5. Intramonthly variations in abundance of 

 larvae are related to moon phase. Most spawning 

 occurred during the waning moon (15-29 days 

 after new moon). 



6. Survival rates are nearly constant through- 

 out the postnauplial larval life, averaging about 

 80.4 percent per day. Differences in the apparent 

 rate of survival at different sampling stations are 

 caused by immigration and emigration of larvae 

 between stations, by losses of larvae from stations 

 in the path of currents which move into the 

 Florida Straits, or by a combination of both. 



7. Recoveries of seabed drifters confirm pre- 

 vious observations that currents in the sampling 

 area are small (probably less than 1.8 km. per 

 day), and that the movement of water is primarily 

 toward the south and west. It is unlikely that 

 larvae disperse directly toward the Everglades in 

 the east. Available evidence indicates that dis- 

 persal may be effected primarily by the current 

 which leaves the Tortugas area through Rebecca 

 Channel, and enters the Florida Current in the 

 Florida Straits. Entry into the Florida Current 

 would result in rapid transport to the area adjacent 

 to Florida Bay. If this migration route is the main 

 method of dispersal and transport of larvae, then 

 the average apparent rate of survival of 80.4 

 percent per day may be an underestimate, and 

 the true rate of survival may be as high as 83 

 percent per day. 



ACKNOWLEDGMENTS 



E. Corcoran developed a method for fragmenting 

 mucilaginous material taken in plankton hauls, 

 thus shortening the task of sorting the plankton. 

 T. J. Costello and D. M. Allen of the Bureau of 

 Commercial Fisheries provided valuable assistance 

 and advice. 



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180 



U.S. FISH AND WILDLIFE SERVICE 



