Biology and life history of Green Sturgeon (Acipenser medirostris Ayres, 1854): state of the science

Green Sturgeon (GRS) Acipenser medirostris is one of the most marine-oriented of all sturgeons. It primarily spawns in the Sacramento, Klamath, and Rogue Rivers, yet lives most of its life in estuarine and coastal waters along the West Coast of North America. Spawning is only known to occur in the Rogue, Klamath and Sacramento rivers and optimal temperatures for egg incubation and larval growth are not always maintained in these dammed and highly regulated systems. Genetic analysis and acoustic telemetry have confirmed the presence of two genetically distinct populations; the southern population is listed as “threatened” under the ESA. Adults only enter natal rivers to spawn every 1–4 years. They make extensive coastal migrations in depths <80 m and move between estuaries where they aggregate in summer. The long marine occupancy of GRS potentially exposes them to mortality from various marine activities such as bottom trawl fishing, dredging, and ocean energy projects, but also provides a theoretical reservoir of fish to support viable populations. Critically-needed information for protection of this species includes: accurate annual population size estimates, data on distribution and habitat requirements for larvae and juveniles, and assessment of mortality due to bycatch, poaching and marine mammal predation.