Ecologic Implications of Size and Growth in Chelonia

Carr, Archie; Goodman, Donald

Among the conspicuous gaps in the natural history of marine turtles is a dearth of information on growth after maturity is reached. During the course of a 15-year tagging program at the nesting ground of the Atlantic green turtle, Chelonia mydas, at Tortuguero, Costa Rica, 447 remigration returns were recorded, all after absences of two years or more. There have been 42 two-time returns to the beach, and three turtles have returned three times after the date on which they were originally measured (Carr and Carr, 1970). Although extremely slow (see Fig. I) the growth of mature females in the west-Caribbean population can now be assessed with some accuracy, and the relation between individual size and population density can be appraised. In the Caribbean, as in other parts of the circumtropical range of Chelonia, a decrease in population density has evidently been in progress for at least a century. While good census data are not available, evidence of the decline can be seen in the cessation of group nesting in many localities; in the disappearance of green turtles from Thalassia beds where once they were abundant; and perhaps in a long-term decline in maximum body size-as indicated by comparison of modern measurements with those of commercial turtling records of the 19th century. At the Tortuguero nesting ground this trend appears to have caused a foreshortening and early termination of the season, a fall in the number of nesting arrivals on the northernmost part of the 22-mile breeding beach, and an almost complete cessation of nesting on the southern six miles of the shore.

Ecologic Implications of Size and Growth in Chelonia

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