Criales and Lee: Larval distribution and transport of penaeoid shrimps 



475 



vae/10 m 2 ) in early June and the other at the sta- 

 tions of NW Patch transect (60.3 larvae/10 m 2 ) in 

 late June. 



Solenocera sp. This species represented the most 

 abundant penaeoid larvae at the Dry Tortugas and 

 lower Florida Keys, accounting for 72% of the total 

 catch (Fig. 4B). The highest densities were located 

 offshore of the Tortugas and Western transects. Abun- 

 dances were lowest in late May, increased consider- 

 ably in early June, and reached their peak in mid- 

 June (Table 1). Of the catch, 29.2% was represented 

 by zoeae and 70.8% by myses. Distribution of early 

 zoeae was patchy; two main peaks occurred at the 

 Western (282.9 larvae/10 m 2 ) and Tortugas transects 

 (135.4 larvae/10 m 2 ), and mysid stages were very 

 widely distributed throughout the area with the high- 

 est abundance at the Tortugas transect (136.6 lar- 

 vae/10 m 2 ) (Fig. 4B). Zoeae and myses showed an 

 offshore distribution, except at stations along the 

 Tortugas transect in early June where high concen- 

 trations of Solenocera sp. larvae were found at the 

 inshore stations while the Tortugas Gyre was well 

 developed (Figs. 4B and 5). 



Vertical distribution 



Depths of the center of mass (Z m ) were calculated 

 for the different larval stages of each species (Table 

 2). Penaeus duorarum larvae showed a shallow dis- 

 tribution (Z m =18 m) which was similar among stages. 

 Sicyonia sp. showed a meanZ m of 27 m, though zoeae 



were distributed deeper than myses. Solenocera sp. 

 larvae were widely spread throughout the water col- 

 umn from to 100 m; the peak concentration occurred 

 at about 42 m, and myses occurred deeper than zoeae 

 (Table 2). 



Penaeus duorarum larvae were distributed be- 

 tween temperatures of 23° and 29°C, Sicyonia sp. 

 larvae between 20° and 28°C, and Solenocera sp. lar- 

 vae between 15° and 29°C. Maximum concentrations 

 were found between 22° and 26°C (Fig. 5). 



Penaeus duorarum postlarvae at the offshore sta- 

 tions of the Marquesas transect (n=6, Z m x=20.8, 

 SD=14.8) were relatively deeper than those at in- 

 shore stations (n=ll, Z m x =11.6, SD=6.7) restricted 

 to the seasonal thermocline «-test, £ 15 =0.09, P>0.05). 



Effect of the Tortugas Gyre on larval 

 abundance and dispersal 



Abundance and vertical distribution at Tortugas 

 transect A general downward slope of the upper 

 seasonal thermocline (23-27°C) toward shore was 

 present during the four legs at the Tortugas transect 

 (Fig. 5). Solenocera sp., Sicyonia sp., and P. duorarum 

 larvae were highly concentrated above or within the 

 seasonal thermocline. The strength of the seasonal 

 thermocline, which is uplifted in the interior of the 

 gyre, appears to have been a limiting factor for ver- 

 tical migrations of these penaeoid larvae. 



Solenocera sp. larvae were very abundant at the 

 inshore stations between 25 and 75 m in depth dur- 

 ing leg 2, corresponding with the strongly developed 



