Threshold to maturity in a long-lived reptile: interactions of age, size, and growth

Bjorndal, Karen A.; Parsons, Joe; Mustin, Walter; Bolten, Alan B.

doi:10.1007/s00227-012-2116-1

Cited by 66 publications

(109 citation statements)

References 40 publications

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“…3). Similar re sults were found by Bjorndal et al (2012) Even though mutilation tagging is a labour-intensive method that takes a long time to produce results, we suggest that it (or DNA sampling) is the only way to ultimately determine the turnover rate of a population. In conclusion, the older age at first reproduction highlights the vulnerability of sea turtles as it has a negative effect on population replacement.…”

Section: Discussionsupporting

confidence: 85%

“…3). Similar re sults were found by Bjorndal et al (2012) This hypothesis is also supported by Hatase et al (2002) who conducted an isotope and telemetry study and found that immature turtles that migrate to coastal waters at a small size grow larger by feeding on nutrient-rich prey, such as benthos, until they reach sexual maturity. In contrast, immature turtles that stay in the pelagic zone for a longer period are smaller because of the scarcity of nutrient-rich prey in this habitat.…”

Section: Discussionsupporting

confidence: 74%

“…Therefore, food accessibility and the rate at which an organism can process food (West et al 2004, Molles 2010) regulate the metabolic investment of energy into reproduction or growth. Thus, the onset of sexual maturity -as indicated by a reduction in energy investment into somatic growth and a greater energy allocation into the growth and maturation of reproductive organs (Hatase et al 2004, Berner & Blanckenhorn 2007, Snover et al 2007, Bjorndal et al 2012) -is dependent on both population characteristics (intrinsic) and the environment (extrinsic).…”

Section: Introductionmentioning

confidence: 99%

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Age-size relationship at reproduction of South African female loggerhead turtles Caretta caretta

Tucek¹,

Girondot²,

Hughes³

2014

Endang. Species. Res.

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Average age and size at first reproduction are important demographic parameters used in the management and conservation of populations. For sea turtles, absolute values for these parameters are still ambiguous, as most species are slow-growing, late-maturing migrants which are rarely encountered during the first 1 to 2 decades of their lives. Additionally, growth is significantly influenced by a variety of intrinsic and extrinsic factors which make it difficult to describe age−size relationships. Extensive notching (mutilation-tagging) of South African loggerhead turtles was used to determine age and size at reproduction (putative first nesting season), and thus to identify the trigger for sexual maturation. To date, 137 clearly identified notched adult females have been encountered at the nesting beach. A Gaussian and log-normal distribution were fitted to the age distribution data but only the Gaussian distribution can be used to safely estimate age at first observation, as the right part ('older ages') of the distribution is still unknown. The estimated age at first observation was corrected for the possibility that a female was not encountered during her first nesting season. Results indicate an average age of 36.2 ± SD 7.71 yr (95% CI 28.2 to 44.3 yr) with a straight carapace length (SCL min ) of 83.7 ± 4.15 cm (95% CI 83.0 to 84.4 cm). It was concluded that size is a more important threshold for the initiation of the maturation process than age and that the onset of sexual maturity is dependent on intrinsic and extrinsic factors. KEY WORDS: Age and size at reproduction · Loggerhead turtle · Mutilation tagging Resale or republication not permitted without written consent of the publisherEndang Species Res 23: [167][168][169][170][171][172][173][174][175] 2014 extrinsic factors. Intrinsic factors that affect the growth rate in sea turtles include species, genotype, health status and sex (Chaloupka & Limpus 1997, Van Dam 1999, Heppell et al. 2003. Extrinsic factors that regulate growth rate are, for example, water temperature, food quality and food availability (Parker 1929, Bjorndal et al. 2003, Balazs & Chaloupka 2004. These factors are easy to regulate in captive studies but are often highly variable and difficult to measure under natural conditions (Mendonca 1981) as sea turtles migrate over thousands of kilometres and experience large habitat variations that additionally affect their growth rate (Musick & Limpus 1997, Casale et al. 2007, Koch et al. 2007). The variability in growth rate has already been documented in different species and several populations. Green turtles from the Hawaiian archipelago (Balazs & Cha loupka 2004) and the southern Great Barrier Reef grow at different rates due to differences in food quality and availability, as well as in sea surface temperatures of their foraging grounds. Furthermore, Hughes (1974) and Bjorndal et al. (2003) found that compensatory growth (accelerated growth) appears in juvenile sea turtles when they move from a suboptimal environment to b...

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Section: Discussionsupporting

confidence: 85%

Section: Discussionsupporting

confidence: 74%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Age-size relationship at reproduction of South African female loggerhead turtles Caretta caretta

Tucek¹,

Girondot²,

Hughes³

2014

Endang. Species. Res.

