as numerous as the females. The representation 

 of the sexes was nearly equal in the open lake at 

 this time. Spawning was most active in the 

 evening and early night in 1954 and in the night in 

 1955. 



Spawning occurred from the first quarter of 

 June through the first quarter of July; peak 

 spawning was in the second quarter of June. 

 The precociously mature I-group fish spawn in 

 late July or later. 



The II-group shad produce the greatest number 

 of eggs — about 379,000. In decreasing order are: 

 Ill-group, 345,000; IV-group, 309,000; Vl-group, 

 215,000; and the precocious fishes of the I-group, 

 59,000. 



On the basis of eggs per gram of fish, relative 

 fecundity triples from age group I to II and then 

 declines to age group VI, which has about the 

 same value as the I group. 



The eggs of the shad hatch in IK to 7 days, 

 depending on the temperature. The movements 

 of young fry are described. 



The gut of a small larva is a nearly straight 

 tube. Sometime after the 10th day the gut 

 begins to fold. The convolutions become more 

 and more complex with increasing size. The 

 gizzard becomes evident in the 22.5-mm. stage. 

 The liver is a diffuse organ, apparently mixed with 

 the pancreas; no pancreas was found. 



The intestine lacks villi but has longitudinal 

 folds and transverse lamellae which increase the 

 absorptive surface and may help move the food 

 along during peristalsis. 



The presence of sand in the gut when ingested 

 food is plentiful and its absence in winter, when 

 the gut is empty, suggest that it may be taken as 

 an aid in grinding the food in the gizzard. 



Food was frequently present in the pharyngeal 

 pockets of large gizzard shad whose gizzard and 

 intestine were packed with food. The presence 

 here of long strands of filamentous algae, and 

 Cladocera and Copepoda with their full comple- 

 ment of appendages, repudiates statements that 

 they are regurgitated into the pockets. In the 

 gizzard, these items were always in some stage 

 of dismemberment. 



Tests were positive for the following digestive 

 enzymes: pepsin, trypsin, amylase, lipase, and 

 rennin. Amylase was found in all areas of the 

 tract. 



The earliest food of gizzard shad appears to be 



Protozoa. At a length of about 20 mm., shad 

 feed almost wholly on the smaller of the zoo- 

 plankters. After the 30-mm. stage, the digestive 

 tract contains greater and greater percentages of 

 phytoplankters. "Filter feeders" best describes 

 the habits of adults. Zooplankters or phyto- 

 plankters may predominate in the gut according 

 to their abundance in the water in which the fish 

 are feeding. By the time the food reaches the 

 intestine it has been macerated and partially 

 digested so that it resembles mud. This fact 

 may explain the frequent statement that shad eat 

 mud. 



ACKNOWLEDGMENTS 



I have had the assistance of the staff members 

 and the students of the Franz Theodore Stone 

 Institute of Hydrobiology, Ohio State University. 

 Thomas H. Langlois suggested an investigation of 

 the gizzard shad in western Lake Erie, made this 

 investigation possible by arranging an Ohio State 

 University Senior Conservation Fellowship, and 

 gave freely of his time in discussing the numerous 

 problems that arose during the study. N. Wilson 

 Britt, Milton B. Trautman, Edward C. Kinney, 

 David Stansbery, and Paul Webster aided in 

 collecting gizzard shad and made helpful sugges- 

 tions. Jacob Verduin assisted in graphical repre- 

 sentations and mathematical interpretations. 

 Ernest Miller, Superintendent of the Ohio State 

 Fish Hatchery at Put-in-Bay, made facilities 

 available for hatching gizzard shad eggs. James 

 W. Moffett, Director of the Biological Laboratory, 

 Bureau of Commercial Fisheries, Ann Arbor, 

 Mich., obtained financial assistance and offered 

 many helpful suggestions. The commercial fisher- 

 men — particularly those island fishermen affiliated 

 with Lay Brothers of Sandusky — brought, in 

 samples of shad from their nets. Staff members 

 of District No. 1 , Ohio Natural Resources Depart- 

 ment, made equipment available. The Ohio 

 Division of Wildlife, through the Onio State 

 University, gave financial assistance. Ralph Hile, 

 Bureau of Commercial Fisheries, Ann Arbor, 

 Mich., read the original manuscript and offered 

 suggestions for its improvement. 



LITERATURE CITED 



Forbes, S. A. 



1SSS. Studies of the food of fresh-water fishes. 

 Bulletin Illinois State Laboratory of Natural 

 History, vol. 2, pp. 433-473. 



424 



U.S. FISH AND WILDLIFE SERVICE 



