Caillouet et al.: Relationship between sea turtle stranding rates and shrimp fishing intensities 



247 



1990) and that some turtles incidentally caught dur- 

 ing shrimping operations become stranded ( Manzella 

 et al., 1988; Fontaine et al., 1989). The surprising 

 aspect of our findings comes from the expectation 

 that TED regulations would lead to a reduction or 

 elimination of the statistical association between sea 

 turtle stranding rates and fishing intensities in the 

 northwestern Gulf. To explain this continued statis- 

 tical association, we offer the following hypotheses: 



1 legal and properly installed TED's failed to eject 

 all of the sea turtles caught incidentally in shrimp 

 trawls; 



2 sea turtles were captured and ejected repeatedly 

 from trawls containing legal and properly installed 

 TED's, and eventually succumbed to the stresses 

 of repeated passage through such trawls; 



3 sea turtles were captured incidentally in shrimp- 

 ers' try nets that had no TED's; 



4 violations of TED regulations resulted in inciden- 

 tal capture of sea turtles; 



5 nonshrimping causes of sea turtle mortality were 

 in synchrony with shrimping effort. 



Legal and properly installed TED's may have failed 

 to eject all of the sea turtles caught incidentally in 

 shrimp trawls (hypothesis 1). Prior to June 1994, 

 supporting floats were not required on bottom-open- 

 ing hard TED's (Mitchell 4 ). Tests by NMFS showed 

 that use of such legal TED's without floats could re- 

 sult in sea turtle mortality (Mitchell 4 ). Therefore, 

 NMFS issued new rules to ensure sea turtle escape. 

 Other NMFS studies have shown that sea turtles are 

 sometimes caught in TED-equipped shrimp trawls 

 (Renaud et al., 1990, 1991; Epperly et al., 1995). Each 

 type of TED certified for use by the shrimp industry 

 has been tested under an established scientific pro- 

 tocol (Federal Register, vol. 55, no. 195, p. 41882- 

 41883, 9 October 1990). NMFS-certified TED's that 

 were properly installed and "tuned" (adjusted) were 

 required to be no less than 97% effective in ejecting 

 incidentally captured sea turtles. The actual rate of 

 ejection could vary below 979r under less than ideal 

 shrimp trawling conditions. 



There is no evidence that individual sea turtles 

 were captured and ejected repeatedly from certified, 

 properly installed TED's during commercial shrimp 

 trawling operations (hypothesis 2). If they had been, 

 they would have undergone repeated stress. To de- 

 termine whether sea turtles are captured and ejected 

 repeatedly from TED's during commercial trawling 



operations, underwater observations would be re- 

 quired and the sea turtles would have to be marked 

 for repeated recognition. During TED certification 

 trials conducted near Panama City, Florida, Kemp's 

 ridley turtles, released into TED-equipped shrimp 

 trawls and submerged for less than 8 min before ejec- 

 tion and surfacing, developed blood acidosis. The 

 acidosis was, for the most part, metabolic (caused by 

 accumulation of lactate) and to a lesser degree res- 

 piratory (caused by accumulation of C0 9 )(Stabenau 

 et al., 1991). The turtles released excess C0 2 when 

 they hyperventilated after surfacing (Stabenau et al., 

 1991). Other research showed that at least 20 h were 

 required for complete recovery from lactate acidosis 

 in loggerhead sea turtles caught in shrimp trawls 

 during sea turtle surveys in Port Canaveral Ship 

 Channel, Florida (Lutz and Dunbar-Cooper, 1987). 

 It is doubtful that a sea turtle in a state of severe 

 blood acid-base disequilibrium, resulting from sub- 

 mergence and struggling to escape a shrimp trawl, 

 would dive soon after release from a TED (Stabenau 5 ). 

 If it dived, the blood acidosis would be exacerbated. 

 On the other hand, if the turtle remained at or near 

 the surface it could take frequent breaths and re- 

 cover from the acid-base disturbance. As standard 

 practice, sea turtles submerged in shrimp trawls for 

 less than 10 minutes during TED certification trials 

 are allowed at least 48 h of recovery before being 

 submerged in a second test (Fontaine 6 ). 



Sea turtles may have been captured incidentally 

 in shrimpers' try nets (hypothesis 3) within which 

 TED's were not required. Even though these small 

 trawls are towed for relatively brief intervals, direct 

 observations aboard shrimp trawlers have shown 

 that sea turtles are caught incidentally in try nets 

 (Renaud et al., 1990, 1991; Mitchell 4 ). 



Violations of TED regulations have been shown to 

 result in incidental capture of sea turtles in shrimp 

 trawls (hypothesis 4). For example, unprecedented 

 numbers of sea turtles were stranded in Louisiana 

 in 1993 and in Texas in 1994 and 1995, concomitant 

 with concentrations of shrimp trawling. These 

 stranding events were attributed, at least in part, to 

 violations of TED regulations, including, but not lim- 

 ited to, various illegal alterations of TED's (Grouse, 

 1993a; Shaver, 1994, 1995; Steiner, 1994; Shrimp 

 Trawling in the Southeastern United States Under 

 the Sea Turtle Conservation Regulations, Endan- 



4 Mitchell, J. 1995. Pascagoula Laboratory, Southeast Fish. 

 Sci. Cent., Natl. Mar. Fish. Serv.. NOAA, P.O. Drawer 1207, 

 Pascagoula, MS 39568-1207. Personal commun. 



5 Stabenau, E. 1994. Department of Physiology, School of 



Medicine, East Carolina University, Greenville, NC 27858- 



4354. Personal commun. 

 e Fontaine, C. 1995. Galveston Laboratory, Southeast Fish. 



Sci. Cent., Natl. Mar. Fish. Serv, NOAA, 4700 Ave. U, Galveston, 



TX 77551-5997. Persona] commun. 



