Table 16. — Sex ratios for gizzard shad caught in the shallow waters of Fishery Bay and in the deeper waters of Lake Erie 



for June and for all other months combined in 1952-55 



on the spawning site; in the deeper waters the 

 percentage of males is greater between spawnings 

 than during the spawning season. 



The sex ratios of mature shad captured in 

 Fishery Bay and in the deeper waters of the lake 

 within 7- or 8-day periods in May, June and July 

 of 1954 and 1955 (table 17) indicate that the 

 percentage of males in the population of shad 

 captured in the bay increased during early and 

 mid-June and reached a high in the third quarter; 

 the females were relatively most numerous in the 

 last quarter. Males were scarce in deeper water 

 in June (exception, June 9-15), and with the 

 exception of one sample (July 1 6-23) , this scarcity 

 continued through July. Data are few on the 

 sex ratio in Fishery Bay in July; females pre- 

 dominated strongly in the single sample. The 

 generally small percentages of males in all July 

 samples account for the low monthly percentage 

 for July, mentioned in the earlier description of 

 table 15. 



DEVELOPMENT AND MATURATION OF THE EGG 



For convenience in description, the development 

 of the egg has been divided arbitrarily into six 

 stages (fig. 11). The following descriptions were 

 made from ovary sections fixed in Bouin's solution 

 and stained with hematoxylin and eosin. 



Stage 1. — The young oocyte is 10 to 20 n in 

 diameter and has a large nucleus with a centrally 

 located nucleolus. The nucleolus and nuclear 

 membrane stain darkly with the hematoxylin, 

 whde the cytoplasm and the nucleoplasm stain 

 with eosin. 



Stage 2. — The oocyte, now 20 to 70 p in diameter, 

 has not yet acquired its follicle-cell envelopment. 

 The nucleus has grown at a faster rate than the 



Table 17. — Sex ratios for mature gizzard shad captured in 

 the shalloiv waters of Fishery Bay and the deeper waters of 

 Lake Erie during May, June, and July, 1954 and 1955 



cytoplasm. This cytoplasm is now accepting 

 some of the hematoxylin, while the ground sub- 

 stance of the nucleus still stains with eosin. The 

 nucleolus, if present, is lost among the darkly 

 staining chromatin materials which are somewhat 

 scattered throughout the nucleus. 



Stage 3. — This stage includes oocytes which 

 range from 0.07 mm. to 0.15 mm. in diameter. 

 The nucleus and cytoplasm appear to have grown 

 at the same rate from the last stage. The cyto- 

 plasm now stains darkly with hematoxylin; the 

 nuclear sap stains pink. The dark- staining chro- 

 matin material is more plentiful and is arranged 

 circumferentially along the periphery of the 

 nucleus. Flat follicle cells are arranged as a 

 single-celled layer around the oocyte. 



Stage 4- — The follicle is mostly in the 0.15-to 

 0.30-mm. size range in this stage. The dark- 

 staining cytoplasm is growing more rapidly than 

 the nucleus. As the follicle approaches the 0.30- 



GIZZARD SHAD IN WESTERN LAKE ERIE 



409 



