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IBI’s: How It’s Done

IBI’s: How It’s Done. Components of IBI Development. (1) Regional Fish Fauna. The physico-chemical environment determines community structure and composition A fish’s habitat requirements and tolerances speaks toward the local environmental conditions

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IBI’s: How It’s Done

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  1. IBI’s: How It’s Done

  2. Components of IBI Development

  3. (1) Regional Fish Fauna • The physico-chemical environment determines community structure and composition • A fish’s habitat requirements and tolerances speaks toward the local environmental conditions • Distribution and life history very prominent in literature

  4. (1) Evaluation of Metric Suitability • Scoring range • Broad range desirable • Variability • Signal / Noise test • Responsiveness • Sensitivity to physical and chemical variables • Redundancy • Attempt to reduce among metrics (Hughes et al. 1998)

  5. (1) Reference Condition • Least impacted sites within the area of study • May be stratified by watershed, ecoregion, etc. • Typically use a quantile approach where the highest or lowest* 5-10% set the baseline conditions *Highest or lowest depends whether the metric is positive or negative scoring

  6. (2) Sampling Approaches / Design • Probabilistic • Targeted • Hybrid Approaches

  7. Site Selection • Representative reach with at least 1 riffle-pool sequence • Reach length based on mean stream width with a maximum and minimum length

  8. Sampling the Fish Community • Backpack electrofishing with a seine net

  9. Identification and Tabulation • Fish are generally not weighed and measured but identified to species • Fish often examined for DELT anomalies (deformities, eroded fins, lesions, and tumors)

  10. IBI Metrics • Individuals provide little information but proportions of the community are very telling • Scaling allows for comparisons across a variety of sizes of waterbodies

  11. Calculation of IBI score • Raw metrics are divided by scores from reference sites • Scored metrics are summed and total is corrected for a 100 point scale

  12. Assignment and Interpretation • Total score is assigned to some predetermined integrity class • Example: 80-100 = Good • 60-80 = Fair • < 60 = Poor • Interpretation is based on assignment and goals and objectives of assessment

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