Sipe and Chittenden: A comparison of calcified structures for aging Paralichthys dentatus 
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based on overlap in back-calculated sizes at the 
second and third marks on whole otoliths (Powell, 
1982). However, size in any year class can vary 
greatly because summer flounder spawn over a 
protracted season (Smith, 1973; Morse, 1981; Able 
et al., 1990). Therefore, fish in adjacent year class- 
es can be expected to overlap in size, and Pow- 
ell’s results do not necessarily mean that the first 
mark becomes obscured with age. 
Smith et al. ( 1981) reported that summer floun- 
der otoliths deviated from the general pattern of 
opaque and translucent zone formation seen in 
other temperate fishes and suggested that opaque 
zones formed in fall-winter, the reverse of the 
usual spring-summer formation in other temper- 
ate species. We saw no evidence of this reversal. 
Our fish were collected from October through De- 
cember, so we should have observed opaque edg- 
es on the otolith if the timing of mark formation 
were reversed from other temperate fishes. In- 
stead, we observed relatively wide translucent 
zones on the otolith edges. In addition, other stud- 
ies have not found a reversal in the time of mark 
formation (Poole, 1961; Powell, 1982; Wenner et 
al., 1990), and Desfosse (1995) found that opaque zones 
appeared to form on whole otoliths at approximately the 
same time as scale marks (May through July). Finally, 
Smith et al. (1981) presented no data to support their hy- 
pothesis that opaque zones formed in the fall and winter. 
Indeed, their Figure 5 shows an opaque edge on a whole 
otolith from a summer flounder captured in June. 
In agreement with studies in other species (see referenc- 
es below), we found the translucent zone to be wider than 
the opaque zone on summer flounder otoliths. Smith et 
al. (1981) felt this was an anomalous occurrence and used 
it to reject whole otoliths. We disagree with their analy- 
sis, however, because many other fishes in our study area, 
including Atlantic croaker (Barbieri et al., 1994a), weak- 
fish (Lowerre-Barbieri et al., 1994), and Spanish macker- 
el (Gaichas, 1997) have otoliths with a wide translucent 
zone and a narrow opaque zone. Such a pattern reflects 
the fact that opaque zones form over a short time period in 
these species: April-May in Atlantic croaker and weakfish 
(Barbieri et al., 1994a; Lowerre-Barbieri et al., 1994) and 
May-June in Spanish mackerel (Gaichas, 1997). In addi- 
tion, although the sample size was limited (n=93), Des- 
fosse (1995) found evidence, using marginal increments, 
that opaque zone formation on summer flounder otoliths 
occurs over a similarly short time period (May to July). Fi- 
nally, regardless of whether opaque zones are narrower or 
wider than translucent zones, otoliths can be used for age 
determination if the mark can be proven annual. 
Comparative evaluation of scales 
Our findings indicate that scales are inferior to, and much 
less desirable than, both sectioned and whole otoliths for 
aging summer flounder. Scales had significantly lower con- 
fidence scores and much higher reading times than sec- 
tioned and whole otoliths because marks on scales were 
often difficult to interpret using objective aging criteria. 
False marks were common, and different scales from the 
same fish often indicated different ages. As a result, both 
within- and between-reader percent agreement and agree- 
ment with whole and sectioned otolith age were undesir- 
ably low in scales, especially in fish over age 4. We feel that 
scales should not be used for aging summer flounder if oto- 
liths, especially sectioned otoliths, are available. 
The difficulties we found with summer flounder scales 
generally agree with reports in the literature. Dery (1988), 
Desfosse (1995), and Bolz et al. (2000), for examples, have 
reported similar problems interpreting scale marks. Like 
us, Desfosse (1995) found low within-reader scale agree- 
ment (only 46%) in fish over age 4. Desfosse (1995) re- 
ported high agreement between scales and whole otoliths 
(98%) for ages 0 to 5, much higher than the 85% agree- 
ment we found for ages 0 to 4. However, 90% of his fish 
(rc=170) were ages 0 to 2 and only one was age 5, a likely ex- 
planation for his high percent agreement. Shepherd ( 1980) 
reported high agreement (91%) between scales and whole 
otoliths for moderately old fish (ages 4 to 6), but his sample 
size was only 21 fish, only one of which was age 6. Our 
study reported lower overall agreement between whole oto- 
liths and scales (76%), but we examined fish over a much 
wider age range (ages 0 to 10) than previously reported. 
Comparative evaluation of opercular bones 
Our comparative studies have found opercular bones to be 
inferior to both sectioned and whole otoliths in summer 
flounder, and even to scales. Opercular bones had the 
lowest confidence scores, the highest reading times, only 
46% within reader agreement, and they often exhibited 
unclear transitions from translucent to opaque zones, par- 
ticularly at early ages. For these reasons, we feel that oper- 
cular bones should not be used for aging summer flounder. 
