Norfolk/VA Beach Bottlenose Dolphin Photo-ID Surveys

Original provider:
HDR Environmental, Operations and Construction, Inc.

Dataset credits:
The U.S. Navy Marine Species Monitoring Program

Abstract:
A combination of visual line-transect survey, photo-
identification (photo-ID), and automated acoustic
monitoring methods was used to gather important baseline
information on the occurrence, distribution, and density
of marine mammals near Naval Station Norfolk (NSN) and
adjacent areas. The study area was designed to cover areas
where United States Navy activity is substantial,
including Chesapeake Bay waters near NSN and Joint
Expeditionary Base Little Creek-Fort Story, as well as a
Mine Exercise (MINEX) Area (W-50) in the Atlantic Ocean
off the coast of Virginia Beach, Virginia. Sixty-one line-
transect surveys were completed in two zones (INSHORE and
MINEX) between August 2012 and August 2015, with 6,550
kilometers (km) and 349.6 hours completed on-effort. The
majority of sightings were of bottlenose dolphins
(Tursiops truncatus), although humpback whales (Megaptera
novaeangliae), harbor porpoises (Phocoena phocoena), and
short-beaked common dolphins (Delphinus delphis) were also
sighted in the study area on occasion. In addition,
loggerhead sea turtles (Caretta caretta), leatherback sea
turtles (Dermochelys coriacea), and a Kemp’s ridley sea
turtle (Lepidochelys kempii) were sighted during surveys.
Conventional line-transect analysis of bottlenose dolphin
sightings showed both spatial and seasonal variation in
density and abundance, with greatest density in the
INSHORE zone during fall months. Densities in the INSHORE
zone were calculated as 3.88 individuals per square
kilometer (km2) (abundance[N]=1,203) in fall, 0.63
individuals per km2 (N=195) in winter, 1.00 individuals
per km2 (N=311) in spring, and 3.55 individuals per km2
(N=1,101) in summer. Densities in the MINEX zone were
calculated as 2.14 individuals per km2 (N=1,277) in fall,
0.06 individuals per km2 (N=37) in winter, 1.53
individuals per km2 (N=913) in spring, and 1.39
individuals per km2 (N=829) in summer. Twenty-seven photo-
ID surveys were completed, and a photo-ID catalog was
created using photos taken during both dedicated photo-ID
and line-transect surveys through May 2014; it contains
878 identified individuals to date. Subsequent photos will
continue to be added and analyzed. One hundred ten
individuals were re-sighted; however, most re-sightings
were less than 4 months and 30 km apart. Additional survey
effort and further analysis will be required before any
clear movement patterns can be determined. C-POD acoustic
data-loggers were initially deployed at four sites
throughout the study area to cover areas of high United
States Navy activity. Bottlenose dolphins were detected in
each deployment location during all deployments from
August 2012 to December 2015. Though deployments did not
provide consistent coverage in all seasons for all sites
due to loss of gear, results from two deployment sites
nearest to NSN showed a greater level of occurrence during
fall months, and a diel pattern of occurrence with
increased detections during nighttime hours for three
deployment sites.