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—Spiny dogfish (Squalus 
acanthias) are traditionally aged by 
counting band pairs on dorsal-fin 
spines; however, wear and tear of the 
spines make obtaining accurate age 
estimates of older spiny dogfish diffi- 
cult. Vertebral centra are an alternate 
structure that can be used to estimate 
age, but success in their use has been 
varied. We conducted a tag-recapture 
study using oxytetracycline injections 
to validate annual deposition in both 
dorsal-fin spines and vertebral centra 
of spiny dogfish. When band pairs in 
vertebral centra were used, time at lib- 
erty was significantly underestimated. 
Additionally, band-pair counts were 
found to change along the vertebral col- 
umn of an individual, further refuting 
the use of vertebral centra to generate 
age estimates. Band-pair deposition 
in dorsal-fin spines was confirmed to 
be annual in spiny dogfish at liberty 
for up to 2.6 years. Dorsal-fin spines 
should continue to be used to age spiny 
dogfish, and vertebral centra are not a 
viable alternative. 
Manuscript submitted 14 July 2020. 
Manuscript accepted 26 March 2021. 
Fish. Bull. 119:41—49 (2021). 
Online publication date: 8 April 2021. 
doi: 10.7755/FB.119.1.6 
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. 
Validation of the use of vertebrae and dorsal-fin 
spines for age determination of spiny dogfish 
(Squalus acanthias) in the western North 
Atlantic Ocean 
Kelsey C. James (contact author)! 
Lisa J. Natanson' 
Christopher Flight? 
Cindy Tribuzio? 
John Hoey' 
Camilla McCandless’ 
Email address for contact author: kelsey.james@noaa.gov 
" Northeast Fisheries Science Center 
National Marine Fisheries Service, NOAA 
28 Tarzwell Drive 
Narragansett, Rhode Island 02882 
Present address for contact author: Southwest Fisheries Science Center 
National Marine Fisheries Service, NOAA 
8901 La Jolla Shores Drive 
La Jolla, California 92037 
* Dauphin Island Sea Lab 
101 Bienville Boulevard 
Dauphin Island, Alabama 36528 
3 Alaska Fisheries Science Center 
National Marine Fisheries Service, NOAA 
17109 Point Lena Loop Road 
Juneau, Alaska 99801 
Spiny dogfish (Squalus acanthias) 
range from Labrador, Canada, to 
Florida in the western North Atlan- 
tic Ocean but are most common from 
Nova Scotia, Canada, to Cape Hat- 
teras, North Carolina (Collette and 
Klein-MacPhee, 2002). In the western 
North Atlantic Ocean, spiny dogfish 
have been landed in commercial fish- 
eries on a small scale since the 1930s 
(Rago and Sosebee, 2009). Landings 
of spiny dogfish soared in the 1970s 
until foreign fishing ceased in 1977, 
when the Fishery Conservation and 
Management Act of 1976 became 
effective (Fishery...2018), and spiny 
dogfish were declared “underutilized” 
by the late 1980s (Rago and Sose- 
bee, 2009; DFO, 2020). In the United 
States, a large-scale directed fishery 
targeting mature females began in 
the 1990s, resulting in a significant 
reduction in female spawning stock 
biomass (NEFSC, 1998). In Canada, 
smaller scale directed fishing during 
1998-2008 targeted mostly adult 
males with a mix of juvenile males 
and mature females (DFO, 2020). The 
population of spiny dogfish in the 
western North Atlantic Ocean was 
declared overfished in 1998 (NEFSC, 
1998). Effective management prac- 
tices led to population rebuilding, 
and as of the stock assessment com- 
pleted in 2006, spiny dogfish in the 
western North Atlantic Ocean are 
no longer considered overfished and 
no overfishing has been occurring 
(NEFSC, 2006). These stock assess- 
ments rely on accurate life history 
characteristics, including validated 
age and growth. 
