California freshwater shrimp prefer streams that have water flowing year round with predominately low gradient flows. In the summer months with little precipitation and surface runoff the flow rates can be very low with larger pools but they characteristically transport heavy runoff during the rainy winter season. Within a given stream, "S. pacifica" prefers slow- to medium-flowing pools and glide areas with overhanging banks. They do not inhabit even slightly brackish stream segments, but have been found to survive a minimum of 13 days in 50% seawater, perhaps allowing seed populations to colonize nearby streams as was possibly seen in Olema Creek.