3.   Aquatic Life Standards  

b. Aquatic Life Indices

To better define the terminology used in water quality standards, the following example on Big Darby Creek will be used from Ohio EPA sampling data. 

Ohio EPA utilizes both aquatic life (fish and bugs) and habitat (See Stream Habitat Assessment section) to determine the appropriate use attainment of a stream segment.  Ohio EPA developed different levels of aquatic life uses that illustrate the range of fish, bugs, and habitat potential that exists in Ohio Streams.  There are three aquatic life indices.  The indices listed below evaluate the fish and bug communities at a site.  The numerical values given are the typical minimum value within a defined category (for ICI a score of 46 is the typical low score before it drops to a WWH). 

ICI (Invertebrate Community Index) – Evaluates and ranks the bugs at a site

            MWH - 24

            WWH - 36

            EWH - 46

IBI (Index of Biotic Integrity) – Evaluates and ranks the fish found at the site

            MWH - 24

            WWH - 36
            EWH - 46

MIwb (Modified Index of Well-Being) – Evaluates and ranks fish at a site. 

**Streams must be larger to receive this score.  For example the headwaters of the Big Darby in Logan County do not have a MIwb score whereas portions in Madison County have a MIwb score.

            MWH – 5.8

            WWH – 7.8

            EWH – 8.9

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Last updated: November 18, 2008.