Gillanders: Trace metals in four structures of fish and their use for estimates of stock structure 
411 
Figure 1 
Map showing sampling locations along the coast of New South Wales, 
Australia. 
posited, they are unlikely to be resorbed or altered 
(Campana and Neilson, 1985). Recently, Dove and 
Kingsford (1998) found that eye lenses may be suit- 
able for differentiating populations of fish because 
the eye lens has no efficient mechanism for remov- 
ing ions from the tissue. Eye lenses also grow by 
the addition of protein-rich cells to their outer sur- 
face. Bone, scales, and other soft tissues (e.g. gills, 
liver, muscles) will reflect a variety of factors includ- 
ing composition during growth, but resorption and 
remineralization may occur in some species (Gauldie 
and Nelson, 1990). The temporal stability of the el- 
emental concentrations in other tissues is therefore 
questionable (Campana and Gagne, 1995). In some 
species, however, the market value of the fish is like- 
ly to be reduced by removing otoliths and eye lenses; 
therefore, structures such as scales or spines may be 
easier to obtain. If scales and spines show similar el- 
emental fingerprints (for fish caught at different lo- 
cations) to otoliths and eye lenses, then their use in 
stock discrimination studies may be warranted. The 
use of scales and spines would also allow sampling 
without the need to kill the fish, with the result that 
broodstock could be kept alive and individuals from 
rare or endangered stocks could be sampled. With 
the exception of two studies (Dove and Kingsford, 
1998; Wells et al., 2000), who compared elemental 
fingerprints of otoliths with eye lenses and scales, 
respectively, there have been no comparative studies 
of more than two structures. 
The aim of my study was to compare the elemental 
fingerprints obtained from different structures (oto- 
liths, scales, eye lenses, and dorsal spines) to determine if 
there were correlations among structures. Because otoliths 
are not subject to resorption (but see Mugiya and Uchimu- 
ra, 1989), their use in studies of stock discrimination ap- 
pears justified; therefore all comparisons were made be- 
tween otoliths and the other three structures. These four 
structures chosen for the present study are also very dif- 
ferent in terms of their composition. Otoliths are com- 
posed primarily of calcium carbonate, whereas scales and 
spines are composed primarily of calcium phosphate, and 
eye lenses, largely of water and structural proteins. There 
may, therefore, be differences in the affinities of ions for the 
different structures and this difference could have implica- 
tions for the elemental chemistry of each structure. 
The damselfish Parma microlepis is a territorial species, 
both juveniles (Moran and Sale, 1977) and adults (territo- 
ry sizes 2-17 m 2 , Tzioumis, 1995) remain attached to their 
natal sites. Therefore it is an excellent model species for 
this kind of research. Otoliths and eye lenses of P. microle- 
pis have been shown to contain microconstituents that can 
be detected with ICP-MS, some elements of which may be 
site-specific (Dove et al., 1996; Dove and Kingsford, 1998). 
Juvenile fish are distinguished from adults on the basis of 
coloration and are generally less than 3 years of age (Tzi- 
oumis and Kingsford, 1999). By comparison adults reach a 
maximum age of 37 years, and fish larger than 120 mm SL 
may represent a wide range of age classes (Tzioumis and 
Kingsford, 1999). Adults will therefore have longer and 
potentially more variable age- integrated elemental finger- 
prints than those of juvenile fish. 
Materials and methods 
Parma microlepis was collected from each of ten locations 
along the coast of New South Wales, Australia (Fig. 1). Fish 
were not collected from multiple sites within each location 
because small-scale differences in trace elements of otoliths 
and eye lenses (sites separated by 50 to 200 m) were not 
found in a previous study (Dove and Kingsford, 1998). All 
fish were collected by divers using SCUBA and a hand-spear 
between January and April 1998. Between five and seven 
replicate adult and juvenile fish were collected from each 
location. Juveniles and adults were distinguished from each 
other on the basis of differences in patterns of coloration. 
Fish were stored on ice during transportation to the lab- 
oratory. In the laboratory, the standard length of each fish 
was measured (Table 1). Otoliths, eye lenses, and approx- 
imately five non-regenerated scales were removed from 
each fish and rinsed in MilliQ water. Otoliths and scales 
were stored dry at room temperature, and eye lenses were 
stored at -70°C in Eppendorf microcentrifuge tubes in 
preparation for ion analysis. Dorsal spines were removed 
and frozen (-4°C) prior to removal of surrounding flesh. 
After flesh was removed, spines were also stored dry at 
room temperature. 
