KENDALL and NAPLIN: DIEL-DEPTH DISTRIBUTION OF ICHTHYOPLANKTON 



Table 12. — Timetable of development of snake eel eggs based 

 on collections made during the vertical distribution study of 

 ichthyoplankton in the Middle Atlantic Bight, July 1974. 



Sampling times (EST) 



Figure 12. — Number of snake eel eggs during the vertical 

 distribution study of ichthyoplainkton in the Middle Atlantic 

 Bight, July 1974, plotted by time of day. 



than the original sampling site. Because more 

 eggs were taken each day, it was not possible to 

 estimate the total size of any one batch. 



A rough estimate of egg mortality within indi- 



vidual batches based on numbers of eggs at 

 different times during their development and at 

 corresponding points of the tidal cycle is approxi- 

 mately 0.5 to 0.6% /h, totaling 48 to 57.6% over the 

 96 h development time. 



Applying Stokes' law to snake eel eggs results in 

 an overall time of only 2.1 h required for eggs to 

 rise from the bottom to the surface. The rapid 

 rising velocity of the eggs is a result of their large 

 diameter (X = 2.60 mm). Slightly more time 

 would be required for eggs to rise to the surface if 

 their density is somewhat greater immediately 

 after spawning. In any case, if Stokes' law still 

 holds for eggs of this size, it is inadequate for 

 determining the depth of spawning for snake eel 

 although from behavior of the adults it is likely to 

 occur on or near the bottom. 



Few snake eel larvae were caught during the 

 cruise. 



Frigate Mackerel 



No frigate mackerel eggs were taken during the 

 cruise. Due to nomenclatural confusion, the spe- 

 cies of Auxis larvae in our collections cannot be 

 determined. However, only one type of larva 

 appears to be represented, and an overall mean of 

 54 larvae/100 m^ was caught during the cruise. 

 There were highly significant differences in days, 

 diel, and depth factors (Table 2), indicating that 

 we were not sampling a uniformly distributed 

 population during the experiments. The larvae 

 were more abundant at night than during the day, 

 and more were caught on the second day than on 

 the first or third. Larvae were most abundant 

 overall in the 4 m tow, and more were taken at the 

 surface during day than at night. Catches at 15 

 and 30 m were so small in both day and night tows 

 that contamination of the nets in shallower water 

 as they passed through the water column could 

 account for them (Figure 3). In the second experi- 

 ment, the 2 m tow caught most fish at 1800 h, 

 while the 6 m tow caught more at other times. 

 Thus Auxis larvae were mostly in the upper 6 m of 

 the water column above the thermocline and were 

 found closer to the surface during the evening. 



Smallmouth Flounder 



Smallmouth flounder eggs have not been de- 

 scribed. Based on the similarity of the early 

 larvae, however, it is likely that they closely 

 resemble Gulf Stream flounder eggs. In view of 



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