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200 — 



FiGTTHE 10. — Map of the Tortugas Shelf area showing track of Cruise 6416 (October 2 to 6, 1964) and the estimated 

 abundance of P. duorarum larvae (first number) and postlarvae (second number) under 10 m.^ surface area at each 

 of the stations occupied. Probable migration route of larvae is indicated by wide dark arrows. 



We, therefore, conclude that if the variations in 

 survival at specific stations are a result of emigra- 

 tion in a southerly direction at the western stations 

 and not the result of eastern stations receiving 

 immigrants from the west, then the average rates 

 of survival calculated from all catches may err in 

 being sUghtly too low. They might be best repre- 

 sented by the survival at stations 40.70, 40.80, 

 and 50.70, which are centrally located and 

 farthest removed from the influence of Rebecca 

 Channel and the Northwest Channel (fig. 8). 

 Survival at these stations averages about 83 

 percent per day. 



SUMMARY 



1. The 95-percent confidence limits applicable 

 to estimates of abundance of P. dvx)rarum proto- 

 zoeae are such that a single estimate cannot be 

 considered significantly different unless it is less 

 than 29 percent or greater than 348 percent of the 

 sample with which it is compared. This variability 



PINK SHRIMP ON FLORIDA TORTUGAS SHELF 



is greater than that normally encountered in 

 studies of this type, but part of the variability 

 may be ascribed to the fact that the analysis was 

 based upon replicate tows and not upon paired 

 tows. 



2. Gross annual production of first protozoeae 

 of P. duorarum within the sampling area was in 

 the order of 870X10"' individuals. 



3. Spawning in each year usually reached a 

 peak during the month of the highest bottom- 

 water temperatures. The month in which the 

 bottom water was warmest varied from year to 

 year, and the months of maximum spawning 

 activity varied accordingly. 



4. The center of spawning tended to move 

 toward deeper water as the season progressed, and 

 the last heavy spawning was in depths of more 

 than 30 m. (16.7 fathoms). This movement may 

 be correlated with temperature decreases in shal- 

 low water, but the movement of adult shrimp into 

 deeper water is the factor wliich is most directly 

 responsible. 



179 



