36 
Fishery Bulletin 1 14(1) 
Figure 1 
Locations where samples of red flying squid ( Ommastreph.es bartramii ) were collected for 
this study in the North Pacific Ocean from July through November in 2011. 
then processed with Adobe Photoshop CS 5.0 (Adobe 
Systems Inc., San Jose, CA). Two readers counted the 
number of increments, and readings were accepted 
only when the difference in mean counts between the 
2 independent readers was less than 10% (Chen et ah, 
2013) . Beak growth increments in previous studies 
were assumed to be deposited daily for several octopu- 
ses species (Raya and Hernandez-Gonzalez, 1998; Her- 
nandez-Lopez et al., 2001; Perales-Raya et al., 2010, 
2014; Canali et al., 2011; Castanhari and Tomas, 2012; 
Rodriguez-Dominguez et al., 2013; Barcenas et al., 
2014) . A strict age validation for ommasterphid squids 
with the use of statolith and beak measurements has 
been performed and the results of those experiments 
indicate that the beak is a reliable material for age 
estimation (Hu et al., 2015; Liu et al., 2015). If the 
beak is a reliable structure for age estimates, we can 
back-calculate hatching dates from the capture dates 
documented in our study. 
The relationships between age and ML, BW, and 
URL were established with 4 types of curves: linear, 
power, exponential, and logarithmic. Akaike’s informa- 
tion criterion was used to compare the fits of models, 
by following the calculations of Haddon (2001). Differ- 
ences in growth curves between sexes also were evalu- 
ated by using analysis of covariance (ANCOVA). 
Instantaneous growth rate (G) and absolute daily 
growth rate (DGR) of ML or BW were measured in mil- 
limeters per day or grams per day and estimated for 
each 50-d interval by sex. The G and DGR were calcu- 
lated with the following models proposed by Forsythe 
and Van Heukelem (1987): 
and 
ln(S 2 )-ln(S 2 ) inn(V 
— x 100 % 
t 2 -t 1 
DGR= S2 ~ S \ 
t 2 — ti 
( 1 ) 
( 2 ) 
where Si and S 2 = mean ML or BW at the beginning 
Gl) and end (£ 2 ) of the time interval. 
Statistical analyses were conducted with SPSS, vers 
19.0 (IBM Corp, Armonk, NY). 
Results 
Microstructure of growth increments in red flying squid 
The microstructure of a beak RSS of a red flying squid 
in this study is shown in Figure 2. The longitudinal 
increments in the transverse surface were easily vis- 
ible from the tip of rostrum to the joint of the hood 
and crest (Fig. 2B), and the hood was darker than the 
crest because of pigmentation (Fig. 2B). The tip of the 
rostrum was missing in some samples because of ero- 
sion from feeding behavior. Increments were more obvi- 
ous in the center of the focal line and were visible as 
bands that were alternately dark and light (Fig. 2C). 
The increments in the middle of each internal rostral 
axis were much thicker than those in the anterior and 
posterior areas. The middle parts of the RSS had the 
widest incremental width in relation to other RSS 
parts (Fig. 2C). The interval widths tended to vary in 
different parts of the RSS at increased magnification 
