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Fishery Bulletin 108(2) 
Table 1 
Average size distribution of tautog ( Tautoga onitis) collected in Rhode Island for analysis of otolith elemental concentrations and 
stable isotopic signatures. The numbers of fish measured at each station ( n ) to obtain average fork lengths (FL in mm) in each 
year are shown. Numbers in parentheses are standard errors. 
Station 
2005 
2006 
n 
FL 
n 
FL 
Gaspee Point (GP) 
17 
59.6(1.2) 
Mount Hope Bay (MH) 
17 
59.1 (2.1) 
21 
63.0(2.9) 
Rose Island (RS) 
20 
52.1 (1.2) 
17 
45.3(3.5) 
Point Judith, lower pond (PJ) 
18 
49.4 (2.1) 
19 
57.3 (1.5) 
Charlestown Pond (CP) 
17 
50.2(3.0) 
18 
54.9(2.7) 
weight and otolith elemental composition and isotopic 
signatures with analysis of covariance (ANCOVA). If 
there was a significant relationship, we removed the 
effect of size (otolith weight used as a proxy for fish size) 
to ensure that differences in fish size among samples did 
not confound any site-specific differences in otolith chem- 
istry. Concentrations of elements were weight-detrended 
by subtraction of the product of the common within- 
group linear slope multiplied by the otolith weight from 
the observed concentration (Campana et al., 2000). 
To detect differences in the concentrations of par- 
ticular elements and multi-element fingerprints among 
stations and between years, we performed ANOVA and 
multivariate analyses of variance (M ANOVA). Pillai’s 
trace statistic was chosen as the multivariate test sta- 
tistic because it is more robust than other multivari- 
ate statistics (Wilkes’s lamda, Hotelling’s T-test) to 
small sample sizes, unequal cell sizes, and situations in 
which covariances are not homogeneous. Tukey’s HSD 
test was used to detect a posteriori differences among 
means (a=0.05). Before statistical testing, residuals 
were examined for normality and homogeneity among 
stations. To meet model assumptions, all analyses were 
performed on natural log-transformed data. We also 
used linear discriminant function analyses (DFAs) on 
tautog juvenile data to visualize spatial differences in 
juvenile otolith chemistry data within sites and to ex- 
amine classification success for juveniles from different 
sites or regions. Classification success is the percentage 
of fish that are correctly assigned to their actual region 
given the information on location where the fish was 
collected and the chemical signature of each fish. Cross 
validations were performed by using jackknife (“leave 
one out”) procedures in SYSTAT (vers. 11, Systat Soft- 
ware, Inc., Chicago, IL). 
Results 
Size distribution 
Mean (FL) of juvenile tautog at stations in Rhode Island 
ranged from 45 to 63 mm (Table 1). There were sig- 
nificant differences in mean length among stations 
(ANOVA, PcO.OOl) and between years (ANOVA, P<0.05) 
within Rhode Island stations. There were no significant 
differences in mean FL among stations within Narra- 
gansett Bay. However, in 2005, mean FL from all sta- 
tions within Narragansett Bay were significantly longer 
than that for individuals caught in the coastal ponds 
(Point Judith, lower pond, Charlestown Pond) (Tukey 
test, P<0.05). In 2006; only Mount Hope Bay had fish 
significantly longer than those from Rose Island (Tukey 
test, P<0.05). 
Otolith chemistry 
Results of MANOVA showed that the chemical signa- 
tures of trace metals and stable isotopes combined in 
tautog otoliths differed significantly among stations 
(MANOVA, F 18 384 = 20.72, PcO.OOl) and years (MANOVA, 
P 6 126 = 9.05, P<0.001) within Rhode Island. Signifi- 
cant interaction between station and year (MANOVA, 
F 18 3g4 =5.18, P<0.001) implied that chemical signatures 
differed between years depending on the station studied. 
Classification success for tautog by using both trace 
metals and stable isotopes for stations within Rhode 
Island for each of the two years ranged from 85% to 
92% (Table 2). 
Individual elemental concentrations 
In Rhode Island, one trace element (Rb) and one stable 
isotope (d 13 C) showed significant relationships with the 
covariable otolith weight in the ANCOVA (P<0.001) 
and therefore required the effect of otolith weight be 
removed for subsequent ANOVA analysis. The ele- 
mental concentrations and isotope signatures varied 
significantly among stations (ANOVA, P<0.001), and 
between years (ANOVA, P<0.001) (Fig. 2). Significant 
interaction between station and year (ANOVA, PcO.OOl) 
indicated that concentration of individual elements dif- 
fered between years depending on the station studied. 
In Rhode Island, elemental concentrations of Sr, Ba, 
Mg, Rb, and the stable isotopes d 13 C and <5 18 0 varied 
significantly among stations in 2005, whereas only Ba 
