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Movements of loggerhead sea turtles ( Caretta caretta ) in the Gulf ofCalifornia: integrating satellite telemetry and remotely sensed environmental
variables
Article in Journal of the Marine Biological Association of the UK · July 2020
DOI: 10.1017/S0025315420000636

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Movements of loggerhead sea turtles (Caretta
caretta) in the Gulf of California: integrating
satellite telemetry and remotely sensed
environmental variables
Alejandra G. Sandoval-Lugo1,2, T. Leticia Espinosa-Carreón1,

Original Article

Jeffrey A. Seminoff3

Cite this article: Sandoval-Lugo AG, EspinosaCarreón TL, Seminoff JA, Hart CE, LeyQuiñónez CP, Aguirre AA, Jones TT, ZavalaNorzagaray AA (2020). Movements ofloggerhead sea turtles (Caretta caretta) in the
Gulf of California: integrating satellite
telemetry and remotely sensed environmental
variables. Journal of the Marine Biological
Association of the United Kingdom 1–8. https://doi.org/10.1017/S0025315420000636

A. Alonso Aguirre5, T. Todd Jones6 and Alan A. Zavala-Norzagaray1,2

Received: 9 September 2019
Revised: 22 June 2020
Accepted: 24 June 2020
Key words:
Chlorophyll concentration; Gulf of California;
loggerhead turtle; Platform Transmitter
Terminal (PTT); satellite tracking; Sea ofCortez; sea surface temperature
Author for correspondence:
Alan A. Zavala-Norzagaray,
E-mail: anorzaga@gmail.com, Catherine E. Hart2,4, César P. Ley-Quiñónez1,2,

1Instituto Politécnico Nacional, CIIDIR- SINALOA, Guasave, Sinaloa, Mexico; 2Grupo Tortuguero de las Californias
A.C., La Paz, B.C.S., Mexico; 3NOAA-Southwest Fisheries Science Center, La Jolla, California, USA; 4Investigación,
Capacitación y Soluciones Ambientas y Sociales A.C. Tepic, Nayarit, Mexico; 5Department of Environmental
Science and Policy, George Mason University, Fairfax, Virginia, USA and 6NOAA- Pacific Islands Fisheries Science
Center, Honolulu, Hawaii, USA

Abstract
The loggerhead turtle (Caretta caretta) is a circumglobal species and is listed as vulnerable
globally. The North Pacific population nests in Japan and migrates to the Central North
Pacific and Pacific coast of North America to feed. In the Mexican Pacific, records of loggerhead presence are largely restricted to the Gulf of Ulloa along the Baja California Peninsula,where very high fisheries by-catch mortality has been reported. Records of loggerhead turtles
within the Sea of Cortez also known as the Gulf of California (GC) exist; however, their ecology in this region is poorly understood. We used satellite tracking and an environmental variable analysis (chlorophyll-a (Chl-a) and sea surface temperature (SST)) to determine
movements and habitat use of five juvenile loggerhead turtles ranging in straight carapace
length from 62.7–68.3 cm (mean: 66.7 ± 2.3 cm). Satellite tracking durations ranged from73–293 days (mean: 149 ± 62.5 days), transmissions per turtle from 14–1006 (mean: 462 ±
379.5 transmissions) and total travel distance from 1237–5222 km (mean: 3118 ± 1490.7
km). We used travel rate analyses to identify five foraging areas in the GC, which occurred
mainly in waters from 10–80 m deep, with mean Chl-a concentrations ranging from 0.28–
13.14 mg m−3 and SST ranging from 27.8–34.4°C. This is the first study to describe loggerhead
movements in the Gulf of California and our data suggest that loggerhead foraging movements are performed in areas with eutrophic levels of Chl-a.

