American Shad - Alosa sapidissima (Wilson)

Page 3-1 Herrings TR9

Spawning

Location Main channel of Sacramento River, up to Red Bluff (Skinner 1962; Stevens 1972). Some individuals reach Keswick Dam on the Sacramento River (R. E. Painter, California Department of Fish and Game, personal communication, 1979), the lower reaches of San Joaquin River and its tributaries, and the Mokelumne and Stanislaus rivers (Skinner 1962; Moyle 1976); a landlocked population has been found in the upper San Joaquin River in Millerton Lake.
Season Ripe females observed from February through June (Ganssle 1966); May through June (Erkkila et al. 1950); March through July (Skinner 1962; Stevens 1972); April through July, peaking in June and July in the Sacramento-San Joaquin river system; and as late as September in the upper San Joaquin River at Millerton Lake.
Temperature Water temperatures of 8-26 C (Walburg and Nichols 1967); maximum 15-20 C (Skinner 1962; Stevens 1972); ca. 12-17 C in upper San Joaquin River at Millerton Lake.
Salinity Freshwater, possibly brackish water (Leim 1924).
Substrates None. Egg survival is apparently higher when deposited over sandy and gravel areas (R. E. Painter, personal communication, 1979).
Fecundity 155,000-410,000 (Reintjes and Hettler 1967); 2,000-150,000 (Scott and Crossman 1973); 30,000-300,000 (Moyle 1976).

Eggs

Figure 3-1. Egg, morula, 3.5 mm diameter.
Figure 3-2. Egg, early embryo, 3.2 mm diameter.
Figure 3-3. Egg, late embryo, 3.5 mm diameter.

Shape Spherical (Ryder 1887).
Diameter 2.5-3.8 mm (Milner 1874; March and Jacobson 1976); 2.5-4.4 mm.
Yolk Pale amber to pink (Mansueti 1955), granular yolk (Bigelow and Welsh 1925; Lippson and Moran 1974); pale yellow to yellow, with coarse, granular yolk.
Oil globule No oil globule (Lippson and Moran 1974; Wang and Kernehan 1979).
Chorion Transparent (Mansueti 1955); transparent, smooth, and very thin.
Perivitelline space Very wide, ca. 1/2 egg radius (Bigelow and Welsh 1925).
Egg mass Broadcast singly.
Adhesiveness Initially adhesive (Chittenden 1969); slightly adhesive (Wang and Kernehan 1979); later, non-adhesive (Hildebrand 1963).
Buoyancy Demersal (Manuseti 1955; Hildebrand 1963); semi-demersal or slightly heavier than fresh water, suspended by water current (Wang and Kernehan 1979).

Larvae

Figure 3-4. Prolarva, 10 mm TL.
Figure 3-5. Postlarva, 12.2 mm TL.
Figure 3-6. Postlarva, 16.5 mm TL.

Length at hatching 5.7-10 mm TL (Marcy and Jacobson 1976); 7.0-10.0 mm TL (Moran and Lippson 1974); ca. 6.5 mm TL (Wang and Kernehan 1979); ca. 6.5-10.0 mm TL.
Snout to anus length Ca. 80-83 percent of TL of prolarvae; ca. 73- 80 percent of TL of postlarvae.
Yolk sac Spherical, head detached from yolk (Ryder 1887); spherical to oval, in thoracic region.
Oil globule None.
Gut Straight, elongated, segmented.
Air bladder Apparent in postlarval stage; shallow, located midway between pectorals and anus.
Teeth None on jaw, one row develops in the middle of tongue in late postlarvae.
Size at completion of yolk-sac stage 9-12 mm TL (Lippson and Moran 1974); ca. 10-12 mm TL.
Total myomeres 55-57 (Lippson and Moran 1974); 53-58.
Preanal myomeres 41-47 (Lippson and Moran 1974); 41-49.
Postanal myomeres 10-16 (Lippson and Moran 1974); 8-16.
Last fin(s) to complete development Pectoral.
Pigmentation Single row of dashed melanophores along jugular to thoracic region; stellate or dotted melanophores in midventral and dorsal gut region; scattered melanophores also found along postanal and caudal regions.
Distribution Pelagic (Marcy and Jacobson 1976); newly hatched larvae gradually move to the sea (Moyle 1976); pelagic in lower reaches of Sacramento River, Delta, Mokelumne River, Suisun Bay, and upper San Joaquin River at Millerton Lake.

Juveniles

Figure 3-7. Juvenile, 83 mm TL.

Dorsal fin 15-19 (Miller and Lea 1972; Moyle 1976); 17-19 (Hildebrand and Schroeder 1928); 18-19 (R. L. Lavenberg, Los Angeles County Museum of Natural History, personal communication, 1980).
Anal fin 19-23 (Miller and Lea 1972; Moyle 1976); 18-25 (Hill 1959); 19-21 (R. L. Lavenberg, personal communication, 1980).
Pectoral fin 13-18 (Carscadden and Leggett 1975; Hill 1959).
Mouth Terminal, upper jaw as long as lower jaw (Scott and Crossman 1973; Wang 1969); maxillary reaches midway of eye.
Vertebrae 55-58 for West Coast population (Miller and Lea 1972); 51-60 (Leim 1924; Hill 1959).
Distribution Inshore as well as open water. Some remain in Delta for several months after hatching (Moyle 1976); some juveniles remain in the estuary several months after hatching, and move to the sea in fall and early winter.

