High-use areas, seasonal movements and dive patterns of juvenile loggerhead sea turtles in the Southwestern Atlantic Ocean

Abstract

Characterizing the behaviors of sea turtles and identifying high-use areas as they vary in time and space is important for conservation planning, particularly when turtles overlap with fisheries that may unintentionally harm them. Between July 2006 and March 2010, 27 satellite transmitters were deployed at sea on juvenile loggerheads Caretta caretta captured as bycatch in the Uruguayan and Brazilian pelagic longline fisheries operating in the Southwestern Atlantic Ocean. Tracking duration ranged from 3 to 639 d (mean ± SD: 259 ± 159 d; n = 27), during which turtles moved between latitudes of 25 to 45°S and longitudes 35 to 54° W. High-use areas for the tracked turtles were over the continental shelf and slope within the Uruguayan, Argentinian, and Brazilian exclusive economic zones and in adjacent international waters. Diving information was available for 5 turtles. The maximum dive depth recorded varied between 100 and 300 m. Two turtles demonstrated potential bottom-feeding behaviors by diving to depths that corresponded closely with the depth of the seafloor (< 200 m) at their given location. The sea surface temperature encountered by tagged turtles was on average 19.8 ± 2.3°C (range: 10.2 to 28.4°C), and turtles showed an affinity for waters supporting moderate to high primary productivity levels (0.43 ± 0.89 mg m −3 chlorophyll a). Latitudinal movements varied by season and sea surface temperature. These findings, along with those of other studies conducted in the region, demonstrate the need to strengthen ongoing collaborative efforts between neighboring countries and other international partnerships to further the research and management of sea turtles in this area.

The use of mesoscale eddies by juvenile loggerhead sea turtles (Caretta caretta) in the southwestern Atlantic

“…It is important to note that drifters are constrained to the surface, whereas turtles are not, an important caveat noted by other studies [15]. Analysis of the pressure recording tags affixed to a subset of 5 turtles revealed that when the turtles were below the surface, they attained a maximum depth between 10 and 100 m 84% of the time (see [16] for a summary of dive depths for these turtles), suggesting that when diving, turtles often occupy the zone near where the drifters are drogued. Even in light of the differences in drifter configuration and turtle behavior, the comparison of the passive advection of drifters to the movement of turtles has yielded valuable insight into the active movement and foraging behavior of turtles ( e .…”

“…Scientific observers of PNOFA-DINARA (the Uruguayan National Program of Scientific Observers Onboard the Tuna Fleet) [16, 17] and Projeto TAMAR-ICMBio (the national Brazilian sea turtle conservation program) [18] deployed satellite transmitters on loggerhead sea turtles incidentally captured in Brazilian and Uruguayan pelagic long-line fisheries operating in the southwestern Atlantic Ocean between July of 2006 and November of 2009. The turtle trajectories used in this study span a 5-year period between July 2006 and December 2011(Fig 1E) and are available in S1 File.…”

“…As described in [16] satellite transmitters were attached to the turtles on the second central carapacial scute using quick-drying two-part epoxies, PoxipolTM (Uruguay) and DurepoxiTM (Brazil), and allowed to dry for 30 minutes to one hour on deck before release. A total of 24 tracked loggerheads with mean curved carapace length of 61.8 ± 6.9 cm (range: 49 to 83 cm, see Table 1 of [15]) that transmitted more than 30 days are included in this study.…”

“…ARGOS-linked Wildlife Computers (Redmond, WA, USA) PTTs, models SPLASH and SPOT 5 , were attached to 5 and 10 turtles, respectively, on Uruguayan vessels. See [16] for further turtle tracking details.…”

Incidental capture and mortality of sea turtles in the industrial double‐rig‐bottom trawl fishery in south‐eastern Brazil

“…The proximity of nesting beaches may help explain the high rate of subadult/adult bycatch of this species in the study area, as previously suggested by Guimarães et al (). In addition, C. caretta subadults and adults prefer neritic habits, foraging near the bottom (Barceló et al, ; Monteiro, ), where this fishery operates. The large volume of bycatch discarded by trawls may also attract sea turtles (Beneditto, Moura, & Siciliano, ; Tomas, Aznar, & Raga, ), creating a high density of turtles in areas being actively fished, thereby increasing the rates of turtle bycatch (Shoop & Ruckdeschel, ).…”