ABUNDANCE AND DISTRIBUTION OF THE LARVAE OF THE PINK SHRIMP 

 (PENAEUS DUORARUM) ON THE TORTUGAS SHELF OF FLORIDA, 

 AUGUST 1962-OCTOBER 1964 '- 



By J. L. MUNRO' AND A. C. Jones,* Fishery Biologists, and D. Dimitriou,' Fishery Technician 



Institute of Marine Sciences, University of Miami 

 Miami, Florida 33149 



A 2-year study has shown that an estimated 870 x 10'° 

 first protozoeae of pink shrimp are produced each year 

 within the main part of the Tortugas spawning 

 grounds. Survival rates are nearly constant and average 

 80.4 percent per day throughout larval life. Estimates 

 of larval survival at specific sampling stations are 

 influenced by the migration patterns of the larvae and 

 vary considerably, depending on whether the sampling 

 station receives older larvae from adjacent areas or 

 loses larvae to other areas. 



An investigation of bottom currents on the Tortugas 

 grounds has shown that the prevailing westerly and 



ABSTRACT 



southwesterly currents may carry the larvae into the 

 Florida Current, which, in turn, may transport the 

 larvae to the nursery grounds in the Everglades National 

 Park. 



Spawning, measured by the relative abundance of 

 first protozoeae, is influenced by moon phase; most 

 spawning occurs during the last half of the lunar 

 month. Spawning activity reaches a maximum when 

 bottom water temperatures are highest; the center of 

 spawning shifts from shallow water into deeper water 

 as the spawning season progresses. 



The early life history of the pink shrimp, 

 Penaeus duorarum Burkenroad, has received con- 

 siderable attention in recent years. Dobkin (1961) 

 described the early larval stages of P. duorarum 

 hatched from eggs spawned in the laboratory, and 

 Ewald (1965) succeeded in rearing all stages in 

 the laboratory. These studies have provided 

 evidence upon which identifications of the larvae 

 in the plankton can be based. Eldred, WiUiams, 

 Martin, and Joyce (1965) studied the inshore and 

 offshore distribution and abundance of larval and 

 postlarval P. duorarum in the Tampa Bay area. 

 Jones, Dimitriou, Ewald, and Tweedy (unpub- 

 hshed manuscript)^ described the distribution of 

 pink shrimp larvae over a wide area of the Tor- 

 tugas Shelf of Florida and located the main 

 spawning grounds. 



The purposes of the study reported here were to 

 (1) define quantitatively the seasonal abundance 

 of the planktonic shrimp larvae in the main 

 spawning area on the Tortugas Shelf; (2) investi- 

 gate the relation between spawning intensity and 

 environmental factors; (3) estimate the mortaUty 

 rates of various larval stages; and (4) describe 

 how immigration and emigration of larvae affect 

 mortahty estimates pertaining to specific samphng 

 stations. 



PROCEDURES 



The methods we have used covered four activi- 

 ties: selection of study stations, sampling pro- 

 cedures, laboratory techniques, and computer 

 conversion of data. 



STUDY AREA 



We sampled on a grid system that covered the 

 Tortugas Shelf area (fig. 1) ; stations were 18.5 km. 

 apart. Ten stations were selected for regular 

 sampling in the area considered by Jones et al. 

 (footnote 6) to be the center of spawning. The 

 stations are designated 50.100, 50.90, 50.80, 50.70, 

 40.90, 40.80, 40.70, 40.60, 32.70, and 30.58 and 

 were located over depths between 10 and 36 m. 

 (5.5 and 20.0 fathoms). (The latter two stations 



Published September 1968. 



FISHERY BULLETIN: VOL. 67, NO. 1 



I Contribution No. 235, Bureau of Commercial Fisheries Biological Labora- 

 tory, Galveston, Tes. 77562. 



' This work was financed by the Bureau of Commercial Fisheries under 

 Contract No. 14-17-0002-98, with funds made available under the Act of 

 July 1, 1954 (68 Stat. 376), commonly known as the Saltonstall-Kennedy Act. 



' Present address: Zoology Department, University of the West Indies, 

 Kingston, Jamaica. 



* Bureau of Commercial Fisheries Tropical Atlantic Biological Laboratory, 

 Miami, Fla. 33149. 



' Present address: 10045 Montego Bay Drive, Miami, Fla. 33157. 



'"Distribution of early developmental stages of pink shrimp, Penaeus 

 duorarum, in Florida waters," by A. C. Jones, D. Dimitriou, J. J. Ewald, 

 and J. Tweedy, Institute of Marine Sciences, University of Miami, for Bureau 

 of Commercial Fisheries Biological Laboratory, Galveston, Tei., 64 MS. 

 pp., 13 figs. 



165 



