Torre et al.: Abundance and diversity of fish species and blue crab in Delaware Bay 
559 
Table 1 
Frequency of occurrence and mean density (individuals/100 m 2 ), with standard error (SE), of dominant (>1% total catch for 
diel period) nekton species during day and night in the shore zone of lower Delaware Bay (see Fig. 1) from June through 
September 2013. Catch data from sites A and B are combined. Significant differences in mean density between day and night 
are indicated by asterisks according to the criteria: *=P<0.01, **=P<0.005, ***=P<0.001. The critical level of significance 
was adjusted from a=0.05 to a=0.01 to account for multiple testing. P-values are provided for differences between day and 
night; values for site interaction effect are not shown because no significant effects were detected. P-values are given for 
species that were not included in a species-specific test (>1% total catch for diel period). Species unique to the shore zone 
(not observed in the nearshore area) are denoted by s . N/A=no statistical comparison was made because of low abundance. 
Species 
Total 
Day 
Night 
P-value: 
day vs. 
night 
Number 
% catch 
Frequency 
of 
occurrence 
Mean 
density 
(SE) 
Frequency 
of 
occurrence 
Mean 
density 
(SE) 
All species 
6545 
100.0 
100.00 
24.53 (4.63) 
100.00 
72.22(11.82) 
<0.001 *** 
Menidia menidia s 
3368 
51.3 
96.88 
17.97 (6.71) 
100.00 
32.23 (8.76) 
0.03 
Anchoa mitchilli 
2129 
32.4 
59.38 
2.18 (0.58) 
96.88 
31.05(9.97) 
<0.001 *** 
Cynoscion regalis 
275 
4.2 
12.50 
0.47 
56.25 
7.10(3.27) 
<0.001 *** 
Pomatomus saltatrix 
154 
2.3 
65.63 
2.94 (0.97) 
37.50 
0.90(0.13) 
<0.001 *** 
Brevoortia tyrannus 
110 
1.7 
18.75 
8.10 (1.94) 
15.63 
0.66(0.11) 
0.06 
Mugil cephalus s 
88 
1.3 
15.63 
5.09 (1.02) 
34.38 
1.46(0.20) 
0.27 
Callinectes sapidus 
85 
1.3 
25.00 
0.53 (0.04) 
59.38 
1.89(0.37) 
<0.001 *** 
Leiostomus xanthurus 
70 
1.1 
12.50 
0.59(0.06) 
43.75 
2.19(0.59) 
<0.001 *** 
Trachinotus carolinus 
55 
0.8 
31.25 
1.08 (0.12) 
25.00 
1.89 (0.32) 
N/A 
Micropogonias undulatus 
51 
0.8 
9.38 
0.79 (0.07) 
40.63 
1.67 (0.61) 
N/A 
Strongylura marina s 
39 
0.6 
3.13 
0.47 
34.38 
1.63 (0.41) 
N/A 
Bairdiella chrysoura 
35 
0.5 
15.63 
2.64 (0.08) 
15.63 
0.66 (0.06) 
N/A 
Menticirrhus saxatilis 
34 
0.5 
18.75 
0.86 (0.12) 
37.50 
0.90 (0.15) 
N/A 
Paralichthys dentatus 
10 
0.2 
3.13 
0.47 
21.88 
0.61 (0.05) 
N/A 
Selene vomer 
7 
0.1 
12.50 
0.47 
9.38 
0.47 (0.05) 
N/A 
Fundulus heteroclitus s 
6 
0.1 
0.00 
0.00 
9.38 
0.94 (<0.Q1) 
N/A 
Sphoeroides maculatus s 
6 
0.1 
6.25 
0.47 
9.38 
0.63 (<0.01) 
N/A 
Fundulus majalis s 
4 
0.1 
6.25 
0.71 (0.08) 
3.13 
0.47 (0.06) 
N/A 
Pseudopleuronectes americanus 
4 
0.1 
6.25 
0.47 
6.25 
0.47 
N/A 
Chilomycterus schoepfii 
3 
0.0 
0.00 
0.00 
9.38 
0.47 
N/A 
Pogonias cromis 
3 
0.0 
6.25 
0.47 
3.13 
0.47 
N/A 
Astroscopus guttatus s 
2 
0.0 
0.00 
0.00 
6.25 
0.47 
N/A 
Clupea harengus s 
1 
0.0 
0.00 
0.00 
3.13 
0.47 
N/A 
Dasyatis americana s 
1 
0.0 
0.00 
0.00 
3.13 
0.47 
N/A 
Hyporhamphus meeki s 
1 
0.0 
3.13 
0.47 
0.00 
0.00 
N/A 
Lagodon rhomboides s 
1 
0.0 
0.00 
0.00 
3.13 
0.47 
N/A 
Ophidion marginatum s 
1 
0.0 
0.00 
0.00 
0.00 
0.47 
N/A 
Peprilus triacanthus 
1 
0.0 
0.00 
0.00 
3.13 
0.47 
N/A 
Syngnathus fuscus 
1 
0.0 
3.13 
0.47 
0.00 
0.00 
N/A 
species assemblage data that was due to explanatory 
variables (day and night). The number of permutations 
used was 999. 
Results 
Shore zone and nearshore temperature ranged from 
~20.5-25.0°C during June through September 2013. 
Slightly higher temperatures were measured in the 
shore zone during the day (20.6-25.0°C) than at night 
(20.7-23.4°C). Nearshore temperatures were also 
slightly higher during the day (22.0-23.5°C) than at 
night (20.0-23.1°C). Salinity values ranged from ~21- 
29 and were similar between day and night and be¬ 
tween the shore zone and nearshore areas. 
A total of 9719 fish and blue crab were captured in 
the shore zone and nearshore area, representing 38 
species. The assemblage comprised members of the 
families Atherinopsidae, Engraulidae, Sciaenidae, Po- 
matomidae, Clupeidae, Mugilidae, and Portunidae. 
Fish density in the shore zone (Table 1) was domi¬ 
nated by Atlantic silverside (Menidia menidia, 51%), 
bay anchovy (Anchoa mitchilli, 32%), weakfish (Cy- 
noscion regalis, 4%), and bluefish (Pomatomus salta- 
trix, 2%). Total nekton density in the shore zone was 
