117 



Abstract— Skeletochronological data 

 on fjniu ih changes in humerus diam- 

 eter were used to estimate the age 

 nf Hawaiian gi'een seaturtlos ranging 

 from 28.7 to 96.0 cm straight carapace 

 length. Two age estimation methods, 

 correction factor and spUne integration, 

 were compared, giving age estimates 

 ranging from 4.1 to 34.6 and from 3.3 

 to 49.4 yr, respectively, for the sample 

 data. Mean growth rates of Hawaiian 

 green seaturtles are 4-5 cm/yi- in early 

 juveniles, decline to a relatively con- 

 stant rate of about 2 cm/yr by age 10 

 yr. then decline again to less than 1 

 cm/yr as turtles near age 30 yr. On 

 average, age estimates from the two 

 techniques differed by just a few years 

 for juvenile turtles, but by wider mar- 

 gins for mature turtles. The spline-inte- 

 gration method models the curvilinear 

 relationship between humerus diame- 

 ter and the width of periosteal gi'owth 

 increments within the humerus, and 

 offers several advantages over the cor- 

 rection-factor approach. 



Age and growth of Hawaiian green seaturtles 

 (Chelonia mydas): an analysis based 

 on skeletochronology 



George R. Zug 



Division of Amphibians and Reptiles 

 Department of Systematic Biology 

 National Museum of Natural History 

 Washington, DC. 20560-0162 

 E-mail address: zuggeorgeiSnmnhsiedu 



George H. Balazs 

 Jerry A. Wetherall 



Honolulu Laboratory 

 Southwest Fisheries Science Center 

 National Manne Fishenes Service, NOAA 

 2570 Dole St, Honolulu Hawaii 96822-2396 



DenJse M. Parker 

 Shawn K. K. Murakawa 



Joint Institute for Manne and Atmosphenc Research 



2570 Dole St 



Honolulu, Hawaii 96822-2396 



Manuscript accepted 20 August 2001. 

 Fish. Bull, 100:117-127 (20021. 



The Hawaiian population of the green 

 seaturtle {Chclonia mydas) provided 

 some of the first published gi-owth data 

 (Balazs, 1979, 1980. 1982) for this spe- 

 cies. These early data showed how slowly 

 seaturtles grow and how long a female 

 must survive simply to lay her first 

 clutch of eggs. Twenty or more years to 

 reach sexual maturity seemed biologi- 

 cally unrealistic, yet slow growth and 

 late maturity has been repeatedly con- 

 firmed for some seaturtle species, e.g. 

 Bahamian C. mydas (Bolten et al,, 19921, 

 West Atlantic Caretta caretta (Parham 

 and Zug. 1998). Slow growth and the 

 resulting delayed maturity greatly affect 

 the demography of a population (Grouse 

 et al., 1987; Chaloupka and Musick, 

 19961. An understanding of growth and 

 gi-owth-pattern variation in seaturtles is 

 an important prerequisite to the devel- 

 opment of population models that are 

 required to guide seaturtle population 

 recovery and conservation. 



Green seaturtles within the Hawai- 

 ian Islands contribute to the larger In- 

 do-Pacific C. mydas gene pool, yet the 

 nesting females of the Hawaiian popu- 

 lation comprise a distinct genetic unit 



and contain a unique intDNA haplotype 

 (Bowen et al., 1992), Except during their 

 posthatching pelagic phase, the gi'eat 

 majority of Hawaiian green seaturtles 

 reside in coastal waters, primarily 

 around Hawaii. Kauai, Maui, Molokai, 

 Oahu, and other islands in the south- 

 eastern part of the Hawaiian chain. 

 Most reproduction takes place at French 

 Frigate Shoals in the Northwestern Ha- 

 waiian Islands (Balazs, 1980; Wether- 

 all et al,. 1999), The population of Ha- 

 waiian Chelonia mydas has benefited 

 from over two decades of intense con- 

 servation management (Balazs, 1998). 

 Despite important early research on 

 the Hawaiian population of C. mydas 

 (Balazs, 1982), the patterns of growth 

 within and among the geographic habi- 

 tat components of this population have 

 remained incompletely documented 

 ( Balazs et al„ 1994, 2000 ), The chief rea- 

 son for this has been a lack of methods 

 to age sea turtles. This deficiency has 

 been overcome recently by the devel- 

 opment of skeletochronological tech- 

 niques that estimate age from the num- 

 ber of growth increments formed on the 

 humerus (Parham and Zug, 1998), 



