Staghorn sculpin are commonly found in bays and estuaries with sandy bottoms. Staghorn sculpin individuals can breathe air when out of water. Although some individuals may spend their entire life in highly saline waters, some newly metamorphosed young move from the estuarine spawning sites to completely fresh water and may remain there for up to 6 weeks.
Adults apparently tend to remain in the shallow lower estuary, or farther offshore. Their diet consists mostly of crabs, shrimps, and amphipods, but they will also take larval, juvenile and adult fishes, as well as sea worms, mollusks and other invertebrates. They will expand their gill covers and produce a low pitched humming sound when stressed.
The Pacific staghorn sculpin has a slender body that is grayish olive in color with pale creamy yellow sides, a white belly, a large flattened head, and a large mouth. The soft dorsal fin is dusky, with a black spot near its rear with a white band below, and the pectoral fins are yellow with five or six dark greenish bands. They can reach lengths of 30 cm.
The Pacific staghorn sculpin spends most of their lives in salt and brackish waters, though they are capable of adapting to fresh water as well as extremely saline waters. The larvae begin their lives in the estuary where they spread out onto a soft and sandy substrate. As they develop into juveniles, the young fish depart in many directions including into freshwater. Most fish found in freshwater or less salty areas are the young juveniles which feed on amphipods, invertebrates, small fish, and aquatic insect larvae. The older Pacific staghorn sculpins tend to be the farthest upstream, giving way for more young fish to push up from the marine or estuary environments. The marine dwelling fish may follow the tide and have a diet of crabs, shrimp, and fish. Most Pacific staghorn sculpins feed actively at night, they may also eat throughout the day. Throughout the west coast, spawning occurs in saltwater or brackish water from October to April.