PROGRESSIONS OF FIN CHANGE DUE TO DORSAL FIN TAGGING

PROGRESSIONS OF FIN CHANGE DUE TO DORSAL FIN TAGGING
Kristen T. Mazzarella¹, Danielle Waples², Kim Urian³, Brad Hanson⁴, Forrest Townsend⁵, Aleta Hohn⁶, Susan Barco⁷, Nan Bowles⁸, Richard Mallon-Day¹, Keith Rittmaster⁸, Victoria Thayer^2,8

¹Nags Head Dolphin Watch,
²Duke University Marine Lab,
³University of North Carolina, Wilmington, NC,
⁴National Marine Fisheries Service, Seattle, WA,
⁵TracPac Inc.,
⁶National Marine Fisheries Service, Beaufort, NC,
⁷Virginia Marine Science Museum,
⁸North Carolina Maritime Museum

ABSTRACT
We present a series of photos documenting tag loss in bottlenose dolphins (Tursiops truncatus). Fourteen bottlenose dolphins were equipped with VHF radio and/or satellite-linked radio telemetry devices as part of a NMFS live capture study in Virginia Beach, VA in September 1998 and Beaufort, NC in November 1999 and April 2000. Eleven of these animals were resighted at different field sites of the western north Atlantic between November 1999 and May 2001. Their dorsal fins were photographed by independent field efforts, providing the opportunity to monitor changes due to tagging and the process of tag loss. Ideally the tags were designed so that all bolts would corrode and release after approximately 180 days resulting in tag loss and bolt-holes in the dorsal fin. Photo-documentation revealed that tags detached as designed for 2 individuals. There was considerable variation in tag detachment for the remaining dolphins. For some dolphins, patterns of notches and tears in the dorsal fin emerged as a consequence of the tag detachment. Tag attachment longevity ranged from 34 to 487 days. For five individuals, tag loss occurred in under 180 days. Two individuals retained their tags in excess of 203 days. The remaining four individuals retained their tags a minimum of 137 days and a maximum of 367 days. Understanding the process of tag loss, tag attachment longevity and short and long- term effects of tags on the dorsal fin are essential to the development of more effective tagging methods in the future.

METHODS
Images and sightings of 11 of 14 bottlenose dolphins tagged during a NMFS live-capture study conducted in Virginia Beach, VA and Beaufort, NC were compiled from opportunistic photo identification efforts from the following research groups in coastal and estuarine waters of North Carolina and Virginia:

DUML	Duke University Marine Laboratory, Beaufort, NC
NCMM	North Carolina Maritime Museum, Beaufort, NC
NHDW	Nags Head Dolphin Watch, Nags Head, NC
NMFS	National Marine Fisheries Service, Beaufort, NC
UNCW	University of North Carolina, Wilmington, NC
VMSM	Virginia Marine Science Museum, Virginia Beach, VA

Our goal was to provide a chronological record of changes in the tags and on the dorsal fin of tagged individuals while the tag was attached and following tag loss.

TAGS
The tags displayed in this study were of three designs:

NMFS/NMML #15 with four 6.3mm Delrin bolts and zinc plated nylock nuts.
Two versions of TracPacs with four 5/16" Delrin bolts, 5/16" zinc coated steel nuts with nylon inserts and brass flat washers.
1. 1999 version included lateral chines parallel to the leading edge of the dorsal fin to protect the bolts from trauma in inshore waters.
2. 2000 version omitted chines as not necessary but found they had an effect of helping to prevent the uplift on the front of the tags.

TAG DESIGNER’S NOTE: Nylon inserts in the lock nuts should be cut in order to allow for the timely release of the washers and ultimately the bolts. (F. Townsend, pers.comm.)

SUBJECTS
FB	Tag Type	Tag Design	Capture Date	Sex	Previous History
FB400	TracPac	with Chine	8-Nov-99	M	Yes
FB401	NMFS/NMML	#15	30-Sep-98	F
FB403	NMFS/NMML	#15 - right side only	11-Nov-99	F
FB404	TracPac	with Chine	9-Nov-99	M
FB407	NMFS/NMML	#15	9-Nov-99	F
FB408	NMFS/NMML	#15	11-Nov-99	M
FB412	TracPac	without chine	17-Apr-00	M	Yes
FB413	TracPac	without chine	16-Apr-00	F
FB415	TracPac	without chine	17-Apr-00	F	Yes
FB417	TracPac	without chine	20-Apr-00	F w/calf	Yes
FB418	TracPac	without chine	20-Apr-00	M	Yes
FB420	TracPac	without chine	20-Apr-00	M	Yes
FB421	TracPac	without chine	21-Apr-00	F
FB708	TracPac	without chine	20-Apr-00	M	Yes

F
B
4
0
3

11-Nov-99	Capture
6-Mar-00	Left ventral, posterior bolt gone, 3 bolts sliding posterior
5-Jun-00	Left ventral, anterior bolt sliding dorsally, algal fouling
13-Jul-00	Tag off

6 Mar 00 (NCMM)

5 Jun 00 (DUML)

19 Jul 00 (DUML)

30 Oct 00 (NCMM)

F
B
4
0
8

11-Nov-99	Capture
14-Mar-00	All bolts/sides on
17-Aug-00	Left side of tag gone
18-Mar-01	Tag off

