Steele et aL; Efficiency of bycatcti reduction devices in small otter trawls in tfie Florida shrimp fishery 



341 



Side view 



Accelerator funnel 



TED 



Codend 



Figure 3 



Stylistic diagram of the bycatch reduction devices used in this study: I A) Control net equipped with 

 an accelerator funnel in front of the TED; (B) net with Florida fisheye (FFEi, the device is inserted 

 into the tailbag behind the TED; (C) net with large-mesh extended-mesh funnel (EMF) inserted 

 directlv behind the TED. 



Sampling protocol 



Our sampling protocol was established in consultation with 

 representatives from the NMFS Pascagoula Laboratory and 

 the FMFC. Coleman and Koenig^ estaWished that TEDs 

 did not work as finfish excluder devices in inshore waters; 

 therefore we did not test their exclusion efficiencies. 



Sampling was conducted aboard a 35-ft, diesel-pow- 

 ered, Bruno & Stillman trawler boat, modified with out- 

 riggers. The nets were deployed and retrieved with a hy- 

 draulic powered system. Prior to instalHng and testing the 

 BRDs, we equipped all pairs of nets of each size with the 

 combined TED and accelerator-funnel sections and tested 

 them for comparable catchability. 



To test each BRD type in each size of net. we conducted 

 twenty paired tows at night diuing a three-week sampling 

 period in each season. Each pair of nets was towed 10 times 

 within a two-week time period. To minimize any jx)tential bias 

 inherent to a particular net or side of the boat, the two nets 

 of each pair were switched to opposite sides of the boat after 

 10 tows were completed. All paired nets were towed in water 

 depths of 3.5 to 5.0 m for 30-min bottom time at an average 

 speed of 2.5 kn; speed was determined through use of the glob- 



al positioning system (GPS). All trawling was conducted in ar- 

 eas where the commercial shrimp fishery operates. 



The catches from the paired nets (BRD and control) 

 were maintained separately and were sorted onboard the 

 vessel. After each tow, the shrimp, finfish, invertebrates 

 (horseshoe crabs, portunid crabs, sponges, tunicates) and 

 "trash" (seagrass, rocks, shells, anthropogenic debris, etc.) 

 from each net were separated. The large invertebrates 

 (horseshoe crabs, blue crabs, etc.) and trash were weighed 

 separately, the invertebrates were counted, and both the 

 invertebrates and the trash were discarded. The total 

 catch of shrimp and finfish from each net was weighed 

 separately. The shrimp were counted, sex was determined 

 for 10 randomly chosen individuals, and their carapace 

 lengths (CL) were measured to the nearest 0.1 mm. These 

 measurements from the 20 replicate tows were combined 

 to obtain length-frequency distributions for the shrimp. 

 The remaining bycatch, composed of finfish and small in- 

 vertebrates, was weighed. If the total weight of the by- 

 catch was less than or equal to 4.5 kg, the entire sample 

 was kept; if the weight of the sample exceeded 4.5 kg, a 

 subsample weighing a total of 4.5 kg + 20% of the total 

 bycatch weight was kept. All species of vertebrates and in- 



