Witzell et al : Origin of Caretta caretta at Hutchinson Island 



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Atlantic 

 Ocean 



UNITED STATES 



Figure 1 



Locations for which are known loggerhead sea turtle nesting haplotypes and the location of the 

 Hutchinson Island foraging population. 



gists and marine resource managers are presented with 

 complex challenges that reinforce the need for complete life 

 history information. In particular, the origin of immature 

 loggerhead sea turtles foraging in coastal nearshore waters 

 needs to be determined for the development of effective 

 regional conservation and management strategies. Recent 

 research has demonstrated that most sea turtle nesting 

 colonies are genetically distinct as indicated by mitochon- 

 drial (mt) DNA haplotype frequency shifts. This finding 

 allows the possibility of using mtDNA data to identify rook- 

 ery cohorts on feeding grounds (Bass et al., 1998; Broderick 

 et al., 1994). By using an existing database (Encalada et al., 

 1998) and molecular techniques, tissue samples from juve- 

 nile marine turtles can be analyzed to estimate the origin 

 of animals inhabiting developmental habitats. These data 

 are collected and analyzed faster than results from tagging 

 studies and may provide information on cryptic migratory 

 behavior (Bowen et al, 1995; Bolten et al.. 1998). Both pe- 

 lagic and coastal benthic zones are believed to be essential 

 developmental habitats for sea turtles, and molecular 

 markers have recently been used to document shifts in the 

 demographic composition between these habitats (Laurent 

 et al., 1998). This article examines the mtDNA composition 

 of juvenile loggerhead sea turtles using the coastal waters 



off Hutchinson Island, Florida, to determine whether the 

 turtles are primarily from the adjacent nesting subpopu- 

 lation or whether this foraging population is composed of 

 individuals from multiple rookeries. 



Materials and methods 



Sea turtles are routinely captured in the canal that sup- 

 plies cooling water at the St. Lucie Power Plant on Hutch- 

 inson Island, Florida (Fig. 1). The power plant intake oper- 

 ates year round — collecting sea turtles from 365 m offshore 

 and providing an excellent opportunity to sample sea 

 turtles in the nearshore developmental habitat (Bass and 

 Witzell, 2000). Power plant biologists collect these turtles 

 daily in an ongoing research and conservation program. 

 Turtles are measured, flipper-tagged, and released in good 

 condition promptly into the adjacent coastal waters. 



A total of 109 juvenile loggerhead sea turtles were sam- 

 pled at the St. Lucie power plant from January through 

 May 1999 for our study. The minimum straight carapace 

 length (SCL) was measured with calipers. Tissue samples 

 were collected by using a 6-mm biopsy punch and placed 

 in 15 mL of saturated salt preservation buffer developed 



