632 
Fishery Bulletin 99(4) 
Figure 2 
Right whole otoliths showing an early, presumably false, mark. 
(A) is from a 299-mm-TL age-1 fish collected in September, and 
( B ) is from a 442-mm age-4 fish collected in October. White arrows 
point to the early marks. Black arrows indicate primary counting 
path (anterior field), dots indicate secondary counting path (pos- 
terior field). 
clear transitions from translucent to opaque zones; 
the first one or two marks were particularly difficult 
to distinguish, even on young fish. Zone transitions 
were often easier to interpret towards the edge of 
the structure in older fish, although this too varied 
greatly from fish to fish. The example in Figure 1C is 
unusually clear and easy to read. 
Presumed annual marks on scales (Fig. ID) were 
clearer than those on opercular bones, but they still 
required much subjective interpretation. Figure ID 
shows some of the common problems encountered 
with scales, including presumably false marks (as- 
terisks) and marks that were present on only some 
scales from the same fish (white arrows). In addi- 
tion, many fish had regenerated, asymmetrical, or 
otherwise damaged scales, making it difficult and 
time-consuming to choose acceptable scales to press. 
For example, about 20 scales were pressed in order 
to obtain two scales that were adequate to show in 
Figure ID. Interpretation of age from scales of older 
fish was extremely difficult because marks at the 
scale edges were often obscured or crowded together, 
particularly in the narrow lateral fields. Finally, a 
major source of disagreement in age determination 
from scales resulted from an early, presumably false, 
mark that often occurred prior to the first presumed 
annual mark (Fig. ID, asterisk). Because this early 
mark did not appear consistently in all fish or even 
on several scales from the same fish, we tried not to 
count it in our age readings. 
Preparation times, reading times, and 
confidence in clarity of marks 
Preparation times were short and reasonable for all 
structures, at less than 15 minutes per fish. Whole oto- 
liths took by far the shortest time because no preparation 
was required before reading (Table 1). Sectioned right 
otoliths and opercular bones required 4 to 6 minutes to 
prepare, whereas scales and sectioned left otoliths took 
much longer to prepare, about 11 and 14 minutes, respec- 
tively. Left sectioned otoliths took much longer to prepare 
than right sectioned otoliths primarily because they broke 
much more frequently during sectioning. 
Reading times were short and reasonable for all struc- 
tures, at less than three minutes per fish. Sectioned right 
otoliths had by far the shortest reading time, at only 0.27 
minutes per fish (Table 1). Whole otoliths and sectioned left 
otoliths had the next shortest reading time, at only about 
0.4 to 0.6 minutes per fish. Scales (1.2 min) and opercular 
bones (2.4 min) both required much more reading time than 
otoliths, indicating that otoliths could be aged more easily. 
Reader confidence scores varied greatly between struc- 
tures. Sectioned otoliths had by far the highest confidence 
scores, with values of 4.9 and 4.8 for the right and left, re- 
spectively (Table 1). Whole otoliths had somewhat lower 
confidence scores, with values of 4.1 and 3.8 for the right 
and left, respectively. Confidence scores were much lower 
for scales (3.2) and especially for opercular bones (2.3), indi- 
cating that these structures were not as easily interpreted. 
All confidence scores were significantly different from one 
another (Z=2.10 to 4.18; P<0.0001 to 0.013; individual val- 
ues not reported). 
Regression of structure size on fish size 
All calcified structures grew in size as summer flounder 
body length grew, indicating that each structure could 
be useful for back-calculation studies. All regressions of 
structure size on total length were significant at P < 0.001, 
and all slopes were positive (Table 2). All regressions were 
strong and explained much of the variation in structure 
size, generally 90% or more, with coefficient of determina- 
tion values (100 r 2 ) ranging from 72% to 98%. Values for 
100 r 2 were less than 91% only for right and left sectioned 
otoliths, which were 72% and 85%, respectively. 
Agreement in age determinations 
for the same structure 
Agreement ( precision) between repeated age readings varied 
greatly between calcified structures. Precision by the same 
reader was highest by far (95% to 97%) for sectioned right 
and left otoliths and left whole otoliths (Table 3). Precision 
was somewhat lower in right whole otoliths (89%) than in 
