program. We recommend choosing methods that are 1) quantifiable, that is, data can be statistically analyzed, 2) follow an appropriate sampling design, and 3) are repeatable and flexible enough to change on the basis of needs and personnel. Ideally, monitoring and assessment methods need to incorporate both target and nontarget impacts, collect data that are objective and can be quantified, and are labor and cost effective.