Abstract. As part of the Southeast 



Florida and Caribbean Recruitment 

 Project (SEFCAR), penaeoid shrimp lar- 

 vae were collected during the spring and 

 summer cruise of the RV Longhorn in 

 the Lower Florida Keys and Dry Tbrtugas 

 from 29 May to 30 June 1991. Larvae of 

 the pink shrimp, Penaeus duorarum, and 

 the rock shrimp, Sicyonia sp., were dis- 

 tributed inshore close to the Dry 

 Tortugas Grounds, whereas larvae of 

 the oceanic shrimp Solenocera sp. 

 showed mainly an offshore distribution. 

 Significant concentrations of Solenocera 

 sp., Sicyonia sp., and P. duorarum lar- 

 vae at the Tortugas transect in early 

 June were found within and above the 

 seasonal thermocline while the cold 

 cyclonic Tortugas Gyre was intensively 

 developed. For Solenocera sp., which 

 spawn on the outer edge of the gyre, 

 high concentrations of larvae were 

 found at the inshore stations of the 

 Tortugas transect in early June, pre- 

 sumably as a result of the cyclonic cir- 

 culation of the gyre followed by onshore 

 Ekman transport. Penaeus duorarum, 

 which spawn in the shallow Tortugas 

 Grounds, showed a mode of zoea II — III 

 progressing to postlarvae I at the 

 Tortugas Grounds during the 15 days 

 in which the drifter Halley recirculated 

 in the interior of the Tortugas Gyre. Re- 

 tention of P. duorarum larvae by the 

 internal circulation of the gyre at the 

 spawning grounds may be an important 

 mechanism for local recruitment of 

 these shrimp to the nursery grounds of 

 Florida Bay. 



Larval distribution and transport of 

 penaeoid shrimps during the 

 presence of the Tortugas Gyre 

 in May-June 1 99 1 



Maria M. Criales 



Department of Marine Biology and Fisheries 



Rosenstiel School of Marine and Atmospheric Science 



University of Miami, 4600 Rickenbacker Causeway, Miami, Florida 33 1 49 



Thomas N. Lee 



Department of Meteorology and Physical Oceanography 



Rosenstiel School of Marine and Atmospheric Science 



University of Miami, 4600 Rickenbacker Causeway, Miami, Florida 33149 



Manuscript accepted 7 December 1994. 

 Fishery Bulletin 93:471-482 ( 1995). 



Penaeoid shrimps constitute the sec- 

 ond most valuable segment of the 

 U.S. fishing industry and are argu- 

 ably one of the most valuable groups 

 of marine species in the world. An- 

 nual stocks fluctuate widely and few 

 spawning stock/recruitment rela- 

 tionships have been demonstrated 

 (Garcia, 1983). The penaeid shrimp 

 Penaeus duorarum, or pink shrimp, 

 supports an important commercial 

 fishery in south Florida. Pink 

 shrimp yielded a stable catch of 9.6 

 million pounds per year from 1960 

 to 1986 (Klima et al., 1986). How- 

 ever, this catch has declined by 

 more than 50% in the last four years 

 (NMFS 1 ). This fishery is directly 

 dependent on young shrimp that 

 migrate from nursery areas onto the 

 fishing grounds (Nance and Patella, 

 1989). Animals with short life spans 

 (=2 years), such as pink shrimp, de- 

 pend almost entirely on one year 

 class being recruited during the 

 year. 



The life history of P. duorarum of 

 the Dry Tortugas (shallow banks 

 located about 100 km west from Key 

 West) involves one oceanic and one 

 estuarine phase (Garcia and Le 

 Reste, 1981). Adults spawn offshore 

 on the Dry Tortugas, where females 

 lay demersal eggs (Fig. 1). The lar- 



vae undergo several changes in 

 feeding habits and morphology in- 

 cluding five naupliar stages, three 

 zoeal or protozoeal, and three mysid 

 stages. The last mysis undergoes a 

 moult at which time it transforms 

 into a postlarva. The average time 

 required by P. duorarum to reach 

 the first postlarval stage is approxi- 

 mately 20 days at 26°C (Ewald, 

 1965). 



The first postlarval stages are 

 still planktonic whereas those that 

 follow are benthic. Postlarvae mi- 

 grate inshore, entering the Florida 

 Bay nursery grounds where they 

 metamorphose to juveniles. When 

 they have reached a length of about 

 10 cm, they return to the Tortugas 

 spawning area (Allen et al., 1980). 



Advective processes of P. duorarum 

 and their relation to oceanographic 

 and environmental factors are not 

 fully understood. Research on the 

 larval phase was performed in the 

 mid 1960's. Munro et al. (1968) and 

 Jones et al. (1970) studied the abun- 

 dance and distribution of larvae of P. 

 duorarum on the Tortugas Shelf and 

 in the Florida Keys. These authors 



1 Jones, A. Southeast Fish. Sci. Center, Natl. 

 Mar. Fish. Serv., NOAA, 75 Virginia Beach 

 Dr., Miami, FL 33149. Unpubl. data, 1993. 



471 



