34 
NOAA 
National Marine 
Fisheries Service 
Fishery Bulletin 
established 1881 
Spencer F. Baird 
First U S. Commissioner 
of Fisheries and founder 
of Fishery Bulletin 
Age, growth, and population structure of 
the red flying squid ( Ommastrephes bartramii) 
in the North Pacific Ocean, determined from 
beak microstructure 
Abstract— To explore the feasibility 
of using beak microstructure to esti- 
mate the age of oceanic squid, sagit- 
tal sections in the upper beak were 
used to validate the age of the red 
flying squid ( Ommastrephes bartra- 
mii) in the North Pacific Ocean. The 
growth rates of mantle length (ML) 
and body weight (BW) were estimat- 
ed on the basis of beak increments. 
We compared growth curves derived 
from previous statolith-based stud- 
ies and those from this study. Re- 
sults indicate that the mean age of 
females and males was 203 d (stan- 
dard deviation [SD] 55) and 180 
d (SD 45). The hatching period oc- 
curred during October-June of the 
following year, and hatching peaked 
during January-April on the ba- 
sis of back-calculation. All sampled 
squid belonged to the winter-spring 
cohort. Females and males had a 
similar growth pattern in ML and 
BW with increased ages, except for 
male ML after age 301-350 d. An 
exponential model best described 
the relationships between age and 
ML as well as BW for both sexes. 
The difference in growth curves and 
lower growth rates reported here, 
compared with those of previous 
studies, may result from different 
stock structures and extreme weath- 
er. This study confirmed that beak 
length works well for estimating the 
age of oceanic squid. 
Manuscript submitted 18 February 2015. 
Manuscript accepted 19 October 2015. 
Fish. Bull. 114:34-44 (2016). 
Online publication date: 5 November 2015. 
doi. 10.7755/FB.114.1.3 
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. 
Zhou Fang 1 54 
Jianhua Li '- 2 ' 3 - 5 
Katherine Thompson 4 
Feifei Hu 1 
1 College of Marine Sciences 
Shanghai Ocean University 
999 Hucheng Ring Road 
Shanghai 201306, China 
2 National Engineering Research Center for 
Oceanic Fisheries 
Shanghai Ocean University 
999 Hucheng Ring Road 
Shanghai 201306, China 
3 Key Laboratory of Sustainable Exploitation 
of Oceanic Fisheries Resources 
Ministry of Education 
Shanghai Ocean University 
999 Hucheng Ring Road 
Shanghai 201306, China 
The red flying squid ( Ommastrephes 
bartramii ) is distributed in subtropi- 
cal and temperate waters worldwide 
but is commercially exploited only 
in the North Pacific Ocean, where it 
plays an important role in the ma- 
rine ecosystem (Jereb and Roper, 
2010; Navarro et al., 2013). It has 
become a primary target species in 
East Asian countries since the ocean- 
ic squid fishery began in the 1970s. 
This squid is not only important as a 
fishery resource but also serves as an 
indicator of large-scale oceanographic 
changes (Chen et al., 2007; Nishika- 
wa et al., 2014). The population of 
red flying squid in the North Pacific 
Ocean consists of 2 main cohorts, 
the autumn cohort that yields large 
squid (>350 mm mantle length [ML] ) 
and the winter-spring cohort that is 
represented by relatively small squid 
Xinjun Chen (contact author ) 1 - 2 ' 3 ' 5 
Bilin Liu 1 - 2 - 3 - 5 
Yong Chen 45 
4 School of Marine Sciences 
218 Libby Hall 
University of Maine 
Orono, Maine 04469 
5 Collaborative Innovation Center for Distant- 
water Fisheries 
999 Hucheng Ring Road 
Shanghai 201306, China 
(<350 mm ML) (Chen and Chiu, 
2003). Abundance of both cohorts 
fluctuates greatly with large-scale 
oceanographic and climatic changes 
(e.g., El Nino or La Nina), as well 
as with regional-scale environmental 
changes (Yatsu et al., 2000; Chen et 
al., 2007). 
Age estimation and growth analy- 
ses provide critical information for 
fisheries stock assessments and man- 
agement. Hard structures often are 
used for aging squid and most stud- 
ies measure statoliths (Spratt, 1978; 
Lipinski, 1986; Jackson et al., 1993; 
Durholtz et al., 2002). Although 
statolith-based age determination 
methods have advanced greatly 
over the past 30 years (Arkhipkin 
and Shcherbich, 2012), the process 
of preparing statoliths for aging is 
rather complicated and often has a 
Email address for contact author: xjchen@shou.edu.cn 
