Interactions between platform terminal transmitters and turtle excluder devices.
|Abstract:||Satellite telemetry is a common tool for examining sea turtle movements, and many research programs have successfully tracked adults. Relatively short satellite track durations recorded for juvenile Kemp's ridley sea turtles, Lepidochelys kempii, in the northwestern Gulf of Mexico raised questions regarding premature transmission loss. We examined interactions between juvenile sea turtles outfitted with platform terminal transmitters (PTT's) and turtle excluder devices (TED's) and the potential for transmission loss due to this interaction. A pilot study was conducted with eight 34-month-old, captive-reared loggerhead sea turtles, Caretta caretta; a larger trial the following year used twenty 34-month-olds. Half of the turtles in each trial were outfitted with dummy PTT's (8x4x2 cm), and all turtles were sent through a trawl equipped with a bottom-opening Super-Shooter TED. No apparent damage was sustained by any PTT, but four of five PTT-outfitted loggerheads encountering the TED carapace-first exhibited increased escape times when the PTT wedged between the TED deflector bars (10.2 cm apart). Overall, 15 loggerheads (54%) impacted the TED carapacefirst. Attachment of PTT's to smaller sea turtles may slow or, in worst cases, inhibit escape from TED's. Likewise, loose or poorly secured PTT's could impede escape or be shed during such an interaction. Researchers tracking small turtles in or near regions with trawling activity should consider PTT size and shape and the combined PTT/adhesive profile to minimize potentially detrimental interactions with TED's.|
Communications equipment (Usage)
Seney, Erin E.
Higgins, Benjamin M.
Landry, Andre M., Jr.
|Publication:||Name: Marine Fisheries Review Publisher: Superintendent of Documents Audience: Academic Format: Magazine/Journal Subject: Agricultural industry; Business Copyright: COPYRIGHT 2010 U.S. Department of Commerce ISSN: 0090-1830|
|Issue:||Date: Summer, 2010 Source Volume: 72 Source Issue: 3|
|Topic:||Event Code: 310 Science & research Computer Subject: Cellular transmission equipment; Telecommunications equipment|
|Product:||Product Code: 3660000 Communications Equipment; 9108315 Telecom Equip & Service Standards NAICS Code: 3342 Communications Equipment Manufacturing; 92613 Regulation and Administration of Communications, Electric, Gas, and Other Utilities|
|Geographic:||Geographic Scope: Texas; United States Geographic Code: 1U7TX Texas; 1USA United States|
Advances in the global satellite network, satellite transmitter miniaturization, and new deployment techniques have allowed for increased use of satellite telemetry as a tool for examining long-term movements of sea turtles and other vertebrate species (Coyne and Godley, 2005). The Texas A&M University at Galveston (TAMUG) Sea Turtle and Fisheries Ecology Research Laboratory attached platform terminal transmitters (PTT's) to eight Kemp's ridley sea turtles, Lepidochelys kempii, using Power-Fast+ (1) two-part marine epoxy during 2004-05 (Seney, 2008). All transmitted for considerably shorter periods than expected, with five immature individuals tracked for 12--57 d ([bar.x] [+ or -] 1 SD = 37 [+ or -] 17 d) and three adult females for 20--50 d ([bar.x] [+ or -] 1 SD = 38 [+ or -] 16 d). Several different transmitter models were utilized, but battery lives of 180--365 d or more were anticipated for all units. This discrepancy prompted concerns regarding causes for premature transmission loss including turtle mortality, biofouling, antenna damage, and attachment failure (Tucker et al., 2007; Seney and Landry, 2008; Seney et al., 2010).
Antenna damage or loss of the entire PTT could be due to multiple factors in eluding insufficient attachment method, rapid turtle growth, or an "impact" event such as a boat strike or contact with the grid of a turtle excluder device (TED). We conducted trials to examine interactions between PTT-outfitted loggerhead sea turtles, Caretta caretta, and TED-equipped shrimp trawls and assessed potential for subsequent antenna and PTT damage and loss.
