Beck and La Peyre: Effects of oyster harvesting activities on Louisiana reef habitat and resident nekton communities 
333 
TabSe 1 
Mean measurements of water quality and reef structure for sampled oyster reefs in Louisiana during summer and fall 
2010. Degrees of freedom (dD for P-values are provided in parentheses and apply to all results except for reef vertical re- 
lief, for which df=2 and a 2-sample f-test was used to compare treatments. Significant differences (P< 0.05) between harvest 
treatments are indicated with asterisks (*). Standard errors of the mean are provided in parentheses. NH=not harvested; 
AH=actively harvested. 
Summer Fall 
Parameter 
Sabine 
Lake 
(NH) 
Sister 
Lake 
(AH) 
F - value 
P-value 
North 
Calcasieu 
(NH) 
South 
Calcasieu 
(AH) 
E-value 
P-value 
Temperature (°C) 
31.0 (0.2) 
31.1 (0.2) 
0.02 
0.89 
26.4 (0.8) 
24.9 (1.1) 
1.28 
0.32 
Salinity 
13.0 (1.2) 
12.0 (0.4) 
0.56 
0.49 
20.0 (0.2) 
19.2 (0.1) 
12.53 
0.024* 
Dissolved oxygen (mg/L) 
Total particulate 
5.2 (0.3) 
4.4 (0.3) 
0.38 
0.57 
6.9 (0.1) 
6.3 (0.2) 
2.55 
0.19 
matter (mg/L) 
17.9 (3.5) 
44.2 (3.2) 
9.78 
0.04* 
75.6 (1.1) 
90.2 (5.3) 
6.36 
0.07* 
Chlorophyll-a (pg/L) 
8.2 (0.4) 
18.0 (2.0) 
18.89 
0.01* 
8.6 (0.3) 
16.9 (0.4) 
244.88 
<0.0001* 
Cluster volume (L) 
3.9 (0.1) 
2.9 (0.2) 
3.82 
0.12 
4.4 (0.1) 
1.8 (0.1) 
221.38 
<0.0001* 
Loose shell volume (L) 
0.3 (0.1) 
0.8 (0.2) 
1.8 
0.25 
0 
2.0 (0.1) 
80.7 
0.0008* 
Reef integrity (unitless) 
0.8 (0.1) 
0.6 (0.1) 
10.06 
0.004* 
0.9 (0.1) 
0.8 (0.1) 
4.52 
0.04* 
Reef depth (m) 
2.6 (0.02) 
1.9 (0.03) 
10.58 
0.03* 
1.2 (0.01) 
1.8 (0.01) 
88.32 
0.0007* 
Reef vertical relief (m) 
Total oyster density 
0.20 (0.00) 
0.17 (0.03) 
1.00 (df=2) 
0.42 
0.67 (0.03) 
0.10 (0.00) 
1.00 (df=2) 
0.42 
(no./tray) 
Market size oyster density 
67.0 (2.9) 
114.8(16.4) 
0.83 
0.41 
70.5 (4.5) 
20.7 (1.1) 
131.22 
0.0003* 
(no./tray) 
Seed size oyster density 
32.3 (1.8) 
9.2 (1.1) 
40.54 
0.003* 
17.5 (0.4) 
12.6 (0.7) 
6.42 
0.06 
(no./tray) 
34.7 (2.3) 
101.5 (16.5) 
2.02 
0.23 
43.1 (3.9) 
6.0 (0.7) 
58.12 
0.0016* 
Mussel density (no./tray) 
636.4 (61.0) 
319.2 (79.2) 
2.39 
0.2 
1424.7 (22.5) 
54.7 (5.7) 
3724.47 
<0.0001* 
Reef structure In the summer, there were no differenc- 
es in the volume of loose shells, shell clusters, vertical 
relief, total oyster density, seed oyster density, or mus- 
sel density (Table 1). Reef integrity, depth, and density 
of market-size oysters were lower at the harvested site 
(0.6 [SE 0.1], 1.9 m [SE 0.03], and 9.2 individuals/tray 
[SE 1.1], respectively) than at the nonharvested site 
(0.8 [SE 0.1], 2.6 m [SE 0.02], and 32.3 individuals/tray 
[SE 1.8], respectively). 
In the fall, there were no differences in vertical relief 
or in density of market-size oysters (Table 1). Volume 
of shell clusters was higher at the nonharvested site 
than at the harvested site: 4.4 L (SE 0.1) versus 1.8 L 
(SE 0.1). Conversely, loose shell volume was higher at 
the harvested site than at the non-harvested site: 2.0 L 
(SE 0.1) versus 0.0 L (SE 0.0). Reef depth was greater 
at the harvested site than at the nonharvested site: 
1.8 m (SE 0.01) versus 1.2 m (SE 0.01). Total oyster 
density, seed oyster density, and mussel density were 
higher at the nonharvested site (70.5 individuals/tray 
[SE 4.5], 43.1 individuals/tray [SE 3.9], 1424.7 individ- 
uals/tray [SE 22.5], respectively) than at the harvested 
site (20.7 individuals/tray [SE 1.1], 6.0 individuals/tray 
[SE 0.7], 54.7 individuals/tray [SE 5.7], respectively). 
Nekton community In the summer, 14 tray samples 
were collected at the nonharvested site, and 12 tray 
samples were collected at the harvested site (48% tray 
retrieval success rate) for a total of 26 trays. Densities 
of naked goby and estuarine mud crabs ( Rhitliropano - 
peus harrisii ) were higher at the harvested site (102.8 
individuals/m 2 [SE 21.4], 20.1 individuals/m 2 [SE 6.3]) 
than at the nonharvested site (9.4 individuals/m 2 [SE 
1.6], 0.7 individuals/m 2 [SE 0.4]) (Table 2). The num- 
ber of invertebrate species and total number of species 
also were greater at the harvested site (5.5 individu- 
als/m 2 [SE 0.4], 9.0 individuals/m 2 [SE 0.5]) than at 
the nonharvested site (3.4 individuals/m 2 [SE 0.2], 6.2 
individuals/m 2 [SE 0.3]). 
In the fall, 15 tray samples were collected at the 
nonharvested site, and 17 tray samples were collected 
at the harvested site (66% tray retrieval success rate) 
for a total of 32 trays. Densities of grass shrimp were 
greater at the nonharvested site, with a mean of 132.6 
individuals/m 2 (SE 17.0) than at the harvested site, 
with a mean of 65.6 individuals/m 2 (SE 12.7) (Table 
2). The number of fish species was also greater at the 
non-harvested site than at the harvested site: 2.5 indi- 
viduals/m 2 (SE 0.2) versus 1.5 individuals/m 2 (SE 0.2). 
Species environment The CCA indicated a significant 
relationship between nekton assemblage structure 
and environmental variables (P=0.001; Fig. 4). The 
horizontal axis, which explained 58.3% of the variation 
