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Fishery Bulletin 118(4) 
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Figure 7 
Distribution of male and female common thresher sharks (Alopias vulpinus) and of both sexes combined in the western North 
Atlantic Ocean between 1964 and 2019, by season and aggregated in grid cells (0.5° x 0.5°). The lack of capture records in maps 
for waters of Canada is a result of missing data on sex of sharks. Records from the Gulf of Mexico are presented in the inset. The 
200-m depth contour delineates the boundary of the continental shelf. 
California, Mexico, to as far north as British Columbia, 
Canada (Hanan et al., 1993; Cartamil et al., 2016; Kinney 
et al., 2020). The distribution of common thresher sharks 
in the WNA was more contracted during the winter than 
in any other season, with individuals being most com- 
monly taken in relatively small areas off the coast from 
Virginia to North Carolina (outside of the barrier islands) 
and off the east coast of Florida. 
The seasonal distribution of common thresher sharks 
changes markedly over ontogeny. Parturition for this spe- 
cies occurs from May through August in the mid-Atlantic 
states and in southern New England (Natanson and 
Gervelis, 2013; Young et al., 2016), consistent with the ele- 
vated occurrence of YOY throughout these areas during 
the summer months (Fig. 5). In the winter, YOY were taken 
almost exclusively in depths <50 m off the coast of North 
Carolina from Oregon Inlet to Cape Lookout. These results 
align with previous hypotheses that inshore waters from 
North Carolina to Massachusetts support nursery habitat 
for YOY and juvenile common thresher sharks (Natanson 
and Gervelis, 2013) and indicate that specific areas off 
New York, New Jersey, and Cape Hatteras (Fig. 5) may 
be of particular importance to individuals in these life 
stages. Investigation into why YOY occur more frequently 
in these areas than in others was beyond the scope of this 
study; however, their presence may be related to environ- 
mental preferences (see subsequent paragraphs) or prey 
distribution. 
The distribution of common thresher sharks expands 
and individuals move into deeper waters of the WNA as 
they grow to maturity. A similar range expansion has been 
documented for juveniles and adults of this species off the 
U.S. west coast (Smith et al., 2008; Kinney et al., 2020) 
and may be related to changes in diet or physiological lim- 
itations imposed by environmental variation (Knip et al., 
2010). Note that the inability to assign a life stage to 