Materials and Methods
A pilot study was conducted with eight 34-month-old captive-reared loggerheads on 22 June 2006 (mean straight carapace length [SCL] = 42.5 cm, SD = 1.2 cm), and a follow-up trial was conducted with twenty 34-month olds on 22 and 24 June 2007 (mean SCL = 47.0 cm, SD = 1.1 cm). Loggerheads were transported from the NMFS Sea Turtle Facility in Galves ton, Tex., to Panama City, Fla., in mid May of each year and then semi-wild conditioned in outdoor pens for about 4 weeks (Higgins, 2003). Turtles were evenly split between experimental (PTT) and control (no PTT) groups. Replica (dummy) Sirtrack KiwiSat 202 PTT's measuring approximately 8x4x2 cm were attached along the first two vertebral scutes (Seney et al., 2010) of each experimental loggerhead. In 2006, PTT's were attached with Power-Fast+ two-part marine epoxy (PF-only, n = 2) or PowerFast+ covered with Sonic-Weld steel-reinforced epoxy putty (PF/SW, n = 2), whereas the 2007 trial utilized the PF/SW attachment (n = 4) and a new method incorporating neoprene to the PF-only protocol (PF/neoprene, n = 6; Seney et al., 2010). Two modifications were made to the basic attachment protocol in 2007: 1) 60-grit sandpaper was utilized instead of 100-grit to sand the turtles' carapaces and PTT's; and 2) the first 10-15 cm of Power-Fast+ epoxy discharged from an applicator nozzle was discarded after discovery that epoxy initially discharged from a new nozzle and/or cartridge may not ever fully cure due to inadequate mixing (Morehead (2)).
Two trials examining TED-PTT interactions were conducted near Panama City from the NMFS RV Caretta and in accordance with the NMFS standard small turtle TED test protocol (NMFS, 1990). The trials were conducted over substrates with relatively low finfish and shellfish biomass, resulting in trawl tows with very little or no catch (i.e. a "clean" trawl). Control and experimental loggerheads were individually sent through a 15.2 m (50 ft) "Western jib" trawl equipped with a bottom-opening Super-Shooter (BOSS) TED installed at a 50-degree angle. The space between TED deflector bars was 10.2 cm (4 in), which is the maximum permitted in the U.S. (NMFS, 1999). Each turtle was released into the trawl at the headrope by one member of a three-person NMFS dive team. A stopwatch was started upon the turtle's release, and each loggerhead allowed up to 5 min to escape through the TED. If at the end of 5 min, the turtle was still within the trawl, it was removed by a diver and scored as a "capture." Loggerheads were returned to the surface using floats immediately following their exit or removal from the trawl. All turtles were video-recorded while in the trawl by a diver with a hand-held underwater video camera. Dummy PTT's were removed after each trial, and loggerheads were later released at Sebastian Inlet, Fla., in July 2006 and July 2007.
Video footage was examined to time each loggerhead's passage through the trawl accurately and record outcome (capture or escape) and orientation of the turtle with respect to the TED (carapace-, plastron-, or head-first). Data were compared between the two years using analysis of variance, and the merged dataset was subsequently examined using the Levene's F test, Shapiro-Wilk test, and Mann-Whitney U test.
Two loggerheads out of 8 in the initial trial (1 experimental and 1 control) and 1 out of 20 in the second trial (1 control) failed to escape within 5 min and were recorded as "captures" (Tables 1 and 2); however, the PTT did not impede the "captured" experimental individual's passage through the trawl. The other 25 turtles successfully escaped via the TED, but 4 experimental loggerheads (2 per trial) were slowed after they encountered the TED carapace-first and their PTT's temporarily wedged between its bars (Fig. 1). None of the 14 dummy PTT's, their antennas, or adhesives sustained any obvious damage after passage through the trawl and TED.
Among all turtles in the first trial, 5 individuals encountered the TED carapace-first (Fig. 2a) in 2006, whereas 2 hit plastron-first (Fig. 2b), and 1 control did not reach the TED within 5 min (Table 1). Experimental loggerheads in the second trial encountered the TED in varied orientations (2 carapace-first, 6 plastron-first, 2 head-first), whereas most controls did so carapace-first (8 carapace-first, 2 plastron-first; Table 2).
