889 



Abstract— Sea turtles are subjected to 

 involuntary submergence and potential 

 mortality due to incidental capture by 

 the commercial shrimp fishing indus- 

 try. Despite implementation of turtle 

 excluder devices (TEDs) to reduce at- 

 sea mortality, dead stranded turtles 

 continue to be found in near-record 

 numbers along the coasts of the west- 

 ern Atlantic Ocean and northern Gulf 

 of Mexico. Although this mortality may 

 be due to an increase in the number of 

 turtles available to strand, one alterna- 

 tive explanation is that sea turtles are 

 repetitively submerged (as one fishing 

 vessel follows the path of another) in 

 legal TEDs. In the present study, labo- 

 ratory and field investigations were 

 undertaken to examine the physiologi- 

 cal effects of multiple submergence of 

 loggerhead sea turtles iCaretta caretta ). 

 Turtles in the laboratory study were 

 confined during the submersion epi- 

 sodes, whereas under field conditions, 

 turtles were released directly into 

 TED-equipped commercial fishing 

 nets. Under laboratory and field condi- 

 tions, pre- and postsubmergence blood 

 samples were collected from turtles 

 submerged three times at 7.5 min per 

 episode with an in-water rest interval 

 of 10, 42, or 180 min between submer- 

 gences. Analyses of pre- and postsub- 

 mergence blood samples revealed that 

 the initial submergence produced a 

 severe and pronounced metabolic and 

 respiratory acidosis in all turtles. Suc- 

 cessive submergences produced sig- 

 nificant changes in blood pH, Pco„ and 

 lactate, although the magnitude of the 

 acid-base imbalance was substantially 

 reduced as the number of submergences 

 increased. In addition, increasing the 

 interval between successive submer- 

 gences permitted greater recovery of 

 blood homeostasis. No turtles died 

 during these studies. Taken together, 

 these data suggest that repetitive sub- 

 mergence of sea turtles in TEDs would 

 not significantly affect their survival 

 potential provided that the animal has 

 an adequate rest interval at the surface 

 between successive submergences. 



The physiological effects of multiple forced 

 submergences in loggerhead sea turtles 

 (.Caretta caretta) 



Erich K. Stabenau 



Kimberly R. N. Vietti 



Department of Biology 



Bradley University 



1501 W Bradley Ave. 



Peoria, Illinois 61625 



E-mail address (for E, K. Stabenau): eks@bradleyedu 



Manuscript approved for publication 

 25 March 2003 by Scientific Editor. 



Manuscript received 26 June 2003 



at NMFS Scientific Publications Office. 



Fish. Bull. 101:889-899 (2003). 



The five sea turtle species inhabiting 

 the waters of the U.S. Gulf of Mexico 

 and Atlantic Ocean are considered to 

 be threatened or endangered. One con- 

 tributing factor to sea turtle mortality 

 is incidental capture in the nets of com- 

 mercial shrimping vessels. The National 

 Research Council's Committee on Sea 

 Turtle Conservation (1990) suggested 

 that as many as 5500 to 55,000 log- 

 gerhead (Caretta caretta) and Kemp's 

 ridley (Lepidochelys kempi) sea turtles 

 were killed annually during shrimp- 

 ing-related activities. More recently, 

 two independent studies statistically 

 confirmed the relationship between 

 shrimping activity and the appearance 

 of stranded sea turtles in the U.S. Gulf 

 of Mexico and the Atlantic Ocean (Cail- 

 louet et al., 1991; Crowder et al., 1995). 

 Because of the impact of trawl-related 

 mortality on sea turtle populations, the 

 U.S. government passed regulations 

 in 1987 requiring that commercial 

 shrimping vessels pull nets equipped 

 with certified turtle excluder devices 

 (TEDs). TEDs are designed to exclude 

 any turtle that may enter into shrimp- 

 ing nets, while not affecting the catch of 

 the target species. Crowder et al. (1995) 

 reported that the sea turtle population 

 off the coast of South Carolina contin- 

 ued to decline when TED regulations 

 were implemented; however, the rate 

 of decline decreased significantly after 

 full-time TED use. 



In spite of the TED regulations, 

 near-record numbers of dead stranded 

 sea turtles have been found on U.S. Gulf 

 of Mexico and Atlantic Ocean beaches 

 (Shaver-Miller'). Although there may 



be other man-related or natural causes 

 for this continued sea turtle mortality, 

 there are two plausible reasons for the 

 increased mortality during shrimping 

 activities. First, commercial shrimp 

 fishermen generally do not carry le- 

 gally certified TEDs in their trawl 

 nets and the TEDs that are used are 

 often installed incorrectly or purposely 

 sewn shut. Second, the shrimp fisher- 

 men may pull legal TEDs; however, 

 the turtles are repetitively submerged 

 as they are caught in the TEDs of ves- 

 sels that follow each other These suc- 

 cessive submergences may exacerbate 

 the physiological effects experienced 

 by sea turtles during a forced submer- 

 sion, and thus, may limit their survival 

 potential. 



Sea turtles spend approximately 

 99% of their time under the surface 

 of the water. During the brief period 

 at the surface, the turtle will exhale 

 and inhale a solitary breath and then 

 dive under the surface (Jackson, 1985). 

 In fact, multiple breaths by sea turtles 

 are generally seen only after prolonged 

 dives. Minimal information is available 

 on the physiological effects of forced 

 submergences of sea turtles. It has been 

 suggested that voluntary dives by sea 

 turtles are aerobic in nature (Wood et 

 al., 1984), whereby oxygen availability 

 minimizes the metabolic production of 

 lactic acid. The turtles may accumulate 

 carbon dioxide, resulting in a respira- 



Shaver-Miller, D. 2002. Personal com- 

 mun. Texas coordinator, Sea Turtle 

 Stranding and Salvage Network, USGS, 

 Corpus Christi, Texas 78406. 



