FISHERY BULLETIN: VOL. 79, NO. 4 



at temperatures near 22° C (Salekhova 1959; 

 Deuel et al. 1966) and bluefish larvae hatch at 

 about 3.0 mm, the larvae we caught averaging 4.3 

 mm were probably several days old. Apparently 

 bluefish spawned rather steadily over a period of 

 several days somewhere "upstream" from our 

 drogue a few days prior to our experiment, and the 

 larvae drifted continuously through our sampling 

 area. Alternate hypotheses that the larvae did not 

 grow during the experiment, or that larvae >4.3 

 mm avoided the nets, do not seem as tenable. 



Atlantic Whiting 



Atlantic whiting eggs were the most numerous 

 among the species taken, with an overall mean of 

 258 eggs/100 m^ taken during the cruise. All three 

 primary factors (depth, time of day, and days) 

 showed significant differences: egg number de- 



creased with increasing depth (Figure 5), more 

 eggs were taken at night than during the day, and 

 significantly fewer eggs were taken on the second 

 sampling day than on the other two (Table 4). 



The uneven distribution of various develop- 

 mental stages over time allows separation of eggs 

 into distinct groups or batches whose development 

 can be traced from spawning through hatching 

 (Table 5). At each sampling time, eggs from two 

 distinct batches were taken which apparently 

 represented the daily spawning products of adults 

 in the area. Very early stages appeared daily in 

 the afternoons from about 1500 to 1800 h. These 

 eggs continued developing throughout the next 

 day and began hatching at 0300 h the second day 

 after being spawned. After 0900 h, virtually all 

 eggs had hatched. Therefore, the total incubation 

 time at the surface temperature we observed, 

 22.2°-23.2° C (mean = 22.7° C), was about 39 h. 



Table 4. — Transformed i log,,. A' + Dmean num bers of eggs per 100 m 'and F- values from analysis of variance 

 for si.x species offish taken during the vertical distribution study of ichthyoplankton in the Middle Atlantic 

 Bight, July 1974. 



712 



