Rogers et ai : Effectiveness of bycatch reduction devices in Louisiana inshore waters 
557 
six species were much more abundant in the spring. 
The catches from Lake Borgne were typically much 
smaller than catches from the other areas. Brown 
shrimp, hardhead catfish, sand seatrout, and gulf men- 
haden were most abundant in Calcasieu Lake, whereas 
Atlantic croaker and blue crab were most abundant in 
Lake Barre. Penaeid shrimp constituted 36% of the 
catch in the spring and 27% of the catch in the fall. 
The numbers of organisms collected by the three 
control nets did not differ significantly. Control-net 
catches did not differ significantly with respect to 
the excluder with which they were paired. Length- 
frequency distributions of the abundant species dif- 
fered between areas (Fig. 3). 
The side of the trawl on which the control or BRD 
net was towed did not significantly affect catches of 
the abundant species. Each BRB was towed equally 
on each side of the twin trawl. 
BRD's versus control nets 
Fish All BRD nets had significantly different 
catches of fish from those of the control nets. Nu- 
merically, the Cameron BRD had the highest overall 
reduction of fish (-51%) compared with the catch of 
the control nets (Table 2). The Eymard BRD caught 
26% more fish than the control nets. In terms of bio- 
mass, the Authement-Ledet BRD had the highest re- 
duction (-42%), and the Eymard BRD had a 19% 
lower catch than the control nets. 
The Authement-Ledet, Lake Arthur, and Cameron 
BRD nets caught fewer fish than the control nets in 
all size categories (Fig. 4). The Cameron BRD, in 
particular, had the highest reduction of small fish 
(<75 mm). The Eymard BRD caught more small fish 
(<85 mm) and fewer large fish than the control net. 
The Cameron BRD had the best reduction in num- 
bers of Atlantic croaker (49%), and the Authement- 
Ledet the best reduction in biomass (39%) (Table 3). 
The Authement-Ledet and Eymard BRD’s caught 
50% or fewer spot in terms of numbers and biomass; 
in contrast, the Cameron had very poor reductions 
for spot. Both the Cameron and Authement-Ledet 
BRD’s caught 50% or fewer hardhead catfish than 
the control nets. The Cameron BRD caught 75% 
fewer bay anchovy than the control net, and the 
Authement-Ledet and Lake Arthur reduced bay an- 
chovy by 37%. For most bycatch species, the Eymard 
BRD caught more than the control nets, although 
catches of the bay anchovy were markedly higher 
(83% numbers, 86% biomass). 
Shrimp The catch of shrimp with all BRD nets dif- 
fered significantly from the control net catch. The 
Cameron, Authement-Ledet, and Lake Arthur BRD’s 
caught fewer shrimp than the control nets; shrimp 
catch with the Eymard was higher (38% numbers, 
25% biomass) (Table 2). Numerically, the Cameron 
BRD had 16% fewer shrimp, and both the Cameron 
and Authement-Ledet had 14% lower shrimp bio- 
mass than the control nets. 
Most of the catch difference between the BRD nets 
and corresponding control nets appeared to be 
smaller (<85-90 mm) shrimp (Fig. 5). Catch differ- 
Table 2 
Comparison of numbers and biomass of fish and shrimp collected in bycatch reduction nets and corresponding control nets in 
selected inshore waters of Louisiana in 1992. SDis the standard deviation of the difference. Significance levels are 0.01 (**) and 
0.05 (*). n= 72. Superscripted letters denote significance levels of paired t-tests on log-transformed data: 0.01 (“). BRD = bycatch 
reduction device. 
Numbers Biomass (g) 
Mean catch/tow Percent Mean catch/tow Percent 
Type of catch 
and BRD 
Control 
Device 
catch 
difference 
SD 
P>t-value 
Control 
Device 
catch 
difference 
SD 
P>t-value 
Fish 
Authement-Ledet 
170.5 
109.0 
-36 
102.6 
0.01**“ 
2,541.8 
1,464.1 
-42 
1,363.1 
0.01**“ 
Lake Arthur 
171.4 
134.7 
-21 
124.9 
0.01**“ 
2,904.4 
2,282.6 
-21 
1,616.5 
0.01**“ 
Cameron 
181.7 
88.3 
-51 
109.8 
0.01**“ 
3,068.5 
2,068.1 
-33 
1,233.3 
0.01**“ 
Eymard 
190.4 
239.7 
26 
167.6 
0.01**“ 
2,980.3 
2,406.3 
-19 
2,059.8 
0.02*“ 
Shrimp 
Authement-Ledet 
84.8 
69.3 
-18 
58.1 
0.03*“ 
483.1 
417.5 
-14 
240.7 
0.02* 
Lake Arthur 
93.2 
70.9 
-24 
57.5 
0.01**“ 
514.0 
425.0 
-17 
218.1 
0.01**“ 
Cameron 
110.9 
93.0 
-16 
77.7 
0.05*“ 
579.3 
500.3 
-14 
220.5 
0.01**“ 
Eymard 
98.9 
136.4 
38 
97.4 
0.01**“ 
517.2 
645.3 
25 
340.1 
0.01**“ 
