An unresolved problem with radio-tagging small cetaceans is premature tag loss associated with dorsal fin tissue degeneration and attachment pin out-migration. Pressure necrosis at the pin/tissue interface has been suspected of causing this tissue degeneration. However, it is unknown if the stresses that the tags generate are sufficient to cause tissue breakdown, or if it is associated with dynamic loads that disrupt the tissue healing process. The objective of this dissertation was to determine if a relationship exists between these load-related tissue degradation factors and the duration of small cetacean tag attachments. The specific approach included estimating the loads that previously deployed tag configurations generated using a model porpoise mounted in a wind tunnel. Based on these results and the incorporation of basic hydrodynamic/engineering principles, the load of a new, lower drag, tag design was quantified. The major structural components of the harbor porpoise dorsal fin (epidermis/dermal papillae, ligamentous sheath, and central core) were determined using histological techniques. This aspect was complimented by quantifying the material properties of these component tissues using standard mechanical testing. The data from these efforts were incorporated into a finite element analysis (FEA) to quantify the stress levels of each tag design. The final aspect of this study was to deploy the redesigned tag on small cetaceans with a dedicated resighting effort to assess its attachment performance. This paired side-mount tag appeared to provide a longer duration of attachment compared to the other two designs, exceeding a year, with some tags causing no apparent tissue damage. The FEA showed that paired side-mount also consistently developed only low to moderate stresses compared to the front-mount, which generally had the highest stresses and shortest attachment durations. The single side-mount tag had stresses and attachment durations which were intermediate of the other tag designs. Several limitations to the FEA preclude determination if any of the tags generate stresses sufficient to cause tissue degeneration. Future improvements in attachment performance will likely result from investigations which use the general approach outlined in this study.
An Evaluation of the Relationship Between Small Cetacean Tag Design and Attachment Durations: A Bioengineering Approach
Title: An Evaluation of the Relationship Between Small Cetacean Tag Design and Attachment Durations: A Bioengineering Approach
May 16, 2001
Thesis Type: Doctoral Dissertation
Academic Department: Aquatic and Fisheries Sciences
Hanson, M. (2001). An Evaluation of the Relationship Between Small Cetacean Tag Design and Attachment Durations: A Bioengineering Approach. Doctoral Dissertation, University of Washington.