Date of Award

1989

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Science

First Advisor

C. Robert Shoop

Abstract

The leatherback sea turtle, Dermochelys coriacea, is a highly migratory and pelagic endangered species. Leatherbacks are globally distributed, with pantropical nesting populations frequenting the Caribbean, Atlantic, Indian and Pacific oceans. These nesting groups appear to have cohesive and predictable occurrence, but the true demic structure of any population subgroup has never been demonstrated. Using two independent iso-electric focusing •methods to analyze blood proteins, this study shoved that the North Atlantic population of leatherback turtles is indeed subdivided into at least two, though probably many more, genetically distinct stocks.

That the Atlantic population of Dermochelys, previously assumed to be a contiguous, panmictic assemblage, is subdivided has important implications for management. First, since nesting groups appear to exhibit no gene flow, each nesting population needs to be treated as a separate management unit. Second, managers will have to look at demes objectively to determine where a concentration of effort and funds will produce the greatest recovery for the species. Lastly, demes will have to be monitored to determine if they are approaching minimum viable population size and to quantify the level of inbreeding.

Information on the structure and movement of populations is critical for predictive modeling of population growth and for attempted management of the species based on such population models. For example, a demographic model such as the Leslie matrix can demonstrate how a defined population will react to decreased mortality in any population sector. The results of theoretical modeling in this study show that for the North Atlantic leatherback turtle, as for the loggerhead population modeled by Crouse et al., protection of large juveniles is the most critical management action that can be taken. The implications of this finding are of major importance to management, since current conservation measures for this and all other sea turtle species focuses almost exclusively on protection of eggs at the nesting beaches.

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