Date Awarded

1999

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Virginia Institute of Marine Science

Abstract

I present here an investigation of several aspects of the biology of sea turtles in the mid-Atlantic Bight. During 19 years of data collection, included in this study, strandings have increased for all species of sea turtles in Virginia. Most sea turtle strandings occurred during the spring when juvenile turtles migrate into the Bay (Kemp's ridleys had a second significant stranding peak, during fall migration) along the Southern Bay and Virginia Beach Oceanfront. Sea turtles utilize the Chesapeake Bay as a feeding area when the water temperature approaches 20??C, and they leave after the water temperature drops below 20??C. Although some turtles have stranded at much lower temperatures. The number of possible anthropomorphic interactions with turtles has increased as recreational boating & fishing has increased in popularity. The cause of death attributed to the largest number of strandings is boat and propeller damage. Commercial fishery interactions (entanglement) were second in importance, but such interactions, while usually resulting in turtles drowning, were less easily detected. The vast number of the strandings having an unknown cause of death maybe attributed to carcass decomposition and lack of observer training. The VIMS data set provided the basis for morphometric analysis. Regressions calculated from the data often explain more than 90% of the variation in the measurements. These regressions may be used to estimate missing values required by State and Federal management agencies. The carapace morphology of loggerheads and Kemp's ridleys changes as they grow. The carapace flattens out in larger individuals, presumably to maintain a relatively constant amount of lift while swimming at higher cruising velocities. The extra lift may be needed by hatchlings because of their low swimming speed. Using satellite imaging technology and sea turtle abundance and distribution data from coastal aerial surveys, off North Carolina, I confirmed a behavioral temperature range of 13??C to 29??C, which is well within previously established physiological limits and also encompass values recorded in the Chesapeake Bay. Magnetic resonance imaging techniques, were used to image juvenile Kemp's ridley and loggerhead sea turtle heads. The location of magnetic particles in the sea turtle heads appears to be in the ethmoid, in the same region as in birds and fishes. The anomalies were bilaterally paired suggesting a possible use as a sensory system. Results from an oxytetracycline injected adult loggerhead sea turtle show that bone rings are laid down on an annual basis. Examination of whole cross sections of the humerus suggests that the dorsal and ventral regions used for taking bone cores used in previous studies is inappropriate. The failure in other studies to detect growth rings may have been due to samples being taken from the dorsal surface of the bone. The lateral edges of the humerus should be used for future oxytetracycline studies. Growth rates and ring deposition support previous data, supporting the notion that sexual maturity may occur over a very large size range.

DOI

https://dx.doi.org/doi:10.25773/v5-hxkm-sb75

Rights

© The Author

Download

Share Feedback

Share

COinS