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Biological assessment (bioassessment) is an evaluation of the condition of a waterbody based on the organisms living within it. It involves surveying the types and numbers of organisms present in the water and comparing the results to established swamplogobenchmarks of biological health. Scientists and managers around the world use this approach to directly and quantitatively measure the ecological health of a waterbody and to monitor the cumulative impacts of environmental stressors on surface waters.

Benthic macroinvertebrates (BMIs) and benthic algae are the primary biota used for bioassessments in California. BMIs are a diverse group of small but visible animals that live at the bottom of rivers and streams. They are comprised mostly of aquatic insects but also include crustaceans, mollusks, and worms. BMI assemblages are found in most waterbodies and are reliable indicators of biological health because they are relatively stationary and respond predictably to a variety of environmental stressors. Benthic algae are also sensitive to environmental stressors and provide environmental condition information that is often complementary to that derived from BMI assemblages. Because of their short lifespans and rapid reproduction rate, algae can respond quickly to changing water conditions. They are also more directly responsive to nutrients (such as nitrogen and phosphorus) and are therefore suited for monitoring nutrient runoff, one of the major environmental stressors in California.

SWAMP began conducting bioassessment in 2000. The program continues to work closely with the California Department of Fish and Wildlife's (CDFW) Aquatic Bioassessment Laboratory, which has been the primary producer of this technical work. Other major partners include the Southern California Coastal Water Research Project (SCCWRP) and the California State University experts at Chico and San Marcos.

CA Department of Fish and Wildlife
Aquatic Bioassessment Laboratory
CSU Chico
CSU San Marcos

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Contact Information

For any questions on the Statewide Bioassessment Program please contact Shuka Rastegarpour at 916-327-1277

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Statewide Bioassessment Program

An overview of SWAMPs statewide bioassessment program, consisting of the Perennial Streams Assessment (PSA) probability survey and Reference Condition Management Program (RCMP).


Data and Interpretive Tools

SWAMP-developed tools for data entry, interpretation, and reporting. Includes the California Stream Condition Index (CSCI) and ecoregion-based Indices of Biological Integrity (IBIs).


SWAMP Information and Quality Assurance Center

Data management and quality assurance/quality control for biological assessments.

taxonomic sample

Taxonomic Resources

Tools and other helpful resources for identifying BMIs and algae. Includes worksheets, datasheets, and online tools.


Standard Operating Procedures

Standard Operating Procedures (SOPs) are instructions describing how to perform a specific method or activity. In order to be SWAMP-comparable, bioassessment sampling must be conducted according to SWAMP’s SOPs.


Training, Field QA, and Collection Permit

SWAMP offers various training opportunities in bioassessment through the CDFW and Water Boards Training Academy. Includes calibration exercises, field audits, and the California Aquatic Bioassessment Workgroup meeting.


Reports and Publications

A selection of technical reports, management memos, fact sheets, and other documents related to SWAMP’s work in bioassessment.


Bioassessment links and resources

Online resources related to SWAMP and bioassessment.