White Sturgeon - Acipenser transmontanus (Richardson)

Page 2-2 Sturgeons TR9

Spawning

Location Upper Sacramento River and Feather River (Stevens and Miller 1970; Moyle 1976); Sacramento River above the Delta (Fry 1973); mostly in Sacramento River between Knights Landing and Colusa (Kohlhorst 1976); eggs were collected in the Sacramento River between Freeport and Rio Vista; major spawning occurs between Freeport and Colusa on the Sacramento River (P. Lutes, Univ. Calif., Davis, personal communication, 1982).
Season Mid-February to late May (Kohlhorst 1976); March through June (Moyle 1976); spring through summer (Dees 1961; Hart 1973;); May and June (Scott and Crossman 1973); eggs were collected in April and May.
Temperature 7.8-17.8 C, peaking at 14.4 C (Kohlhorst 1976); 10-22 C (Moyle 1976); 8.9-16.7 C (Scott and Crossman 1973); ambient temperature at hatchery 12-16 C (Beer 1981); hatchery temperature 12-19 C (P. Lutes, personal communication, 1982); 14-15 C during the peak of catch of Acipenser spp. larvae (Stevens and Miller 1970).
Salinity Freshwater.
Substrates Rocky bottom (Scott and Crossman 1973); over sandy or muddy bottom (S. Doroshov, Univ. of Calif., Davis, personal communication, 1980); hard clay and other various substrates (P. Lutes, personal communication, 1982).
Fecundity 3-4 million (Migdalski 1962); 700,000 (Scott and Crossman 1973); ca. 3 million eggs for a 3-m long 50-year-old female (Dees 1961); 100,000 (Moyle 1976); 3,000-12,000 eggs per kg per batch, and several batches of eggs can be produced by a single female during spawning (P. Lutes, personal communication, 1982).

Eggs

Figure 2-2. Acipenser transmontanus, white sturgeon egg, 4-cell stage, long axis 3.8 mm, short axis 2.6 mm diameter.
Figure 2-3. Acipenser transmontanus, white sturgeon egg, morula, long axis 3.9 mm, short axis 3.3 mm diameter.

Shape Spherical, oval, or slightly irregular; unfertilized eggs ovoid (Beer 1981).
Diameter Unfertilized eggs, short axis 3.3 mm, long axis 3.6 mm; fertilized eggs with jelly coat, short axis 3.8 mm and long axis 4.0 mm (Beer 1981); fertilized eggs, short axis 3.3-3.5 mm and long axis 3.5-4.0 mm.
Yolk Overall, slate gray, animal pole whitish (Beer 1981); brown (Scott and Crossman 1973); dark gray brown with light yellow spots at animal pole.
Oil globule None (Cherr and Clark 1982).
Chorion Clear, thick with 4 layers (Cherr and Clark 1982).
Perivitelline space Prominent at animal pole (Beer 1981); overall, narrow.
Egg mass Assumed to be broadcast singly (P. Lutes, personal communication, 1982).
Adhesiveness Adhesive (Beer 1981); sticky (Scott and Crossman 1973); more substrates attached to vegetable pole.
Buoyancy Demersal.

Larvae

Figure 2-4. Prolarva, 11.6 mm TL.
Figure 2-5. Postlarva, 31 mm TL.

