Origin of immature loggerhead sea turtles (Caretta caretta) at Hutchinson Island, Florida: evidence from mtDNA markers

Loggerhead sea turtles (Caretta caretta) are migratory, long-lived, and slow maturing. They are difficult to study because they are seen rarely and their habitats range over vast stretches of the ocean. Movements of immature turtles between pelagic and coastal developmental habitats are particularly difficult to investigate because of inadequate tagging technologies and the difficulty in capturing significant numbers of turtles at sea. However, genetic markers found in mitochondrial DNA (mtDNA) provide a basis for predicting the origin of juvenile turtles in developmental habitats. Mixed stock analysis was used to determine which nesting populations were contributing individuals to a foraging aggregation of immature loggerhead turtles (mean 63.3 cm straight carapace length [SCL]) captured in coastal waters off Hutchinson Island, Florida. The results indicated that at least three different western Atlantic loggerhead sea turtle subpopulations contribute to this group: south Florida (69%), Mexico (20%), and northeast Florida-North Carolina (10%). The conservation and management of these immature sea turtles is complicated by their multinational genetic demographics

Growth Rates Of Juvenile Green Turtles Chelonia Mydas From Three Ecologically Distinct Foraging Habitats Along The East Central Coast Of Florida, Usa

A generalized additive mixed modeling approach was used to assess somatic growth for juvenile green turtles Chelonia mydas at 4 sites in 3 ecologically distinct foraging habitats along the east central coast of Florida, USA. The 3 habitats were a man-made nuclear submarine turning basin (Trident Submarine Basin), an estuary (Indian River Lagoon), and oceanic sabellariid worm rock reefs (Sebastian Inlet and St. Lucie Power Plant). Turtles from the Indian River Lagoon site grew significantly faster than turtles from the Trident Submarine Basin and sabellariid worm rock reef sites. There were no significant differences in growth rates between the sabellariid worm rock reef and Trident Submarine Basin sites. Non-monotonic or dome-shaped growth rate functions reflecting an immature peak in growth rates were observed for all 3 habitats. Growth rates peaked in 1998 for turtles in the Trident Submarine Basin and sabellariid worm rock reef habitats; since then growth rates have declined. This temporal decline in growth rates may reflect density-dependent effects on growth as more juveniles recruit to Florida for aging grounds, a direct result of increases in nest production at the primary rookeries (Costa Rica, Florida and Mexico). Developmental habitats are important for the survival of juvenile marine turtles. This study illustrates the degree to which juvenile growth rates vary among developmental habitats, which ultimately can affect the rate of growth and recovery potential of nesting stocks. © Inter-Research 2009

No evidence of selection against anomalous scute arrangements between juvenile and adult sea turtles in Florida

Variations in the number and arrangement of scutes often are used for species identification in hard-shelled sea turtles. Despite the conserved nature of scute arrangements, anomalous arrangements have been noted in the literature for over a century, with anomalies linked to sub-optimal environmental conditions in the nest during development. Long-held assumptions suggest that anomalous scute arrangements are indicative of underlying physiological or morphological anomalies, with presumed long-term survival costs to the individual. Here, we examined a 25-year photo database of two species of sea turtle (Caretta caretta and Chelonia mydas) captured incidentally and non-selectively on the eastern coast of Florida. Our results suggest that C. mydas is substantially more variable with respect to the arrangement of carapacial scutes, while C. caretta had a relatively higher proportion of individuals with anomalous plastron scute arrangements. We also show evidence that (a) the forms and patterns of anomalous scutes are stable throughout growth; (b) there is limited evidence for selection against non-modal arrangements in the size classes that were examined; and (c) that their frequency has remained stable in juvenile cohorts from 1994 until present. These findings indicate that there may not be a survival cost associated with anomalous scute arrangements once the turtles reach juvenile size classes, and that variation in scute arrangements within populations is relatively common

Characterization of a Subtropical Hawksbill Sea Turtle (<i>Eretmocheyles imbricata</i>) Assemblage Utilizing Shallow Water Natural and Artificial Habitats in the Florida Keys

<div><p>In order to provide information to better inform management decisions and direct further research, vessel-based visual transects, snorkel transects, and in-water capture techniques were used to characterize hawksbill sea turtles in the shallow marine habitats of a Marine Protected Area (MPA), the Key West National Wildlife Refuge in the Florida Keys. Hawksbills were found in hardbottom and seagrass dominated habitats throughout the Refuge, and on man-made rubble structures in the Northwest Channel near Cottrell Key. Hawksbills captured (N = 82) were exclusively juveniles and subadults with a straight standard carapace length (SSCL) ranging from 21.4 to 69.0cm with a mean of 44.1 cm (SD = 10.8). Somatic growth rates were calculated from 15 recaptured turtles with periods at large ranging from 51 to 1188 days. Mean SSCL growth rate was 7.7 cm/year (SD = 4.6). Juvenile hawksbills (<50 cm SSCL) showed a significantly higher growth rate (9.2 cm/year, SD = 4.5, N = 11) than subadult hawksbills (50–70 cm SSCL, 3.6 cm/year, SD = 0.9, N = 4). Analysis of 740 base pair mitochondrial control region sequences from 50 sampled turtles yielded 12 haplotypes. Haplotype frequencies were significantly different compared to four other Caribbean juvenile foraging aggregations, including one off the Atlantic coast of Florida. Many-to-one mixed stock analysis indicated Mexico as the primary source of juveniles in the region and also suggested that the Refuge may serve as important developmental habitat for the Cuban nesting aggregation. Serum testosterone radioimmunoassay results from 33 individuals indicated a female biased sex ratio of 3.3 females: 1 male for hawksbills in the Refuge. This assemblage of hawksbills is near the northern limit of the species range, and is one of only two such assemblages described in the waters of the continental United States. Since this assemblage resides in an MPA with intensive human use, basic information on the assemblage is vital to resource managers charged with conservation and species protection in the MPA.</p></div

Rookery contribution estimates for juvenile hawksbill turtles foraging in the KWNWR based on mixed stock analysis weighted by rookery size.

<p>Rookery source codes are explained in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0114171#pone.0114171.s001" target="_blank">S1 Table</a>.</p

Pairwise comparisons for 740 base pair control region haplotype frequencies for hawksbill turtle juvenile foraging aggregations in the Greater Caribbean region.

<p>Pairwise FST values are above the diagonal (all values significant for alpha  = 0.01). P-values for exact tests of differentiation are below the diagonal. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0114171#pone.0114171.s001" target="_blank">S1 Table</a> for code explanations.</p><p>Pairwise comparisons for 740 base pair control region haplotype frequencies for hawksbill turtle juvenile foraging aggregations in the Greater Caribbean region.</p

Location of the Key West National Wildlife Refuge, Monroe County, Florida.

<p>Location of the Key West National Wildlife Refuge, Monroe County, Florida.</p

Hawksbill turtle sighting locations in the northeast KWNWR, 2001–2011.

<p>Hawksbill turtle sighting locations in the northeast KWNWR, 2001–2011.</p

Hawksbill turtle sighting locations in the central KWNWR, 2001–2011.

<p>Hawksbill turtle sighting locations in the central KWNWR, 2001–2011.</p

Straight standard carapace length (SSCL) size-class distribution of hawksbill turtles for all captures in the Key West National Wildlife Refuge, 2002–2011.

<p>Straight standard carapace length (SSCL) size-class distribution of hawksbill turtles for all captures in the Key West National Wildlife Refuge, 2002–2011.</p