Hueter et a!.: Horizontal and vertical movements of isurus paucus in the northwestern Atlantic Ocean 
113 
dive to greater maximum depths than those attained 
by smaller specimens (Sepulveda et aL, 2004). As with 
all other lamnid shark species, the longfin mako has 
the capacity to maintain its visceral temperature sub- 
stantially above ambient sea temperature through a 
suprahepatic rete (Carey et al., 1985; Bernal et aL, 
2012), which may be a mechanism for enhancing rates 
of digestion and food assimilation (Goldman 1997; 
Newton et al., 2015). 
Implications for consereatisn strategies 
Pelagic longline fisheries pose a principal threat to 
longfin makes (Reardon et ai., 2006). Although bycatch 
data for this species are insufficient, there are pub- 
lished accounts of longfin makos having been captured 
in gear that targeted swordfish (Dodrill and Gilmore, 
1979; Buencuerpo et ah, 1998; Queiroz et al., 2006; 
Mucientes et al., 2013). In a report on the swordfish 
fishery along the east coast of Florida, Berkeley and 
Campos (1988) noted that more shark species than tar- 
get species were captured and that the overall mortal- 
ity rate was 66% for 13 species of hooked sharks. Fur- 
thermore, in a recent 1-year survey (conducted from 
October 2010 through November 2011) of the pelagic 
longline fishery along the northwestern coast of Cuba, 
the longfin mako was the second-most abundant shark 
species landed (by number), exceeded only by the short- 
fin mako, out of the 15 different shark species observed 
(Aguilar et al., 2014). A nearly 5-year (from October 
2010 through April 2015) pilot monitoring program of 
the same fishery documented the longfin mako as the 
most abundant pelagic shark species landed (MINAL, 
2015). Currently, there are no restrictions on catches 
of longfin makos in the waters of Cuba. In U.S. waters, 
the year-round or seasonal closing of areas to pelagic 
longline fisheries in the GOM and Atlantic Ocean ap- 
pear to offer minimal protection for this species. Al- 
though based on only 2 tracks from 2 individuals, our 
data do not indicate that these sharks spent much time 
inside these closed areas, where they could have been 
protected from pelagic longlining. 
The effect of this fishing pressure may be profound 
for the longfin mako, given its lower fecundity (2-8 
pups per litter; Guitart Manday, 1975; Compagno, 
2001) than that of the shortfin mako (4-25 pups per 
litter; Mollet et al., 2000; Compagno, 2001). The combi- 
nation of this low productivity and high susceptibility 
of longfin makos to longline gear has led to this species 
being ranked as highly vulnerable in ecological risk as- 
sessments of shark species caught in pelagic longline 
fisheries (Cortes et al., 2010, 2015). With this vulner- 
ability and generally lower abundance in comparison 
with its conspecific, for which it is often misidentified, 
the longfin mako is a shark species of special conserva- 
tion concern in today’s oceans. 
The depths at which sharks distribute themselves 
profoundly affect their susceptibility to commercial 
fisheries (Speed et al., 2010). The diel vertical move- 
ment pattern of the longfin mako contributes to its 
vulnerability to pelagic longline fisheries, especially to 
fisheries that target swordfish. Results from a recent 
study, in v/hich the satellite tracks of sharks were 
compared with fishing vessel movements in the North 
Atlantic Ocean, indicate how effectively pelagic long- 
line fleets are exploiting key oceanic shark habitats, 
almost entirely overlapping fishing effort with pre- 
ferred habitat of shark species for much of the year 
(Queiroz et al, 2016). With only 2 satellite tracks of 
longfin makos that covered periods of 3-5 months, the 
results of our study reveal connectivity in the range 
of this species among the territorial waters of 4 coun- 
tries — the United States, Cuba, Mexico, and the Ba- 
hamas — and hence the vulnerability of this species to 
fishing fleets from multiple nations. More than 75% 
of species of pelagic sharks and rays have an elevat- 
ed risk of extinction due to overfishing (Dulvy et al., 
2008), and large pelagic shark species, such as the 
longfin mako, have an approximately 80% probabil- 
ity of being threatened (Dulvy et al., 2014). Effective 
management and assessment efforts, however, are of- 
ten impeded by a lack of species-specific fishery and 
biological data. Although our study contributes new 
information to the limited knowledge of the longfin 
mako, continued efforts to improve data collection and 
the monitoring of pelagic shark catches, particularly 
in areas of concentrated abundance of longfin makos, 
such as those off the northern coast of Cuba, are war- 
ranted. The recent implementation of the first Nation- 
al Plan of Action for conservation and management of 
species of sharks and rays by Cuba (MINAL, 2015) is 
a positive step toward this goal. 
Acknowledgments 
We are indebted to the captains and crews of Florida 
Institute of Oceanography’s RV Weatherbird II and of 
the MV Marinabella and FV Poco a Poco in Cuba. We 
sincerely thank our many Cuban colleagues, including 
L. Garcia Lopez, A. Alvarez Aleman, and C. Aguilar 
Betancourt of the Centro de Investigaciones Marinas, 
Universidad de la Habana, and F. Pina of the Centro de 
Investigaciones de Ecosistemas Costeros. Special grati- 
tude is extended to Tandem Stills + Motion, Herzog & 
Co., and Discovery Communications for documenting 
the work in Cuba. Permission to deploy satellite tags 
in Cuba was made possible through the dedicated ef- 
forts of D. Whittle of the Environmental Defense Fund 
and of Mundo Latino TV of Cuba. We thank J. Stewart 
for the R script used to generate likelihood surfaces 
and B. Galuardi for his helpful advice in constructing 
figures of sea-surface temperatures. We are grateful to 
R Rogers and 2 anonymous reviewers for their input 
toward improving the manuscript. This work was fund- 
ed by the Gulf of Mexico Research Initiative through 
the Florida Institute of Oceanography and by the Guy 
Harvey Ocean Foundation, Christopher Reynolds Foun- 
dation, Environmental Defense Fund, and Discovery 
Communications. 
