Temporal, spatial, and body size effects on growth rates of loggerhead sea turtles (Caretta caretta) in the Northwest Atlantic

Bjorndal, Karen A.; Schroeder, Barbara A.; Foley, Allen M.; Witherington, Blair E.; Bresette, Michael J.; Clark, David R.; Herren, Richard M.; Arendt, Michael D.; Schmid, Jeffrey R.; Meylan, Anne B.; Meylan, Peter A.; Provancha, Jane A.; Hart, Kristen M.; Lamont, Margaret M.; Carthy, Raymond R.; Bolten, Alan B.

doi:10.1007/s00227-013-2264-y

Cited by 51 publications

(65 citation statements)

References 21 publications

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“…5a, b; Table 1), as observed in other studies of this population (summarized in Bjorndal et al 2013b). However, for SCL, a transient increase in growth response was observed around the size at which juvenile turtles are expected to transition from oceanic to neritic habitat .…”

Section: Growthsupporting

confidence: 71%

“…This approach allowed estimation of annual, somatic growth rates for different life stages over decadal time frames, as well as size-at-age relationships Fig. 4 Graphical comparison of size class-specific growth rates back-calculated using skeletochronology (black bars; current study, and measured through mark recapture (white bars; Bjorndal et al 2013b) for US Atlantic loggerhead sea turtles. Horizontal line through each bar represents the mean and extent of bar to either side represents range within one standard deviation.…”

Section: Discussionmentioning

confidence: 99%

“…a GAMM All_Age ; b, c GAMM All_SCL (see Table 1 for statistical output). d Graphical output of growth response by year for GAM incorporating mark-recapture growth rate data collected along the US Atlantic coast (Bjorndal et al 2013b) for comparison with (c). For each factor plotted, the solid line represents the mean growth response (on a response scale centered around 0) for the covariate conditioned on other covariates included in the model and the dashed lines represent the extent of the 95 % Bayesian credible interval.…”

Section: Discussionmentioning

confidence: 99%

“…Despite some variation, the overall observed convergence demonstrates that the annual growth rates generated using this approach are representative of loggerheads inhabiting areas along the US Atlantic coast and highlights the utility of skeletochronology for obtaining long-term growth rate data, both for individuals and for populations. However, because growth rates have been found to vary in the northwestern Atlantic, increasing significantly at lower latitudes (Bjorndal et al 2013b), the growth and size-at-age relationships described herein are specific to the US Atlantic coast and should not be applied outside the geographic scope of the study. Additional skeletochronological analysis of loggerhead samples from other geographic areas (e.g., the Gulf of Mexico and Caribbean) is needed to allow regional comparison of growth patterns and resulting estimates of ASM.…”

Section: Growthmentioning

confidence: 93%

“…Regional sea turtle populations comprise considerable diversity in genetic composition (Jensen et al 2013), migratory behavior and habitat use (Musick and Limpus 1997;Plotkin 2003), and mortality pressures (Lewison et al 2013). Combinations of these influences are likely to underlie the extremely variable somatic growth rates observed within and among both individuals and populations (e.g., BraunMcNeill et al 2008;Bjorndal et al 2013b), which in turn have the potential to broaden the possible scope of ASM and SSM. Recent data indicate that captive green sea turtles (Chelonia mydas) reared together under the same conditions exhibit a wide range in both ASM and SSM (Bjorndal et al 2013a).…”

Section: Introductionmentioning

confidence: 98%

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Age and size at maturation- and adult-stage duration for loggerhead sea turtles in the western North Atlantic

et al. 2015

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mark associated with maturation were 90.5 for females (range 75.0-101.3) and 95.8 for males (range 80.6-103.8). Ages at maturation estimated from (1) the rapprochement skeletal growth mark; (2) back-calculated SCL-at-age data; and (3) bootstrapping and fitting Fabens modified von Bertalanffy growth curve to back-calculated growth data were very similar between approaches, but demonstrated a wide possible range. Mean age predictions associated with minimum and mean maturation SCLs were 22.5-25 and 36-38 years for females and 26-28 and 37-42 years for males. Post-maturation longevity (i.e., adult-stage duration) was similar for males and females, ranging from 4 to 46 years (mean 19 years).

