70 
National Marine 
Fisheries Service 
NQAA 
Fishery Bulletin 
n* established in 1881 ■<?. 
Spencer F. Baird 
First U S. Commissioner 
of Fisheries and founder 
of Fishery Bulletin 
Presence of a resting population of female 
porbeagles (Lamna nasus), indicating a 
biennial reproductive cycle, in the western 
North Atlantic Ocean 
Email address for contact author: lisa.natanson@noaa.gov 
Abstract —The porbeagle (Lamna 
nasus) is a slow-growing, late-ma¬ 
turing, long-lived pelagic shark that 
inhabits cold temperate waters. Pre¬ 
vious research based on specimens 
collected from the western North 
Atlantic Ocean has indicated that 
this lamnid shark has an annual 
reproductive cycle. However, the re¬ 
sults of a recent evaluation of repro¬ 
ductive tracts from a geographically 
segregated group of porbeagles with¬ 
in the western North Atlantic Ocean 
indicate the presence of females in a 
resting stage of maturity. The obser¬ 
vation of a resting stage has impli¬ 
cations not only in the reproductive 
cycle, biennial versus annual, of this 
species but also in the lifetime pro¬ 
ductivity. This finding indicates that 
this shark follows the typical lamnid 
resting period between pregnancies, 
a period that would decrease the 
lifetime output of young sharks and 
their resilience to direct and indirect 
fishing pressure. 
Manuscript submitted 9 October 2018. 
Manuscript accepted 8 March 2019. 
Fish. Bull. 117:70-77 (2019). 
Online publication date: 25 March 2019. 
doi: 10.7755/FB.117.1-2.8 
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. 
Lisa J. Natanson (contact author) 1 
Bethany M. Deacy 2 
Warren Joyce 3 
James Sulikowski 4 
1 Northeast Fisheries Science Center 
National Marine Fisheries Service, NOAA 
28 Tarzwell Drive 
Narragansett, Rhode Island 02882 
2 Riverside Technologies, Inc. 
for National Marine Fisheries Service, NOAA 
3500 Delwood Beach Road 
Panama City, Florida 32408 
The porbeagle (Lamna nasus), a pe¬ 
lagic shark in the family Lamnidae, 
inhabits the cold temperate waters of 
the North and South Atlantic, South 
Pacific, and southern Indian Oceans 
as well as the subantarctic region of 
the Southern Ocean (Castro, 2011). 
In the western North Atlantic Ocean, 
the porbeagle ranges from the Grand 
Banks of Newfoundland, Canada, to 
the Gulf of Maine and rarely south to 
New Jersey (Castro, 2011). Seasonal 
abundance is related to north-south 
migrations and reproductive stage 
(Aasen 1 ; Aasen, 1963; Campana et 
al., 2008; Campana et ah, 2010a). 
Reproductive migrations are indicat¬ 
ed by the occurrence of both mature 
males and mature females off the 
Grand Banks of Newfoundland in 
fall for mating (Jensen et ah, 2002). 
Juveniles are found along the en¬ 
tire range, but a presumed nursery 
area is located in the Gulf of Maine 
1 Aasen, O. 1961. Some observations 
on the biology of the porbeagle shark 
(Lamna nasus L.). ICES C.M. Docu¬ 
ment 1961/109, 7 p. 
3 Population Ecology Division 
Bedford Institute of Oceanography 
P.O. Box 1006 
Dartmouth, Nova Scotia, Canada, B2Y 4A2 
4 Department of Marine Sciences 
University of New England 
11 Hills Beach Road 
Biddeford, Maine 04005 
(senior author, unpubl. data; J. Su¬ 
likowski, unpubl. data) and the loca¬ 
tion of a pupping ground has been 
reported to be in the Sargasso Sea 
(Campana et ah, 2010b). Like most 
large elasmobranchs, the porbeagle 
is slow growing and long lived (over 
25 years) and has a relatively late 
age at maturity (8 years for males 
and 13 years for females), traits that 
make this species vulnerable to over- 
exploitation and population depletion 
by direct and indirect fisheries (Na¬ 
tanson et ah, 2002). 
In the western North Atlantic 
Ocean, commercial fisheries that tar¬ 
get porbeagles have existed since the 
1960s, but catches rapidly declined 
in the latter part of that decade 
(Aasen 1 ; Aasen, 1963; Campana et 
al. 2 ). In the 1990s, Canadian fisher- 
2 Campana, S., L. Marks, W. Joyce, and S. 
Harley. 2001. Analytical assessment 
of the porbeagle shark (Lamna nasus) 
population in the Northwest Atlantic, 
with estimates of long-term sustainable 
yield. Dep. Fish. Oceans, Can. Sci. 
Advis. Seer. Res. Doc. 2001/067, 17 p. 
[Available from website.] 
