National Marine 
Fisheries Service 
NOAA 
Fishery Bulletin 
@ established in 1881 < 
Spencer F. Baird 
First U.S. Commissioner 
of Fisheries and founder 
of Fishery Bulletin 
Abstract—The blue shark (Prionace 
glauca) in the North Atlantic Ocean is 
caught in large numbers in commercial 
fisheries and faces the possibility of 
overfishing. Reproductive parameters, 
such as size and age at maturity, are 
important descriptors of life history 
characteristics used for understanding 
and managing marine organisms but 
have not been evaluated for the west- 
ern North Atlantic Ocean since 1979. 
To address this gap in knowledge, we 
used samples from 369 female and 
488 male blue sharks collected during 
1971-2016 and examined whether 
maturity parameters have changed 
over time. We compared sex-specific 
fork length (FL) (L;)) and weight (W;,) 
at median maturity between 2 time 
periods (1971-1977 and 2003-2016). 
No evidence of change in either Ls, or 
W; 9 was observed for females. Males 
had a statistically significant increase 
in both parameters; however, this 
increase was likely the result of dif- 
ferences in sample size range between 
the time periods. Thus, all data from 
1971 through 2016 were combined to 
obtain new estimates of age and size at 
50% maturity for both sexes. The Lso 
and W;, are 192.5 cm FL and 49.5 kg 
for male blue sharks and 190.9 cm FL 
and 50.1 kg for female blue sharks. 
These updated L;, and W;, increase 
reliability of data inputs for fisheries 
management. 
Manuscript submitted 14 September 2021. 
Manuscript accepted 16 December 2021. 
Fish. Bull. 120:26—38 (2021). 
Online publication date: 5 January 2022. 
doi: 10.7755/FB.120.1.3 
The views and opinions expressed or 
implied in this article are those of the 
author (or authors) and do not necessarily 
reflect the position of the National 
Marine Fisheries Service, NOAA. 
Reproductive characteristics for the blue shark 
(Prionace glauca) in the North Atlantic Ocean 
Katie Viducic' 
Lisa J. Natanson (contact author) (retired)? 
Megan V. Winton? 
Austin Humphries* 
Email address for contact author: mangrules@yahoo.ca 
" Lynker Technologies LLC 
for Apex Predators Program 
Northeast Fisheries Science Center 
National Marine Fisheries Service, NOAA 
28 Tarzwell Drive 
Narragansett, Rhode Island 02882 
* Northeast Fisheries Science Center 
National Marine Fisheries Service, NOAA 
28 Tarzwell Drive 
Narragansett, Rhode Island 02882 
The blue shark (Prionace glauca) is a 
pelagic species with a circumglobal dis- 
tribution in tropical, subtropical, and 
warm temperate seas, including the 
Mediterranean Sea (Compagno, 1984). 
This species has long been considered 
the most abundant of the Atlantic 
pelagic sharks (Bigelow and Schroeder, 
1948), ranging from Newfoundland, 
Canada, to Argentina in the west, from 
Norway to South Africa in the east 
(Bigelow and Schroder, 1948; Castro, 
2011), and over the entire mid-Atlantic 
(Aasen, 1966). Evidence from tagging 
data indicates that North Atlantic blue 
sharks constitute a single stock with 
seasonal latitudinal migrations (Kohler 
et al., 2002; Kohler and Turner, 2019). 
Additionally, results from genetic stud- 
ies indicate not only a single North 
Atlantic population but a single global 
blue shark population (Verissimo et al., 
2017). However, differences do exist in 
various geographic areas in maximum 
and average size and in size and age 
at maturity (Skomal and Natanson, 
2003; Mejuto and Garcia-Cortés, 2005), 
3 Atlantic White Shark Conservancy 
235 Orleans Road 
Chatham, Massachusetts 02650 
“ University of Rhode Island 
120 Flagg Road 
Kingston, Rhode Island 02881 
making regional studies on life history 
important for local management. 
Different stages of the blue shark 
reproductive cycle are believed to occur 
in different areas of the North Atlantic 
Ocean (Pratt, 1979). The blue shark is 
a placental viviparous species, with 
broods usually ranging from 25 to 50 
young born after a gestation period of 
9-12 months (Pratt, 1979), and Aasen 
(1966) suggested an average brood size 
of 45 young in the same area. Brood size 
in the blue shark appears to be region- 
ally variable (Mejuto and Garcia-Cortés, 
2005; Castro, 2011) with up to 135 young 
reported from a brood in the Indian 
Ocean (Gubanov and Grigor’yev, 1975) 
and averages varying from 25.6 young 
in the North Pacific Ocean (Nakano, 
1994) to 37 young in the Gulf of Guinea 
(Castro and Mejuto, 1995). Brood size 
has also been shown to increase with 
female size (Mejuto and Garcia-Cortés, 
2005). Although few gravid females 
in the western North Atlantic Ocean 
have been reported (Pratt, 1979), many 
have been caught off the coast of Africa, 
