Channel as a route to the Tortugas grounds 

 (migrations), the known limit of the Tortugas 

 population would be extended northeastward on 

 the Atlantic side of the Keys. 



South, southeast, and east of Hawk Channel, 

 pink shrimp have been caught in the Straits of 

 Florida in depths to 60 fathoms (Bureau of Com- 

 mercial Fisheries, 1961 and 1962). South of the 

 Tortugas trawling grounds, pink shrimp have been 

 taken in depths to 37 fathoms (Springer and 

 Bullis, 1954). At these depths, however, pink 

 shrimp have not been found abundant. The rela- 

 tionship of these "deep water" shrimp to those 

 inhabiting the relatively shallow water of the 

 Tortugas grounds has not been determined. 



Sanibel Stocks 



The Sanibel grounds comprise two distinct areas 

 of trawlable bottom and are located northwest 

 and south of Sanibel Island. Most trawling is 

 confined to depths of less than 10 fathoms The 

 southern boundary of the south Sanibel grounds 

 is about 50 miles north of the Tortugas northern 

 boundary (fig. 1). The northwest portion of the 

 Sanibel shrimp grounds represents the southern 

 extremity of a sporadic, undefined pink shrimp 

 fishery which parallels a large portion of the 

 Florida west coast. 



Recoveries of marked shrimp reveal that Pine 

 Island Sound serves as a nursery ground for both 

 sections of the Sanibel grounds. 



In this discussion the two Sanibel areas will be 

 treated separately since there are indications that 

 the northwest Sanibel grounds may support stocks 

 of pink shrimp differing from those of the south 

 Sanibel grounds. This is suggested by the fact 

 that while 2,496 marked shrimp were released on 

 south Sanibel (13), and 563 recovered there, none 

 was recovered on northwest Sanibel despite mod- 

 erate fishing effort in the latter area. One marked 

 shrimp, however, from the Indian Key release (14) 

 was recovered in the northwest Sanibel fishery. 

 This shrimp very likely passed through the south 

 Sanibel grounds en route to northwest Sanibel, 

 linking all three areas. These apparently con- 

 tradictory results may indicate that movement of 

 shrimp from the southeast to northwest Sanibel 

 is seasonal or sporadic. Because no marked 

 shrimp have been released on northwest Sanibel, 

 the relationship of shrimp from this area to shrimp 

 stocks to the south is unknown. 



The coastal distribution of shrimp recruited to 

 the south Sanibel fishery extends from at least 

 Pine Island Sound (10) to Indian Key (14). Juve- 

 nile shrimp recruited to the south Sanibel fishery 

 probably issue from estuaries between and in- 

 cluding these release sites. Since 22 of the marked 

 shrimp released at Indian Key were recovered on 

 the south Sanibel grounds, as compared with 8 

 on the Tortugas grounds, the southeastern limits 

 of the south Sanibel shrimp population probably 

 lie south of Indian Key but north of Shark River. 

 The latter point is emphasized by the fact that 

 releases of 16,638 marked shrimp at Shark River 

 and 23,971 in Florida Bay have resulted in numer- 

 ous recoveries on the Tortugas grounds but none 

 on the Sanibel grounds. 



The distribution of recoveries from coastal and 

 offshore releases provides good evidence that the 

 Tortugas and Sanibel shrimp stocks overlap in 

 the general area of Indian Key (14) and offshore, 

 between the Tortugas and Sanibel grounds. Two 

 stain-marked shrimp, mentioned previously, mi- 

 grated from the Sanibel to the Tortugas grounds, 

 apparently crossing the intervening area. The 

 bottom in this area is rough and usually precludes 

 successful trawling with conventional shrimping 

 gear. Despite low fishing effort in the area, two 

 pink shrimp tagged and released on the Tortugas 

 grounds were recovered 11 and 14 miles north of 

 the present northern border of the Tortugas 

 grounds (Iversen and Jones, 1961). In addition, 

 one stain-marked shrimp from the Bottle Key 

 release was recovered 6 miles north of the Tortugas 

 border (fig. 3). There is no evidence, however, 

 of migration from the Tortugas to the Sanibel 

 grounds. Of 4,441 stain-marked shrimp released 

 on the Tortugas grounds, none was recovered on 

 or near Sanibel grounds. Because the movement 

 of pink shrimp is generally into deeper water, 

 migration from the Tortugas grounds to the 

 shallower Sanibel grounds seems unlikely. 



SUMMARY AND CONCLUSIONS 



1. In south Florida, mark-recovery experiments 

 with biological stains as the marking agents 

 demonstrated the importance of certain shallow 

 coastal waters as nursery grounds for pink shrimp 

 that eventually frequent the offshore Tortugas 

 and Sanibel grounds. 



2. Some shrimp from shallow coastal waters 



MIGRATIONS OF FLORIDA PINK SHRIMP 



457 