View full text Add to dashboard Cite

show abstract

“…However, all studies of growth rates of sea turtles in captivity of which the authors are aware have reported high levels of variation (e.g. Stokes et al 2006, Reich et al 2008, Bjorndal et al 2013a.Pre-maturity length growth rates have a significant negative relationship with AgeSM and account for a substantial proportion of the variation ( Fig. 3a; linear regression; p < 0.0001, R 2 = 0.87), but are not related to either LengthSM or MassSM (Spearman rank tests, p > 0.05).…”

mentioning

confidence: 99%

Variation in age and size at sexual maturity in Kemp’s ridley sea turtles

Bjorndal¹,

Parsons²,

Mustin³

et al. 2014

Endang. Species. Res.

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Age at sexual maturity (AgeSM) is one of the most serious demographic data gaps for sea turtle populations. Better estimates of AgeSM and associated variance would improve evaluation of population dynamics and responses of populations to disturbances and conservation measures. A population of Kemp's ridleys Lepidochelys kempii was raised in captivity under the same conditions from hatchlings to several years after maturity. Data collected from 14 female Kemp's ridleys at Cayman Turtle Farm over a 16 yr period allowed us to determine mean and variance in age, length, mass, and body condition at maturity, average pre-maturity growth rates, and post-maturity growth rates, as well as interactions among these parameters. Age, length, and mass at maturity exhibited considerable variance, with ranges of 5 to 12 yr, 47.0 to 61.0 cm, and 20.0 to 36.8 kg, respectively. Pre-maturity length growth rate is the best single predictor of AgeSM, accounting for 87% of the variation in AgeSM. Pre-maturity mass growth rate is the best single predictor of size at maturity, accounting for 51 and 65% of variation in length at maturity and mass at maturity, respectively. Although estimates of age and size at maturity from captive Kemp's ridleys cannot be applied to wild populations because of the effect of nutrition, the amount of variation around age and size at maturity in Kemp's ridleys from Cayman Turtle Farm is a good first approximation of inherent (or genetic) variation in these parameters for wild Kemp's ridleys. Population models for Kemp's ridleys that now employ a knife-edge estimate of AgeSM would be improved by incorporating a maturity schedule that reflects the variation in AgeSM.KEY WORDS: Age at sexual maturity · Size at sexual maturity · Indeterminate growth · Lepidochelys kempii · Sea turtle Resale or republication not permitted without written consent of the publisherEndang Species Res 25: 57-67, 2014 This variation is primarily a result of variation in LengthSM and not of growth after sexual maturity, because growth rates are largely negligible after maturity (Carr & Goodman 1970, Bjorndal et al. 1983, 2013a, Broderick et al. 2003, Price et al. 2004. Whether the variation in LengthSM is a result of inherent (or genetic) variation or environmental factors is not known. Whatever the cause, selection of an appropriate population-wide LengthSM for estimating AgeSM is problematic. Several measures have been used; minimum size and mean size of nesting females are the most common.A few records of AgeSM in sea turtles have resulted from marking hatchlings so they can be recognized at maturity or by tagging head-started turtles -turtles that have been reared in captivity usually for a year before release (Bell et al. 2005, Shaver & Wibbels 2007, Limpus 2009). Individual records of age at sexual maturity are very valuable and are not known for most populations. However, as these rare estimates trickle in, the extent to which they can be used to represent population estimates depends upon the amount of variation i...

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“…In the present study, 39.3% of the turtles had an SCL shorter than 69.2 cm, which is the minimum SCL of Japanese nesting loggerhead turtles reported by Kamezaki et al (1995); 74.8% had an SCL shorter than 74.1 cm, which is the minimum SCL reported by Hatase et al (2002bHatase et al ( , 2004; and 98.1% had an SCL shorter than 82.1 cm, which is the mean SCL at maturity . Although the size of sea turtles at maturity is variable among individuals (Musick & Limpus 1997, Bjorndal et al 2013, the wide size range of the individuals in dicates that the feeding area in Sanriku may include both juveniles and adults.…”

Section: Discussionmentioning

confidence: 99%

Genetic composition of loggerhead turtle feeding aggregations: migration patterns in the North Pacific

Nishizawa¹,

Narazaki²,

Fukuoka³

et al. 2014

Endang. Species. Res.

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Threshold to maturity in a long-lived reptile: interactions of age, size, and growth

Cited by 66 publications

References 40 publications

Age-size relationship at reproduction of South African female loggerhead turtles Caretta caretta

Age-size relationship at reproduction of South African female loggerhead turtles Caretta caretta

Variation in age and size at sexual maturity in Kemp’s ridley sea turtles

Genetic composition of loggerhead turtle feeding aggregations: migration patterns in the North Pacific

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