860 
Fishery Bulletin 95(4), 1997 
veligers still produced statolith rings without struc- 
tural change implies that age estimates of veligers 
from statolith increment counts are robust. Period- 
icity of statolith growth in larval S. costatus and «S. 
gigas is sufficiently reliable to be considered a bet- 
ter tool for age determination than diameter of sta- 
tolith or measurement of shell length. Counts of in- 
crements were measurably less variable with age 
than were measurements of statolith diameter, or 
shell length. 
In fishes, otoliths have been used to address ques- 
tions regarding larval dispersal (Thresher and Broth- 
ers, 1985); settlement dynamics (Victor, 1983); 
growth rates (Radtke and Bean, 1982); mortality 
rates (Essig and Cole, 1986); and larval patch-size 
estimation (Victor, 1984). Statolith-based age and 
growth determination, however, has not been used 
in early life history studies of mollusks; characteris- 
tics such as size, shell structure, and distance off- 
shore have been used to infer relative age or length 
of planktonic life (e.g. Scheltema, 1978; Jablonski and 
Lutz, 1980, 1983; Pechenik et al., 1984; Pechenik, 
1986). Our results here indicate a more highly quan- 
titative method for ageing larvae. 
Acknowledgments 
This project was supported by funds from the Uni- 
versity of Puerto Rico Sea Grant College Program, 
Office of Research and External Funding of the Fac- 
ulty of Arts and Sciences, and Department of Ma- 
rine Sciences. We thank D. L. Ballantine for supply- 
ing facilities and algal cultures for rearing larvae, 
and M. Davis and C. Hess for supplying samples from 
the Trade Wind Industries Caicos Conch Farm. D. 
L. Ballantine, P. M. Yoshioka and numerous anony- 
mous reviewers gave valuable criticism. 
Table 2 
Variability in statolith increment counts within laboratory-reared larval Strombus costatus. Age = days after hatching. 
Statolith A 
Statolith B 
Counts Counts 
Age 
(d) 
1 
2 
3 
Mean 
SE 
1 
2 
3 
Mean 
SE 
0 
6 
6 
6 
6.00 
0.00 
6 
5 
5 
5.33 
0.58 
0 
6 
6 
6 
6.00 
0.00 
5 
5 
5 
5.00 
0.00 
0 
6 
7 
7 
6.67 
0.58 
7 
7 
6 
6.67 
0.58 
(average) 
6.22 
0.44 
5.67 
0.87 
1 
6 
6 
6 
6.00 
0.00 
7 
7 
7 
7.00 
0.00 
1 
7 
7 
8 
7.33 
0.58 
8 
6 
8 
7.33 
1.15 
(average) 
6.67 
0.82 
7.17 
0.75 
2 
8 
8 
9 
8.33 
0.58 
9 
9 
9 
9.00 
0.00 
2 
10 
8 
9 
9.00 
1.00 
9 
9 
9 
9.00 
0.00 
2 
9 
9 
9 
9.00 
0.00 
10 
10 
8 
9.33 
1.15 
(average) 
8.78 
0.67 
9.11 
0.60 
4 
10 
10 
10 
10.00 
0.00 
10 
9 
9 
9.33 
0.58 
6 
11 
12 
11 
11.33 
0.58 
12 
13 
12 
12.33 
0.58 
6 
11 
11 
11 
11.00 
0.00 
11 
12 
11 
11.33 
0.58 
(average) 
11.17 
0.41 
11.83 
0.75 
7 
10 
10 
11 
10.33 
0.58 
11 
11 
12 
11.33 
0.58 
7 
13 
11 
13 
12.33 
1.15 
12 
10 
13 
11.67 
1.53 
7 
14 
14 
12 
13.33 
1.15 
15 
13 
13 
13.67 
1.15 
7 
14 
14 
15 
14.33 
0.58 
15 
13 
13 
13.67 
1.15 
(average) 
12.58 
1.73 
12.58 
1.51 
8 
15 
14 
15 
14.67 
0.58 
14 
13 
16 
14.33 
1.53 
8 
13 
15 
14 
14.00 
1.00 
12 
14 
13 
13.00 
1.00 
(average) 
14.33 
0.82 
13.67 
1.37 
10 
15 
14 
14 
14.33 
0.58 
16 
15 
15 
15.33 
0.58 
10 
14 
16 
15 
15.00 
1.00 
15 
14 
16 
15.00 
1.00 
(average) 
14.67 
0.82 
15.17 
0.75 
