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BioNet Documentation

Fish Habitat Index (FHI)

Physical habitat characteristics such as stream width and depth, instream cover, and substrate composition are important environmental factors that shape Iowa’s stream fish species assemblages. Therefore, habitat data are often collected and used to help interpret stream fish sampling results. The Fish Index of Biotic Integrity (FIBI) is the primary tool used by the Iowa Department of Natural Resources (IADNR) stream biological assessment program to assess fish assemblage health condition and the attainment status of designated aquatic life uses.

The General Fish Habitat Index (GFHI) yields a normalized score between 0 and 100 that equates to qualitative categories (Excellent, Good, Fair, Poor) of fish assemblage health condition in Iowa’s wadeable streams. It can be used to quickly compare and rank habitat conditions across multiple sampling sites throughout Iowa. It also identifies which of 25 individual habitat metrics are the most likely to limit the resident stream fish assemblage from attaining a higher condition level.

The Ecoregional Fish Habitat Index (EFHI) can be used more specifically in the stream bioassessment process. By adjusting for ecoregion effect, the EFHI provides a more accurate prediction of the Fish Index of Biotic Integrity (FIBI). Analysis of regression analysis residuals from least disturbed reference sites were used to establish guidelines for interpreting the difference between the observed (sampled) FIBI score and the EFHI-predicted FIBI score. These guidelines should be useful for distinguishing streams in which fish assemblage condition appears to match expectations based on physical habitat conditions from those in which fish assemblages are limited by other environmental factors such as water quality.