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 Distribution and life history very prominent in literature

(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)

(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

(2) Sampling Approaches / Design Probabilistic Targeted Hybrid Approaches

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

Sampling the Fish Community Backpack electrofishing with a seine net

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)

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

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

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