Introduction© Marine Biological Association of the United
Kingdom 2020

Knowledge about distribution and movements of threatened species is crucial for effective conservation and management (NRC, 2010; NMFS, 2013; Rees et al., 2016). This information isuseful for gauging population-level impacts of anthropogenic threats such as directed harvest
and fisheries by-catch mortality (Koch et al., 2006). Studying movements and habitat use of
sea turtles is often difficult due to logistic and technological constraints of monitoring individual animals, which live in marine habitats where they spend vast periods of time submerged
and thus difficult to monitor through time and space. They have complex life histories characterized by slow growth, late maturity, long life and multiple stages of development that can
span entire ocean basins over several decades (Wallace et al., 2009; Bailey et al., 2012). In
recent years, satellite telemetry has provided important information regarding sea turtle movement patterns and habitat use (e.g. Luschi et al., 1998; Coyne & Godley, 2005; Godley et al.,2008). These data can be used to inform conservation managers and governing bodies on priority areas for conservation (Blumenthal et al., 2006; Hawkes et al., 2012) and can provide
insights about redesigning Marine Protected Areas (MPAs) and/or the effectiveness of preexisting conservation initiatives (Dawson et al., 2017).
Loggerhead turtles (Caretta caretta) inhabit temperate, subtropical and tropical waters
worldwide. In the North Pacific, most loggerheads have an extensive migration, travellingfrom nesting areas in Japan to distant developmental and foraging habitats in the Central
North Pacific (Polovina et al., 2006; Abecassis et al., 2013) and eastern North Pacific(Seminoff et al., 2014; Zavala-Norzagaray et al., 2017; Eguchi et al., 2018). After spending
years foraging, these turtles return to their Japanese natal nesting beaches to reproduce(Resendiz et al., 1998; Nichols et al., 2000) and the remainder of their life cycle is spent in
the western Pacific (Sakamoto & Bando, 1997; Hatase et al., 2002; Kamezaki et al., 2003).
Loggerhead turtle movements have been well-studied in the Central North Pacific(Kobayashi et al., 2008; Abecassis et al., 2013; Briscoe et al., 2016) and along the west coastof the Baja California Peninsula, Mexico (Peckham et al., 2007). However, loggerheads arealso present in the Sea of Cortez or Gulf of California (GC) (Seminoff et al., 2004;

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2

Zavala-Norzagaray et al., 2017) although few data are available on
their movements and habitat use.
The objective of this study was to develop a greater understanding of loggerhead turtle movements and habitat use in thecontext of oceanographic conditions. Movement data fromtracked loggerhead turtles using Argos-linked satellite transmitters were integrated with sea surface temperature (SST) and
chlorophyll-a (Chl-a) concentration, used as proxy for marine
productivity. These are the first satellite tracks for loggerhead turtles in the GC, to our knowledge, and may support the identification of key areas for the conservation of this endangered species.
Methods
Study area
The Gulf of California is a narrow and partially enclosed sea,
characterized by strong tidal mixing and upwelling, which support productive marine benthic communities dominated by marine algae (Lavín et al., 2014). The length of the GC is about 1400
km and it is up to 3000 m deep (Roden, 1958). Local physicaloceanographic processes (e.g. wind, large tidal flux) maintainhigh nutrient concentration in the euphotic zone. The highest
phytoplankton biomass values are presented in the northernand central Gulf (Gaxiola-Castro et al., 1995).
Turtle captures and measurement
During 2004, one loggerhead turtle (Turtle A) was foundentangled alive in an artisanal set-net by a local fisher in Baja
California. In 2014 and 2015, four loggerheads were by-caught
alive by local shark fishers in drift gillnets (25 cm mesh size,
stretched) in northern Sinaloa. Due to long-term community
environmental outreach and education conducted by the
Wildlife Department at the Instituto Politécnico Nacional(IPN), Guasave, Sinaloa, fishers immediately reported the incidental captures of the latter four turtles. All turtles were in apparent good health, although one turtle (E) had a tomium injury andhad substantial numbers of marine leeches and barnacles. Turtles
were measured with Forester’s callipers for straight carapace
length (SCL), weighed with a spring balance, and tagged on theposterior flippers with inconel tags (Style 681, National Bandand Tag Co., Newport, NY).
Satellite telemetry
Each loggerhead turtle was equipped with an ARGOS-linked platform terminal transponder (PTT) (one Sirtrack Kiwisat PTT(Turtle A; Havelock North, Hawkes Bay, New Zealand) and
four Wildlife Computers Spot 5 PTTs (Turtles B–E; Redmond,
WA, USA)). The transmitters were attached to the carapaces following the recommendations of Hays et al. (2014). Briefly, thecarapace was lightly sanded and cleaned with alcohol, andtransmitters were attached using two-part quick-drying epoxy
adhesives (Devcon® and Quicksteel®). The epoxy material adhering the transmitter was shaped into a hydrodynamic form to
reduce the drag, as previously described (Jones et al., 2014).
The data collection duty cycle for all the tags was 24h On/0h
Off from Days 1–3 and 24 h On/24 h Off thereafter. Turtle
positions were determined with the Argos satellite system,
which categorized each location message received into one ofsix location classes (LC): 3, 2, 1, 0, A and B. Argos assigns accuracy estimations of <150 m for LC3, 150–350 m for LC2, 351–1000 m
for LC 1 and >1000 m for LC 0. No accuracy estimation is provided for LC A or LC B. However, rather than limiting our
track construction to the use of LCs with optimal accuracy

