An Index of Biological Integrity for First to Third Order Russian River Tributary Streams


California Department of Fish and Game - Water Pollution Control Laboratory

2005 Nimbus Rd.  Rancho Cordova, CA 95670 (916) 358-2858;

California Aquatic Bioassessment Web Site at 




The conceptual model described by the U.S. Environmental Protection Agency for development of biocriteria was followed to produce a first iteration of an Index of Biological Integrity for the Russian River Watershed (RRIBI).  Benthic macroinvertebrate (BMI) were collected from 35 reaches within 21 tributary streams and the mainstem Russian River during the fall 1995 and spring 1996 and 1997 using the California Stream Bioassessment Procedure.  A set of core biological metrics, commonly used for bioassessment of California stream were used to describe the BMI communities in the 35 reaches.  Monitoring reaches within the first to third order streams classified as similar with different channel type having no influence on mean biological metric values.  The biological metrics, Taxa Richness, EPT Taxa, Modified EPT Index, Shannon Diversity, Tolerance Value and Percent Dominant Taxa were chosen as the most appropriate to be included in producing the RRIBI.  These six metrics were integrated into a single scoring criteria by producing a histograms of the values for each of the biological metrics and visually determining breaks in their distribution.  This approach of determining scoring criteria was more intuitive and probably most appropriate given the data came from streams that could have been moderately impaired and not actually representative of pristine reference conditions.  Although there was no indication of strong seasonal variability in the BMI communities, it was recommend that the index period for the Russian River tributary streams be in the spring.  It was also recommend that the RRIBI be considered preliminary and that data on more Russian River tributaries and the mainstem be collected to 1) test the effectiveness of this scoring criteria on other first to third order Russian River tributaries, 2) test the appropriateness of using other biological metrics, 3) evaluate the use of the RRIBI in other north coast California streams to test its effectiveness at assessing biological integrity of streams outside the Russian River watershed, and 4) produce an IBI for fourth order and larger stream reaches.





Biological Metric


Visual Distribution  Score


How to Use the Russian River Index of Biological Integrity


Obtain a sample of benthic macroinvertebrates following the state standard procedures (California Stream Bioassessment Procedures - May 1999 version).  There must be at least three replicate samples collected at each monitoring location.   The samples should be processed by a professional bioassessment laboratory using the Level 3 Taxonomic Effort.  Determine the mean values for the six listed biological metrics, compare them to the values in the columns and add the scores listed in the column headings.  The total score will be between a low of 6 and high of 30.  Determine biotic condition of the monitoring location from the following categories:

                          Excellent        Good             Fair            Poor 

                           30 - 24           23 - 18         17 - 12         11 - 6 









Taxa Richness









% Dom. Taxa









EPT Taxa









Mod EPT Index









Shannon Diversity 









Tolerance Value