Mateo et al.: Otolith chemistry for Tautoga onitis in Narragansett Bay and Rhode Island coastal ponds 
159 
Table 2 
Classification success (as a percentage) results determined by jack-knife cross validation procedure for linear discriminant func- 
tion analysis of chemical concentrations in tautog (Tautoga onitis) otoliths collected at Rhode Island stations in 2005 and 2006, 
with the use of solution-based inductively coupled plasma mass spectrometry for the combined trace metals (Sr, Ba, Mg, Rb): 
[Sr/Ca], [Ba/Ca], [Rb/Ca], [Mg/Ca]) and for d 13 C and stable isotopes. Names of the stations are Gaspee Point (GP), Mount 
Hope Bay (MH), Rose Island (RS), Point Judith, lower pond (PJ), Charlestown Pond (CP). 
GP 
MH 
RS 
PJ 
CP 
Classification success {%) 
2005 
GP 
14 
0 
0 
0 
1 
93 
MH 
0 
13 
0 
2 
1 
81 
RS 
0 
0 
19 
1 
0 
95 
PJ 
0 
0 
0 
16 
1 
94 
CP 
0 
1 
0 
0 
16 
94 
Total 
14 
14 
19 
19 
19 
92 
2006 
GP 
0 
0 
0 
0 
0 
MH 
0 
13 
0 
2 
1 
81 
RS 
0 
0 
14 
2 
1 
82 
PJ 
0 
2 
0 
15 
0 
88 
CP 
0 
0 
0 
2 
15 
88 
Total 
15 
14 
21 
17 
85 
and 6 18 0 varied significantly among stations in 2006 
(ANOVA, P<0.001) (Fig. 2). For example, 6 18 0 was high- 
est at Rose Island at the mouth of Narragansett Bay, 
whereas <5 13 C magnitudes were similar across years for 
all Narragansett Bay stations. Sr concentrations within 
Narragansett Bay and the coastal ponds also remained 
similar in magnitude throughout the years of study. 
Discussion 
The elemental composition of juvenile tautog otoliths 
varied considerably within and among estuaries and 
between years. We found very strong differences in the 
concentrations of Mg, Sr, Ba, and Rb, as well as in the 
stable isotopic signatures of d 13 C and 6 18 0, among sta- 
tions within RI. High classification success rates (gener- 
ally >85%) of the discriminant functions derived from 
trace element and stable isotope signatures together 
confirmed their use as an effective natural tag of the 
estuarine nursery area of juvenile tautog. Although 
most of the variance in trace element signatures was 
concentrated among estuaries, we also found signifi- 
cant differences in elemental fingerprints and stable 
isotopes in tautog otoliths among sites about 10 to 25 
km 2 apart within Narragansett Bay resulting in 100% 
classification success within that water body. These 
data indicate that the physicochemical characteristics 
of specific sections of the estuaries may vary enough to 
generate the differences in otolith chemistry that we 
observed within each estuary. 
Elemental fingerprints, however, should not be regard- 
ed as permanent markers of actual estuarine habitat or 
environment (Forrester and Swearer, 2002; Swearer et 
ah, 2003). Estuarine habitats are very dynamic; seawa- 
ter properties and composition at a particular location 
can vary over tidal to annual time scales (Peters, 1999). 
As a result, it may be expected that the magnitude of 
variations in elemental fingerprints in otoliths among 
estuaries will not remain constant over time. The sig- 
nificant interannual differences we report among year 
classes in age-0 tautog otolith elemental signatures is 
similar to interannual differences in otolith chemis- 
try reported for other marine fishes (Gillanders and 
Kingsford, 2000; Gillanders, 2005). Thus, interannual 
differences indicate that age-0 tautog elemental signa- 
tures must be analyzed on a year-class-specific basis 
because there were stations where concentrations were 
not consistent between years. 
It is not surprising to see such clear differences 
in otolith chemical signatures among the stations 
sampled in Narragansett Bay. Data from RIDEM show 
that there were also significant differences in salinity 
regimes in these regions during the late spring and 
summer of 2005 and 2006 (H. Stoffel, and J. McNa- 
mee, unpubl. data 1 ). The proximity of Rose Island 
station to the mouth of Narragansett Bay meant that 
high salinities (up to 30 %c) would be observed. On 
the other hand, the lower-salinity stations within the 
upper region of Narragansett Bay are located much 
closer to the industrial area and watershed and there- 
fore potentially more prone to terrestrial influences 
from freshwater runoff resulting in reduced salinities 
(20-25%*). 
1 Stoffel, H., and J. McNamee. 2008. Rhode Island Dept. 
Environmental Management (RIDEM), Jamestown, RI 
02879. 
