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by counting band pairs (one opaque and one translucent 
band) from the otolith core (birth) to the otolith edge (age 
at capture), making the assumption that one band pair 
equals 1 year in a fish’s life (Beamish and McFarlane, 
1983). Errors occur when growth layers identified as 
annuli (yearly growth bands) do not truly correspond to 
1 year of growth (McBride, 2015). Validation of an aging 
method is a process that verifies that putative annuli 
occur once per year. Although there have been attempts 
to validate otolith aging methods for the northern stock of 
black sea bass, these studies were limited by small ranges, 
few age classes, or modest sample sizes (Mercer, 1978; 
Robillard et al.”). Thus far, no large-scale age validation 
study has been done for the northern stock of black sea bass 
with samples representative of those included in the stock 
assessment process (i.e., samples caught with a variety of 
gear types and from a variety of locations, sources, and age 
classes). Furthermore, no work has yet been published that 
validates the first annulus on otoliths for black sea bass in 
the northern stock, an imperative step to validating abso- 
lute age (Campana, 2001). 
Verifying the location of the first annulus is a necessary 
step in validating aging methods; otherwise, age estimates 
could be biased in either direction (Campana, 2001). Addi- 
tionally, the identification of the first annulus is often a pri- 
mary source of error in aging practices (Campana, 2001) 
and is a known issue in reading otoliths of black sea bass 
(Dery and Mayo, 1988; ASMFC'). Reported discrepan- 
cies between identification of age-0 versus age-1 fish con- 
tributed to the exclusion of fall indices in the latest stock 
assessment (NEFSC, 2017). 
The goal of this study was to identify the timing of annu- 
lus deposition and validate the current otolith aging method 
for the entire geographic range and observed age classes of 
the northern stock of black sea bass in the Atlantic Ocean, 
by using marginal increment analysis (MIA) and first 
annulus validation for young of the year (YOY). 
Materials and methods 
Sample collection and selection 
The most common method of age validation is MIA, which 
measures growth from the last fully completed annulus 
to the edge of the aging structure (i.e., measures the mar- 
ginal increment) at different times throughout the year 
(Campana, 2001). Marginal increment analysis requires 
samples to be collected across an entire year, preferably 
monthly, as well as across the observed age range of the 
selected species (Beamish and McFarlane, 1983; Campana, 
2001). Constraints related to obtaining adequate sample 
? Robillard, E., J. W. Gregg, J. Dayton, and J. Gartland. 2016. 
Validation of black sea bass, Centropristis striata, ages using 
oxytetracycline marking and scale margin increments, 17 p. 
Stock Assess. Rev. Comm., SARC 62 working paper. [Available 
from Northeast Fish. Sci. Cent., Natl. Mar. Fish. Serv., NOAA, 
166 Water St., Woods Hole, MA.] 
sizes for individual ages led to the creation of 3 age bins, 
ages 1-2 (AB1), ages 3-4 (AB2), and ages 5 and older (AB3), 
which also account for growth differences among the age 
groups (Pilling et al., 2000; Winner et al., 2017). Age deter- 
minations supplied by collaborating institutions were used 
to classify samples to begin processing. Otoliths without 
an age estimate were assigned to classes on the basis of 
an age—length key created from samples previously aged 
by staff of the Massachusetts Division of Marine Fisheries 
(MA-DMF) (senior author, unpubl. data). 
To capture potential growth variability between regions, 
a goal of 40 samples per age bin was chosen for MIA. Sag- 
ittal otoliths from samples of black sea bass were provided 
by collaborators across the northeastern United States who 
acquired them from both fishery-dependent and fishery- 
independent sources (Table 1, Fig. 1). A total of 1440 oto- 
liths from black sea bass were initially subsampled for this 
study; however, 49 of those otoliths were excluded because 
they were broken or poorly sectioned and could not be reli- 
ably aged or measured. Additionally, marginal increment 
ratios (MIRs) could not be calculated for fish that were 
age 1 prior to annulus formation as a result of the use of 
1 January as the year-class advancement date (Dery and 
Mayo, 1988) and were removed from analysis (number of 
samples [n]=23). Samples of black sea bass used for MIA 
(n=1335) were collected every month of the year, and they 
ranged in size from 100 to 605 mm TL and in age from 1 
to 12 years (Table 2, Fig. 2). Sex data was available for 854 
samples: 490 females (110-500 mm TL) and 364 males 
(130-546 mm TL). 
Assessment of the first annulus can be completed 1) 
by measuring the completed first annulus of YOY in the 
season of annulus formation and 2) by tracking the modal 
length frequency of the smallest fish in the population to 
confirm that measured samples are YOY (Campana, 2001; 
Carvalho et al., 2017). Age-O samples for first annulus 
validation were collected in the fall during the MA-DMF 
resource assessment survey (September 2017, n=30) and 
during the Northeast Fisheries Science Center (NEFSC) 
bottom-trawl survey (October 2016, archive, n=3). Age-1 
samples caught in the summer and used in MIA were also 
used for comparison. These samples were collected during 
the MA-DMF ventless-trap survey (July and August 
2015-2017, otolith archive, n=36). Total lengths ranged 
from 35 to 120 mm for age-0 fish and from 110 to 207 mm 
for age-1 fish. 
A reference collection (n=100) with ages spanning from 
0 to 10 years was created by using otoliths archived by the 
MA-DME. These samples were used to assess reader error 
before and after otolith aging was completed for this project 
and were independent of the samples used in MIA. 
Sample preparation 
Age estimates made by using whole otoliths tend to under- 
estimate fish age and use of otolith sections has resulted 
in higher accuracy (Hyndes et al., 1992; Fowler and Short, 
1998). Therefore, sectioned otoliths were used in this study. 
Additionally, completing marginal increment measurements 
