410 
Fishery Bulletin 118(4) 
184 176 327 253 265 340 360 319 236 
Season 
ga Winter 
Spring 
& Summer 
& Fall 
Jan Feb Mar Apr May Jun Jul Aug Sep Oct 
Figure 9 
Box plot of sea-surface temperatures (SST) recorded, by month and season, 
as part of capture records from fishery-dependent data of common thresher 
sharks (Alopias vulpinus) in the western North Atlantic Ocean between 1964 
and 2019. The numerals above the boxes indicate the number of records for 
each month. The upper and lower parts of each box represent the first and 
third quartiles (the 25th and 75th percentiles), and the horizontal white line 
is the median. The whiskers that extend above and below the box correspond 
to 1.5 times the interquartile range, and the black circles represent values 
outside this range. 
commonly observed life stage, possibly because the 
restricted distribution of YOY in depths <50 m. There are 
no minimum commercial size limits for this species in 
the U.S. waters of the Atlantic Ocean and a review of the 
data provided by the Northeast Fisheries Observer Pro- 
gram indicate that many YOY are retained for sale. For 
example, between January and April 2018, at least 367 
YOY were captured by gill nets during observed trips in 
the vicinity of Cape Hatteras. Assuming an average 
brood size of 3.7 young (Natanson and Gervelis, 2013), 
these captured sharks represent the reproductive output 
of approximately 100 adult females. Given the bi- or tri- 
ennial reproductive cycle of this species in the WNA 
(Natanson and Gervelis, 2013) and the fact that the total 
number of YOY removed in the fishery may be many 
times greater than what was observed, such removals 
may represent a significant loss in recruitment in the 
WNA. However, because of their small size, landed 
weight of YOY common thresher sharks may not consti- 
tute a large percentage of the total quota for pelagic 
sharks in the Atlantic Ocean (i.e., 488.0 metric tons in 
dressed weight; NMFS, 2006). 
Our results provide new insight into the environmental 
conditions and habitats used by common thresher sharks 
for each life stage and will assist managers in the designa- 
tion of EFH by life stage off the U.S. east coast, as required 
Nov Dec 
under the Magnuson-Stevens Fishery 
Conservation and Management Act. 
Because of insufficient data on individ- 
ual life stages, all life stages currently 
share a single EFH that spans conti- 
nental shelf waters from Cape Lookout 
to Georges Bank and from Cape Ann, 
Massachusetts, to Bar Harbor, Maine 
(NMFS, 2017). However, our results 
provide information that should be suf- 
ficient to differentiate EFH for YOY. 
Although the extent of fishery-dependent 
data compiled for YOY common thresher 
sharks ranges from the Gulf of Maine 
to off South Carolina (consistent with 
Natanson and Gervelis, 2013), our anal- 
yses clearly identify areas of high levels 
of interaction off New York and New 
Jersey during the summer and off Cape 
Hatteras during the winter. Additional, 
direct information on the residency and 
movements of YOY common thresher 
sharks in these areas, however, is needed 
to confirm whether they warrant desig- 
nation as nursery areas (Heupel et al., 
2007). Additional fishery-independent 
(e.g., tagging and survey) data are also 
needed to better define juvenile and 
adult EFH and to confirm the broader 
conclusions regarding distribution and 
habitat use of common thresher sharks 
presented herein. 
Acknowledgments 
This study would not have been possible if not for the 
extensive efforts of those who worked to collect, edit, 
and compile the fishery-dependent data used herein. We 
thank L. Beerkircher, S. Cushner, J. Carlson, A. Mathers, 
E. Orbesen, and D. Snodgrass of the Southeast Fisheries 
Science Center for providing data. This work was supported 
by award NAI6NMF4270231 from the NOAA Saltonstall- 
Kennedy Grant Program. This article is Massachusetts 
Division of Marine Fisheries contribution number 117. 
Literature cited 
Amante, C., and B. W. Eakins. 
2009. ETOPO1 1 Arc-Minute Global Relief Model: proce- 
dures, data sources and analysis. NOAA Tech. Memo. 
NESDIS NGDC-24, 19 p. 
Baum, J. K., and W. Blanchard. 
2010. Inferring shark population trends from generalized lin- 
ear mixed models of pelagic longline catch and effort data. 
Fish. Res. 102:229-239. 
Baum, J. K., R. A. Myers, D. G. Kehler, B. Worm, S. J. Harley, and 
P. A. Doherty. 
2003. Collapse and conservation of shark populations in the 
Northwest Atlantic. Science 299:389-329. 
