Age and growth of loggerhead sea turtles in southern Brazil

Petitet, Roberta; Secchi, Eduardo R.; Avens, Larisa; Kinas, Paul Gerhard

doi:10.3354/meps09681

Cited by 21 publications

(17 citation statements)

References 43 publications

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“…Because the relationship between bone and somatic measurements may change throughout life, the complete size range of all ontogenetic stages must be represented when developing an equation that describes the relationship. Establishing such a relationship has allowed LAG diameters to be converted to previous carapace lengths for Kemp's ridley Lepidochelys kempii (Snover et al 2007b), loggerhead (Snover et al 2007a;Casale et al 2011b;Piovano et al 2011;Petitet et al 2012;Avens et al , 2015, hawksbill Eretmochelys imbricata , olive ridley Lepidochelys olivacea (Zug et al 2006;Petitet et al 2015), and green turtles (Zug and Glor 1998;Goshe et al 2010;Avens et al 2012;Murakawa 2012). In tagged turtles, agreement between carapace lengths estimated or back-calculated from the diameter of the LAG thought to be deposited closest to the time of tagging and those measured at the time of capture provides indirect validation of the frequency of LAG deposition because identification of the LAG associated with tagging is based on the assumption that one LAG is deposited each year (e.g., .…”

Section: Introductionmentioning

confidence: 99%

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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Section: Introductionmentioning

confidence: 99%

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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“…Skeletochronology has been applied to estimate age, regional demographics, and growth patterns for multiple sea turtle species in a variety of regions (e.g. Zug and Glor 1998, Bjorndal et al 2003, Avens et al 2012, Petitet et al 2012). …”

Section: Introductionmentioning

confidence: 99%

Age and residency duration of loggerhead turtles at a North Pacific bycatch hotspot using skeletochronology

Tomaszewicz

Seminoff

Avens

et al. 2015

Biological Conservation

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For migratory marine animals, like sea turtles, effective conservation can be challenging because key demographic information such as duration of life stages and exposure to spatially explicit threats in different habitats are often unknown. In the eastern Pacific near the Baja California Peninsula (BCP), Mexico, tens of thousands of endangered North Pacific loggerhead sea turtles (Caretta caretta) concentrate at a foraging area known to have high rates of fishery bycatch. Because stage survivorship of loggerheads in the BCP will vary significantly depending on the number of years spent in this region, we applied skeletochronology to empirically estimate residency duration in this loggerhead hotspot. The observed age distribution obtained from skeletochronology analysis of 146 dead-stranded loggerheads ranged from three to 24 years old, suggesting a BCP residency of >20 years. Given the maximum estimated age and a one-year migration to western Pacific nesting beaches, we infer age-at-maturation for BCP loggerheads at ~25 years old. We also examine survivorship at varying BCP residency durations by applying our findings to current annual mortality estimates. Predicted survivorship of loggerheads spending over 20 years in this BCP foraging habitat is less than 10%, and given that ~43,000 loggerhead turtles forage here, a significant number of turtles are at extreme risk in this region. This is the first empirical evidence supporting estimated age-at-maturation for BCP North Pacific loggerheads, and the first estimates of BCP stage survivorship. Our findings emphasize the urgent need for continued and effective international conservation efforts to minimize bycatch of this endangered species.

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“…LAGs consistent in appearance with annuli have been found in oceanic stage juvenile loggerheads as well (Petitet et al . ; Avens et al . ).…”

Section: Methodsmentioning

confidence: 99%

“…; Petitet et al . ). Dead loggerhead turtles are frequently found stranded in the extreme south of Brazil, about 1270 km south from the nearest nesting areas and may provide valuable samples to elucidate many aspects of biology for the species in the region.…”

Section: Introductionmentioning

confidence: 97%

“…Information regarding age and growth rates of loggerhead turtles in this area is restricted to a single study based on specimens collected during 1 year (November 2008 to December 2009) in the oceanic and neritic environments from southern Rio Grande do Sul (Petitet et al . ). The current study aims to expand our knowledge on the age structure and growth rates of loggerhead turtles in the western South Atlantic based on specimens collected over a period of 16 years on the north coast of Rio Grande do Sul.…”

Section: Introductionmentioning

confidence: 97%

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Skeletochronological estimation of age and growth of loggerhead sea turtles (Caretta caretta) in the western South Atlantic Ocean

et al. 2016

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Age and growth are important parameters for better understanding of life history and population dynamics of animal species, as well as for formulating management strategies. However, these data are difficult to obtain for sea turtles because of overall slow growth, delayed maturation and highly migratory behaviour. The loggerhead sea turtle, Caretta caretta, is a widely distributed species, globally listed as endangered. Although the species has been well-studied in some regions, little is known about various aspects of its biology in other populations, such as those in the waters of the western South Atlantic Ocean, especially outside nesting areas. To address age and growth, loggerhead turtles found dead stranded on the northern coast of the state of Rio Grande do Sul during a period of 16 years (1994-2010) were utilized for estimation of age and growth rates using skeletochronology. The individuals analyzed were predominantly neritic juveniles, ranging from 53 to 101 cm curved carapace length (CCL; mean = 71 cm), with estimated ages between 10 and 29 years (mean = 15 years). Mean estimated annual growth rate was 2.1 cm CCL year À1 (1.9 cm SCL yr À1 ), showing large variation among individuals and between successive years in the same individual. Generalized additive mixed models analysis indicated that growth response was influenced by age, CCL and year. The results demonstrated that the southern coast of Brazil is an important area for the development of neritic juveniles of this species, which appear to recruit to this region beginning at about 12 years of age and sizes greater than 55 cm CCL.

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Age and growth of loggerhead sea turtles in southern Brazil

Cited by 21 publications

References 43 publications

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

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

Age and residency duration of loggerhead turtles at a North Pacific bycatch hotspot using skeletochronology

Skeletochronological estimation of age and growth of loggerhead sea turtles (Caretta caretta) in the western South Atlantic Ocean

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