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McSorley Creek

Biomonitoring Program

Friends of Saltwater State Park regularly assess the water quality of the McSorely Creek using protocols from the Global Water Watch Program using the training they received from the Sno-King Watershed Council. Water quality assessments include chemical tests, bacteriological tests, and stream biomonitoring. 


McSorely Creek is a salmon spawning stream. Volunteers trained through the  Duwamish Chapter of Trout Unlimited count spawning salmon from October through December. Results of the annual counts vary from year to year. 


The newly hatched salmon’s diet is dependent on the presence of tiny aquatic invertebrates. The presence of a diverse population of macro invertebrates is a good indication of a healthy stream that can support juvenile salmon. Macro invertebrates include insects that are in their larval stage as well as their adult stage, various types of worms, small molluscs, and small crustaceans. Macro invertebrates vary in their ability to tolerate adverse conditions, and a biotic index can be used to calculate the abundance of pollution sensitive organisms. A higher score of sensitive invertebrates indicates a better stream quality than a lower score, showing an increase in pollution tolerant species.

Biomonitoring collections involve using a kick net to collect samples of benthic (bottom dwelling) macro invertebrates from multiple parts of the stream. The collection is then sorted at the Order level into the categories of Sensitive, Somewhat Sensitive, and Tolerant.


Friends of Saltwater State Park park participates in the Washington Sea-Grant Shoreline Monitoring program, including surveying terrestrial insects. Terrestrial insects are a good indication of shoreline conditions and an important prey component for juvenile salmon. For this survey, we set out passive fallout traps to collect samples of insects that could fall on the surface of the water as a food source for juvenile salmon in the sound.

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