Length at hatching Mean length (TL) 11.0 mm (Beer 1981); 10.0-11.1 mm TL.
Snout to anus length Ca. 68-70 percent of TL of prolarvae at 10.0-11.1 mm TL; ca. 56-59 percent of late prolarvae at 16.7-17.8 mm TL; ca. 53 percent of TL of larvae at 31.0 mm TL.
Yolk sac Ovoid, light pigmentation on ventral surface; dark pigmentation on dorsal and posterior portions (Beer 1981); gray-yellowish, very large, extends from jugular to midabdominal region.
Oil globule None.
Gut Straight.
Size at completion of yolk-sac stage Ca. 15.5-15.8 mm TL (Beer 1981); 17.6-18.5 mm for Acipenser spp. larvae (Stevens and Miller 1970; Kohlhorst 1976).
Total myomeres Newly hatched larvae, 55-60 somites (Beer 1981); ca. 60- to 70- for larvae less than 31.0 mm TL.
Preanal myomeres 37-40.
Postanal myomeres Ca. 25- to 30-.
Last fin to complete development Pelvic.
Pigmentation Newly hatched larvae, scattered melanophores on side of body and head (Beer 1981); prolarvae, scattered melanophores on head, body, lateral portion of yolk sac; eye is a dark pit; late prolarvae, melanophores on head, body, and finfolds except the ventral side of yolk sac and barbels; in postlarvae, pigment covers entire body.
Distribution Initially pelagic, becoming demersal when pectoral fins are fully developed (Beer 1981); channels and deeper waters near bottom in lower reaches of Sacramento and San Joaquin river and the Delta (Stevens and Miller 1970; this study); near bottom in upper Sacramento River (Kohlhorst 1976).

Juveniles

Figure 2-6. Juvenile, 237 mm TL.

Dorsal fin 44-48 (Miller and Lea 1972; Scott and Crossman 1973; Hart 1973; Moyle 1976).
Anal fin 28-31 (Miller and Lea 1972; Hart 1973; Moyle 1976); 28-30 (Scott and Crossman 1973).
Pectoral fin I, 35-39. The pectoral spine consists of at least 3 fused pectoral rays.
Dorsal bony plate 11-14 (Miller and Lea 1972; Scott and Crossman 1973; Hart 1973).
Lateral bony plate 38-48 (Miller and Lea 1972; Scott and Crossman 1973; Hart 1973; Moyle 1976).
Ventral bony plate 9-12 (Miller and Lea 1972; Scott and Crossman 1973; Hart 1973; Moyle 1976).
Mouth Ventral, toothless, wide and tranverse (Scott and Crossman 1973; Hart 1973); on ventral side, a short distance behind the eyes (Fry 1973).
Distribution From San Francisco Bay to Sacramento and San Joaquin rivers and the Delta, most of them concentrating in the upper estuary.