Alejandra G. Sandoval‐Lugo et al.

estimates (i.e. LC 3, 2 and 1), we instead used a series of filtersthat excluded biologically unreasonable results based on travel
speed (> 5 km h–1) or indicated turning angles that did not conform to a directional track line (<10°), as this approach has
been shown to maximize the utility of Argos-derived positions
for wildlife tracking (Coyne & Godley, 2005). Based on the LC
classification, we determined the coverage (percentage of traveldays with successful transmissions) and accuracy (percentage ofdays with at least one LC 1, 2 or 3 transmission) of each transmitter following Etnoyer et al. (2006).

Identification of foraging areas
Foraging areas were inferred for sites where turtles showed
restricted movements (slower travel rates and multidirectional
movements in the same area), which were distinct from rapidtransit movements that are typically characterized by higher travel
rates and unidirectional movement trajectories. We calculated a‘movement type’ threshold value according to Narazaki et al.
(2013) using mean values of foraging and transit speeds (meanspeed − standard deviation (SD) × 2). We inferred travel rates
below the threshold (9.18 km day–1) to indicate foraging movements, whereas speeds above the threshold were considered transit or migratory movements. Foraging ranges were determinedthrough an effort-weighted kernel density analysis (KDA) of
2311 filtered positions (cumulative from all tracked turtles) toderive an index of turtle residence probability per unit area. We
weighted the kernel density estimate of turtle days in each cellby multiplying it by the number of individual turtles using that
cell, providing probability contours for the 50%, 75% and 100%
utilization distributions (UDs) with the 100% contour reflecting
the total range (Peckham et al., 2007). Furthermore, a migration
straightness index (MSI) was calculated for each turtle’s movements, based on the ratio of straight line distance between firstand last Argos locations to the total track length to distinguishbetween migration or search strategies (Luschi et al., 1998).
Oceanographic data
Five-day composite images (1-km resolution) of Chl-a concentration and sea surface temperature (SST) were obtained from the
MODIS Aqua (MODISAQUA 2014, 2015 Satellite Data
California Current) and AVHRR sensors to avoid low quality satellite images from cloudy days. A total of 72 images were obtained
for the foraging areas identified based on telemetry data andmovement threshold analyses. These foraging areas (and spatial
locations) included the Upper Gulf (30.183122 to 31.16581°N−113.334961 to −114.543457°W), Bahía de Los Angeles(28.979312 to 29.118574°N −113.312988 to −113.477783°W),
Tiburón Island (28.594169 to 28.72913 N −112.104492 to−112.456055°W), Guaymas Basin (27.332735 to 27.858504°N−110.720215 to −111.159668°W); the Northern Limit of theLower Gulf (NLLG) (24.44715 to 25.363882°N −108.742676 to−110.478516°W), per year of study, from which we calculated
SST and Chl-a mean values using Mat LAB 7.8 program(Matrix Laboratory). Overall 216 Chl-a and SST mean values
were obtained of each area for all three years of study (2004,
2014 and 2015).

Results
Turtle size and condition
The loggerheads included in this study were large juveniles ranging from 62.7–68.3 cm SCL and from 35–55 kg in body weight.
All had a good Body Condition Index (BCI) ranging from

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16.20
–
0.15
2284
224
120
–
40
47
2015/11/16
2015/07/19
1.42
E

35
62.7

D

BLA, Bahía de los Ángeles; UG, Upper Gulf; LTO, Loreto; SC, Sinaloa Canyon; TI, Tiburón Island; GB, Guaymas Basin; SINMLS, San Ignacio-Navachiste-Macapule Lagoon System; MSI, Migration Straightness Index; FTR, Foraging Travel Rate; TTR, Transit Travel Rate; SCL,
straight carapace length.
Coverage represents the percentage of travel days with successful transmissions; Accuracy represents the percentage of days with transmission accuracy better than 1 km.

