524 
Fishery Bulletin 95(3), 1997 
(Table 2; Fig. 3). Increments in the higher ra- 
tion treatments remained relatively wide 
throughout the experimental period. Narrow- 
ing of increment width in the 17% and 32% MR 
treatments ensued immediately and continued 
to decrease after the first week of the experi- 
ment (Fig. 2). For all treatments, mean IW was 
lower during week 2 than week 1; significant 
differences occurred between weeks in the 17%, 
32%, and 66% MR treatments (Table 2). By 
week 2, there were significant among- treatment 
differences in mean IW among the 46% MR and 
the 32% and 17% MR treatments. Mean IW 
among the higher feeding levels did not differ 
throughout the entire experiment except for the 
66% MR level. During several days of the first 
week, this group had a significantly higher mean 
IW compared with other treatments (Table 2). 
Daily variability in IW was high in all treatments 
(Fig. 2). 
There was a positive correlation (IW = 2.58 + 
1.49(log{G+l|), r=0.86, P<0.05) between mean 
daily IW and mean specific growth rate for each 
treatment (Fig. 4). Although some fish lost 
weight at the lowest ration level, daily increments 
continued to be produced. There was a positive 
correlation between mean IW and mean daily 
Table 2 
Results of two-way analysis of variance and multiple-range tests 
from comparisons of mean weekly increment width from differ- 
ent ration treatments and one-way analysis of variance between 
weeks. MR is the maximum ration. * = P<0.05, ns = not signifi- 
cant; letters indicate the results of Tukey’s HSD comparison 
among treatments. SE is the standard error associated with treat- 
ment means. 
Treatment 
feeding Treatment 
levels (% MR) 
Week 1 
SE 
Week 2 
SE 
means 
17 
3.042 
0.0243 
2.310 
0.0378* 
2.68“ 
32 
3.021 
0.0465 
2.616 
0.1203* 
2.82“ 6 
46 
3.121 
0.1402 
3.027 
0.1495ns 
3.07 6 
58 
3.823 
0.7427 
3.817 
0.5864ns 
3.82“ 
66 
4.514 
0.2835 
3.766 
0.8348* 
4.14“ 
100 
3.864 
1.2942 
3.755 
0.6493ns 
3.81“ 
Overall 
3.538 
3.215* 
3.38 
feeding rate and between mean specific growth rate 
and K at day 14 (Table 3; Figs. 3 and 4). This relation 
(P<0.05) developed during week 1 of the experiment 
and strengthened during week 2 (Table 3). 
Discussion 
Figure 1 
Relation between otolith increments distal to the fluorescent mark 
and days after tetracycline injection in juvenile weakfish, Cynoscion 
regalis. Symbols may represent more than one observation. 
Injection of oxytetracy cline hydrochloride solu- 
tion produced clear fluorescent bands in the 
otoliths of juvenile weakfish, and increment 
deposition occurred daily. Several other juve- 
nile sciaenids have shown daily increments: spot 
( Leiostomus xanthurus ), red drum ( Sciaenops 
ocellatus), spotted seatrout (Cynoscion nebulosus), 
and silver perch ( Bairdiella chrysoura ) ( Gjosaeter 
et al., 1984; Hettler, 1984; Peters and McMichael, 
1987; McMichael and Peters, 1989; Hales and 
Hurley, 1991). The present study provides vali- 
dation for ageing juvenile weakfish, thus en- 
abling estimates of growth and providing, in 
combination with abundance data, a means of 
estimating accurate age specific mortality rates 
during this life history stage. 
The rapid response of IW to changes in ra- 
tion and the strong relation with SGR suggest 
that IW’s may be used to infer growth history. 
Furthermore, significant differences in IW be- 
tween high (58-100% MR) and low (17—46% 
MR) feeding levels suggests that IW may be 
used to approximate feeding history. Because 
of approximately a one-week lag time prior to 
stabilization of IW among treatments, the full 
magnitude of the change in IW cannot be as- 
sessed by examining just a few increments. At 
