shore while maturing. The larger individuals 

 eventually occupy the deeper waters (Iversen, 

 Jones, and Idyll, 1960). 



To study the Tortugas and Sanibel pink shrimp 

 stocks as biological units, we must define the 

 areas supporting these populations (or this popu- 

 lation). This definition requires delineation of the 

 shallows and estuaries that sustain young pink 

 shrimp before they migrate to the Tortugas or 

 Sanibel grounds, as well as the deeper, offshore 

 waters frequented by the adult shrimp. 



The extensive shallow waters surrounding and 

 penetrating the southern portion of peninsular 

 Florida and the adjoining Florida Keys support 

 an abundance of juvenile pink shrimp, some of 

 which are captured and sold as bait (fig. 1). 

 Florida Bay, lying between the southern tip of 

 Florida and the Florida Keys, is considered an 

 important nursery area supplying pink shrimp to 

 the Tortugas grounds (Iversen and Idyll, 1960). 

 These nursery grounds may extend southwestward 

 into the grassy shallows west of Marquesas Keys 

 (Ingle, Eldred, Jones, and Hutton, 1959). Broad 

 (1950) notes that "ample nursery grounds are to 

 be found on the Florida west coast between Cape 

 Sable and Cape Romano where the coastline is 

 broken by numerous bays, creeks and rivers." 



Maturing and adult pink shrimp are found in 

 most offshore waters adjacent to south Florida, 

 sometimes in depths of 60 fathoms 2 (Bureau of 

 Commercial Fisheries, 1961 and 1962). On the 



# 



HAWK CHANNEL GROUNDS ' 



bi'oo' ^> etroo' 



Florida shelf, however, much of the bottom is too 

 rough for conventional trawling gear. South of 

 lat. 27°00' N., the region under discussion, large 

 pink shrimp are generally taken commercially 

 only on the Sanibel, Tortugas, and Hawk Channel 

 grounds where relatively smooth bottom can be 

 found. Pink shrimp are fished commercially to a 

 maximum depth of about 33 fathoms. The 

 greater depths of the Straits of Florida, to the 

 south and east of the Tortugas grounds, and the 

 Gulf of Mexico, to the west, may serve as barriers 

 to the migration of juvenile and adult pink shrimp. 



In 1958, a total of 1,157 pink shrimp were 

 tagged with Petersen disks and released near 

 Flamingo in Everglades National Park. From 

 this group, 1 tagged shrimp was recovered on the 

 Tortugas grounds (Iversen and Idyll, 1960). 

 Prior to this recovery no direct evidence linked 

 small pink shrimp from south Florida estuaries to 

 those larger shrimp supporting offshore fisheries. 

 In addition, the relationship of pink shrimp 

 occurring on the Hawk Channel and Sanibel 

 grounds to the Tortugas pink shrimp was un- 

 known. In 1958, the Bureau of Commercial 

 Fisheries began a series of mark-recovery ex- 

 periments in the waters of south Florida. One 

 result of these experiments has been to demon- 

 strate that certain shallow coastal waters are im- 

 portant contributors of recruits to the Tortugas 

 and Sanibel shrimp fisheries. These experiments 

 also outlined much of the range of the Tortugas 

 and Sanibel pink shrimp stocks. 



In studying pink shrimp, we were also con- 

 cerned with the incidence of similar species that 

 might be mistaken for pink shrimp. Two species 

 closely related to pink shrimp have been reported 

 from the waters of south Florida. These are 

 Penaeus brasiliensi? (Eldred, 1960) and Pentu us 

 azteeus (Burkenroad, 1939; Tabb ami Manning, 

 1961; Bureau of Commercial Fisheries, 1961). 

 In Biscayne Bay and Hawk Channel, a relatively 

 small number of P. brasiliensis were marked and 

 released with P. duorarum. P. brasiliensis has 

 not been noted from the Tortugas or Sanibel 

 grounds despite examination of many shrimp 

 from these areas. Two specimens of P. aztecus 

 have been recorded from the northwest portion of 

 the Sanibel grounds, but none from the Tortugas 

 grounds. 



Figure 1. — Distribution of pink shrimp in the waters of 

 south Florida. 



3 On" the western edge of the Oreat Bahama Bank pink shrimp have been 

 fomul in depths up to 200 fathoms (Bureau of Commercial Fisheries. 1961). 



450 



U.S. FISH AND WILDLIFE SERVICE 



