Great Smoky Mountains National Park Fish Index of Biotic Integrity

National Park Service - Great Smoky Mountains National Park

These data show only the locations of Fish IBI study and monitoring sites within the park. The Index of Biotic Integrity (IBI) provides a consistent framework for evaluating fish assemblages using 12 biological metrics describing taxonomic composition, trophic structure, abundance, and fish condition. Multiple-parameter indices like the IBI allow objective evaluation of complex ecological systems. Originally developed for small Midwestern warmwater streams, the IBI has been adapted widely for various regions and waterbody types. The IBI assesses stream condition using ecological metrics applied to resident fish communities (Karr 1981). Each metric is scored as 1 (poor), 3 (intermediate), or 5 (best expected), based on comparison to reference sites. Scores are summed to produce an IBI ranging from 12 (very poor) to 60 (excellent), and sites are classified following Karr et al. (1986). Additional background on methods and metrics is available in Plafkin et al. (1989). Although the IBI uses professional judgment, it does so in a structured manner with defined criteria. Metrics are scored based on expected values from regional reference conditions; values near, slightly below, or far below expectations receive scores of 5, 3, or 1. Regional substitutions for metrics may be needed due to differences in species distributions or ecosystem types. Summary of the 12 IBI metrics: Species Richness and Composition Metrics: 1. Total number of fish species: Counts native species and salmonid age classes. 2. Number and identity of darter species: Substitutes include sculpins, benthic insectivores, or round-bodied suckers depending on region. These taxa are sensitive to benthic habitat degradation. 3. Number and identity of sunfish species: Substitutes include cyprinids, water column species, salmonids, or headwater species depending on stream type and region. 4. Number and identity of sucker species: Substitutes include adult trout, minnows, or combinations thereof. These long-lived species integrate physicochemical conditions over time. 5. Number and identity of intolerant species: Sensitive species, amphibians, or brook trout may substitute. These species disappear quickly after disturbance. 6. Proportion of individuals as tolerant species: Measures dominance of highly tolerant species (e.g., carp, white sucker, creek chub), which increase with degradation. Trophic Composition Metrics: 7. Proportion of individuals as omnivores: Increases as habitat quality declines. 8. Proportion of individuals as insectivorous cyprinids: Declines as invertebrate prey decreases; evaluates midrange biological condition. 9. Proportion of individuals as top carnivores: Piscivores or large salmonids indicate higher integrity; pioneering species may be used in headwater streams. Fish Abundance and Condition Metrics: 10. Number of individuals in sample: Indicates abundance; unusually low counts may reflect toxicity. Biomass may substitute in larger streams. 11. Proportion of individuals as hybrids: Substitutes include introduced species or simple lithophils. Hybridization and introduced species often increase with degradation. 12. Proportion of individuals with disease or anomalies: Reflects fish health; deformities and lesions are more frequent in polluted areas. Together, these metrics provide an integrated evaluation of fish assemblage condition, with different metrics responding to different stressors. Regional adaptations maintain the theoretical foundation of the IBI while accommodating biological and ecological variation.

Great Smoky Mountains National Park Fish Index of Biotic Integrity

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