Life History

White sturgeon are found from Ensenada, Mexico, northward to the Gulf of Alaska (Miller and Lea 1972), but they are rare south of Monterey (Fry 1973). In the study area, white sturgeon have been reported in San Francisco Bay (Aplin 1967), San Pablo Bay (Pycha 1956, Ganssle 1966), Carquinez Strait (Messersmith 1966), the lower reaches of the Sacramento and San Joaquin rivers and the Delta (Radtke 1966; Stevens and Miller 1970; Miller 1972), and at the Tracy Pumping Plant (A. Pickard, California Department of Fish and Game, personal communica- tion, 1982). In this study white sturgeon were observed from the vicinity of Red Bluff on the Sacramento River to the intake areas of the Potrero and Hunters Point power plants on San Francisco Bay, but most of the specimens were captured by bottom trawl in Suisun Bay and the Delta. Spawning occurs from February through June (Kohlhorst 1976; Moyle 1976). Suitable water temperatures are 12-15 C (Beer 1981). The major spawning locations are in the Sacramento River between Freeport and Colusa (Kohlhorst 1976; P. Lutes, personal communication, 1982). This species may also use the Feather River as spawning ground (Moyle 1976; Kohlhorst 1976). In this study, white sturgeon eggs were also collected between Rio Vista and Freeport on the Sacramento River in April and May 1978. The water temperatures were 13.0-13.5 C at the bottom at the collecting sites, the depth of the channel was over 10 m, and the river had considerable flow. The eggs are adhesive (Scott and Crossman 1973; Beer 1981). The egg chorion is very thick and has 3-15 micropyles (Cheer and Clark 1982). Sturgeon eggs engage in holoblastic (unequal) cleavages. The details of the embryonic development and early life stages of the white sturgeon are well documented by Beer (1981). Eggs hatch in a little over 4 days at 16 C (Beer 1981) or 8-12 days at 12 C (P. Lutes, personal communication, 1982). The average of the total length of newly hatched larvae is 11.0 mm, with a large yolk sac and small, underdeveloped eyes (Beer 1981). Larvae swim vertically after hatching, and a few days later swim in a horizontal position (Beer 1981). The initial behavior of vertical swimming is estimated to be the result of downstream drifting (Beer 1981). When the pectoral fin is well developed, the sturgeon larvae swim near the bottom (S. Doroshov, personal communication, 1980; Beer 1981). The yolk sac is absorbed after 7-10 days, depending upon water temperature. The majority of the white sturgeon larval population is believed to be in the upper Sacramento River. Stevens and Miller (1970) collected 85 yolk-sac larvae and larvae of Acipenser spp. in the lower reaches of the Sacramento River, the lower San Joaquin River, the Delta, and Suisun Bay during their 1966-1967 sturgeon survey; Kohlhurst (1976) collected 9 eggs and 246 larvae of Acipenser spp. between the mouth of the Feather River and Colusa on the Sacramento River in 1973. The bulk of those collections are believed to be white sturgeon (Stevens and Miller 1970; Kohlhurst 1976). In this study a total of 2 eggs and 11 larvae were collected in the Sacramento River below Freeport and downstream to Suisun Bay. Larvae collected in the field are found to be identical to white sturgeon larvae artificially hatched at the University of California at Davis. Juvenile sturgeon achieve fully developed bony plates at about 40 mm TL. Juvenile sturgeon this size and larger were commonly captured by trawl in Montezuma Slough, in the vicinity of the Contra Costa and Pittsburg power plants, and lower reaches of the Sacramento-San Joaquin rivers. Pycha (1959) reported that young sturgeon are nonmigratory, but Bajkov (1951) and Scott and Crossman (1973)have suggested that juveniles moved upstream in late summer and fall and moved downriver in spring and summer. The primary purpose of the migration may be for feeding. In the Sacramento-San Joaquin estuary, Moyle (1976) described young sturgeon living mostly in the upper reaches of the estuary. Movements of this species in the mid-Columbia River were also studied by Haynes et al. (1978). Tagged white sturgeon from the Sacramento-San Joaquin estuary have been recaptured in Oregon (Chadwick 1959); however, their migra- tion patterns in the Pacific Ocean are not well documented. Juveniles feed on mysid shrimps, amphipods (Schreiber 1962), small clams, polychaetes, and fish eggs (Ganssle 1966). Feeding is concentrated during the night, and then the fish rest during the day (P. Lutes, personal communication, 1982). The growth rate of the larvae and juveniles on various artificial diets (pellets)have been studied by Monaco et al. (1981) and Buddington and Doroshov (1983). Female white sturgeon generally mature at 11-12 years and 1.1-1.5 m FL; the males become mature at smaller sizes than females (Moyle 1976). The most recent study (P. Lutes, personal communication, 1982) found that male sturgeon reach sexual maturity as early as 3-4 years and females at 5 years. White sturgeon do not spawn every year; the input energy for developing ova is apparently very large. The interval between spawning is about 4 years for young females and 9-11 years for older females (Scott and Crossman 1973). White sturgeon support an important sport fishery in the Sacramento-San Joaquin estuary. Angler interest is more concerned with the flesh than the use of eggs for caviar. White sturgeon has the potential to be developed into an excellent aquacultural species through artificial propagation.

References

Aplin 1967; Bajkov 1951; Beer 1981; Buddington and Doroshov 1983; Chadwick 1959; Cherr and Clark 1982; Dees 1961; Fry 1973; Ganssle 1966; Hart 1973; Haynes et al. 1978; Kohlhorst 1976; Messersmith 1966; Migdalski 1962; Miller and Lea 1972; Miller 1972; Monaco et al. 1981; Moyle 1976; Pycha 1956; Schreiber 1962; Scott and Crossman 1973; Stevens and Miller 1970.