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Tuesday, May 27, 2008
291
Defining management trigger points in aquatic macroinvertebrate monitoring programs
Craig D. Snyder and David R. Smith. Leetown Science Center, U. S. Geological Survey, Aquatic Ecology Branch, 11649 Leetown Road, Kearneysville, WV 25430
The “site” is usually the fundamental unit of inference in stream monitoring programs. That is, decisions regarding whether conditions have changed are made at the site or stream reach level, and watershed, park-wide, regional or national inferences are derived by compiling site-specific inferences (e.g., fraction of sites degrading, improving, or remaining the same). However, there is considerable uncertainty in these decisions stemming from sampling error, natural variation, and the complexity of macroinvertebrate data. This uncertainty results in unavoidable tradeoffs between monitoring costs and resource protection, and these tradeoffs are governed in part by management trigger points (i.e., the point or zone that triggers a management action). For example, if management trigger points are set to be more protective (e.g., early warning indicator) the consequence of errors would be unnecessary increases in monitoring costs associated with adaptive monitoring, cause-effect research, or unwarranted mitigation. In contrast, if the trigger point is set too conservatively the risk is that degradation of the resource will go undetected.
We used simulation to evaluate the effects of management trigger points on these tradeoffs. Long-term (20-yr) macroinvertebrate data collected from small streams in Shenandoah National Park were used to parameterize simulated communities, and management trigger points were defined by Type I error rates. We simulated community responses (assemblage metrics) to a range of stressors that varied with respect to magnitude (change per year) and timing (abrupt change versus gradual change), and evaluated errors in status and trend decisions across a range of management trigger points. We believe our simulations provide considerable insight to stream monitoring.
We used simulation to evaluate the effects of management trigger points on these tradeoffs. Long-term (20-yr) macroinvertebrate data collected from small streams in Shenandoah National Park were used to parameterize simulated communities, and management trigger points were defined by Type I error rates. We simulated community responses (assemblage metrics) to a range of stressors that varied with respect to magnitude (change per year) and timing (abrupt change versus gradual change), and evaluated errors in status and trend decisions across a range of management trigger points. We believe our simulations provide considerable insight to stream monitoring.
Web Page: aquatic macroinvertebrates, monitoring, management trigger point
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See more of The Nabs 56th Annual Meeting (25-28 May, 2008)
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See more of The Nabs 56th Annual Meeting (25-28 May, 2008)