558 
Fishery Bulletin 11 5(4) 
and Ih before sunrise, during mid-tide and separate 
24-h periods. In total, 64 seine-hauls were conducted, 
32 during daytime and 32 at night. 
Seining covered the intertidal and shallow subtidal 
area to ~1.5 m depth. The following procedure (after 
Giordano ) was used to quickly enclose the sampling 
area and minimize loss of large mobile fish: 1) One 
end of the net was held on the shoreline; 2) the oth¬ 
er end was deployed quickly (<45 s) off the bow of a 
boat, along an elliptical path from that shore point, 
to enclose the area immediately adjacent to the -27 
m section of shore; 3) both ends of the net were then 
slowly moved together along the shore; and 4) once the 
ends were together the net was pulled in, forcing all 
enclosed fish and crabs into the bag. During nighttime 
sampling, headlamps were illuminated immediately 
after step 2 to facilitate the subsequent steps and to 
observe the catch as it was brought into the net. 
The adjacent nearshore area (Fig. 1) was sampled 
once each month during day and night in July, August, 
and September. Each sampling effort consisted of 3 
tows (10 min at 1-1.5 m/s) in 3-6 m depth with a 6-m 
otter trawl (10-mm mesh; 5-mm mesh bag liner) during 
day and night. In total 18 trawl tows were conducted, 
9 during the day and 9 at night. 
Fish and blue crab were counted and measured to 
the nearest millimeter (for species with >20 individu¬ 
als, a random subsample of 20 was measured); fork 
length (FL) for fish with forked tails, total length (TL) 
for other species, and carapace width (CW) for blue 
crab. The area sampled was calculated to convert rela¬ 
tive measures of abundance into density. For the shore 
zone the formula for a half ellipse was used: 
Area = —nab, 
2 
where a = half the length of the enclosed shoreline; and 
b = the distance between shoreline and the apo¬ 
gee of the net. 
Values for a and b were measured by setting the seine 
5 times during a nonsampling trial and estimated val¬ 
ues were a = 13.5 m and 6=10.0 m. For the nearshore, 
the following equation was used: 
Area - wl, 
where w = the estimated average width of trawl during 
operation (6 m); and 
l - the tow length. 
Water temperature and salinity at the time of sampling 
were measured 0.5 m below the water surface using a 
dissolved oxygen meter (YSI, Inc. 4 , Yellow Springs, OH). 
Data analyses 
Mean density and species richness of fish and blue crab 
at both day and night were compared for both shore 
4 Mention of trade names or commercial companies is for iden¬ 
tification purposes only and does not imply endorsement by 
the National Marine Fisheries Service, NOAA. 
zone and nearshore samples. Potential differences in 
sampling efficiency and species selectivity between the 
seine net used in shore zone sampling and the otter 
trawl used in nearshore sampling precluded statistical 
comparisons between the 2 areas. Two-factor analysis 
of variance (ANOVA) was used to test for significant 
(a=0.05) diel and site differences in total nekton den¬ 
sity and species richness in the shore zone. Significant 
diel and site differences in density of individual species 
that accounted for >1% of the total catch in the shore 
zone were tested with randomization tests for 2-factor 
ANOVA (oc=0.01). The latter analysis is a nonparamet- 
ric version of a 2-factor ANOVA that is more robust 
for the non-normally distributed data and frequent oc¬ 
currence of zeros (Anderson and Braak, 2003) that re¬ 
sulted from subsetting total nekton density data into 
individual species. Student’s /-tests were used to test 
for diel differences in total nekton density and species 
richness in the nearshore. Significant diel differences 
in the density of individual species that accounted for 
>1% of the total catch in the nearshore area were test¬ 
ed with a randomization test (a=0.01) in place of Stu¬ 
dent’s /-test for the same reasons noted above (Tebbs 
and Bower, 2003). Randomization tests were carried 
out with R software, vers. 2.11.0 (R Core Development 
Team, 2010), and the critical level of significance was 
adjusted from a=0.05 to a=0.01 to account for multiple 
testing. 
One-factor ANOVA was used to test for significant 
(a=0.01) diel differences in the length of species that 
accounted for >1% of total catch in shore zone and 
nearshore samples. When unequal variances violated 
the assumptions of the ANOVA, a Kruskal-Wallis H test 
was used instead and the critical level of significance 
was adjusted from a=0.05 to oc=0.01 to account for mul¬ 
tiple testing. 
Differences in species assemblages between day and 
night in the shore zone and the nearshore were ana¬ 
lyzed by using a multivariate approach with nonmetric 
multidimensional scaling (NMDS) and adonis proce¬ 
dures. The vegan package, vers. 1.13-8, within R soft¬ 
ware (vers. 2.11.0) was used for this analysis (Oksanen 
et al., 2008; R Core Development Team, 2010). This 
approach allows comparison of species assemblages by 
considering all species present and their abundances. 
Mean density of each species during day and night was 
calculated by pooling data from the 2 replicate seine 
hauls at each site to reduce variability in the analy¬ 
sis. Density data were square root transformed and 
similarity matrices were constructed for each site with 
the Bray-Curtis similarity measure. 2D plots depict¬ 
ing similarity of faunal assemblages between day and 
night were generated from similarity matrices gener¬ 
ated with NMDS. Spider diagrams were overlaid upon 
2D NMDS plots to show group centroids and spread. 
Significant variation in species assemblages was tested 
by using the adonis function in the vegan package (Ok¬ 
sanen et al., 2008). This function performs a permu- 
tational multiple analysis of variance (MANOVA) with 
Bray-Curtis similarity matrices to assign variation in 
