136 



Fishery Bulletin 9 1 [ I ). 1993 



ing the first 6 months of this study. Higher losses of 

 shrimp from these nets may be due to (1) initial inex- 

 perience by shrimpers using TEDs, (2) high losses of 

 shrimp in rough-bottom areas, and (3) absence of a 

 funnel in the TED. The lack of an accelerator funnel 

 to assist shrimp movement past the escape opening of 

 the TED could also account for some shrimp loss. The 

 Georgia TED with an accelerator funnel exhibited a 

 3.6% reduction in shrimp CPUE compared with 13.6% 

 by the Georgia TED without a funnel. Nets equipped 

 with the Super Shooter TED exhibited the lowest re- 

 duction (1.4%) in shrimp CPUE when compared with 

 the standard nets. This may have been due to (1) 

 shrimpers having more experience with TEDs when 

 this model was introduced during the second year of 

 the study, and (2) more effective shrimp retention by 

 the TED. The Super Shooter design also reduces clog- 

 ging of TED bars by seagrasses and algae and may 

 reduce shrimp loss. Although this TED exhibited the 

 lowest reduction in shrimp CPUEs, it accounted for 

 more problems during trawling than the other TEDs. 

 These problems evidently did not affect shrimp 

 catchability, since there was no significant difference 

 between its catch rate and that of the paired standard 

 net. 



Areal differences in shrimp abundance may be con- 

 founded with CPUEs due to different types of TEDS 

 and standard nets (flat nets, semiballoon nets, mon- 

 goose nets, etc.). Some TEDs work better on hard- 

 bottom than on soft-bottom or with different types and 

 abundances of bycatch. Georgia TEDs with funnels 

 were the most common TED tested in Texas, Louisi- 

 ana, and Florida. Super Shooter TEDs with funnels 

 were used in North Carolina. The effectiveness of the 

 TED type does influence the catch rates of shrimp. 



Phares ( 1978), in describing the selectivity of shrimp 

 nets, indicated that loss rates varied by area and sea- 

 son and affected an extensive size-range of lost shrimp. 

 We have assumed ( 1 ) that shrimp escaping through 

 either a TED-equipped net or a standard net will not 

 die because of that episode, and (2) that escaping 

 shrimp will grow and experience the same subsequent 

 natural and fishing mortality as the rest of the stock. 

 Thus, survival rates of shrimp escaping through the 

 cod end of a standard net should be the same as those 

 of shrimp escaping through the cod end of a TED net. 

 Shrimp escaping through TED openings probably are 

 not injured and are subject to subsequent recapture. 

 Although decreases in CPUE may impact a given 

 fisherman on any particular tow, these lost shrimp 

 will still be available to fishermen for capture by suc- 

 ceeding tows. 



Mathematical models indicated that a TED-induced 

 decrease of 5% in F would result in an undetectable 

 change in yield in the brown or white shrimp fisheries 



and a 1% reduction in the annual yield of the pink 

 shrimp fishery in the U.S. Gulf of Mexico. Because of 

 the asymptotic nature of the yield curves, only slight 

 decreases in yield would be observed in some shrimp 

 fisheries even if loss rates from TEDs were in the 

 10-20% range. With a 10% loss rate, we calculated a 

 reduction from the pink shrimp fishery of 2% and no 

 decreases in yield from either the white or brown 

 shrimp fisheries. A 20% loss rate would result in a 4% 

 reduction of the annual yield of pink shrimp and a 

 1-2% reduction for brown and white shrimp fisheries. 



Acknowledgments 



We would like to acknowledge several organizations 

 and their personnel for assistance in securing vessels 

 to participate in this study: Gary Graham and Hollis 

 Forrester, Texas A&M University Sea Grant Marine 

 Extension Service; David Harrington and Paul Chris- 

 tian, University of Georgia Sea Grant Marine Exten- 

 sion Service; Bill Hogarth, North Carolina Fish and 

 Wildlife; numerous NMFS Port Agents; Texas and Loui- 

 siana Shrimp Associations, and the Gulf and South 

 Atlantic Fisheries Development Foundation. Wil Seidel, 

 John Watson, Windy Taylor, Dale Stevens, and James 

 Barber with NMFS Pascagoula assisted in vessel re- 

 cruitment, TED construction, gear tuning and back- 

 ground information on the development of the TED, 

 its installation and proper use. Jo Williams and Frank 

 Patella, NMFS Galveston, prepared figures for the 

 manuscript and assisted in various statistical analy- 

 ses. Much credit also goes to the NMFS Galveston 

 observers who painstakingly collected the data for this 

 project. Finally, we would like to thank the shrimpers 

 who participated in the study. Without their coopera- 

 tion, the study could not have been conducted. 



Citations 



Federal Register 



1987 52(1241:24244-24262. 



Klima, E.F., G.A. Matthews, & F.J. Patella 



1986 Synopsis of the Tortugas pink shrimp fishery, 

 1960-1983, and the impact of the Tortugas Sanc- 

 tuary. N. Am J. Fish. Manage. 6:301-310. 

 Magnuson, J.J., K.A. Bjorndal, W.D. DuPaul, G.L. Gra- 

 ham, D.W. Owens, C.H. Peterson, P.C.H. Pritchard, 

 J.I. Richardson, G.E. Saul, & C.W. West 



1990 Decline of the sea turtles: Causes and pre- 

 vention. Natl. Res. Counc. Natl. Acad. Sci. Press, 

 Wash. DC, 190 p. 

 Nance, J.M., & S. Nichols 



1988 Stock assessment for brown, white and pink 

 shrimp in the U.S. Gulf of Mexico, 1960-1986. NOAA 



