686 



Fishery Bulletin 102(4) 



Annulus ending 

 GM-1 



3 "t 4 



LAG-2 ' \ 

 LAG - 3 LAG-4 



Figure 3 



Image of humerus cross-section from a coded-wire-tagged Kemp's ridleys (L. 

 kempii). Black bar represent 1 mm in length. GM-1 refers to growth mark 

 one; LAG-2, LAG-3, and LAG-4 refer to the lines of arrested growth ending 

 growth marks two, three, and four. Curved black lines highlight LAGs or 

 annuli. This specimen, LK-13, was 4.75 years old. 



resorbed in all other parts of the bone (Fig. 4C). There 

 had been a great deal of remodeling within the bone and 

 much of the inner portion of the bone had been resorbed. 

 Summing all of these GMs, we gave a minimum age esti- 

 mate of 24 years without prior knowledge of the history 

 of the animal. The outermost 20 GMs contained well- 

 defined LAGs that were spaced close together, whereas 

 the four interior-most visible GMs contained LAGs or 

 annuli that were spaced farther apart (Fig. 4). The 

 number of layers completely resorbed was five. 



A second known-age loggerhead sea turtle, CC-2, was 

 eight years old. We assigned a minimum age estimate 

 of five years. Just outside of the resorption area was 

 a series of three LAGs that were very close together 

 (Fig. 5). In our initial analysis, we assumed that three 

 LAGs so close together could not each be deposited an- 

 nually and we interpreted the triple LAGs as a single 

 LAG with an anomalous appearance. We re-evaluated 

 this assumption after learning its history. The animal 

 was in captivity for two years and then released at 

 42.7 cm SCL in October 1994. Counting back from the 

 outside of the bone, the outermost of the triplet LAGs 

 would represent spring 1996. Given this evidence, our 

 best interpretation of this bone section was that the 

 innermost of the triplets of LAGs indicated release and 

 was therefore not an annual mark. The next LAG was 

 likely deposited the following spring (1995) and was 

 likely an annual mark. The third of the closely spaced 

 LAGs likely represented spring 1996, indicating that 

 the animal did not grow significantly in its first year 

 in the wild (Fig. 5). Following the three closely spaced 

 LAGs. there were four additional indistinct LAGs or 



annuli that represented the remaining years at large. 

 The outermost of these was very close to the edge of the 

 bone, indicating that the animal did not grow much, if 

 at all, during the last summer of its life. 



Indirect validation of annual growth marks 



For Kemp's ridley sea turtles, there was a significant 

 increase in the amount of bone deposited after the last 

 LAG from 20 June to 30 November (Fig. 6). The LAGs 

 near the outer edges of the bones were fully visible in 

 strandings that occurred after 20 June. Earlier detec- 

 tion of the outer LAGs was unlikely because a certain 

 amount of bone formation must occur following the LAG 

 before it can be discerned from the edge. There was not 

 a significant relationship between bone growth and date 

 from 1 December to 19 June. The slope of this regression 

 was very close to zero (6 = -0.003). indicating no trend, 

 either increasing or decreasing, in the amount of bone 

 deposited during this time (Fig. 6). 



Validation of the relationship between LAG diameter 

 and body size 



The regressions of the eight morphometric measure- 

 ments of loggerhead and Kemp's ridley sea turtle humeri 

 against SCL revealed high correlations between bone 

 dimension and body size (Table 2). Most importantly for 

 purposes of back-calculation, the lateral diameter at the 

 sectioning site of the humerus i distal to the insertion 

 scar of the deltopectoral muscle) and the body length of 

 the animal was highly correlated. 



