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

Abstract

Summary 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.

A feeding experiment using captive green sturgeon (Acipenser medirostris Ayres, 1854): Testing non-invasive methods to assess condition and growth

“…Condition factor ( K ) of wild green sturgeon reported in the literature is generally higher than we observed for this captive group; however, there is quite a bit of variability among populations and times of year (Moser et al., ; Van Eenennaam et al., ). Green sturgeon ( n = 6) captured in Willapa Bay in July 2011 had mean K = 0.49 (±0.04).…”

“…This was slightly higher than the mean K for experimental fish held at the lowest ration ( K = 0.46 ± 0.06), but similar to K of fish fed the highest ration ( K = 0.50 ± 0.03). Wild Willapa Bay fish were likely from the southern DPS, which may exhibit a different body form than the northern DPS fish we used (Moser et al., ; Schreier, Langness, Israel, & Van Dyke, ). In addition, the fish in our experiments were forced to reside in freshwater for their entire life.…”

Temperature, discharge and development shape the larval diets of threatened green sturgeon in a highly managed section of the Sacramento River

“…We define larvae as those individuals which have not yet taken on juvenile phenotypes (Balon, 1975), measured by scute count. The composition of larval diets has been identified as a priority area of research in recent management reports on green sturgeon (Heublein et al, 2017;Moser et al, 2016). Studies on other sturgeon species, such as shortnose sturgeon (Acipenser brevirostrum) and white sturgeon (Acipenser transmontanous), have found that larvae consume primarily drifting prey (Buckley & Kynard, 1981;Kynard, Parker, Kynard, & Horgan, 2014;Kynard et al, 2016), while juveniles shift to benthic prey (Radtke, 1966).…”

Energetic requirements of green sturgeon (Acipenser medirostris) feeding on burrowing shrimp (Neotrypaea californiensis) in estuaries: importance of temperature, reproductive investment, and residence time

“…Standing stock of 2.33-7.56 · 10 6 kg would produce enough burrowing shrimp to support 14,800-48,000 age-20 green sturgeon. Our estimate of estuarine capacity likely meets or exceeds the current population size of the southern DPS of green sturgeon using Willapa Bay each year (Moser et al 2016). This analysis provides a preliminary reference point of broad confidence to guide near-term management and should be used with caution.…”