Koob et al.: Age validation of the northern stock of Centropristis striata in the Atlantic Ocean 269 
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Figure 7 
Box plots of marginal increment ratios for sagittal otoliths from black sea bass (Centro- 
pristis striata) captured in the Atlantic Ocean off the northeastern United States during 
2013-2017, by season for the regions (A) north and (B) south of the Hudson Canyon. 
Letters above the boxes denote significant differences (significance level=0.05; tested 
with Tukey’s honestly significant difference by using estimated marginal means). In 
each box plot, the thick horizontal line indicates the median, the areas above and below 
the median represent the 25th and 75th percentiles, the thin vertical lines indicate the 
95% confidence limits, and the points indicate outliers. 
words, the opaque annulus is being completed when MIRs 
are at a maximum before dropping to a minimum, which 
indicates new growth. The timing of annulus completion 
in this study was dependent on age bin. Maximum MIR for 
AB1 was observed in March-April (Fig. 6A); however, the 
decline in May—June (prior to the minimum in July) indi- 
cates that some fish were completing the annulus in these 
months. Therefore, annulus completion occurred between 
April and June for AB1. This variability was not surpris- 
ing given the extensive spatial range from which these 
samples were collected (from Maine to Virginia). Miller 
et al. (2016) reported that overwintering adult black sea 
bass gathered along a defined shelf contour but that juve- 
niles were scattered across the shelf and were exposed to 
a wider range of temperatures and salinities. Variation 
between individuals in this youngest age group, therefore, 
may be magnified by the environmental conditions experi- 
enced while overwintering. 
The maximum MIR for AB2 was observed in June, fol- 
lowed by a stark decline to a minimum in July and August 
and a continuation of growth thereafter (Fig. 6B). Annu- 
lus completion largely occurred in June for this age bin, 
and new, translucent material began to be deposited on 
otoliths in July. Reduced variability in the timing of annu- 
lus deposition in this age group, compared with that in 
AB1, was likely a result of a more consistent growth rate 
between ages and regions. 
Maximum and minimum MIRs for AB3 occurred in 
June and August, respectively (Fig. 6C). The mean MIR 
in July fell between these extremes, similar to the pattern 
observed in May—June in AB1. This finding indicates that 
some otoliths had new, translucent growth in July (a small 
amount of growth at the otolith margin); whereas, for oth- 
ers the opaque annulus was still being deposited (a large 
amount of growth at the otolith margin). The delay in 
annulus deposition for some samples in AB3 (with the 
minimum MIR occurring in August, as compared with in 
July for AB1 and AB2) could be related to energy allocated 
to spawning rather than to growth during this period. 
Morales-Nin and Ralston (1990) observed a decline in 
otolith growth as spawning season progressed and stated, 
“during the maturity period the metabolic energy seems 
to be diverted from growth, causing the formation of thin 
increments [as] seasonal growth rings.” The northern 
stock of black sea bass typically spawns between April and 
October, with spawning peaking in June—July (Mercer, 
1978; Wuenschel et al., 2013; McBride et al., 2018). Of the 
44 black sea bass in AB3 that were measured in July, 25 
samples were classified as fish in spawning condition (i.e., 
maturity data associated with otolith samples indicated 
the fish were ripe or ripe and running). 
In other studies of black sea bass in the northern stock, 
annulus formation appears to have been associated with 
spawning period (Mercer, 1978; Alexander, 1981; Caruso, 
1995); however, this connection may be coincidental 
(Beckman and Wilson, 1995). Instead, annulus deposition 
timing is likely the result of a combination of environmen- 
tal and physiological processes (Fowler and Short, 1998). 
Additionally, black sea bass have a variety of reproductive 
strategies, including maturation as young, small males 