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Section: Growthsupporting

confidence: 71%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Growthmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 98%

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Age and size at maturation- and adult-stage duration for loggerhead sea turtles in the western North Atlantic

et al. 2015

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Validation of back‐calculated body lengths and timing of growth mark deposition in Hawaiian green sea turtles

Goshe

Snover

Hohn

et al. 2016

Ecology and Evolution

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Somatic growth rate data for wild sea turtles can provide insight into life‐stage durations, time to maturation, and total lifespan. When appropriately validated, the technique of skeletochronology allows prior growth rates of sea turtles to be calculated with considerably less time and labor than required by mark‐–recapture studies. We applied skeletochronology to 10 dead, stranded green turtles Chelonia mydas that had previously been measured, tagged, and injected with OTC (oxytetracycline) during mark–recapture studies in Hawaii for validating skeletochronological analysis. We tested the validity of back‐calculating carapace lengths (CLs) from diameters of LAGs (lines of arrested growth), which mark the outer boundaries of individual skeletal growth increments. This validation was achieved by comparing CLs estimated from measurements of the LAG proposed to have been deposited closest to the time of tagging to actual CLs measured at the time of tagging. Measureable OTC‐mark diameters in five turtles also allowed us to investigate the time of year when LAGs are deposited. We found no significant difference between CLs measured at tagging and those estimated through skeletochronology, which supports calculation of somatic growth rates by taking the difference between CLs estimated from successive LAG diameters in humerus bones for this species. Back‐calculated CLs associated with the OTC mark and growth mark deposited closest to tagging indicated that annual LAGs are deposited in the spring. The results of this validation study increase confidence in utilization of skeletochronology to rapidly obtain accurate age and growth data for green turtles.

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Sympatry or syntopy? Investigating drivers of distribution and co‐occurrence for two imperiled sea turtle species in Gulf of Mexico neritic waters

Hart

Iverson

Fujisaki

et al. 2018

Ecology and Evolution

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Animals co‐occurring in a region (sympatry) may use the same habitat (syntopy) within that region. A central aim in ecology is determining what factors drive species distributions (i.e., abiotic conditions, dispersal limitations, and/or biotic interactions). Assessing the degree of biotic interactions can be difficult for species with wide ranges at sea. This study investigated the spatial ecology of two sea turtle species that forage on benthic invertebrates in neritic GoM waters: Kemp's ridleys (Lepidochelys kempii) and loggerheads (Caretta caretta). We used satellite tracking and modeled behavioral modes, then calculated individual home ranges, compared foraging areas, and determined extent of co‐occurrence. Using six environmental variables and principal component analysis, we assessed similarity of chosen foraging sites. We predicted foraging location (eco‐region) based on species, nesting site, and turtle size. For 127 turtles (64 Kemp's ridleys, 63 loggerheads) tracked from 1989 to 2013, foraging home ranges were nine to ten times larger for Kemp's ridleys than for loggerheads. Species intersected off all U.S. coasts and the Yucatán Peninsula, but co‐occurrence areas were small compared to species' distributions. Kemp's ridley foraging home ranges were concentrated in the northern GoM, whereas those for loggerheads were concentrated in the eastern GoM. The two species were different in all habitat variables compared (latitude, longitude, distance to shore, net primary production, mean sea surface temperature, and bathymetry). Nesting site was the single dominant variable that dictated foraging ecoregion. Although Kemp's ridleys and loggerheads may compete for resources, the separation in foraging areas, significant differences in environmental conditions, and importance of nesting location on ecoregion selection (i.e., dispersal ability) indicate that adult females of these species do not interact greatly during foraging and that dispersal and environmental factors more strongly determine their distributions. These species show sympatry in this region but evidence for syntopy was rare.

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Temporal, spatial, and body size effects on growth rates of loggerhead sea turtles (Caretta caretta) in the Northwest Atlantic

Cited by 51 publications

References 21 publications

Age and size at maturation- and adult-stage duration for loggerhead sea turtles in the western North Atlantic

Age and size at maturation- and adult-stage duration for loggerhead sea turtles in the western North Atlantic

Validation of back‐calculated body lengths and timing of growth mark deposition in Hawaiian green sea turtles

Sympatry or syntopy? Investigating drivers of distribution and co‐occurrence for two imperiled sea turtle species in Gulf of Mexico neritic waters

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