890 



Fishery Bulletin 101(4) 



tory acidosis that is ameliorated by hyperventilation at the 

 surface. Therefore, voluntary diving in the absence of any 

 other external stressor does not limit sea turtle survival 

 potential. 



In contrast, forced submergence of Kemp's ridley and log- 

 gerhead sea turtles produces significant blood respiratory 

 and metabolic derangements. Stabenau et al. ( 1991) report- 

 ed that forced submergence of Kemp's ridley sea turtles for 

 less than 7.5 min in shrimp nets equipped with TEDs re- 

 sulted in significant increases in blood lactic acid and PcOj, 

 and decreases in blood pH. Moreover, several hours were 

 required for these turtles to fully recover blood homeostasis 

 (National Marine Fisheries Service, unpubl. data^). How- 

 ever, the study by Stabenau et al. ( 1991) did not address the 

 physiological effects of multiple forced submergences of sea 

 turtles. It is plausible that repeated submergence induces 

 progressive, significant blood acid-base disturbances, and 

 limits sea turtle survival potential. Therefore, the present 

 study examined the physiological effects of multiple forced 

 submergences on loggerhead sea turtles. 



This investigation was divided into two phases. First, 

 a laboratory component was conducted to examine the 

 feasibility of a multiple submergence study. This phase of 

 the research permitted characterization of the magnitude 

 of the acid-base disturbance under controlled conditions. 

 Second, a field investigation was conducted to expose tur- 

 tles to TED-equipped commercial fishing nets. Data from 

 these studies may offer greater insight into potential sea 

 turtle mortality caused by multiple capture in commercial 

 shrimping nets carrying legal TEDs. 



Materials and methods 



Laboratory study 



Thirty-nine headstarted 2-year-old loggerhead sea turtles 

 reared in captivity at the National Marine Fisheries Ser- 

 vice (NMFS) Galveston Laboratory were used in this phase 

 of the study. Each turtle was randomly placed into experi- 

 mental (submerged, 37.0 ±0.2 cm, 6.51 ±0.06 kg, n=21) or 

 control (nonsubmerged, 36.9 ±0.2 cm, 6.45 ±0.10 kg, n=18) 

 treatments. All turtles were of comparable size and weight 

 and therefore any alterations in blood parameters between 

 experimental and control turtles represented treatment 

 effects rather than size effects. It should be noted that the 

 turtles used in our study were representative of the aver- 

 age size of dead stranded turtles and those animals used 

 in annual TED certification tests. 



The study was initiated by collecting presubmergence 

 blood samples from the experimental turtles immediately 

 prior to their individual confinement in a weighted canvas 

 bag. Each turtle was then submerged for 7.5 min in sea- 

 water filled tanks. Postsubmergence blood samples were 

 collected within 30 s of bringing the turtle out of the water 

 to minimize blood acid-base changes. Following an in-water 



2 National Marine Fisheries Service. 1994. Unpubl. data. 

 (Available from E. K. Stabenau, Bradley University, 1501 W. 

 Bradley Ave., Peoria, IL 61625] 



rest interval of 10 (treatment 1), 42 (treatment 2), or 180 

 (treatment 3) min, a presubmergence blood sample was 

 collected and the turtle was submerged a second time. A 

 postsubmergence blood sample was then collected imme- 

 diately upon surfacing. The turtle was then submerged a 

 third time, following the same rest interval between the 

 first and second submergence episodes, and pre- and post- 

 submergence blood samples were collected as described 

 above. The seventh serial blood sample was collected 180 

 min after the final submergence in all turtles. Blood sam- 

 ples were also collected from control turtles over the same 

 time intervals to ensure that repetitive handling and blood 

 sampling did not alter blood homeostasis. All blood samples 

 were collected into heparinized vacutainers from the dorsal 

 cervical sinus as described by Owens and Ruiz (1980). No 

 more than 4-6% of blood volume was collected during the 

 serial sampling to minimize potential physiological effects 

 associated with blood volume depletion. 



Field study 



Thirty-six headstarted 2-year-old loggerhead sea turtles 

 reared in captivity from the NMFS Galveston Laboratory 

 were used in this phase of the study. The turtles were trans- 

 ported from Galveston, TX, to Panama City, FL, where they 

 were placed into large pens in St. Andrews Bay. The sub- 

 mergence study was initiated after a minimum of 21 days 

 of natural conditioning in the in-water pens. Each turtle 

 was randomly placed into experimental (submerged, 35.9 

 ±0.2 cm, 6.77 ±0.09 kg, n=24) or control (nonsubmerged, 

 35.4 ±0.3 cm, 6.46 ±0.12 kg, n=12) treatments. As in the 

 laboratory study, all experimental and control turtles were 

 of comparable size and weight. 



The study was initiated by collecting presubmergence 

 blood samples from the experimental turtles immediately 

 prior to their individual confinement in a weighted mesh 

 bag. Each turtle was then submerged using the standard 

 protocol for TED certification tests. Briefly, the mesh bag 

 containing a turtle was placed onto a line connecting the 

 trawl vessel to the headrope on the shrimp net. Divers then 

 released the turtle (without handling the animal) into the 

 mouth of the trawl. Often, turtles were observed vigorously 

 swimming in the trawl until being overcome by the net. 

 Although the shrimp net was equipped with a TED, divers 

 held the escape door closed for 5 min. The turtle was then 

 permitted to leave the trawl and surface. Thus, the total 

 submergence time was approximately 7.5 min, including 

 the time for the weighted mesh bag containing the turtle 

 to reach the headrope for release into the trawl, the 5 min 

 within the trawl, and the time for the turtle to surface. 

 Turtles were immediately captured at the surface and 

 returned to the trawl vessel for postsubmergence blood 

 sampling. Typically, postsubmergence blood samples were 

 collected within 1-2 min of the turtle surfacing. Following 

 a rest interval of 10 (treatment 4), 42 (treatment 5), or 180 

 (treatment 6) min in water-filled containers on the trawl 

 vessel, a presubmergence blood sample was collected and 

 the turtle was submerged a second time. A postsubmer- 

 gence blood sample was then collected immediately upon 

 surfacing. The turtle was then submerged a third time, 



