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INITIAL ACCOUNT OF A MASS STRANDING EVENT OF SEA TURTLES ON THE COAST OF ISRAEL-JANUARY 2019

Authors:
  • Israel National Nature and Parks Authority
1
ECOLOGY DEPARTMENT
SCIENCE & CONSERVATION DIVISION
ISRAEL NATURE & PARKS AUTHORITY REPORT:
INITIAL ACCOUNT OF A MASS STRANDING EVENT OF SEA TURTLES ON THE COAST OF ISRAEL- JANUARY
2019
Yaniv Levy1, 3, Itzhak Aizenberg1, 2 & Noam Leader3
1 Israel Sea Turtle Rescue Center, Israel Nature & Parks Authority, Israel, email: yaniv@npa.org.il
2 Hebrew University of Jerusalem, Koret School of Veterinary Medicine, Veterinary Teaching Hospital,
email: zahi.aizenberg@mail.huji.ac.il
3 Ecology Dept., Science Division, Israel Nature & Parks Authority, Israel, email: leader@npa.org.il
REPORT SUBMITTED: MAY 22nd, 2019.
During the month of January 2019, 96 sea (marine) turtles were stranded along Israel's Mediterranean
coastline. 69 Loggerheads (Caretta caretta), 16 Green turtles (Chelonia mydas) and 11 unidentified sea
turtles were located. Only 30% (29) of the turtles were still alive when located, all suffering from serious
injuries, and were brought to the Israel Nature & Park Authority (INPA) Sea Turtle Rescue Center (STRC) for
medical treatment.
The large number of stranded turtles in January 2019 (Fig. 1), represents more than half (53%) of the mean
annual stranding events (182) of turtles during the years 2007 -2015. This also represents an alarming
nearly eight-fold increase in the number of stranded turtles located yearly in the month of January (Fig. 2).
On the 9th of January alone, the rescue center received 9 turtles in severe condition. This unusually high
number of turtles in a single day is the highest ever recorded since the establishment of the STRC 20 years
ago.
Figure 1: Daily number of sea turtles (Green and Loggerhead) strandings along Israel's coast during January
2019 (n=96).
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Figure 2: Monthly mean dead and living stranded sea turtles during the years 2007-2015 (n=1,640)
All turtles documented (alive and dead) were located by civilians, rangers and beach employees who
reported to the local municipal hotline, INPA hotline, through social media or directly to STRC volunteers.
The information included location and usually a photograph. The compiled data was stored on the INPA's
designated computer network using the "Cybertracker" field data collection system.
The geographic distribution of stranded sea turtles along the coastline of Israel was relatively homogenous,
from Rosh HaNikra at the northern border of Israel all the way to Zikim in the south, bordering with the
Gaza Strip (Figure 3).
Medical triage, intensive care treatment, fluid and drug therapy were administrated to all sea turtles
hospitalized at the STRC. Radiological examinations (CT and X-Ray) were performed on survivors at the Kol
Hai veterinary clinic, Rehovot, by Dr. Itzhak Aizenberg. Post mortem was performed on seven turtles.
Tissue samples from Green turtles were taken for establishing the turtle origin using genetic analysis.
Three turtles had fishing hooks and one had fishing lines in their digestive system. Two others had trauma
to their carapace from boat propellers and another had suffered, most probably, a shark bite. During the
veterinarian diagnostics and treatments, ultra sounds, X-ray and emergency surgery were performed for
the extraction of hooks and fishing lines from the digestive system. Additionally, three of the examined
females had developed follicles, indicating their readiness for the reproduction season.
CT scans of live injured sea turtles revealed that 83% (19 of 23 examined) showed symptoms of soft tissue
trauma: pulmonary hemorrhage and accumulation of fluids in the middle ear (Fig. 4). Such symptoms are
consistent with shock-wave trauma, suggesting a fatal exposure to a yet undetermined strong impulsive
sound source, such as underwater explosions, on a significant level.
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ECOLOGY DEPARTMENT
SCIENCE & CONSERVATION DIVISION
Figure 3: Green and Loggerhead sea turtle stranding locations along Israel's coastline. Red marks
Loggerhead; Green marks Green turtle; Light blue unidentified turtle.
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SCIENCE & CONSERVATION DIVISION
Figure 4. CT scans showing symptoms of soft tissue trauma: hemorrhage in the lungs (bottom) or a
progressive infection and fluids in the inner ears (top picture): the left inner ear is filled with fluids, marked
in blue, and the right ear is half way filled, marked in purple). Photo Credit: Dr. Itzhak Aizenberg, Kol Hai
veterinary clinic, Rehovot.