14 Mar 00 (NMFS)

17 Aug 00 (NHDW)

18 Mar 01 (NCMM)

F
B
4
1
2

17-Apr-00	Capture
2-Jul-00	Tag off

8 Jul 00 (DUML)

10 Aug 00 (NHDW)

F
B
4
1
3

16 Apr 00	Capture
23 Jun 00	All bolts on
27 Jun 00	Ventral, posterior bolt gone
4 Jul 00	Dorsal, posterior bolt gone
13 Jul 00	Tag off

27 Jun 00 (NHDW)

4 Jul 00 (DUML)

19 Jul 00 (DUML)

F
B
4
1
5

17 Apr 00	Capture
8 Jun 00	Dorsal, anterior bolt gone
12 Jul 00	Tag tilting up on fin
19 Jul 00	Dorsal, posterior bolt backed out of fin (still attached to tag)
3 Aug 00	Ventral, posterior bolt backed out of fin (still attached to tag)
4 Sept 00	Last sighting with tag
30 Oct 00	Tag off

19 Jul 00 (DUML)

1 Sept 00 (NHDW)

30 Oct 00 (NCMM)

F
B
4
1
7

20 Apr 00	Capture
3 Jul 00	Ventral, anterior bolt gone
6 Oct 00	Dorsal, posterior bolt gone
16 Oct 00	Last sighting with tag on
27 Apr 01	Tag off

3 Jul 00 (DUML)

6 Oct 00 (VGT)

6 Oct 00 (NCMM)

01 May 01 (DUML)

F
B
4
1
8

20 Apr 00	Capture
24 May 00	Ventral, posterior bolt gone
9 Jun 00	Dorsal, posterior bolt gone, Ventral, anterior bolt backed out of fin, tag tilting up on fin.
16 Jun 00	Tag off

24 May 00 (NHDW)

9 Jun 00 (NHDW)

21 Jun 00 (NHDW)

23 Mar 01 (NCMM)

F
B
4
2
0

20 Apr 00	Capture
5 Jun 00	Tag off

6 Jun 00 (NHDW)

F
B
4
2
1

21 Apr 00	Capture
9 Sept 00	Last sighting with tag
14 Apr 01	Tag off

7 Jul 00 (DUML)

14 Apr 01 (DUML)

F
B
7
0
8

20 Apr 00	Capture
24 May 00	Tag off

16 Jun 00 (NHDW)

Tag Life vs. Tag Loss
ID	Expected Transmitter Life (In Days)	Tag Loss* (in Days)	# of Resights Prior To Tag Loss
FB400	180	N/A	0
FB401	90-120a	112-264	1
FB403	90-120a	204-242	3
FB404	180	<=172	0
FB407	90-120a	>=10	1
FB408	90-120a	470-487	5
FB412	>=180	<=75	0
FB413	>=180	78-87	10
FB415	>=180	137-193	17
FB417	>=180	176-367	6
FB418	>=180	49-56	2
FB420	>=180	<=45	0
FB421	>=180	138-353	3
FB708	>=180	<=34	0
*Tag Loss is a range determined by calculating capture-date to date-last-sighted-with-tag and date-first-sighted-without-tag

CONCLUSIONS
Improving tag designs and attachments is an evolutionary process. Although the photo-identification images were collected opportunistically, they proved critical to the evaluation of tags in this study. Image evaluation allowed examination of tag attachment condition, which will guide future design modifications. Specifically, these images documented the process of tag loss allowing estimation of attachment longevity, demonstrated the tag's biocompatibility with dolphin tissues and resistance to biofouling, and illustrated the process of wound healing. However, photo-documentation alone cannot be used to document the effect tags have on dolphin behavior, such as associations with conspecifics and movements patterns. Therefore we agree with Mate et al. (1995) and Irvine et al. (1982) that comprehensive follow-up monitoring including photo-documentation and behavioral data collection is imperative in tagging studies to document both the physical and behavioral effects of tagging so that tag design may continue to evolve.

REFERENCES

Hanson, M. B. 2001. An evaluation of the relationship between small cetacean tag design and attachment durations: a bioengineering approach. Unpubl. Ph.D. dissertation, Univ. of Washington, Seattle, WA. 208 pp.
Irvine, A. B., R. S. Wells, and M. D. Scott. 1982. An evaluation of techniques for tagging small odontocete cetateans. Fishery Bulletin 80(1):135-142.
Mate, B. R., K. A. Rossbach, S. L. Neukirk, R. S. Wells, A. B. Irvine, M. D. Scott, and A. J. Read. 1995. Satellite-monitored movements and dive behavior of a bottlenose dolphin (Tursiops truncatus) in Tampa Bay, Florida. Marine Mammal Science 11:452-463.
Scott, M. D., R. S. Wells, A. B. Irvine and B. R. Mate. 1990. Tagging and marking studies on small cetaceans. Pages 489-514 in S. Leatherwood and R. R. Reeves, eds. The bottlenose dolphin. Academic Press, San Diego, CA.

ACKNOWLEDGEMENTS
My sincerest gratitude to all the photographers and data collectors from all the study sites without whom this poster and important tag design modifications would not be possible.