18.87
1.39
0.75
457
42
65.5

C

42

1.49

2014/05/23

2014/08/04

67

TI, GB,SC,
SINMLS

73

1237

12.31
7.59
0.33
1007
54
68.3

B

53

1.66

2014/05/23

2014/10/23

73

UG, LTO,
SC

153

3569

13.38
6.84
0.44
609
74
66.4

A

46

1.57

2014/05/23

2014/09/05

73

UG, LTO

105

3277

19.18
2.42
0.56
5222
46
237
28
68.3

Turtle55

1.73

2004/07/04

2004/04/27

4.7

BLA

Total
transmissions
Accuracy(%)
Coverage(%)
Date of lasttransmission
Release
date
SCL
(cm)

Weight(kg)

Body
Condition
Index
(BCI)

Table 1. Morphometric data and tracking summary for five loggerhead turtles studied in the Gulf of California, Mexico

Foragingarea

Transmission
duration(days)

Total
movement
distance
(km)

MSI

FTR
(km
day−1)

TTR(km
day−1)

Journal of the Marine Biological Association of the United Kingdom

3

1.42–1.73 (mean: 1.58 ± 0.12) (Table 1) and were apparently
healthy upon release.
Satellite tracking
Tracking durations ranged from 73–293 days (mean: 149 ± 62.5
days) and total travel distance ranged from 1237–5222 km(mean: 3118 ± 1490.7 km) (Table 1, Figure 1). The total transmissions per turtle ranged from 45–1006 (mean: 468.4 ± 370.56)(Table 1). Travel rates (km day−1) ranged from 12.31–19.18(mean: 15.98 ± 3.12) (Table 1). The travel rates (km day−1) werelower when foraging movement occurred, ranging from 1.39–
7.59 km day−1 (mean: 4.56 ± 3.10) (Table 1). Tracking efforts
and movement threshold analyses suggest that the rehabilitatedturtle (E) did not demonstrate foraging movements, perhaps
due to a 10-week gap in Argos transmissions.
MSI ranged from 0.11–0.75, and two of the tracked turtles(Turtle A and D) exhibited highly linear movements (Table 1,
Figure 2). We identified five foraging areas: the Upper Gulf
(UG), Bahía Los Angeles (BLA), Guaymas Basin (GB), Tiburon
Island (TI) and the Northern Limit of the Lower Gulf (NLLG).
The NLLG foraging area is composed by three different subregions, which are all highly productive areas, including the San
Ignacio-Navachiste-Macapule Lagoon System (SINMLS), offcoast Loreto (LTO) and the Sinaloa Canyon (SC) (Figure 3).
Oceanographic data
Chlorophyll-a concentrations during the study period (2004, 2014
and 2015), were significantly different between identified foraging
areas (P > 0.05) (Minitab® 17.1.0; Minitab Inc., State College,
Pennsylvania, USA) (Table S1, Supplementary material). The
highest mean values occurred in the lower Gulf (NLLG), withchlorophyll concentrations ranging from 0.28–13.14 mg m−3(mean: 3.85 mg m−3); followed by BLA with Chl-a values ranging
from 1.71–8.21 mg m−3 (mean: 2.45 mg m−3). Lowest values wereregistered in the GB with values ranging from 0.12–7.09 mg m−3(mean: 0.66 mg m−3). SST in the identified foraging areas during
the times that turtles were present ranged from 27.8–34.4°C.
During migration/transit movements, turtles were tracked inwaters >200 m deep, whereas during foraging movements, turtles
mainly inhabited waters ranging from 10–80 m deep.
Discussion
A better understanding of the population structure, movements
and habitat use of North Pacific Loggerheads is necessary
throughout their range to minimize threats such as incidental
capture in marine fisheries (NMFS and USFWS, 2009). To thebest of our knowledge, this is the first satellite telemetry study
characterizing loggerhead turtle movements in the GC. Our
results provide novel insights about the location of foraging hotspots for the species in this temperate sea. These data build uponprevious loggerhead tracking studies in the Gulf of Ulloa at the
Pacific coast of the Baja California Peninsula, the closest known
loggerhead foraging hotspot outside of the Gulf.
The mean size of the loggerheads tracked during this study is
consistent with the 18 loggerheads reported by Zavala et al. (2017)
in the same capture site of the turtles presented here. It is among
the largest for loggerheads at foraging sites in the Mexican Pacific(Ramírez-Cruz et al., 1991; Resendiz et al., 1998; Nichols 2002;
Seminoff et al., 2004; Peckham et al., 2011). Due to this, andthe minimum drag associated with the tags we used in thisstudy (calculated by Jones et al., 2014 for the tags used for olive
ridley (Lepidochelys olivacea) and green (Chelonia mydas) turtles),
we infer that drag caused by satellite transmitter placement was

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4

Alejandra G. Sandoval‐Lugo et al.