Life History

American shad are anadromous and native to the Atlantic Coast. They were first introduced into the Sacramento River in 1871 and planted there for the next 10 years (Skinner 1962). Once established, American shad spread quickly along the West Coast. Their current distribution is from Todos Santos Bay, Baja California, to Alaska and Kamchatka, USSR (Miller and Lea 1972; Hart 1973). In this study, American shad were found in the Sacramento River system, the Delta, and the San Joaquin River system, and a successfully reproducing population was studied in Millerton Lake (C. Toole and M. A. Koeneke, Ecological Analysts, Inc.; D. Mitchell, California Department of Fish and Game; T. Lambert, Pacific Gas and Electric Company, personal communication, 1980). Prior to spawning, shad begin to enter the estuary as early as fall (Stevens 1972); the spawning runs occur in March. Potential spawners were captured in gill nets near Montezuma Slough and the vicinity of the Contra Costa and Pittsburg power plants. Actual spawning takes place about 2-4 weeks later in the main river channels, from April through June (Stevens 1972). Major spawning grounds in the estuary are above Rio Vista on the Sacramento River and its major tributaries, the Feather and American rivers. In the San Joaquin River system the lower reaches of the San Joaquin River have not been used extensively for spawning (Hutton 1940), because of poor water quality, sluggish flow, and reverse flow of the river. Minor spawning was observed in the mouth of the Mokelumne River during this study. Above the estuary, spawning of American shad was observed in the San Joaquin River at Millerton Lake from May through August. Spawning activities were observed from midnight to the early morning hours, between the river's influx into Millerton Lake and the 'plunge point', and were concentrated near shore and at the surface. Eggs are semi-demersal (Mansueti 1958): a moderate current (about 1 meter per second or less)will keep the eggs floating. Eggs hatch in 17 days at 12 C (Ryder 1887) and in 8-12 days at 11-15 C (Scott and Crossman 1973). Newly hatched larvae are pelagic and most abundant at the surface of the water (Marcy and Jacobson 1976). Some larvae moved downstream from the spawning ground soon after hatching, since larvae were collected in the lower reaches of the Sacramento River and Suisun Bay, but the majority of the larvae remain in the river and the Delta for several months (Stevens 1972). In this study, the downstream migration of large juveniles (about 70 mm TL)was reflected in the impingement samples collected at the Contra Costa and Pittsburg power plants from October through January 1978-1979. Some small juveniles apparently move directly through the estuary in the summer months (Stevens 1972; Moyle 1976). Juvenile shad feed on copepods, related crusta- ceans, and insect larvae while in fresh water (Scott and Crossman 1973) and on mysid shrimps and amphipods when they are in the estuary (Stevens 1966). American shad spend from three to five years in the ocean before they return to the river to spawn (Leim 1924; Moyle 1976). In Millerton Lake, individuals reach maturity in two or three years. In the Sacramento-San Joaquin estuary a commercial fishery for American shad had developed by 1879, but commercial fishing was banned by the State of California in 1957 (Moyle 1976). A seasonal sport fishery has developed, especially on the American and Feather rivers. The life history of the Atlantic Coast American shad was investigated exten- sively by Leim (1924) and Leggett (1973). On the West Coast, substantial amounts of information on the early life history of the American shad in the Sacramento-San Joaquin estuary have been compiled by the California Department of Fish and Game (CDFSG) as part of the Delta Fish and Wildlife Protection Study (Chadwick 1958; Skinner 1962; Stevens 1966 and 1972). However, the life history of immature shad in the Pacific Ocean is still unclear. Moyle (1976) has suggested that the wide distribution of shad along the West Coast may indicate that extensive migrations take place similar to those of the native Atlantic Ocean population. R. E. Painter (CDF6G, personal communication, 1979) has further suggested that some shad may remain in the Sacramento-San Joaquin estuary throughout their life. American shad in Millerton Lake are landlocked, and thus cannot make the ocean-to-river spawning run. Instead, a potadromous migration has been noted between the San Joaquin River and Millerton Lake. The shad population is generally found in the lake, but during the spawning run they move up to the narrow canyon portion of the river above (or east of) the lake, where there is a good flow from Kerkhoff Dam and the Pacific Gas and Electric (PGandE) hydroelectric power house. Water flow in this area is important to spawning success, just as flow was important in streams above the estuary. All life stages have been collected from the only known landlocked American shad population in North America.

References

Bigelow and Welsh 1925; Carscadden and Leggett 1975; Chadwick 1958; Chittenden 1969; Clemens and Wilby 1961; Erkkila et al. 1950; Ganssle 1966; Hart 1973; Hildebrand 1963; Hildebrand and Schroeder 1928; Hill 1959; Hutton 1940; Leggett 1973; Leim 1924; Lippson and Moran 1974; Mansueti 1955; Marcy and Jacobson 1976; Miller and Lea 1972; Moyle 1976; Reintjes and Hettler 1967; Ryder 1887; Scott and Crossman 1973; Skinner 1962; Stevens 1972; Walburg and Nichols 1967; Wang and Kernehan 1979.