Abstract
Since the 1970s, telemetry has provided much information about small cetaceans that could not have been learned in any other way. As technology improves and more sensors are added to tags, the potential for data collection will increase tremendously.4,5,8 Tag designs are compromises between minimizing: 1) the risk of injury to the animal, 2) drag, 3) mass, and 4) thermoregulatory effects, while attempting to maximize: 1) signal strength, 2) range, and 3) longevity of the transmissions and the attachment.4,5 Until recently, electronic tags were quite large and required multiple pins to secure them to dorsal fins, sometimes leading to fin injuries.1,3-5 Efforts since 1975 by the Sarasota Dolphin Research Program and collaborators to develop safe and effective electronic dolphin tags have led toward using only a single attachment pin, mounted low along the trailing edge of the dorsal fin, with a trailing tag.2,6 Computational fluid dynamics modeling was used to refine the design of Wildlife Computers SPLASH time-depth-recording tags to reduce drag and improve attachment performance. Modifications were made to the tag shape and size, and lock nuts were replaced with thread-forming flat-head screws, altogether reducing drag by about 50%. Field tests of the resulting design were conducted during May–August 2012, involving health assessment, tagging, monitoring and recapture of long-term resident bottlenose dolphin in Sarasota Bay, FL.7 Ten dolphins were tagged in May 2012. Five of these tags were treated experimentally with Propspeed antifouling coating. The dolphins were observed, photographed, and video-recorded over the 69–92 days they carried tags. Eight of the dolphins were recaptured in July 2012, the tags were removed, and health assessments were performed, 69–75 days after deployment. The remaining male pair was observed until the tags came off their fins, as designed, sometime between post-deployment day 92 and day 119. Preliminary analyses indicate that the new tag design worked very well. Fin damage was minimal compared to earlier tag designs, with little or no migration of the attachment pin through the fin. Observations of the tagged dolphins with the tags found no behavioral differences associated with the tags, in terms of respiration patterns or ranging patterns. No differences in social patterns were observed. Both tagged adult females became pregnant while carrying tags. Follow-up assessments during tag removal in July found no indication of health problems associated with the tags. The anti-fouling coating worked very well. Minimal growth occurred on coated tags as compared to the heavy growth on uncoated tags (Figure 1). While initial indications are that the tag design, attachment, and coating combination developed during this project are a significant improvement over previous designs, in terms of performance and reduction of risk of injury to the animal, further testing involving larger sample sizes and different conditions is advised.
| Figure 1. Adult males F164 (left) and F242 (right) 92 days post-deployment, showing heavy biofouling on F164's uncoated tag, and minimal growth on F242's coated tag. | 
|
|
| |
Acknowledgments
We are grateful to the Office of Naval Research and Dolphin Quest for providing support and to Wildlife Computers for working with us to modify tags for the experiments. The staff, volunteers and collaborators of the Sarasota Dolphin Research Program were crucial to the success of the project. Field tests were performed under National Marine Fisheries Service Scientific Research Permit No. 15543 and IACUC approvals through Mote Marine Laboratory.
* Presenting author
Literature Cited
1. Balmer BC, Schwacke LH, Wells RS. 2010. Linking dive behavior to satellite-linked tag condition for a bottlenose dolphin (Tursiops truncatus) along Florida's northern Gulf of Mexico coast. Aquatic Mammals 36:1–8.
2. Balmer BC, Wells RS, Schwacke LH, Rowles TK, Hunter C, Zolman ES, Townsend FI, Danielson B, Westgate AJ, McLellan WA, Pabst DA. 2011. Evaluation of a single-pin, satellite-linked transmitter deployed on bottlenose dolphins (Tursiops truncatus) along the coast of Georgia, U.S.A. Aquatic Mammals 37:187–192.
3. Irvine AB, Wells RS, Scott MD. 1982. An evaluation of techniques for tagging small odontocete cetaceans. Fish. Bull. U.S. 80:135–143.
4. Lander ME, Westgate AJ, Bonde RK, Murray MJ. 2001. Tagging and tracking. In: Dierauf L, Gulland F., editors. CRC handbook of marine mammal medicine. 2nd edition. Boca Raton (FL): Chemical Rubber Company Press. p. 851–894.
5. Scott MD, Wells RS, Irvine AB, Mate BR. 1990. Tagging and marking studies on small cetaceans. In: Leatherwood S, Reeves, RR, editors, The bottlenose dolphin. San Diego (CA): Academic Press: p 489–514.
6. Wells RS, Fougeres EM, Cooper AG, Stevens RO, Brodsky M, Lingenfelser R, Dold C, Douglas, DC. Accepted. Movements and dive patterns of short-finned pilot whales, Globicephala macrorhynchus, released from a mass stranding in the Florida Keys. Aquatic Mammals.
7. Wells RS, Rhinehart HL, Hansen LJ, Sweeney JC, Townsend FI, Stone R, Casper D, Scott MD, Hohn AA, Rowles TK. 2004. Bottlenose dolphins as marine ecosystem sentinels: Developing a health monitoring system. EcoHealth 1:246–254.
8. Westgate AJ, Read AJ. 1998. Applications of new technology to the conservation of porpoises. Marine Technology Journal 32: 70–81.