Habitat suitability criteria (HSC) are an integral biological component of an instream flow regime assessment. Typically developed within the framework of the Instream Flow Incremental Methodology (IFIM), HSC are input into hydraulic habitat models to predict how the quantity and quality of habitat changes under different flows. HSC incorporate the behavioral response of a species to variability in microhabitat, such as depth, velocity, cover, and substrate. Those microhabitat components influence the use of local stream mesohabitats by different aquatic species and life stages. With recurring drought conditions and cannabis diversions underscoring the need for accurate and reliable tools to inform streamflow management decisions, site-specific HSC can fill a significant data gap in HSC literature for California. We developed HSC for rearing fry and juvenile steelhead trout (Oncorhynchus mykiss) and Coho Salmon (O. kisutch) within Hollow Tree Creek, an unimpaired stream within the South Fork Eel River watershed without any major diversions, dams, or reservoirs. We highlight snorkel survey methods, HSC curve development methods using the modeling program SEFA, steps in the HSC curve development process, and comparison of other HSC literature curves. The results from this study will be used to enhance streamflow and protect optimal salmonid rearing habitat in the South Fork Eel watershed.