Cnales et al Variability in supply and cross shelf transport of Farfontepenaeus duorarum postlarvae into Florida Bay 



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Figure 6 



Outputs of transport simulations of pink shrimp iFarfantepenaeus duorarum) planktonic stages (larvae and postlarvae) 

 developed from in situ current observations and under different scenarios of larval behavior. Each point represents 30 

 days of travel from September 1997 to October 2000; (A and Bi outputs from onshore ADCP A currents, cross-shelf and 

 alongshore constituents, respectively; (C and D) outputs from offshore ADCP B currents, cross-shelf and alongshore 

 constituents, respectively. Scenario 1 (filled circles) = planktonic stages migrating with the instantaneous current and 

 a diel behavior (at night) cued by changes in salinity; scenario 2 (empty circles) = planktonic stages migrating with the 

 instantaneous current and a diel behavior (at night); scenario 3 (filled triangles) = planktonic stages migrating with a 

 diel (at night) and a tidal (eastward current) behavior; scenario 4 (empty triangles) = planktonic stages migrating by an 

 induced ontogenic change of behavior (a diel behavior during the first 15 days and a tidally induced behavior (eastward 

 current) superimposed on the diel behavior (at night) for the remaining 15 days). 



species (Fenneropenaeus merguiensis, Penaeus plebejus. 

 and Penaeus semisulcatus) in the Gulf of Carpentaria, 

 Australia, an ontogenic change in behavior has been 

 (iocumented for planktonic stages (Rothlisberg, 1982; 

 Rothlisberg et al., 1995. 1996; Condie et al., 1999). 

 Results of these studies showed that during the first 

 two weeks of planktonic development, larvae migrate 

 vertically in a diel cycle; later in development, the verti- 

 cal migration is tidally induced. Under those conditions 

 there was little or no systematic cross-shelf displace- 

 ment of larvae during the first two weeks; afterward, 

 cross-shelf displacement occurred rapidly (Rothlisberg 

 et al., 1995; 1996). Simulation of transport for pink 

 shrimp larvae using this ontogenic change of behavior 



indicated that planktonic stages can be transported up 

 to 100 km eastward and 85% of larvae reach 80 km. If 

 this behavior applies to pink shrimp, the location of the 

 spawning grounds needs to be reconsidered in favor of 

 areas closer to Florida Bay. Alternatively, the behavior 

 of early planktonic stages may have been underesti- 

 mated. Results of this research indicated once again 

 the extreme importance of defining larval behavior and 

 including behavior in dispersal models. 



The cue(s) that penaeid postlarvae use to migrate in 

 the water column during the flood tide and to return 

 to the bottom on the ebb tide are not completely un- 

 derstood and could be species specific. Hughes (1969a, 

 1972) demonstrated in laboratory experiments that 



