. Current herpetology. Reptiles; Herpetology. 14 Current Herpetol 20(1) 2001 Table 2. Regression equations for the relationship between the carapace length (Y) and the length of three plastron bones (Xn) in 16 Reeves' turtles from Ishima island. Name of plastron bone Regression equation Epiplastron(Xi) Hypoplastron (X2) Xiphiplastron (X3) Y=+ ¥=+ ¥=+ < < < to obtain the size distribution of dead turtles. When detected, we recorded substrate type, condition of dead bodies, sex, and straight length of carapace if possible. When
. Current herpetology. Reptiles; Herpetology. 14 Current Herpetol 20(1) 2001 Table 2. Regression equations for the relationship between the carapace length (Y) and the length of three plastron bones (Xn) in 16 Reeves' turtles from Ishima island. Name of plastron bone Regression equation Epiplastron(Xi) Hypoplastron (X2) Xiphiplastron (X3) Y=+ ¥=+ ¥=+ < < < to obtain the size distribution of dead turtles. When detected, we recorded substrate type, condition of dead bodies, sex, and straight length of carapace if possible. When broken shells were found, measurements were taken on the lengths of bones comprising the plastron along the body axis from snout to vent. In order to estimate carapace length from the plas- tron bones, appropriate regression equations were established based on measurements of both carapace length and lengths of epi-, hypo-, and xiphi-plastrons for the dead bodies with a complete shell (Table 2). Results We marked 1,123 individuals of C. reevesii. The proportion of newly captured unmarked turtles decreased with advance of the field sur- vey to ca. 5% at the 13th survey and remained constant thereafter (Fig. 2). The estimated pop- ulation size of C. reevesii was 1,179 with a 95% confidence limit of at the 17th sur- vey. Of 1,123 C. reevesii captured, 833 were males, 214 were females, and the remaining 76 were juveniles of undetermined sex. The mean carapace lengths and weights of the old indi- viduals whose ages were unknown were mm (1SD=, range= mm), g (1SD=, range= 136-670 g) in males (N=617), and mm (SD=, range=l mm), g (SD=, range=250-1450g) in females (N=148). In smaller juveniles, it was difficult to distinguish sex by the tail. However, we could determine three-year-old juvenile males. So all turtles of undetermined sex older than three years were assumed to be females. Estimated sex ratio of 100-1 (
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