106 
Fishery Bulletin 115(1) 
40°N 
as^N 
30“N 
25°N 
90°W 85°W 80°W 70°W 
Figure 3 | 
Maximum likelihood tracks for 2 iongfin makes (Isurus paucus) * 
tracked with satellite-linked tags in different years (2012 and I 
2015) in the northwestern Atlantic Ocean. Only the common cal- 
endar days of tracking (28 April-15 July) are shown, which show a 
high degree of seasonal synchronicity. Shaded areas around tracks 
represent 99% likelihood surfaces. Both tracks indicate movement 
largely outside area closures and gear-restricted areas as mandated 
by the National Marine Fisheries Service (yellow and green poly- 
gons). Areas 1-4 with seasonal fishing restrictions are in effect for 
1) 1 April-31 May, 2J 1 Feb-30 April, 3) 1 Dec-30 April, and 4) the 
month of June. 
the shark moved back through the Straits 
of Florida in a westerly direction. After 
reaching the edge of the Yucatan shelf by 
mid-April, LFM2 moved northward into 
the GOM. By the beginning of May, the 
shark initiated southerly movements and 
re-entered the Straits of Florida, and it 
was located south of the Florida Keys by 
the first week of May. Next, LFM2 contin- 
ued on an easterly to northeasterly path 
through the Bahamas (north of Andros Is- 
land), into the open Atlantic Ocean, and off 
the continental shelf. This shark continued 
in a northeasterly direction during the lat- 
ter half of May. Then LFM2 remained in 
pelagic waters and shifted to a northerly 
direction during the month of June. On 24 
June, the shark reached its northernmost 
position (39.38°N, 70.65°W) before moving 
in a southwesterly direction during July to 
the point where its tag was detached (on 
15 July). During late June and the first 
half of July, LFM2 remained within the 
Gulf Stream and off the continental shelf, 
approximately 140-330 km from the coasts 
of New Jersey, Delaware, Maryland, and 
Virginia (Fig. 2, C and D). The total MLT 
covered 8826 km, a mean movement rate 
of 58.8 km/day. 
By comparing the 2 tracks for the calen- 
dar days they had in common, one in 2012 
and the other in 2015, one can observe a 
high degree of synchronicity in the move- 
ments of these sharks in the GOM and 
Straits of Florida, in their parallel tracks 
northward in the Atlantic Ocean, and 
in their convergence in the Mid-Atlantic 
Bight (MAB) (Fig. 3). In U.S. territorial waters, a broad 
system of areas in the GOM and off the Atlantic coast 
are closed year-round or seasonally to pelagic longline 
fishing (NMFS^). Both LFMl and LFM2 stayed largely 
outside these protected areas (Fig. 3). 
Vertical movements 
Both sharks undertook daily vertical movements and 
portions of most days were spent near the surface and 
at depths in excess of 200 m. For LFMl, the depth and 
temperature ranges experienced during its recorded 
track were 6-952 m and 4.6-28.8°C. The mean daily 
vertical range (i.e., difference between minimum and 
maximum depths) was 494.7 m (standard deviation 
[SD] 173.8). For LFM2, the ranges in depth and tem- 
perature were 0-1767 m and 4.0-28.4°C. The mean 
^ NMFS (National Marine Fisheries Service). 2016. Pelagic 
longline restrictions. In HMS commercial compliance guid- 
ance: guide for complying with the Atlantic tunas, swordfish, 
shark, and billfish regulations, p. 17-23. Natl. Mar. Fish. 
Serv., Silver Spring, MD. [Available from website.] 
daily vertical range of this shark was 435.4 m (SD 
147.0). The depth profile for LFM2 indicates a pat- 
tern of diel vertical migration (DVM), with the shark 
spending nighttime toward the surface and daytime 
at greater depths and with periods of dawn and dusk 
spent largely at intermediate depths (Fig. 4). We noted 
evidence of seasonal variation in vertical habitat use; 
LFM2 remained at shallower depths at night during 
June and July than during other months (Fig. 4). The 
mean depth at daytime (321.7 m [SD 107.6]) was sig- 
nificantly deeper for LFM2 than the mean depth at 
nighttime (94.2 m [SD 90.2]; P<0.0001) (Fig. 5). The 
mean depth at dawn (245.1 m [SD 104.5]) was shallow- 
er than the mean depth at dusk (258.7 m [SD 111.9]; 
P=0.023) (Fig. 5). 
The results from a comparison of the histogram 
data for the 2 sharks indicated similar time-at-depth 
distributions (K-S test: F=0.575; Fig. 6A), although 
some differences were noted. For example, LFM2 spent 
26.1% of its time in the depth range of 300-400 m and 
LFMl spent 10.0% of its time within that range. The 
first Iongfin mako spent more time at depths >500 m 
(10.3%) than did LFM2 (1.6%; Fig. 6A). Time-at-tem- 
