The Fine Sediment Sensitivity Index is a diagnostic metric used to identify samples with a high degree of taxa sensitive to fine sendiment. This index is on a scale from 0 on up, with higher values indicating the presences of more sensitive taxa, and more healthy conditions.
Relyea, C. D., G. W. Minshall, and R. J. Danehy. 2012. Development and Validation of an Aquatic Fine Sediment Biotic Index. Environ Manage 49:242-252
If the organism you need is missing, first make sure the above is not checked. If you still cannot find it, contact Doug Henderson (Douglas.Henderson@KingCounty.gov) with its name, its parent taxon, e.g., a species's genus, and, if available, its TSN.