Escape times were not significantly different between the two trials for either control ([F.sub.1,10] = 0.251, p = 0.627) or PTT-outfitted loggerheads ([F.sub.1,11] = 0.105, p = 0.752), and the data were combined for further analyses. The controls that exited the TED during both trials did so in 16-124 sec ([bar.x] [+ or -] 1 SD = 60 [+ or -] 30 sec, median = 56 sec; n = 12, excludes 2 "captures"), whereas the PTT-outfitted loggerheads did so in 14-294 sec ([bar.x] [+ or -] 1 SD = 111 [+ or -] 91 sec, median = 115 sec; n = 13, excludes 1 "capture"). The 2006-07 dataset violated parametric statistical assumptions of normality (Shapiro-Wilk W = 0.833, p = 0.001) and equal variances (Levene's F = 9.132, p = 0.006). As such, the non-parametric Mann-Whitney test was utilized to compare escape times, and results indicated there was no significant difference between control and PTT-outfitted loggerheads (U = 58.000, p = 0.276).
[FIGURE 1 OMITTED]
Passage through a TED installed in a "clean" trawl did not damage any transmitters or attachments, but 4 of 14 PTT-outfitted loggerheads (29%) were slowed when their PTT's became wedged between TED deflector bars. This indicates attachment of PTT's to smaller sea turtles may slow escape from trawls. Orientation of PTT-outfitted loggerheads to the TED likely accounted for some of the difference in variance between the control and PTT-outfitted groups' escape times (Levene's F = 9.132, p = 0.006). This was exemplified by longer exit times for 4 of the 5 experimental loggerheads that struck the TED carapace-first during the trials. Each of these four interactions resulted in the PTT's becoming wedged between the TED's bars, and only after periods of swimming upward (away from the TED opening) was the turtle able to turn and free itself.
[FIGURE 2 OMITTED]
While we did not observe situations in which escape via the TED was prevented by a PTT, we believe such an event is possible, and efforts should be taken by researchers to minimize this worst case scenario. Likewise, while the dummy PTT's utilized in the trials were secure prior to the turtles' passage through the trawl, a loose or poorly secured PTT could impede escape or be shed if it became caught on or wedged between TED deflector bars.
Under typical shrimping conditions, sea turtles come in contact with other organisms and debris in a trawl. Such interactions could either promote or hinder a PTT-outfitted individual's exit from the TED, depending on the size and volume of other items in the trawl. Additionally, interactions with a large animal or piece of debris, or high catch or debris volumes, could also result in PTT damage or loss. Bottom-opening TED configurations, including the BOSS utilized here, probably have the greatest potential for interactions between a carapace-mounted PTT and the TED deflector bars, given the tendency of turtles to swim upward, away from the exit, when trapped against the bars (Mitchell (3)).
Overall, 15 of 28 loggerheads (54%) in the trials impacted the TED carapace-first, suggesting that conditions allowing or promoting carapace-first encounters, and associated TED-PTT interactions, are common. As such, researchers tracking small turtles in or near regions with trawl fisheries that require TED's should consider size and shape of the PTT, adhesive(s), and their combined footprint and profile in order to minimize potentially detrimental interactions with TED's. Specifically, adhesive should be applied around the transmitter to cover a larger surface area and increase the angle between the PTT and carapace (Fig. 3), and/or a PTT design with a lower profile should be employed on smaller turtles.
[FIGURE 3 OMITTED]
Research was conducted under FWC Turtle Permit #015 issued to Roger Zimmerman. Staff at the NMFS Sea Turtle Facility in Galveston, Tex., participated in loggerhead transport, husbandry, and release. Shanna Kethan is especially acknowledged for her assistance during PTT attachment and the 2007 trial. Staff from the NMFS Harvesting System Branch in Pascagoula, Miss., enabled the trials and shared video, photographs, and valuable expertise: Captain Drew Hopper, Kendall Falana, Jack Forrester, Jeff Gearhart, Dominy Hataway, Wayne Hoggard, Nick Hopkins, John Mitchell, and David Saksa. Kevin Lay of Sirtrack, Ltd., provided initial dummy PTT's and facilitated production of later units. EES was supported by a 2008 Texas A&M University Tom Slick Senior Graduate Fellowship during portions of data collection, analyses, and manuscript preparation. We are grateful to the editor and reviewers for their constructive comments.
