193 



Effects of live-bait shrimp trawling on 

 seagrass beds and fish bycatch in 

 Tampa Bay.. Florida 



David L. Meyer 

 Mark S. Fonseca 

 Patricia L. Murphey 



Beaufort Laboratory 



Southeast Fisheries Science Center 



National Manne Fisheries Service, NOAA 



101 Pivers Island Road 



Beaufort, North Carolina 28516 



E-mail address (for D L Meyer) dave meyenSinoaa gov 



Robert H. McMichael Jr. 

 Michael M. Byerly 



Florida Marine Research Institute 

 Florida Department of Natural Resources 



100 8'^^ Avenue, S.E. 



St. Petersburg, Florida 33701 



Michael W. LaCroix 

 Paula E. Whitfield 

 Gordon W. Thayer 



Beaufort Laboratory 



Southeast Fisheries Science Center 



National Manne Fishenes Service, NOAA 



101 Pivers Island Road 

 Beaufort, North Carolina 28516 



The use of live shrimp for bait in 

 recreational fishing has resulted in 

 a controversial fishery for shrimp in 

 Florida. In this fishery, night collec- 

 tions are conducted over seagrass 

 beds with roller beam trawls to cap- 

 ture live shrimp, primarily pink 

 shrimp, Penaeus duorarum . These 

 shrimp are culled from the catch on 

 sorting tables and placed in on- 

 board aerated "live" wells. Beds of 

 turtlegrass, Thalassia testudinum, 

 a species that has highest growth 

 rates and biomass during summer 

 and lowest during the winter (Fon- 

 seca et al., 1996) are predominant 

 areas for live-bait shrimp trawling 

 (Tabb and Kenny, 1969). Because of 

 their use in seagrass beds, roller 

 trawls were designed to roll over the 



bottom to reduce gear penetration 

 and debris collection. Because 

 turtlegrass has an extensive root 

 system, it is not likely to be up- 

 rooted by roller trawls, but the 

 roller on the trawl has been noted to 

 break off and collect old turtle- 

 grass leaves (Woodbum et al. 1957). 

 On the Gulf Coast of Florida, bait 

 shrimp are generally collected from 

 turtlegrass beds year-round, but 

 most shrimp are taken October 

 through February (Berkeley et al., 

 1985). Trawl and culling times for 

 this fishery, including that of Tampa 

 Bay, are typically short, 5-20 and 2- 

 15 min, respectively, to reduce debris 

 collection and both injury and mor- 

 tality to shrimp. Although no data 

 were collected, Berkeley et al. ( 1985) 



suggested that such trawling for 

 shrimp may be destructive to sea- 

 grass beds and juvenile fishes, in- 

 cluding spotted seatrout, Cynoscion 

 nebulosus, snapper, Lutjanus spp., 

 and pigfish, Orthopristis chrysoptera. 

 However, the effects of this type of 

 trawling on finfish bycatch mortal- 

 ity are unknown. 



Numerous studies offish bycatch 

 mortality have used otter trawls. 

 These include consideration of the 

 effects otter trawling has on cod, 

 Gadus morhua, and American pla- 

 ice, Hippoglossoides platessoides, in 

 the Gulf of St. Lawrence, Canada 

 (Jean, 1963); on red snapper, 

 Lutjanus campechanus, in the Gulf 

 of Mexico (Gutherz and Pellegrin, 

 1988); and on bycatch in the Torres 

 Strait, Australia (Wassenberg and 

 Hill, 1989; Harris and Poiner, 1990; 

 Hill and Wassenberg, 1990). In 

 these studies fish mortality ranged 

 from 10% (Jean, 1963) to 80% 

 (Jean, 1963; Wassenberg and Hill, 

 1989), depending on culling times, 

 animal size, and temperature. 

 Trawl and culling times (30-60 

 minutes and 15-45 minutes, re- 

 spectively) in these studies were 

 typically longer than those used by 

 the Florida live-bait shrimp fishery. 



Our study objectives were 1) to 

 determine effects of a roller beam 

 trawl on turtlegrass biomass and 

 morphometries during intensive 

 (up to 18 trawls over a turtlegrass 

 bed), short-term (3-hour duration) 

 use and 2) to examine the mortal- 

 ity of bycatch finfish following cap- 

 ture by a trawl. 



Methods 



Sampling was done in August and 

 November 1990 in Tampa Bay, 

 Florida (Fig. 1). A commercial bait 

 shrimp boat towed two 3.38 m wide, 

 0.8 m high stainless steel roller 

 beam trawls simultaneously, one 



Manuscript accepted 6 April 1998. 

 Fish. Bull. 97(1):193-199 (1999). 



