; i^t 



PERIOD I 

 December 14-27; 1962 



y//A AREA CONTAINING EXPERIMENTAL POPULATION- 



/ZZ. 



961 KM.2 (280 SQUARE NAUTICAL MILES) 



\ 



\ DRY TORTUGAS 





y 



PERIOD 2 



December 28,1962 TO Jonuary 10, 1963 



Y/-"/\ AREA CONTAINING EXPERIMENTAL POPULATION- 

 '///A 1,772 KM2 (516 SQUARE NAUTICAL mIlES) 



PERIOD 3 



January 11-24, 1963 



AREA CONTAINING EXPERIMENTAL POPULATION- 

 2,162 KMZ (630 SQUARE NAUTICAL MILES) 



PERIOD 4 



January 25, TO February 7, 1963 



AREA CONTAINING EXPERIMENTAL POPULATION- 

 '///■^ 2.637 KM2 (768 SQUARE NAUTICAL MILES) 



Figure 6. — Tortugas grounds. Area occupied by the population of marked pink shrimp in successive 2-week periods as 



determined from recapture locations. 



stained similarly to those released on the fishing 

 grounds. A second mark, not visible to processing 

 plant personnel, was placed on these "planted" 

 specimens so that we coidd distinguish them from 

 genuine recoveries. Residts of these and of later 

 similar experiments indicated that 75 to 89 per- 

 cent of marked shrimp which enter the shore 

 processing plants are recovered. 



We have no direct measure of the percentage 

 of marked shrimp recovered from those headed 

 at sea. In similar mark-recovery experiments in 

 the northern Gulf of Mexico, however, Ivhma and 

 Benigno (1965) estimated that 83 percent of re- 



captured marked shrimp were recovered on 

 shrimp boats and 14 percent were recovered in 

 processing plants. They concluded, therefore, that 

 only 3 percent were entirely overlooked. 

 Assumption J^: 



If losses did occur, the ratio of undetected re- 

 captures to recoveries did not change during the 

 periods used in analyses. 



Justification : 



Field personnel concluded, from daily inter- 

 views, that interest in recovering marked shrimp 

 aboard shrimp boats and in processing plants re- 

 mained constant for at least the first 10 weeks of 



PINK SHRIMP MORTALITY ON SANIBEL AND TORTUGAS 



497 



