James et al.: Overwinter habitat use of young-of-the-year Carcharodon carcharias 69 
confirmed that this region functions as a summer nursery 
area, using satellite and acoustic telemetry. During this sea- 
son, YOY white sharks typically occupy waters off the south 
shore of Long Island, New York, in depths <40 m, sea-surface 
temperatures (SST) of 18-22°C, and chlorophyll-a (Chl-a) 
concentrations >2 mg/m? (Shaw et al., 2021). Despite this 
improved understanding of the summertime habitat use of 
YOY white sharks, information on overwinter habitat use 
has been limited to data for only a few individuals tracked to 
coastal waters of North and South Carolina from December 
2016 through April 2017 (Curtis et al., 2018). Larger juve- 
nile and adult white sharks (>2.5 m in total length [TL]) typ- 
ically overwinter over a broad area encompassing the east 
and west coasts of Florida and occasionally offshore pelagic 
waters (Adams et al., 1994; Curtis et al., 2014; Skomal et al., 
2017), but it is not known if YOY white sharks occupy simi- 
lar areas during this season. 
In US. waters of the Atlantic Ocean, the white shark 
is a prohibited species under National Marine Fisheries 
Service (NMFS) Atlantic Highly Migratory Species fish- 
ery regulations. The NMFS also designates EFH for YOY, 
juvenile, and adult white sharks to help minimize adverse 
effects on habitats important to each of these life stages, 
with the current EFH for YOY white sharks covering a 
broad portion of the continental shelf waters from Cape 
Cod, Massachusetts, to southern New Jersey (Federal 
Register, 2017). Although not specifically designed to pro- 
tect white sharks, several fishery time-area closures in 
the U.S. waters of the Atlantic Ocean afford protections to 
coastal and pelagic shark populations (NMFS’). Relative 
abundance of white sharks in the Northwest Atlantic 
Ocean appears to be increasing in response to these fish- 
eries management measures; however, the population 
remains data poor and biologically vulnerable, and there is 
uncertainty in regional population dynamics (Curtis et al., 
2014; Skomal et al., 2017). 
The purposes of this study were to provide the first 
characterization of overwinter distribution and habitat 
use of YOY white sharks and to assess the degree to which 
existing spatial fisheries management measures align 
with that distribution. The results of this work enhance 
the growing body of information on the spatial ecology of 
white sharks in the Northwest Atlantic Ocean off the east- 
ern United States (Curtis et al., 2014; Skomal et al., 2017; 
Curtis et al., 2018; Shaw et al., 2021) and provide data 
necessary for making practical recommendations that 
may improve fisheries management. 
Materials and methods 
Young-of-the-year white sharks were tagged during 
August in 2016 and 2017 by using methods described 
by Curtis et al. (2018) and Shaw et al. (2021). Briefly, 
' NMFS (National Marine Fisheries Service). 2019. Issues and 
options for research and data collection in closed and gear 
restricted areas in support of spatial fisheries management, 27 p. 
Natl. Mar. Fish. Serv., Silver Spring, MD. [Available from website.] 
recreational rod-and-reel shark fishing techniques were 
used to catch sharks offshore of Montauk, New York. Upon 
capture, each shark was guided to a boatlift platform on 
the MV OCEARCH and raised out of the water for tag- 
ging and sample collection, while a raw seawater hose was 
placed in its mouth to irrigate its gills. A satellite-linked 
smart position or temperature transmitter (SPOT-258A7, 
Wildlife Computers Inc., Redmond, WA; 3-year tag life) 
and an acoustic transmitter (Vemco V16-6H, Innovasea 
Systems Inc., Boston, MA; 10-year tag life) were attached 
to each shark. Smart position or temperature tags were 
attached to the first dorsal fin, permitting tag transmis- 
sion to Argos satellites whenever the fin broke the sea sur- 
face. Acoustic transmitters were surgically implanted into 
each shark’s coelomic cavity through a small incision that 
was sutured closed. Handling and tagging of all sharks 
was done in compliance with all applicable guidelines and 
regulations, and the research was conducted under per- 
mits from the NMFS and the New York State Department 
of Environmental Conservation. 
The overwinter period was defined as that from December 
through April on the basis of previous data (Curtis et al., 
2018), and only tag detections from that period were ana- 
lyzed. Acoustic detections were received from moored 
acoustic receivers (Vemco VR2W, Innovasea Systems Inc.) 
maintained by cooperating members of the Mid-Atlantic 
Acoustic Telemetry Observation System (MATOS) along 
the East Coast of the United States (e.g., Bangley et al., 
2020a). Positions transmitted to Argos satellites with 
location quality classes of 0-3, A, and B (i.e., the highest 
quality locations, with estimated errors less than approx- 
imately 15 km) were chronologically combined with pas- 
sive acoustic detections of tags received from the MATOS 
network to produce positions for each shark, following 
Shaw et al. (2021). Erroneous points, including points 
on land, and points with an Argos location quality worse 
than B were removed from the analysis. One unique tag 
transmission per shark per day was selected on the basis 
of location quality, and daily positions were made regular 
by interpolating positions to fill gaps up to 7 d between 
consecutive tag detections with the ArcMET extension 
for ArcGIS 10.3 (Esri, Redlands, CA) (Curtis et al., 2018; 
Shaw et al., 2021). No positions were interpolated for tag 
detection gaps greater than 7 d in duration. 
Four environmental variables were used to characterize 
habitat use: SST, Chl-a concentration, sea-surface height 
(SSH), and bathymetry. Underlying depths were derived 
from the NOAA ETOPO1 Global Relief Model, a data set 
of land topography and ocean bathymetry with a 1-arcmin 
resolution (NOAA National Geophysical Data Center, 
available from website), and each depth was matched to a 
raw coordinate position in ArcGIS. Group for High Resolu- 
tion SST Level 4 data from the Jet Propulsion Laboratory 
were compiled at a spatial resolution of 0.01° (available 
from website). Weekly Chl-a concentrations were compiled 
2 Mention of trade names or commercial companies is for identi- 
fication purposes only and does not imply endorsement by the 
National Marine Fisheries Service, NOAA. 
