Hettler et a I.: Variability in abundance of larval fishes inside Beaufort Inlet 
485 
Size of larvae 
Plots of mean length for the larval species produced 
a variety of seasonal patterns (Fig. 4). Although B. 
tyrannus increased in average size until mid-March 
and then decreased, the mean length of M. undulatus, 
L. xanthurus, and Lagodon rhomboides peaked in 
mid-February, then decreased. M. undulatus seemed 
to share peaks in abundance with peaks in increas- 
ing mean lengths (e.g. 30 December, 17 and 26 Janu- 
ary, and 28 February). Larvae of Paralichthys or 
Mugil did not change substantially in length over 
the season. 
Age and growth of menhaden larvae 
Because SABRE studies have centered around B. 
tyrannus, daily collections of this species provided a 
unique opportunity to test correlations of observed 
larval age structure with waves of immigrating lar- 
vae and environmental conditions. Otoliths of B. 
tyrannus (10-32 mm SL) showed a range in esti- 
mated age of 16 to 106 days (Fig. 5). The Gompertz 
growth equation predicted a size at hatching of 4.96 
mm SL, which is above the reported size at hatching 
of 3. 2-3. 4 mm SL for laboratory-reared specimens 
(Powell, 1993). Average daily growth rate declined 
from 0.32 mm/day between days 30 and 40 to 0.03 
mm/day between days 80 and 90. 
According to back calculations from capture date, 
B. tyrannus ingressing Beaufort Inlet spawned from 
12 October 1991 to 16 February 1992. Expressed as 
a percentage of the total Atlantic menhaden caught, 
two age cohorts, one in mid-December and another 
in late January, made up about 50% of the year’s 
recruitment (Fig. 6). Almost 5% of the Atlantic men- 
haden larvae captured at the sampling station dur- 
ing the season were hatched on 13 December 1991. 
The distribution of estimated ages of larvae by col- 
lection date is shown with an overlay plot of mean 
daily density (Fig. 7). The largest daily mean den- 
sity of 159 larvae per 100 m 3 (18 March 1992) oc- 
curred during a decrease in age distribution of about 
25 days and would suggest a significant import of a 
younger cohort of B. tyrannus. 
Environmental variables 
The environmental conditions (except barometric 
pressure) recorded at the time of sampling are shown 
in Figure 8. Spearman correlation coefficients were 
computed for each of the eight species with each of 
the nine environmental variables (Table 3). Twenty- 
seven of the 72 coefficients were significant (P<0.Q5). 