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ECOLOGY DEPARTMENT
SCIENCE & CONSERVATION DIVISION
Shock waves cause trauma to soft tissues at the linings of gas cavities. The most vulnerable organs in the
sea turtle, as in cetaceans, are the lungs and the inner ears (Aizenberg et al., 2013). These types of injuries
are known to occur from underwater explosions such as fishing with explosives or military actions (Viada et
al., 2008).
Similar stranding events, with identical clinical symptoms of soft tissue trauma (Aizenberg et al., 2013),
were previously documented by the INPA on a smaller scale in 2012 and 2015 (Fig. 5).
Figure 5. The number of live injured sea turtles diagnosed with soft tissue trauma between 2005-2019.
Discussion
A mass stranding event, involving a large number of dead and seriously injured sea turtles, was detected
along the coastline of Israel during January 2019. Many of the injured turtles exhibited similar symptoms of
soft tissue trauma. The irregular numbers and type of injuries suggest a large-scale mortality event of sea
turtles in the Mediterranean Sea involving underwater blasting and the creation of underwater shock
waves.
There is an urgency to ascertain the possible cause leading to this incident, when and where in the
Mediterranean it had occurred, and whether this may pose a significant future risk for endangered
populations of the two threatened turtle species within the entire eastern Mediterranean. In particular, the
increased number of sea turtle strandings of both species has raised INPAs concerns regarding a potential
anthropogenic source originating within Israel's territorial waters or within Israel's Exclusive Economic Zone
(EEZ).
The finding of three Green turtles among the 19 sea turtles diagnosed with soft tissue trauma (together
with 16 Loggerhead turtles), suggests focusing the search for an impact source in the eastern
Mediterranean Sea, as this encompasses the known habitat of this species in the Mediterranean Sea. While
Loggerhead turtles nest both in the central and eastern basins of the Mediterranean, Green turtles are
known to nest only in the eastern (Levantine) basin (Fig.6). Being mainly neritic-feeders, Green turtles
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exhibit relatively localized inshore foraging grounds and a high degree of fidelity over extended time-scales
to nesting beaches, foraging grounds and migratory corridors, most of which are localized within the
Levantine basin (Broderick et al. 2007; Casale et al. 2018). This lends further support to a potential impact
source in relative proximity to Israel and its EEZ (between Egypt, Israel and Turkey; Fig. 6).
Figure 6. Main known migratory corridors for adult female Green turtles, Chelonia mydas, during
reproductive migrations from the breeding sites (yellow stars). Light green areas represent migratory
funnels in the open sea while darker strips represent paths along the coasts, typically in shallow water.
From Casale et al. (2018(. Area in light red marks suggested impact area.
We can only estimate at this stage that the impacted turtles were hurt during the last few days to weeks
prior to their discovery. We base this assumption on the relatively light decomposition state of turtle
carcasses found during this event and the high number of injured, yet living, turtles found. Furthermore,
because the pattern of turtle strandings during January exhibited several spikes (first peak on Jan. 9th,
second peak on January 17th), we cannot rule out that the impact source was a series of events, lasting for
several hours or days, as opposed to a single incident.
The available, yet limited data on Green turtle yearly distribution patterns within the eastern
Mediterranean suggests turtles spend the winter mainly in coastal feeding areas. Therefore, if shallow
water feeding areas attract aggregates of turtles, a localized blast event may be sufficient to explain the
numerical impact observed.
We do not know of any feeding area capable of attracting sea turtles in pelagic waters, yet the use of deep
water might be important as migratory corridors (Stokes et al, 2015). A substantial presence of sea turtles
within Israel's EEZ might thus occur, yet it is not expected to be in aggregated form. Hence, in this scenario,
only a moving blast source, capable of producing many underwater shock waves, while covering large
areas, may suffice to explain the large number of stranded sea turtles.
The Ministry of Environmental Protection has requested information from the Ministry of Defense and the
Ministry of Energy regarding any activity generating underwater blasts or loud level underwater impulse
noise during the mass sea turtle stranding event. Military operations, involving underwater blasts or
powerful underwater sonar, are most obvious candidates, yet at this time we have no knowledge of any
relevant (unclassified) military naval activity. Currently, the only public report is from the Ministry of Energy
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stating that during the time in question, a 3D seismic air-gun survey for gas exploration was conducted in
two areas within Israel's EEZ, about 40 to 90 kilometers offshore.
