Green Sturgeon - Acipenser medirostris (Ayres)

Page 2-1 Sturgeons TR9

Spawning

Location In upper Klamath River (Fry 1973); just above Orleans on the Klamath River (Moyle 1976); upper Sacramento River (Fry 1973); tributaries to the Sacramento River such as the Feather, Yuba, and American rivers.
Season Middle of June to middle of July in the Datta River, USSR (Scott and Crossman 1973); spring and early summer in the Klamath River (Moyle 1976). Similar season to white sturgeon and may be slightly delayed in cold water streams (S. Doroshov, Univ. Calif., Davis, personal communication, 1982).

Juveniles

Figure 2-1. Acipenser medirgstris, green sturgeon juvenile, 275 mm TL.

Dorsal fin 33-42 (Miller and Lea 1972); 33-35 (Scott and Crossman); 33-36 (Hart 1973; Moyle 1976).
Anal fin 22-29 (Miller and Lea 1972); 22-28 (Scott and Crossman 1973; Hart 1973; Moyle 1976).
Pectoral fin I, 31-34; pectoral spine is fused by 2-3 pectoral rays.
Dorsal bony plate 8-11 (Miller and Lea 1972; Moyle 1976); 9-11 (Scott and Crossman 1973); 7-11 (Hart 1973).
Lateral bony plate 23-30 (Miller and Lea 1972; Scott and Crossman 1973; Hart 1973; Fry 1973; Moyle 1976).
Ventral bony plate 7-10 (Miller and Lea 1972; Scott and Crossman 1973; Moyle 1976); 7-11 (Hart 1973).
Mouth Ventral, directed down, transverse (Hart 1973); toothless, protrusible, and sucker-like, on the ventral side beneath the eyes (Fry 1973).
Distribution The Delta, Suisun Bay, San Pablo Bay, and San Francisco Bay.

Life History

The green sturgeon has been found from Ensenada, Mexico, to the Bering Sea and Japan (Miller and Lea 1972). They are also found along the North Pacific coasts of Korea, China, and the Amur River of the USSR (Berg 1948). In the study area, green sturgeon were reported in San Francisco Bay (Aplin 1967), San Pablo Bay (Ganssle 1966; Miller 1972), and the lower San Joaquin River and the Delta (Radtke 1966). They were also recorded in Tomales Bay (Bane and Bane 1971) and Bodega Bay (Standing et al. 1975). Green sturgeon, all juveniles, were collected in San Francisco Bay up to the lower reaches of the Sacramento- San Joaquin rivers and the Delta, including the intakes of the Tracy Pumping Station (A. Pickard, California Department of Fish and Game, personal communication, 1982). At present biologists are unsure of the spawning locations of the green sturgeon. Spawning has been reported at 1.5 km above Orleans on the Klamath River (Moyle 1976) and in the upper inland streams of large rivers such as the Sacramento and Klamath rivers (Fry 1973; S. Doroshov, personal communication 1982). The early developmental biology of this species is essentially unreported. Stevens and Miller (1970), who collected a total of 85 yolk-sac larvae and larvae of Acipenser spp. in the lower reaches of the Sacramento and San Joaquin rivers and Suisun Bay, believed the majority of them to be white sturgeon (L. Miller, California Department of Fish and Game, personal communication, 1982). The smallest of the fish identified as green sturgeon were 20-22 cm FL and were captured by gill net and trawl during 1963-1964 by Radtke (1966). The origin of those juveniles was probably the upper Sacramento River (Fry 1973). The diet of juvenile sturgeon consists mostly of amphipods and mysid shrimps in the Delta (Radtke 1966). Little is known about the age and growth of the green sturgeon. The 138 green sturgeon collected in the Sacramento and San Joaquin rivers and Suisun Bay by Radtke ranged from 20 to 58 cm FL, with two apparent size groups in this range. The green sturgeon's flesh is darker than that of the white sturgeon, and it is considered to be of an inferior eating quality. Some sportfishing for green sturgeon is observed in the Klamath River (Fry 1973).

References

Aplin 1967; Bane and Bane 1971; Berg 1948; Fry 1973; Ganssle 1966; Standing et al. 1975; Hart 1973; Miller 1972; Miller and Lea 1972; Moyle 1976; Radtke 1966; Scott and Crossman 1973; Stevens and Miller 1970.