Northeast Fisheries Science Center Reference Document 01-09
Results
of a field collection of biopsy samples
from
coastal bottlenose dolphin in the Mid-Atlantic
by John
Nicolas1, David C.Potter1, Charles W. Potter2, and Patricia
E. Rosel3
1National Marine Fisheries Service, 166 Water St., Woods Hole, MA 02543
2National Museum of Natural History, 10th & Constitution Ave., N.W., Washington, DC 20560
3National Marine Fisheries Service, 219 Ft. Johnson Rd., Charleston, SC 29412
Print
publication date July 2001;
web version posted July 16, 2001
Citation: Nicolas, J.; Potter, D.C.; Potter, C.W.; Rosel, P.E. 2001. Results of a field collection of biopsy samples from
coastal bottlenose dolphin in the Mid-Atlantic. Northeast Fish. Sci. Cent. Ref. Doc. 01-09; 8 p.
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Abstract
During the period October 15-24, 1999, an attempt was made to collect
biopsy samples, via the use of an 18 foot outboard motor boat and
cross bows, of skin and blubber from coastal bottlenose dolphins, Tursiops
truncatus, at two sites: Ocean City, Maryland (Figure
1) and Chincoteague Island, Virginia (Figure
1). Following two
days of searching at the Ocean City, Maryland site we detected no
animals, and the site was abandoned. The field collection team moved
35 miles south to Chincoteague Island, Virginia where coastal bottlenose
dolphin were located. Following a brief survey of the Chincoteague
Inlet area, the team determined that sufficient dolphins (n = 200
- 250) were in the area to begin biopsy operations. The team worked
with this group of dolphins during the following 3.5 days. Nine biopsy
samples were collected. These biopsy samples will support ongoing
genetic and stable isotope analyses for determining stock structure
and foraging ecology of coastal bottlenose dolphin in the Northwest
Atlantic Ocean.
INTRODUCTION
The coastal migratory stock of bottlenose dolphins, Tursiops truncatus,
was designated as depleted under the Marine Mammal Protection Act of
1972 (MMPA) as a result of an epizootic in the late 1980s. At that
time no information existed on stock structure of coastal bottlenose
dolphin along the Southeast coast of the United States. As a result
of the listing, it became necessary to gain a better understanding
of how many stocks exist in the Southeast, the extent of their ranges,
and their relationship to bottlenose dolphin found offshore (Mead and
Potter, 1995). One aspect of the ongoing stock identification project
is to use genetic information to examine stock structure, and to use
biopsy techniques to collect skin samples for the genetic analyses.
It was determined at a 1997 stock identification workshop (Hohn 1997),
that samples collected from bottlenose dolphins inhabiting coastal
waters north of Chesapeake Bay in the summer were essential for this
study. Only in this area can coastal bottlenose dolphins be unequivocally
classified as belonging to the "coastal migratory stock" which was
designated and listed as depleted under the MMPA. The biopsy field
sampling project describe here was initiated to obtain the necessary
skin samples from animals north of the Chesapeake Bay for genetic analysis
(Hoelzel et al.,1998), and blubber samples for stable isotope analysis
(Walker and Macko, 1999; Walker et al.,1999).
The purpose of this paper is to document cross bow biopsy techniques
used to collect skin and blubber samples from coastal bottlenose dolphin.
Observations on behavioral responses of bottlenose dolphins to vessel
approach are also provided.
METHODS
The goal of the field sampling trip was to obtain 30 to 40 biopsy
samples from coastal bottlenose dolphins inhabiting the area north
of the Chesapeake Bay. The samples were collected for use in ongoing
genetic (P. Rosel, NMFS, Charleston, SC) and stable isotope (S. Wetmore,
University of Massachusetts) analyses aimed at determining stock structure
and foraging ecology of coastal bottlenose dolphins in the waters of
the Southeastern United States.
One week prior to departure to the study site, a letter was drafted
and sent to local law enforcement agencies, including the Coast Guard,
the local police department and the marine patrol. This letter explained
our reason for, and method of, collection, how long we would be in
the area, and included a copy of the Northeast Fisheries Science Center
Marine Mammal Permit #917.
Two members of the biopsy team arrived in Ocean City, Maryland on
October 14, 1999. Using an 5.33 meter rigid-hull inflatable boat (RHIB)
powered with a 60 horsepower outboard motor, the team surveyed the
inland waters from northern Chincoteague Bay to Isle of Wright Bay
north of Ocean City, Maryland on October 16th and 17th (Figure
1). Due to the paucity of dolphins at the Ocean City site on October
18, 1999, the team moved to Chincoteague Island, Virginia, 35 nautical
miles south of Ocean City, Maryland. They were joined by two more members
on October 20th, adding a 2nd marksman and a recorder/sample processor.
Survey operations began on the morning of October 19 and were conducted
in and around the Chincoteague Inlet area, both inside the bay and
along the outer beaches (Figure
1). Several groups of dolphins were
located within the first hour of searching and biopsy procedures were
begun. When a group of dolphins was sighted, the boat was maneuvered
to within 7-9 meters of their location.
Two different techniques were used in approaching dolphins. During
the aggressive approach protocol, the boat operator constantly pursued
the animal changing speed and course as necessary. In the passive approach,
the operator did not change boat speed once the initial approach was
made.
