Green Sturgeon

The green sturgeon (Acipenser medirostris) is the most marine-adapted of the North American sturgeon species, ranging along the Pacific coast from Mexico north to the Bering Sea, with a related population along the Asian Pacific coast. A member of the family Acipenseridae, it spends the majority of its life in open coastal and continental shelf waters, entering large rivers such as the Klamath, Rogue, and Sacramento only to spawn. Portions of its range are listed as threatened under U.S. federal law, reflecting concerns over dam-related habitat loss on key spawning rivers.

Green sturgeon show several features that set them apart from other sturgeons:

• Olive-green body coloration with a pale stripe running along each side
• Long, narrow, pointed snout
• Four barbels positioned closer to the snout tip than the mouth
• Fewer, smoother bony scutes compared to white sturgeon
• Slender build relative to the bulkier white sturgeon Its greenish tone, pale lateral stripe, and narrower snout distinguish it from the grayer, broader-snouted white sturgeon sharing parts of its range. Coloration can deepen toward olive-black in individuals from cooler northern waters.

Green sturgeon spend most of their lives in coastal marine waters and along the continental shelf of the North Pacific, undertaking extensive oceanic movements between estuaries and offshore feeding grounds. They enter large rivers, including the Klamath, Rogue, Eel, and Sacramento, only to spawn, favoring deep pools with cool, well-oxygenated water and coarse substrate. Compared to other sturgeons, they tolerate open ocean conditions far more readily, spending years at sea between spawning events. Coastal bays and estuaries such as San Francisco Bay serve as important seasonal aggregation sites outside the spawning season.

Green sturgeon undertake extensive oceanic migrations, sometimes covering thousands of kilometers between coastal feeding areas and river-mouth estuaries used as staging grounds. They forage opportunistically along the seafloor for invertebrates and small fish, using sensitive barbels to detect prey. Spawning is infrequent, typically occurring only once every three to nine years per individual, with adults ascending rivers in spring and summer before returning to the ocean. This life history makes populations especially sensitive to river barriers and habitat degradation at spawning sites.