564 
Fishery Bulletin 95(3), 1 997 
Table 5 
Comparison of numbers and biomass of fish and shrimp collected by the four bycatch reduction device (BRD) nets and correspond- 
ing control nets for the different seasons. S D is the standard deviation of the difference. Significance levels are 0.01 (**) and 0.05 
(*). n= 36. Superscripted letters denote significance levels of paired i-tests on log-transformed data: 0.01 ( a ), 0.05 (*). 
Numbers Biomass (g) 
BRD and 
type of 
catch 
Mean catch/tow 
Percent 
catch 
difference 
Mean catch/tow 
Percent 
catch 
difference 
Season 
Control 
Device 
SD 
P>£-value 
Control 
Device 
SD 
P>£-value 
Authement-Ledet 
Fish spring 
218.3 
137.8 
-37 
127.7 
0.01**“ 
2,895.3 
1,667.1 
-42 
1,374.2 
0.01**“ 
fall 
122.6 
80.2 
-35 
65.5 
0.01**“ 
2,188.3 
1,261.2 
-42 
1,354.2 
0.01**“ 
Shrimp 
spring 
116.6 
92.1 
-21 
73.2 
0.05** 
650.3 
556.6 
-14 
288.7 
0.06* 
fall 
53.1 
46.5 
-12 
36.4 
0.29* 
316.0 
278.5 
-12 
180.4 
0.22 
Lake Arthur 
Fish spring 
216.1 
165.2 
-24 
157.1 
0.06 
3,459.1 
2,761.7 
-20 
2,119.1 
0.06* 
fall 
126.7 
104.2 
-18 
80.9 
0.10* 
2,349.6 
1,803.6 
-23 
893.6 
0 oi*** 
Shrimp 
spring 
124.8 
96.5 
-23 
75.4 
0.03** 
642.3 
541.1 
-16 
244.8 
0.02** 
fall 
61.7 
45.3 
-27 
31.0 
0.01**“ 
385.7 
308.9 
-20 
190.3 
0.02*“ 
Cameron 
Fish spring 
203.1 
106.5 
-48 
101.5 
0.01**“ 
3,296.6 
2,229.1 
-32 
1,187.8 
0.01**“ 
fall 
160.3 
70.2 
-56 
118.9 
0.01**“ 
2,840.4 
1,907.1 
-33 
1,290.5 
0.01**“ 
Shrimp 
spring 
157.9 
134.9 
-15 
104.4 
0.19“ 
773.1 
677.9 
-12 
252.8 
0.03*“ 
fall 
64.0 
51.2 
-20 
35.8 
0.04* 
385.4 
322.8 
-16 
184.8 
0.05* 
Eymard 
Fish 
spring 
233.8 
301.1 
29 
197.3 
0.05*“ 
3,386.9 
2,773.0 
-18 
2,029.4 
0.08* 
fall 
147.1 
178.3 
21 
131.7 
0.16* 
2,573.8 
2,039.7 
-21 
2,117.8 
0.14 
Shrimp 
spring 
145.1 
199.8 
38 
119.5 
0.01**“ 
716.1 
883.0 
23 
380.7 
0.01**“ 
fall 
52.6 
73.0 
39 
65.9 
0.07“ 
318.2 
407.7 
28 
294.3 
0.08 
The BRD nets tested here did not appear to slow 
water flow in the trawl net. Other studies, however, 
have indicated that flow rate around and through 
the BRD may be a key factor in fish and shrimp es- 
capement. Watson et al. (1993) found that juvenile 
fish could exit a BRD at flow rates between 0.2 and 
0.5 m/sec. However, shrimp accumulated in areas of 
reduced flow and crawled along the webbing against 
the flow to escape some devices (Watson et al., 1993). 
Devices can be designed to create a 0.2 to 0.5 m/sec 
flow rate, but debris can alter the flow rate and af- 
fect BRD performance. The ability to sustain swim- 
ming appears to be related to length, but this rela- 
tionship often differs for each species (Bainbridge 
1960). Further testing is necessary to acquire escape 
flow rates for the major species of concern. 
Reduction rates for numbers and biomass of many 
species differed for the four BRD’s, reflecting size- 
dependent selectivity. Escape rates of different spe- 
cies also varied considerably owing to differences in 
size and behavior. These differences, coupled with 
the high variability in organisms between areas, in- 
dicate that the performance of BRD’s should be evalu- 
ated at the species and size level. 
Future studies should continue to involve mem- 
bers of the industry. The advisory committee provided 
suggestions and valuable insight that greatly en- 
hanced the success of this project and the accept- 
ability of the results. Other studies have reported 
successful industry involvement (Rulifson et al., 
1992; McKenna and Monaghan 4 ). The design and 
construction of BRD’s should be a dynamic process 
which will benefit from the cooperation of industry, 
research, and management personnel. 
Acknowledgments 
This paper is funded in part by a cooperative agree- 
ment with the National Oceanic and Atmospheric 
Administration (NOAAAward No. NA17FF0375-01). 
Additional funding was provided by the Louisiana 
State University Agricultural Center. We are espe- 
cially grateful to J. Watson, I. Workman, W. Taylor, 
