Viducic et al.: Reproductive characteristics for Prionace glauca in the North Atlantic Ocean 27 
the Madeira Islands, and the Canary Islands (Aasen, 
1966; Mejuto and Garcia-Cortés, 2005; Kohler and Turner, 
2008), indicating the possibility of offshore parturition 
grounds. Pratt (1979) suggested that parturition occurs 
between March and July in the eastern North Atlantic 
Ocean but noted that young-of-the-year (YOY) individuals 
are infrequently encountered in coastal waters. In the cen- 
tral North Atlantic Ocean, the presence of mature females 
in advanced stages of pregnancy during spring and the 
appearance of the smallest size classes of YOY in early 
summer indicate that the archipelago of the Azores is a 
parturition area (Aasen, 1966; Vandeperre et al., 2014). 
Additionally, the occurrence of neonate- and YOY-sized 
sharks on the Grand Banks of Newfoundland, a widely 
used fishing ground off Newfoundland, indicates that this 
area may also be a parturition or nursery area for the blue 
shark (L. Natanson, unpubl. data). 
Blue sharks represent the most frequently captured 
shark in the U.S. Atlantic pelagic longline fishery, with 
high catch rates in the Grand Banks of Newfoundland 
(Mandelman et al., 2008). Throughout the world’s oceans, 
blue sharks are taken by using diverse fishing gear, but 
they are caught mostly as bycatch on pelagic longlines 
targeting tuna and billfish (Bonfil, 1994; Mandelman 
et al., 2008). Additionally, as other stocks of large pelagic 
fish species declined, several nations bordering the North 
Atlantic Ocean specifically targeted blue sharks for their 
fins and meat (Castro et al., 1999; Mejuto et al., 2002). 
Data reported by the International Commission for the 
Conservation of Atlantic Tunas (ICCAT) indicate that the 
overall catch of blue sharks in the North Atlantic Ocean 
increased between 1993 and 2016 (from 9589 metric tons [t] 
to 44,067 t), followed by a decrease between 2016 and 2017 
(from 44,067 t to 39,675 t) (ICCAT"). The North Atlantic 
blue shark population is not considered overfished at this 
time (ICCAT®); however, there is uncertainty in data inputs, 
such as size, and there were problems with the production 
models fitting the data, leading to uncertainty in the results. 
Therefore, the possibility of the stock being overfished or 
subjected to overfishing cannot be ruled out (ICCAT’). Rec- 
ognizing this uncertainty, and that blue sharks are caught 
in large numbers, the ICCAT recently implemented an 
annual total allowable catch of 39,100 t for the conservation 
of blue sharks in the Atlantic Ocean (ICCAT”). 
As fisheries managers set policy guidelines on the basis 
of the results of stock assessment models that rely on life 
history data (Hilborn and Walters, 1992), there is a need 
to understand and periodically reevaluate the life history 
of a species. Reproductive potential is a vital component of 
1 ICCAT (International Commission for the Conservation of 
Atlantic Tunas). 2018. Report of the Standing Committee on 
Research and Statistics (SCRS) (Madrid, Spain, 1 to 5 October 
2018), 298 p. ICCAT, Madrid, Spain. [Available from website.] 
2 ICCAT (International Commission for the Conservation of 
Atlantic Tunas). 2019. Recommendation by ICCAT amending 
the recommendation 16-12 on management measures for the 
conservation of the North Atlantic blue shark caught in associ- 
ation with ICCAT fisheries. ICCAT Rec. 16-12, 2 p. [Available 
from website.] 
life history data; however, maturity data on highly migra- 
tory pelagic sharks, such as the blue shark, are often lack- 
ing (Cortés, 1998; Castro, 2011). Pratt (1979) is the most 
recent publication specifying sizes at maturity for blue 
sharks in the western North Atlantic Ocean. Since those 
data were collected, changes have occurred in fishing pres- 
sure, which has been suggested to have the potential to 
affect the blue shark population (ICCAT}), and climate 
change could also alter the biology of species because of 
changes in prey that lead to shifts in growth (Pinsky et al., 
2019). Thus, the objectives of this study were 1) to pro- 
vide current estimates of size at maturity for blue sharks, 
including length and weight at median maturity (L;, and 
W;0, respectively) for both sexes, and 2) to determine if 
changes in reproductive characteristics have occurred 
over time in the blue shark. 
Materials and methods 
Specimen collection 
Specimens of blue sharks were collected opportunistically 
between 1971 and 2016 from commercial and recreational 
fishermen, at shark tournaments, and during National 
Marine Fisheries Service research surveys along the 
northeastern coast of North America, between New Jersey 
and the Flemish Cap. A subset of the maturity data ana- 
lyzed (number of samples [n]=338) was previously used to 
estimate maturity parameters by Pratt (1979). For most 
specimens, full dissections were completed by experienced 
personnel using consistent protocols. Because of time 
constraints during shark tournaments, it was not always 
possible to complete a full dissection on each specimen. 
When time was limited, an assignment of maturity was 
made through visual examination of organ condition on 
the basis of the dissectors’ experience of organ maturity 
from previous detailed dissections. 
Morphometrics 
Fork length (FL) was measured in centimeters on each 
specimen following Kohler et al. (1995; from the tip of 
the snout to the fork of the tail, over the curvature of the 
body). Individuals were weighed (in pounds or kilograms) 
when possible; all weights were converted to kilograms. To 
allow direct comparison to data from this study, median 
total lengths (TLs) at maturity presented in other stud- 
ies (Megalofonou et al., 2009; Carrera-Fernandez et al., 
2010; Bustamante and Bennett, 2013; Jolly et al., 2013) 
were converted to FL by using the following equation from 
Kohler et al. (1995): 
FL = 0.8313(TL) + 1.3908 (n=572, r7=0.99). (1) 
Maturity 
Maturity condition was determined by measurements and 
visual examinations noting condition and appearance of 
