The average number of eggs produced per 

 female each season often has been given as 

 about 25,000 or 30,000 (Worth, 1898). This 

 figure referred to the number of eggs that 

 could be taken by spawn-takers for hatchery 

 purposes at any time amd not the total number 

 of eggs a shad could produce in a season 

 (Lehman, 1953). Because only a part of the 

 eggs are ripe and ready for spawning at one 

 time, these earlier records represented but 

 a fraction of the number of ova a female could 

 produce naturally during a spawning season. 

 The number per female depends upon the size 

 and age of the fish as well as the stream in 

 which spawning occurs. The fecundity in the 

 St. Johns River was greater than in the Hudson 

 River, for example, although females from 

 the latter river were older and larger than 

 those from Florida. The estimated egg pro- 

 duction of shad collected in seven rivers along 

 the Atlantic coast of the United States is given 

 in table 3. 



In general, shad eggs hatch in 4 to 6 days at 

 about 15° to 18° C. The stages of early de- 

 velopment of shad eggs were illustrated by 

 Leach (1925). Time required for hatching 

 was measured by various workers who reared 

 eggs under artificial conditions. The hatching 

 time ramged from 3 to 5 days at water tem- 

 peratures from 20° to 23.4° C, to 17 days at 

 12.2° C. Eggs kept for 3 days at 9° C. died, 

 but a few hatched into vigorous larvae when 

 put in 24° C. water (Ryder, 1885). A tempera- 

 ture of 7° C. practically stopped development 

 of the eggs and caused abnormalities to appear, 

 22° C. caused considerable abnormality, and 

 27° C. was definitely unsuitable (Leim, 1924). 



Table 3. --Estimated egg production of shad collected in 

 seven rivers, Atlantic coast of the United States^ 



Data for: Hudson, 1951-- Lehman (1953); Potomac, 

 1952--Davis (1957); York, 1959--Nichols and Massmann 

 (1963); Neuse, I95>-Davis (1957); Edisto, 1955--Davls 

 (1957); Ogeechee, 1954— Davis (1957); St. Johns, 195>- 

 Walburg (1960a). 



The usual period of incubation was 6 to 1 2 days 

 at 12° to 19° C., and these temperatures were 

 near the minimum and maximum for success- 

 ful incubation of the eggs (Leach, I 925). Water 

 temperature appears to be the governing fac- 

 tor during incubation, but other circumstances 

 not well understood may also have an influence. 

 Continuous dark, cloudy weather appears to 

 retard development and strong light to ac- 

 celerate it. 



The appearance of the newly hatched larvae 

 and the stages of development were described 

 by Leach (1925), Leim (1924), and Worth ( 1 898). 

 The larvae are about 0.3 to 0.4 in. long at 

 hatching. The body is slender, surrounded by 

 a wide primitive fin-fold. In 4 to 7 days, the 

 yolk sac is absorbed. Growth is rapid and 

 transformation to the final form, at a length 

 of about 1 in., occurs about 4 to 5 wk. (weeks) 

 after hatching. The young swim vigorously by 

 rapid and continuous vibrations of the tail from 

 the moment they leave the eggs. Minute coni- 

 cal teeth appear in the lower jaw and in the 

 pharynx about the second or third day after 

 hatching. At 3 mo. (months), the jaws are 

 armed with small, slightly curved teeth. Long, 

 slender gill rakers develop and increase in 

 number with age; shad 1.5 to 3.5 in. long have 

 21 to 31 on the lower limb of the first arch, 

 and fish 4 to 5 in. long have 34 to 41. 



FOOD AND FEEDING HABITS 



Adult shad are primarily plankton feeders, 

 characteristically they swim with their mouths 

 open and their gill covers extended, straining 

 the water for food. In the sea, they eat mysids 

 and copepods (Leim, 1924; Willey, 1923). The 

 mysids suggest that part of their life, perhaps 

 much of it, is spent near the bottom of the sea. 

 In the rivers, the young feed on ostracods, 

 isopods, decapod larvae, insects, mollusks, 

 algae, and fish eggs (Hildebrand and Schroeder, 

 1928). 



Little food, if any, has been found in the 

 stomachs of adults taken infresh water (Leidy, 

 1868; Clift, 1874; McDonald, 1884; Smith, 

 1896; Moss, 1946; Nichols, 1959a), probably 

 because the available food is too small to be 

 collected. In salt water, adults feed to a large 

 extent on plamkters 0.3 to 1 in. long. In fresh 

 water, the largest plankton in abundance are 

 copepods, which rarely exceed 0.1 in. Adirect 

 relation exists between the fineness of the 

 sieve formed by the gill rakers aind the mini- 

 mum size of the organisms that could be re- 

 tained. 



In some rivers, shad are taken on spawning 

 grounds by artificial lures, but the absence of 

 food in their stomachs suggests that they attack 

 baits in defense of the grounds rather than as 

 food. Stomachs of several adults that were 

 examined had only green algae and fine de- 

 tritus. 



