44^ Memoir Sears Foundation for Marine Research 



Alfred Larsen (Fishery Biologist, Pennsylvania Fish Commission) wrote that speci- 

 mens of Z). cepedianum killed in Presque Isle Bay, Pennsylvania, early in 1953 ranged 

 from 4 to 19 inches. Fish 10—13 inches long weigh about one pound, individuals 

 14—18 inches, 1—3 pounds; the heaviest recorded specimen weighed 3 pounds, 7 

 ounces (Trautman, 126: 182). 



Development and Growth. The prolarvae perform characteristic alternate sinking 

 and rising movements for the first two days after hatching. The larvae are characterized 

 by a long gut, 1.5—2.0 times the total length of the fish, by the retarded development 

 of the single dorsal fin, and by the elongated anal fin with 22 rudimentary rays at 

 17.5 mm and 30-34 at 19—22 mm TL. 



In contrast to the deep-bodied and strongly compressed adults, the very young are 

 slender, cyprinid-like, and nearly cylindrical; the maxillaries have a few teeth on the 

 lower edge which are lost with age, and unlike the adults with a highly specialized 

 digestive tract, the young have an almost straight intestine and no pyloric caeca. 

 By the end of the first summer of life the young possess the specializations of 

 the adults. 



At the end of the first summer, an average total length of about 4 inches is at- 

 tained in Indiana and Ohio, 4.5 inches in the Chesapeake Bay region, and 5.0 inches 

 in Tennessee and Oklahoma. The sizes in two Indiana ponds, after the first year, have 

 been reported as follows: second summer, 7—9 inches, average 7.6; third summer, 

 9— 1 1 inches, average 9.5; fourth summer, 9—12 inches, average 10.5; fifth summer, 

 10—13 inches, average 11.3; and sixth summer, 11— 15 inches, average 12.8. Al- 

 though they may live as long as 10 years, the life span is usually not more than seven 

 years. In Lake Erie about 75 "/o of the annual growth of the Gizzard Shad takes place 

 during the summer; in winter they grow little if at all and lose considerable weight. 



Maturity typically occurs in the second or third year of life, at about 7—1 1 in- 

 ches, but Vladykov (J27: "^^^ has reported a mature female that was only 6 inches 

 (151 mm) TL. 



Spawning. Gizzard Shad are known to spawn only in fresh water, from late winter 

 (mid-March) through most of the summer (at least to August 20) in sloughs, ponds, 

 lakes, and large rivers. Spawning generally occurs on a rising temperature, usually be- 

 tween about 50° and 70° F. The creamy-yellow eggs, demersal and adhesive, are about 

 0.75 mm in diameter when fertilized and fixed. The embryos hatch after 95 hours of 

 incubation at 62° F, or after about 36 hours at 80° F. 



Precocious females appear to have few eggs. Those belonging to age-group 11 

 have the most, averaging about 380,000 eggs in five females 291 mm long; egg pro- 

 duction then declines with successively older groups. 



Food. Gizzard Shad are essentially filter feeders. Except for a few weeks after 

 hatching, those in fresh water are almost entirely herbivorous, feeding heavily on 

 microscopic plants, phytoplankton, and algae. After they reach a length of about 20— 

 25 mm TL, the diet is remarkably alike at various sizes. The food habits in salt and 

 brackish water have not been studied. 



