454 
Fishery Bulletin 110(4) 
100 
75 
50 
25 
0 
100 
100 
1993 
1994 
1995 
75 
75 
50 
50 
* A i 
25 
* :• : * ;■ 
25 
* A 
* t i i 
0 
0 
m 
-a 
L 
o 
a> 
a 
o 
to 
cn 
tu 
E 
200 
150 
100 
50 
0 
100 
75 
50 
25 
0 
100 
75 
50 
25 
0 
2005 
100 
75 
2006 
4 A 
50 
4 4 * * 
25 
‘ A * i 
0 
3 4 5 7 
2 3 4 5 7 
Sampling interval (days) 
Figure 2 
Estimated annual larval supply (megalopae collector -1 day -1 ) of blue crab ( Callinectes sapidus) megalopae at 
sampling intervals of 2, 3, 4, 5, and 7 days (triangles) compared with annual larval supply from daily sam- 
pling (dotted lines). Estimates were generated by subsampling data sets of daily larval supply for megalopae 
collected from September to November in each year of the 11-year record used in this study. Note that the 
y-axis values for 1996 are twice those for other years. 
mates of annual supply. Heftier et al. (1997) suggested 
that a weekly (7-day) sampling interval was sufficient for 
estimating the annual supply of larval Atlantic menha- 
den in the Newport River estuary, North Carolina, but 
their analysis did not account for interannual variability 
in the pattern of larval supply because it was based 
on a single year of data. We detected large differences 
in the variability of daily larval supply among years, 
suggesting that a single year of daily data collection is 
insufficient to characterize variability in larval supply. 
We recognize that our study is not directly comparable 
to that of Heftier et al. (1997) because of differences in 
sampling gear (settlement collectors vs. plankton nets) 
and potential differences in the temporal dynamics of 
larval supply among species. Regardless of these fac- 
tors, if Heftier et al. (1997) conducted their study in a 
year of unusually episodic larval supply, they may have 
overestimated variability in annual estimates of supply 
at each sampling interval. More important, if their study 
was conducted in a year in which larval supply was rela- 
tively constant over time, they may have dramatically 
underestimated variability. 
The increase of the sampling interval from daily to 
every other day (2 -day interval) decreased the chances 
of detecting a significant correlation between annual 
blue crab larval supply and CPUE in the North Caro- 
lina pot fishery to only 65% when a significant correla- 
tion (r=0.88) was observed for daily data. Significant 
correlations were never detected at a 3-day sampling 
interval but were detected at longer intervals, only 
