McBride et al: Expansion of spawning and nursery grounds of Centropristis striata into a warming Gulf of Maine 
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Materials and methods 
Daily age validation and precision 
Age-0 black sea bass were collected from the Swan Riv¬ 
er (Dennis, Massachusetts) on August 10, 2008, with 
minnow traps (42 cmx20 cm in size, with 7-mm mesh, 
and a 2.5-cm opening) baited with surf clams. Fifty- 
nine individuals were transferred to a 90-L aquarium 
and immersed in a 500 pg/L solution of oxytetracycline 
(OTC) for 5 h at a salinity of 15 and temperatures of 
21-22°C on August 13 (McBride, 2002). These fish were 
then held in a 970 L tank with a supply of flow-through 
sea water at 30-32 salinity and 21-22°C and fed to sa¬ 
tiation a daily diet of squid and clams. After 24 h (day 
2), 5 fish were sacrificed to verify that an OTC mark 
was present (these fish were not aged later). On day 
7, 1 fish was sacrificed to check again the formation 
of an OTC mark. On day 16, 10 fish were sacrificed 
for daily ring counts along the distal edge of the OTC 
mark. Also on day 16, 15 fish were re-marked by im¬ 
mersing them in OTC, in a similar manner as before. 
On day 30, all remaining fish, some with double OTC 
marks, were sacrificed for additional counts. There 
was no other evidence of mortality during the experi¬ 
ment. After fish were sacrificed, sagittal otoliths were 
removed, cleaned, and stored dry. 
Of the 54 marked fish, 17 were selected from each 
date in a simple random fashion: 1 fish at day 7, 8 fish 
at day 16, 8 fish at day 30 (including 1 fish with a dou¬ 
ble mark). One otolith per fish was embedded in epoxy 
resin, and a 300-pm transverse section was cut with a 
double-bladed IsoMet Low Speed Saw 3 (Buehler, Lake 
Bluff, IL). These sections were mounted on microscope 
slides with a clear, thermoplastic adhesive (Crystal- 
bond 509, Electron Microscopy Sciences, Hatfield, PA) 
and polished with 3-pm and 5-pm metallurgical lap¬ 
ping film. OTC marks were identified with an ultra¬ 
violet light, and microincrements were counted with a 
light microscope (200x) and imaging software (Image- 
Pro Plus, vers. 7.0, Media Cybernetics, Inc., Rockville, 
MD). Standard tests for accuracy, bias, and precision 
of these daily ages included plotting the data, using 
Chang’s coefficient of variation (CV; Chang, 1982), and 
using Evans and Hoenig’s test of symmetry (Evans and 
Hoenig, 1998). Age-bias plots follow the bubble format 
advocated by McBride (2015), and the statistic tests 
were produced by the FSA package, vers. 0.8.20 (Ogle, 
2018) in R software, vers. 3.5.0 (R Core Team, 2018) 
(Ogle, 2016). 
Precision (i.e., repeatability) of daily age estimates 
from wild-caught fish was checked for 37 otoliths (10% 
of the 372 fish examined). These otoliths—from 5 ran¬ 
domly selected fish over 10-d intervals (range: 51-129 
d)—were aged a second time, independently but by the 
3 Mention of trade names or commercial companies is for iden¬ 
tification purposes only and does not imply endorsement by 
the National Marine Fisheries Service, NOAA. 
same reader. Bias and precision tests were performed 
as described above. 
Hatching dates and growth rates 
In the estuary, age-0 black sea bass were collected dur¬ 
ing August-September, 2006 and 2007, off southeastern 
Massachusetts, by using minnow traps as described in 
the previous section (Fig. 1). Four sites were sampled 
in Buzzards Bay (Westport River; Clarks Cove; Nas- 
ketucket Bay; Sippican River) and 1 site was sampled 
in Nantucket Sound (Swan River). Estuarine surface 
salinity ranged from 17 to 23 and surface temperature 
ranged from 14° to 23°C during the sampling period. 
Inshore, off southeastern Massachusetts, age-0 black 
sea bass were also collected during the Massachusetts 
Division of Marine Fisheries (MA-DMF) autumn sur¬ 
vey in September 2006 and 2007 by trawl (with 7-mm 
codend liner). Trawl sites were selected following a 
stratified-random design (King et. al. 4 ), and these sites 
were then stratified into two areas (Buzzards Bay and 
Nantucket Sound [Fig. 1]) in analyses. Inshore bottom 
salinity ranged from 31 to 33 and bottom temperature 
ranged from 6° to 20°C in September. 
The TL of each fish was measured to the nearest 
mm from the snout to the posterior of the medial cau¬ 
dal fin ray. Sagittal otoliths were removed, cleaned, 
and stored dry. Otoliths were embedded, sectioned, 
and mounted as described above; however, 400-pm sec¬ 
tions were initially produced, and these became thin¬ 
ner (150-200 pm) after subsequent wet sanding with 
1200-grit wet or dry sandpaper. These otoliths were 
also soaked for 24-96 h in a 2% trypsin solution to en¬ 
hance the visibility of the rings (Roemer and Oliveira, 
2007), and were then polished with metallurgical lap¬ 
ping film, to finish. 
Prepared otoliths were dabbed with immersion oil 
and viewed under a light microscope (lOOx), aided by 
imaging software (Image-Pro Plus). Counts began with 
the first visible ring near the nucleus and continued 
to the edge of the otolith. Variation in clarity of differ¬ 
ent areas of the otolith section meant that no single 
axis was used to count microincrements (‘images’ in 
Tweedie, 2014). 
A total of 1131 black sea bass were collected in 2006 
and 2007 from 5 estuarine sites and 18 different inner 
shelf sites. Fish were selected for age determination by 
simple, random subsampling when more than 20 fish 
were collected within a month-year-area (estuarine, 
inshore, Buzzards Bay, or Nantucket Sound) aggre¬ 
gate, which resulted in 34% (n=381) of these fish being 
aged (Fig. 2). Selected fish were statistically smaller 
than all fish collected in 2006 (Student’s t= 2.7, df=636, 
P=0.006), but by <3 mm; therefore this difference was 
4 King, J. R., M. J. Camisa, and V. M. Manfredi. 2010. Mas¬ 
sachusetts Division of Marine Fisheries trawl survey effort, 
lists of species recorded, and bottom temperature trends, 
1978-2007. Mass. Div. Mar. Fish. Tech. Rep TR-38, 151 p. 
[Available from website.] 