Fig. 1. Displacement (defined as straight-line distancefrom original point of release) plots for five loggerhead
turtles (A–E) tracked in the Gulf of California.

not a determinant for loggerhead movements presented here, as
other studies have reported (Senko et al., 2019).
Tracked loggerheads presented a reduction of travel speedsthat might indicate a shift from migratory (or transit) movements
to localized foraging activity. For example, Turtles B, C and D had
greater travel rates during the initial portion of their tracking
durations, but all three eventually slowed down (from 13.38 to
6.84 km day−1, 12.31 to 7.59 km day−1 and 18.87 to 1.39 km
day−1, respectively) (Table 1), which indicated their shift tomore localized movements and perhaps foraging activity. Thiswas confirmed with the Kernel density analyses that highlightthese travel rate reduction segments of the tracks, as areas ofhigh use. Apparently these loggerhead turtles are largely neritic
foragers in the GC, which contrasts with their life history in theCentral North Pacific where they are exclusively oceanic predators(Polovina et al., 2001, 2006; Parker et al., 2005). Migration
straightness index (MSI) indicated that, except turtle (A), tracked
turtles made exploratory movements within the GC until theyfound a suitable foraging area, indicated by slower movements
and greater tortuosity in the track line (Table 1). Turtle A wasreleased in BLA and performed foraging movements upon releasefor ∼30 days prior to exiting the GC and moving towards theCentral Pacific where it was last tracked nearly 3000 km to thewest of the entrance of the Gulf. This loggerhead was the largest
included in this study (68.3 cm SCL), close to the mean size ofnesting loggerheads in Japan (70 cm SCL; Hatase et al., 2004),
which suggests this turtle may have been returning to its natal

nesting beach in Japan for reproduction. Although turtles D
and A had the highest MSI value (0.75 and 0.56, respectively)
and exhibited the greatest travel rates (mean = 18.87 and 19.18
km days−1 respectively), they presented different migration strategies. While Turtle A remained within the release location, andthen initiated a migration towards the Central North Pacific(CNP), Turtle D departed shortly after deployment further inside
the GC and exhibited a high travel rate (18.87 km day−1) until itreached Tiburon Island where it presented the lowest travel rateof this study (1.39 km day−1) and remained for ∼60 days, ceasing
its search behaviour (Zollner & Lima, 1999; Senko et al., 2019).
Turtles B, C and E showed low MSI values (range = 0.15–0.44),
indicating that they made more sinuous movements, whichaccording to optimal search strategy (Zollner & Lima, 1999), indicates that these turtles performed search behaviour in greatermeasure until their arrival to the identified foraging sites. It has
also been observed in other studies that turtles with less energetic
reserves, such as post-nesting turtles (Luschi et al., 1998; Seminoff
et al., 2008) present higher MSI values than turtles with higher
energetic reserves. This can explain why most turtles tracked forthis study made sinuous movements and presented search behaviour, consistent also with their Body Condition Index (BCI)(Table 1).
The apparent arrival to foraging areas is also supported by
Chl-a values for each of these sites. The areas considered to be
putative foraging habitats (based on reduction in travel speeds)
had mean values of water chlorophyll concentrations ranging

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Journal of the Marine Biological Association of the United Kingdom

Fig. 2. Loggerhead tracks of five loggerhead turtles (A–E) in the Gulf of California. Stars indicate release locations.

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5

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Alejandra G. Sandoval‐Lugo et al.

Fig. 3. Kernel density analysis of loggerhead turtle habitat use in the Gulf of California. The 50%, 75% and 100% UDs (utilization distributions) are colour coded,with the 100% UD reflecting the total range and the 50% UD indicating high use areas. The high use areas in this study included Bahía de Los Ángeles (BLA), Upper
Gulf (UG), Tiburón Island (TI), Guaymas Basin (GB) and the northern limit of the lower Gulf (NLLG).

