Jf. Parham et Gr. Zug, AGE AND GROWTH OF LOGGERHEAD SEA-TURTLES (CARETTA-CARETTA) OF COASTALGEORGIA - AN ASSESSMENT OF SKELETOCHRONOLOGICAL AGE-ESTIMATES, Bulletin of marine science, 61(2), 1997, pp. 287-304
Loggerhead sea turtles stranded on Cumberland Island (CI), Georgia pro
vide skeletal samples to estimate the ages of individual turtles by sk
eletochronology. An initial study in 1986 used an average-thickness of
humeral cross-section protocol to estimate individual ages and the mi
nimum carapace length (CL) of nesting females to predict the average a
ge at sexual maturity for the CI sample. The original data and two new
CI samples are analyzed by average-thickness, correction-factor, and
regression-growth protocols to reassess the original age estimates, to
test the reliability of the three protocols, and to predict growth ra
tes and age of sexual maturity. All protocols show moderate to high va
riation in one or more steps of the calculations of the age-estimates.
The lowest variation occurs in the correction-factor protocol, and th
is protocol's assumption for the estimation of the number of resorbed
growth layers matches best the observed pattern of bone growth in Care
tta. The skeletochronological results show growth patterns (von Bertal
anffy model) with asymptotes of 96 - 117 cm curved carapace length (CC
L) and growth coefficients of 0.040 - 0.106 for the CI samples. These
patterns predict sexual maturity occurring from 20 - 63 yr, assuming 9
2 cm (SCL) as the mean size at sexual maturity. Growth rate estimates
range from 30 - 40 mm yr(-1) for 40 - 49 cm SCL turtles to 10 - 35 mm
yr(-1) for 80 - 89 cm straight carapace length (SCL) turtles.