A review of potential methods of determining critical effect size for designing environmental monitoring programs

Abstract

Abstract-The effective design of field studies requires that sample size requirements be estimated for important endpoints before conducting assessments. This a priori calculation of sample size requires initial estimates for the variability of the endpoints of interest, decisions regarding significance levels and the power desired, and identification of an effect size to be detected. Although many programs have called for use of critical effect sizes (CES) in the design of monitoring programs, few attempts have been made to define them. This paper reviews approaches that have been or could be used to set specific CES. The ideal method for setting CES would be to define the level of protection that prevents ecologically relevant impacts and to set a warning level of change that would be more sensitive than that CES level to provide a margin of safety; however, few examples of this approach being applied exist. Program-specific CES could be developed through the use of numbers based on regulatory or detection limits, a number defined through stakeholder negotiation, estimates of the ranges of reference data, or calculation from the distribution of data using frequency plots or multivariate techniques. The CES that have been defined often are consistent with a CES of approximately 25%, or two standard deviations, for many biological or ecological monitoring endpoints, and this value appears to be reasonable for use in a wide variety of monitoring programs and with a wide variety of endpoints.

Cautions on using the Before-After-Control-Impact design in environmental effects monitoring programs

“…We are unaware of any similar exploration of design and analysis options on environmental effects monitoring results and conclusions. Although others have examined optimal study designs for environmental effects or restoration programs (e.g., Benedetti-Cecchi 2001; Munkittrick et al 2002Munkittrick et al , 2009Liermann and Roni 2008), few have had the duration and consistency of data necessary for such analyses.…”

Increased size and relative abundance of migratory fishes observed near the Athabasca oil sands

“…Monitoring programs are often limited by the absence of information on the relevance of the differences inevitably encountered (Munkittrick et al 2009). Here, thresholds calculated for fish size using tolerance intervals and for relative abundance using parametric bootstrapping identified several unusual observations after 2006.…”

Changes in migratory fish communities and their health, hydrology, and water chemistry in rivers of the Athabasca oil sands region: a review of historical and current data

“…Watershed boundaries (dashed lines) based on Griffiths (1973). considered as a biologically significant change (Munkittrick et al 2009). Our search for historical studies (late 1970s) with a study area that overlapped with the RAMP monitoring program yielded five studies (Table A1; Fig.…”

“…Others (e.g., walleye, lake whitefish) use the mouths of the tributaries as important nursery and resting areas during the migration (e.g., Bond and Machniak 1979). These fish are all long lived and large bodied, and their health and community composition can be used to assess changes of a broad range of trophic levels of the food web over a long time period (McCart and Mayhood 1980;Karr 1981;Munkittrick et al 2009). Moreover, since they use different parts of the river system at different times of the year and at different life stages, migratory fish in the region can be used as bioindicators of large-scale changes occurring throughout the entire drainage network of the mainstem Athabasca and its tributaries (e.g., Karr 1981;Welcomme et al 2006).…”