from 0.88–3.85 mg m−3. Seasonality did not appear to affect productivity in the identified foraging zones, as all sites had eutrophic
Chl-a values (>1 mg m−3) throughout the year, likely due to local
enrichment mechanisms such as tidal mixing and upwelling(Gaxiola-Castro et al., 1995). Although it is well known that loggerhead turtles do not feed directly on primary producers (i.e.
phytoplankton, algae, seagrass), high Chl-a concentration islinked to high primary productivity and affects prey diversity
and abundance (Barceló et al., 2013). It is not surprising thatareas such as the Upper Gulf, Tiburon Island and the San
Ignacio-Navachiste-Macapule Lagoon System – which were determined to be putative foraging areas – are known as productivity
hotspots that host rich marine vertebrate (including other speciesof sea turtles) and invertebrate communities (Gaxiola-Castro
et al., 1995; Valencia, 2013). Loggerhead turtles in the North
Pacific are known to follow the Transition Zone Chlorophyll
Front shifts and are associated with the Kuroshio Extension
Bifurcation Region (KEBR) as these fronts provide the basis forpotential forage in this region (Polovina et al., 2001, 2006;
Kobayashi et al., 2008). The high values of Chl-a concentration
presented in the foraging areas in the GC are linked to the appearance of rich food patches that predators such as sea turtles takeadvantage of and it is possible they also ‘follow’. Furthermore,while there is no literature that reports red crab (Pleuroncodes planipes) occurring inside the Gulf of California, remains of this species of red crab were found in the tracked turtles’ faeces after theircapture. Pleuroncodes planipes occurs in dense patches following
high productivity peaks during upwelling season in the GC(pers. comm). It is possible that loggerhead turtles tracked inthis study were following these rich food patches, performing
an opportunistic habitat use inside the GC as they are recognized
as opportunistic foragers (Peckham et al., 2011).
Loggerhead turtles are known to forage in waters with a wide
range of temperatures worldwide, from 10.2–30.4°C (Polovina
et al., 2001, 2006; Hawkes et al., 2007; Barceló et al., 2013),
although foraging is more prevalent at temperatures above 13°C
(Bentivegna et al., 2007). The turtles tracked in this study foraged
in waters ranging from 27.8–34.4°C with an overall mean value of
30.3 ± 2.4°C. This is a relatively high water temperature for foraging loggerheads, and is likely due to turtles acclimating to the
GC’s overall higher temperatures (coldest SST value estimatedfor this study: 17.4°C in winter), which are caused by its uniquebathymetry, circulation dynamics and semi-enclosed nature(Gaxiola-Castro et al., 1995; Lavín et al., 2014). Indeed, warm
temperatures are favourable for sea turtles (Bentivegna et al.,2007) and although higher temperatures may result in greater
metabolic rate, this was probably offset by more efficient energy
acquisition by the tracked loggerheads, including detection, capture and assimilation of prey (Dunham et al., 1989; Peckham
et al., 2011). Loggerhead residency in the GC is probably due tothe region providing both food availability and thermal
requirements.

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Journal of the Marine Biological Association of the United Kingdom

Conservation implications
So far, loggerheads in the eastern Pacific have primarily beenstudied in the Gulf of Ulloa on the Pacific coast of the Baja
California Peninsula; however, our findings indicate that the GC
should also be considered a key area for the foraging distributionof loggerheads for the eastern North Pacific region. Four of theloggerhead foraging areas identified in this study overlap withknown foraging areas of east Pacific green turtles Chelonia
mydas (Seminoff et al., 2004; Valencia, 2013), and the Upper
Gulf is a key foraging area for leatherback turtles Dermochelys coriacea (Seminoff & Dutton, 2009, NOAA unpubl. data). This lattersite also hosts the highly endangered Gulf harbour porpoise,
Phocoena sinus (known as vaquita marina). These observations
underscore the conservation value of satellite telemetry efforts
focused on loggerhead turtles. In a broader marine conservation
context, it is also apparent that loggerhead conservation efforts
focused on the foraging sites identified in this study may benefit
multiple sea turtle species as well as an endemic cetacean.
Supplementary material. The supplementary material for this article canbe found at https://doi.org/10.1017/S0025315420000636
Acknowledgements. We gratefully acknowledge Adalberto García, Gaspar
Angulo, Vladimir De La Toba and the fishers who turned in the turtles. We
also thank Red Tortuguera A.C., Grupo Tortuguero de las Californias A.C., and
the Wildlife Conservation Program for their help in rehabilitating of Turtle A.
Financial support. This research has been funded through the Secretaría de
Educación y Posgrado – Instituto Politécnico Nacional (projects: SIP20141052;
SIP20151561; SIP20161935).
Conflict of interest. The authors declare that they have no conflict ofinterest.
Ethical standards. This research was supported and approved by
CONACyT and SEMARNAT. Sampling, handling and care of individuals
was carried out under the proper research permits: SGPAC/DGVS/02259/14
and SGPA/DGVS/04478/15.

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