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Tucker, A. D., E. E. Seney, J. A. Beggs, and A. M. Landry, Jr. 2007. Pilot evaluation of methods to reduce biofouling of satellite transmitters. In M. Frick, A. Panagopoulou, A. F. Rees, and K. Williams (Comp.), Book of abstracts: twenty-seventh annual symposium on sea turtle biology and conservation, p. 96. International Sea Turtle Society, Myrtle Beach, S.C.
Erin E. Seney and Andre M. Landry, Jr., are with the Sea Turtle and Fisheries Ecology Research Laboratory, Texas A&M University at Galveston, P.O. Box 1675, Galveston, TX 77553, and the Department of Wildlife & Fisheries Sciences, Texas A&M University, 2258 TAMU, College Station, TX 77843. Benjamin M. Higgins is with the Sea Turtle Facility, Southeast Fisheries Science Center, National Marine Fisheries Service, NOAA, 4700 Avenue U, Galveston, TX 77551. Corresponding author is Erin E. Seney (email@example.com).
(1) Mention of trade names or commercial firms does not imply endorsement by the National Marine Fisheries Service, NOAA.
(2) Morehead, R. 2007. NMFS Sea Turtle Facility, SEFSC, Galveston, Tex. (Volunteer). Personal commun.
(3) Mitchell, J. 2006. NMFS Harvesting Systems Branch, SEFSC, Pascagoula, Miss. Personal commun.
Table 1.--Summary of 2006 PTT-TED interaction trial (pilot study) results. Time Turtle Turtle Transmitter in net orientation attachment (min:sec) to TED 1 None (Control) 01:06 Plastron-first 2 PowerFast only 01:05 Carapace-first 3 None (Control) 01:14 Carapace-first 4 PowerFast/Sonic-Weld 05:00 Plastron-first 5 None (Control) 05:00 N/A--did not reach TED 6 PowerFast/Sonic-Weld 03:03 Carapace-first 7 None (Control) 00:16 Carapace-first 8 PowerFast only 02:13 Carapace-first Turtle Result 1 Escape 2 Escape 3 Escape 4 Capture 5 Capture 6 Escape 7 Escape 8 Escape Table 2.--Summary of 2007 PTT-TED interaction trial results. Time Turtle Turtle Transmitter in net orientation attachment (min:sec) to TED Result 1 None (Control) 01:00 Carapace-first Escape 2 PowerFast/Neoprene 00:38 Plastron-first Escape 3 None (Control) 05:00 Carapace-first Capture 4 PowerFast/Sonic-Weld 04:54 Plastron-first Escape 5 None (Control) 00:44 Plastron-first Escape 6 PowerFast/Neoprene 00:14 Head-first Escape 7 None (Control) 01:12 Carapace-first Escape 8 PowerFast/Sonic-Weld 02:05 Carapace-first Escape 9 None (Control) 00:40 Carapace-first Escape 10 PowerFast/Neoprene 02:13 Plastron-first Escape 11 None (Control) 01:38 Carapace-first Escape 12 PowerFast/Sonic-Weld 04:20 Plastron-first Escape 13 None (Control) 00:46 Plastron-first Escape 14 PowerFast/Neoprene 01:55 Carapace-first Escape 15 None (Control) 02:04 Carapace-first Escape 16 PowerFast/Sonic-Weld 00:14 Head-first Escape 17 None (Control) 00:28 Carapace-first Escape 18 PowerFast/Neoprene 00:51 Plastron-first Escape 19 None (Control) 00:52 Carapace-first Escape 20 PowerFast/Neoprene 00:24 Plastron-first Escape
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