338 



Abstract— Two bycatch reduction de- 

 vices ( BRDs 1 — the extended mesh funnel 

 (EMF) and the Florida fisheye (FFE)— 

 were evaluated in otter trawls with net 

 mouth circumferences of 14 ni, 17 m, 

 and 20 m and total net areas of 45 m-. 

 Each test net was towed 20 times in 

 parallel with a control net that had 

 the same dimensions and configuration 

 but no BRD. Both BRDs were tested 

 at night during fall 1996 and winter 

 1997 in Tampa Bay Florida. Usually 

 the bycatch was composed principally 

 of finfish (44 species were captured); 

 horseshoe crabs and blue crabs sea- 

 sonally predominated in some trawls. 

 Ten finfish species composed 92'^i of the 

 total finfish catch; commercially or rec- 

 reationally valuable species accounted 

 for I'i of the catch. Mean finfish size 

 in the BRD-equipped nets was usually 

 slightly smaller than that in the con- 

 trol nets. Compared with the corre- 

 sponding control nets, both biomass and 

 number of finfish were almost always 

 less in the BRD-equipped nets but nei- 

 ther shrimp number nor biomass were 

 significantly reduced. The differences in 

 proportions of both shrimp and finfish 

 catch between the BRD-equipped and 

 control nets varied between seasons 

 and among net sizes, and differences 

 in finfish catch were specific for each 

 BRD type and season. In winter, shrimp 

 catch was highest and size range of 

 shrimp was greater than in fall. Sea- 

 son-specific differences in shrimp catch 

 among the BRD types occurred only in 

 the 14-m, EMF nets. Finfish bycatch 

 species composition was also highly 

 seasonal; each species was captured 

 mainly during only one season. How- 

 ever, regardless of the finfish composi- 

 tion, the shrimp catch was relatively 

 constant. In part as a result of this 

 study, the State of Florida now requires 

 the use of BRDs in state waters. 



Efficiency of bycatch reduction devices in 



small otter trawls used in the Florida shrimp fishery 



Philip Steele 



Theresa M. Bert 



Kristine H. Johnston 



Sandra Levett 



Florida Fish and Wildlife Conservation Commission 



Florida Manne Research institute 



100 8th Avenue S.E. 



St Petersburg, Flonda 33701-5095 



E-mail address (for T M Bert, contact author) theresa bertiqfwc state fl us 



Manuscript accepted 13 September 2001. 

 Fish. Bull. 100:338-350 (2002). 



Commercial fishermen use a variety of 

 gears to harvest shrimp in southeast- 

 ern U.S. waters, but they have predom- 

 inantly used the otter trawl since the 

 1940s. The otter trawl is an unselective 

 gear that commonly has an associated 

 catch of untargeted organisms (e.g. fin- 

 fish, miscellaneous invertebrates) that 

 are referred to as "bycatch." Numerous 

 definitions for the term " bycatch" have 

 been proposed (Allsopp, 1982; Caddy, 

 1982: Saila, 1983 ). The most comprehen- 

 sive, suggested by Alverson et al. ( 1994 ), 

 refers to nontargeted species retained, 

 sold, or discarded for any reason. 



An estimated average of 27.0 million 

 metric tons (t) (range=17.9-39.5 mil- 

 lion t) of bycatch are discarded annu- 

 ally by the worlds marine fishing fleets 

 (Alverson et al, 1994). Shellfish fisher- 

 ies compose 14 of the top 20 fisheries 

 worldwide in quantity of bycatch dis- 

 cards (Alverson et al., 1994) and ac- 

 count for 9.5 million t of discards an- 

 nually. Because the harvest of bycatch 

 often exceeds that of the targeted spe- 

 cies, the issue of bycatch in marine fish- 

 eries has become a global concern. 



In the southeastern United States, 

 the penaeid shrimp fishery often ranks 

 first in value of all fisheries for com- 

 mercially harvested marine species. In 

 1996, total landings were 98 million 

 kg and were valued at appro.xiniately 

 $434 million, ex-vessel price (size-spe- 

 cific price per unit volume paid to the 

 fisherman for the catch ) (NMFSM. The 

 Gulf of Mexico (referred to as "Gulf" 

 in this study) shrimp fishery accounted 

 for 909( of this volume and 87'^'i of this 

 value. In U.S. waters, the Gulf and the 



southeast U.S. Atlantic (referred to as 

 "South Atlantic") shrimp trawl fisher- 

 ies ranked 5th and 9th, respectively 

 Their ratios of kg finfish bycatch to kg 

 shrimp were 10.3:1 for the Gulf, and 

 8.0:1 for the South Atlantic (Alverson et 

 al., 1994). However, the Gulf and South 

 Atlantic Fisheries Development Foun- 

 dation (GSAFDF-') estimated that the 

 ratio of finfish bycatch to shrimp harvest 

 was 4.2:1 for the Gulf shrimp fishery 

 and 2.8:1 for the South Atlantic shrimp 

 fishery. Thus, using the more conserva- 

 tive ratios reported by GSAFDF and the 

 1996 shrimp landings for the Gulf fish- 

 ery ( 88 million kg) and the south Atlan- 

 tic fishery i9.9 million kg: NMFS'), the 

 estimated total finfish bycatch for these 

 two fisheries is 370 million kg and 28 

 million kg, respectively. 



In 1996, approximately 11.3 million 

 kg of shrimp were landed along the 

 Florida Gulf coast and 1.8 million kg 

 of shrimp were landed along the Flor- 

 ida Atlantic coast (NMFSM. Ratios of 

 finfish bycatch to shrimp for the Flori- 

 da Gulf coast ranged from 2.3:1 (fish- 



' NMFS (National Marine Fisheries Ser- 

 vice). 1997. Bycatch in the southeast 

 shrimp trawl fisherv A data summary 

 report. National Marine Fisheries Ser- 

 vice, Southeast Science Center, 75 Virginia 

 Beach Drive, Miami, FL 33149. 197 p. 



- GSAFDF (Gulf and South Atlantic Fish- 

 eries Development Foundation). 1997. 

 Bycatch and its reduction in the Gulf of 

 Mexico and South Atlantic shrimp fishery. 

 Final report to the National Oceanic and 

 Atmospheric Administration (award NA57 

 FF0285). GFSFDF, Suite 997, Lincoln 

 Center. 5401 West Kennedy Boulevard, 

 Tampa. FL 33609. 27 p. 