It is important to note that during two major turtle stranding events involving soft tissue trauma (Fig. 5), in
2012 and during the current January 2019 event (but not in 2015), air-gun based seismic surveys for gas
exploration were carried out in the territorial waters off the Israeli coast (2012) or within Israel's EEZ
(2019). The temporal overlap between the current and past stranding events and seismic surveys has raised
the possibility of the involvement of these surveys in sea turtle mass stranding events.
Underwater explosions create a strong and quick supersonic pressure wave (shock wave), which can cause
tissue damage and may be lethal to animals or humans in close proximity to the blast. However, pressure
pulses from air guns have longer rise times and are thus less likely than pressure waves from high
explosives to cause damage (Gordon et al. 2004). Accordingly, to date there is no evidence that seismic
pulses can cause acute physical damage such as the ones described in this event to marine mammals or sea
turtles (but see Meirelles et al. 2017). There is however, sufficient evidence that impulse noise from seismic
surveys poses a significant negative impact on both marine mammals and sea turtles which needs to be
addressed, ranging from temporary hearing loss to increased stress, behavioral changes and exclusion of
use of the noise affected area (Nelms et al. 2016; Popper et al. 2014).
The seismic survey in the Israeli EEZ in January 2019 was conducted in accordance with current regulations
regarding minimizing harm to cetaceans and sea turtles. The regulations were updated by the Ministry of
Energy, after consultation with the INPA, following the stranding event in 2012. The guidelines limit shallow
water seismic surveys (<300 m depth) during the sea turtle breeding season (March-October) and require
coordination with the INPA in water shallower than 120 m.
The current seismic survey in deep water employed standardized methods for seismic operations
worldwide, such as soft-start operation of air-guns (progressive increasing of the air-gun shots, in order to
avoid marine animals near the area of these activities), the use of daytime observers and Passive Acoustic
Monitoring (PAM, for detecting vocalizing cetaceans) and application of a shutdown-upon-sighting
protocol, throughout the operation. No sea turtles were documented in the vessel's sightings logs during
the survey.
Conclusions and Future directions
Our preliminary findings suggest that the mass stranding event of sea turtles along the coastline of Israel in
January 2019 was induced by a yet undetermined source of underwater blasts capable of creating
underwater shock waves, which resulted in large-scale mortality event of sea turtles in the Mediterranean
Sea, as observed in the clinical symptoms of soft tissue trauma.
Both Loggerhead and Green sea turtles are protected species by Israeli law, and both species are under
threat of extinction according to the IUCN Red Data Book (IUCN 2019). It is necessary therefore to
determine the possible cause of this turtle mortality event, and if found to be of an anthropogenic source,
to establish the necessary national and regional guidelines and practices (Popper et al., 2014), so as to
mitigate future negative effects of various levels of man-made underwater acoustic activity on sea turtles.
In a meeting held on February 12th, 2019, the Ministry of Environmental Protection, Ministry of Energy and
INPA agreed to summon an ad-hoc investigation, headed by the Ministry of Energy together with
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environmental experts from the Ministry of Environmental Protection, INPA, Israel Oceanographic and
Limnological Research Institute (IOLR) and leading academic professionals. The Terms of References for the
investigative panel are listed in Appendix I. Conclusions and recommendations are expected by July 2019.
Bibliography
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International conference on diseases of zoo and wild animals 2013: May 8th - 11th, 2013, Vienna, Austria.
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Broderick, A. C., Coyne, M. S., Fuller, W. J., Glen, F., & Godley, B. J. (2007). Fidelity and over-wintering of sea
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Casale, P., Broderick, AC., Camiñas, JA., Cardona, L., Carreras, C., Demetropoulos, A., Fuller, WJ., Godley,
BJ., Hochscheid, S., Kaska, Y., Lazar, B ., Margaritoulis, D., Panagopoulou, A ., Rees, AF., Tomas, J., Türkozan,
O. (2018). Mediterranean sea turtles: current knowledge and priorities for conservation and research.
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Gordon, J., Gillespie, D., Potter, J., Frantzis, A., Simmons, M., Swift, R. and Thompson, D. (2004). A
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Meirelles ACO, Silva CPN,, Amancio AC, Motta MRA, Carvalho VL. (2016). Unusual Dolphin standings during
an offshore seismic survey in Ceará Coast, northeastern Brazil. Proceedings XI Congress of the Latin
American Society of Specialists in Aquatic Mammals. Valparaíso, Chile.
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Halvorsen, M.B., Løkkeborg, S., Rogers, P., Southall, B.L., Zeddies, D., Tavolga, W.N. (2014). "Sound
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Committee S3/SC1 and registered with ANSI. ASA S3/SC1.4 TR-2014". Springer and ASA Press, Cham,
Switzerland.
Stokes, K. L. K., Broderick, A. C. A., