628 
Abstract— Calcified structures of sum- 
mer flounder, Paralichthys dentatus, 
were evaluated to identify the best age 
determination method. Scales, the cur- 
rently preferred structure, were com- 
pared with opercular bones and to right 
and left whole and sectioned otoliths 
for ages 0 to 10. All structures showed 
concentric rings that were interpreted 
as annual; however structures differed 
greatly in the clarity of their presumed 
annual marks. Right and left otoliths 
generally gave the same age, although 
they differed in the clarity of marks. Sec- 
tioned otoliths, particularly right ones, 
were the best aging structure. Right sec- 
tioned otoliths consistently showed the 
clearest marks and had the highest confi- 
dence scores, lowest reading times, and 
highest agreement within and between 
readers, 97% and 96%, respectively. Left 
sectioned otoliths took twice as long 
to prepare and were more difficult to 
interpret than right sectioned otoliths. 
Whole otoliths were the second best 
structure and were adequate to age 
4 or 5, after which sectioning greatly 
improved the clarity of marks. Scales 
were inferior to, and often did not 
give the same age readings as, whole 
and sectioned otoliths. Compared with 
otoliths, scales tended to overage at 
younger ages and to underage at older 
ages. Opercular bones were undesir- 
able for aging summer flounder. They 
were often unclear and inconsistent, 
and they had the lowest confidence 
scores, the highest reading times, and 
only 46% within-reader agreement. A 
major source of disagreement in scale 
and otolith age readings was the pres- 
ence of an early, presumably false, mark 
on some structures. We compare the 
formation of this early mark in summer 
flounder with early mark formation on 
otoliths of Atlantic croaker, a species 
with similar life history traits. 
Manuscript accepted 21 March 2001. 
Fish. Bull. 99:628-640 (2001). 
A comparison of calcified structures for 
aging summer flounder, Paralichthys dentatus* 
Ann M. Sipe 
Virginia Institute of Marine Science 
College of William and Mary 
Gloucester Point, Virginia 23062 
E-mail address: amsipe@vims.edu 
Mark E. Chittenden Jr. 
Virginia Institute of Marine Science 
College of William and Mary 
Gloucester Point, Virginia 23062 
The summer flounder, Paralichthys den- 
tatus , ranges from Nova Scotia to Flor- 
ida, although it is most abundant from 
Massachusetts to North Carolina (Gins- 
burg, 1952; Leim and Scott, 1966; 
Gutherz, 1967). In regions of high abun- 
dance, it is one of the most important 
commercial and recreational fishes on 
the Atlantic coast (MAFMC, 1987). In 
the Chesapeake Bay region, for example, 
summer flounder support an extensive 
recreational fishery from about March 
to November, when they are present in 
the lower portions of the Chesapeake 
Bay and in coastal waters (Hildebrand 
and Schroeder, 1928; MAFMC, 1987; 
Desfosse, 1995). They then support a 
strong commercial fishery during the 
fall and winter, when they move offshore 
to the continental shelf (Ginsburg, 1952; 
Bigelow and Schroeder, 1953; Poole, 
1962; MAFMC, 1987). 
Many studies have reported difficul- 
ties with the structures used for age de- 
termination of summer flounder. Prior to 
about 1980, whole left otoliths were the 
most commonly used structure (Poole, 
1961; Eldridge, 1962; Smith and Daiber, 
1977; Powell, 1982). However, there were 
disagreements over the location and in- 
terpretation of the first presumed an- 
nual mark (Poole, 1961; Eldridge, 1962; 
Smith and Daiber, 1977), largely a result 
of uncertainties about first year growth 
rates. This and other problems with 
whole otoliths (summarized in Smith et 
al., 1981) prompted a comparison of age 
determination structures by Shepherd 
(1980), who reported that presumed an- 
nual marks were more distinct on scales 
than on whole otoliths. Consequently, 
scales became the preferred structure 
for aging summer flounder (Smith et 
al., 1981; Dery, 1988; Almeida et al., 
1992). More recently, Szedlmayer et al. 
(1992) examined first year growth rates 
to resolve the location and interpreta- 
tion of the first mark on whole otoliths, 
but scales have remained the preferred 
structure (Bolz et al., 2000). 
Difficulties have also been reported 
in using summer flounder scales (Dery, 
1988; Desfosse, 1995; Bolz et al., 2000). 
Desfosse (1995) used marginal incre- 
ment analysis to validate scales for ages 
1 to 3. He reported only 46% within-read- 
er agreement past age 4, however, indi- 
cating that marks on scales are not very 
distinct at older ages. He attributed dis- 
agreements to false or indistinct annuli 
and to crowding of annuli at the scale 
edge in older fish. Most recently, Bolz 
et al. (2000) reported only 53% agree- 
ment for ages 1 to 5 in a between-agency 
exchange of scales, with agreement in- 
creasing to only 83% after they resolved 
as many disagreements as possible. They 
attributed most of the remaining dis- 
agreements to the choice of a first an- 
nual mark and to differing opinions on 
what constituted a false mark on scales. 
A reexamination of calcified struc- 
tures for aging summer flounder is 
needed, given their economic impor- 
tance and the reported difficulties in 
* Contribution 2380 from the Virginia Insti- 
tute of Marine Science, College of William 
and Mary, Gloucester Point, VA 23062 
