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SENSITIVITY OF INDICES OF BIOTIC INTEGRITY TO SIMULATED FISH ASSEMBLAGE CHANGES - 2
Citation:
Trebitz, A S., B H. Hill, AND F H. McCormick. SENSITIVITY OF INDICES OF BIOTIC INTEGRITY TO SIMULATED FISH ASSEMBLAGE CHANGES - 2. ENVIRONMENTAL MANAGEMENT 32(4):499-515, (2004).
Impact/Purpose:
to examine the use of fish communities to monitor trends within streams
Description:
Multi-metric indices of biotic integrity (IBI) are commonly used to compare fish communities among streams, but their ability to monitor trends within streams is largely unknown. We assessed the IBI trend detection ability using simulations which progressively degraded the fish assemblages of 31 mid-Appalachian streams. The IBI was insensitive to declines that affected all species proportionally (e.g., gradual loss of habitat and carrying capacity), and only somewhat sensitive to declines that altered assemblage composition (e.g. suppressing sensitive or specialized species). The IBI appears more suited to differentiating among streams than for site monitoring because it is designed to detect broad fish community composition differences among sites while downplaying abundance changes and variability increases which were the first indications of within-site changes. The cause of simulated declines could not be diagnosed by community metrics because fish did not exhibit distinct response patterns. Adjustments to scoring the proportional IBI metrics when few fish were present improved sensitivity to species declines, but adjustments to richness metrics when relevant species were absent did not. Statistical responses of fish community metrics to variability simulated according to two different schemes are reported.