Biopsies were collected using 150lb pull cross bows, manufactured
by Barnett International, fitted with 25mm cutting heads mounted on
carbon fiber arrow shafts with molded flotation around the shaft so
that the arrows could be retrieved (designed by Ceta-Dart, F. Larsen,
Copenhagen, Denmark). Date, time, location, shooter(s), number of shots,
hits and samples collected were recorded for each biopsy attempt ,
as described by Mesnick et al. (1999). Location, latitude and longitude
were recorded using a global positioning system. Surface sea water
temperature data were supplied by the United States Coast Guard, Chincoteague,
Virginia.
When a biopsy sample was collected, it was removed from the dart head
using ethanol cleaned forceps, wrapped in aluminum foil, put in a plastic
bag, and placed on ice. In the laboratory, a portion of blubber from
each biopsy was removed using a fresh razor blade, and then wrapped
in foil and frozen at -20°C. The remaining tissue was placed in a labeled
vial of 20% DMSO/saturated sodium chloride and stored at room temperature
(Barrett-Lennard et al., 1996).
Biopsy sampling trips in the Chincoteague Inlet area were conducted
during 19th - 23rd October, 1999.
RESULTS
Although local fishing boat captains and the Coast Guard had indicated
that dolphins were present in the Ocean City, Maryland area in early
October, no dolphins were seen during two days (October 15-16, 1999)
of extensive surveying of the area. At the Chincoteague Inlet site,
dolphins were relatively abundant between October 19-21, but their
numbers declined between October 21 and 23. By October 23rd, no animals
were seen in the Chincoteague Inlet area, nor during surveys north
and south of the inlet along the outer beaches. An additional day,
October 24, was spent searching only to again yield negative results.
During the period from October 19-23, the surface sea water temperature
declined from 17.8 degrees C to 15.6 degrees C.
When dolphins were seen, the boat was maneuvered to within 8-11 meters.
However, it was noted that when animals were in shallow water (1-2
meters deep), it was easier to control their movements, perhaps because
their options to avoid approach were limited. When the boat neared
a group of animals, they would most often surface and roll once, and
then dive for two to four minutes. Water visibility was poor, and as
a result there was no warning for the marksmen that an animal was about
to surface. A total of 76 shots were taken, resulting in 11 hits and
9 biopsy samples (Table
1). The total number
of hits vs shots was 14.5%. There were two instances in which an animal
was hit, but no sample was obtained. In one case, the biopsy bolt did
not release and the animal swam off with it. In the second case, the
biopsy hit the dorsal fin but no sample was retained.
On October 19 a single marksman shooting from the bow of the RHIB
took 17 shots and attained six hits and collected five biopsies (Table
1). The percentage of hits vs shots was 35.3%.
There were approximately five hours of biopsy effort on this day.
During this sampling the aggressive approach was used.
On October 21, the passive approach was used during six hours of biopsy
efforts with two marksman at the bow of the RHIB. A total of 43 shots
were taken, four hits were made and three biopsies were collected (Table
1). The percentage of shots vs. hits was 9.3%.
On October 22, during approximately three hours of sampling effort
the aggressive approach was used with two marksmen. One marksman was
stationed at the bow of the RHIB and a second marksman/helmsman was
stationed at the steering console. The marksman/helmsman was tasked
with covering the aft 180 degree sector. Eight shots were taken, one
hit was made and one biopsy collected. The percentage of shots vs.
hits was 12.5%.
DISCUSSION
Although only nine samples were collected during this pilot study,
the biopsy team concluded that, at the right time of year, sufficient
samples could be collected from bottlenose dolphins in this area. It
was noted that it would be useful to take dorsal fin photos ( Karczmarski
and Cockcroft, 1998) of animals biopsied whenever possible; data sheets
need to be modified to include such information. The Chincoteague Inlet
area may be an appropriate area to conduct live captures because of
its hard, sandy bottom topography and shallow waters. An ongoing cooperative
biopsy program between the Southeast Fisheries Science Center and the
Northeast Fisheries Science Center is important in obtaining samples
for determining the stock structure of bottlenose dolphin for the entire
east coast.
It should be noted that weather, wind and rain, were factors in the
low collection rate.
ACKNOWLEDGMENTS
We thank the following scientists from the Southeast Fisheries Science
Center: Larry Hansen, Aleta Hohn , and Steve Swartz for supporting
us to further our knowledge of the species; and Richard Merrick and
Cheryl Kitts of the Northeast Fisheries Science Center for continued
support of this project. We also thank the USCG in Ocean City, Maryland
and in Chincoteague, Virginia for their logistic support. And a special
thanks to Capt Monty Hawkins of the F/V O.C. Princess for sharing his
extensive knowledge of coastal bottlenose dolphins in the Ocean City,
MD area.
LITERATURE
CITED
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D.A. (1999). Local abundance and distribution of bottlenose dolphins
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Barrett-Lennard L.G.; Smith, T.G.; and Ellis, G.M. (1996). A cetacean
biopsy system using light weight pneumatic darts, and its effect on
the behavior of killer whales. Marine Mammal Science12(1):14-27.
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dolphin. The Royal Society 265:1177-1183.
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Memorandum NMFS-SEFSC-410, 22p.
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techniques applied in studies of free ranging bottlenose and humpback
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Mead, J.G. and Potter, C.W. (1995). Recognizing two populations of
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