ABSTRACT: Growth rates recorded between 1974 and 1991 for 44 immature hawksbill sea turtles in the southern Great Barrier Reef foraging grounds were modelled using nonparametric regression methods. The implicit sampling design in this long-term mark-recapture program was mixed longitudinal and included growth records for both female and male hawksbills ranging between 39 and 85 cm CCL (curved carapace length). Distinct sex-specific growth patterns were found, with immature female hawksbills growing at ca 0.5 cm yr^-1 faster than male immature hawksbills at all recorded sizes. The mean-size specific growth rate function for females was nonmonotonic, rising rapidly from recruitment size (> 35 cm CCL) to a maximum growth rate of 2.2 cm yr^-1 at 60 cm CCL before declining to negligible growth approaching sexual maturity at a size >=80 cm CCL. The mean-size specific growth rate function for males was also nonmonotonic, rising from the same recruitment size to a maximum growth rate of 1.7 cm yr^-1 at 60 cm CCL before declining to negligible growth approaching sexual maturity >=80 cm CCL. No significant inter-annual variation in growth rates was found but the data set was too small to be conclusive. Size-specific growth rates were slower than observed for stocks from western Atlantic-Caribbean waters. Juvenile hawksbill growth spurts around 60 cm CCL, sex-specific growth and slow size-specific growth rates are distinct growth characteristics for immature hawksbill sea turtles resident in southern Great Barrier Reef waters.

KEY WORDS: Somatic growth · Nonparametric regression · Hawksbill turtles · Great Barrier Reef

Published in MEPS Vol. 146 (1997) on January 30
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1997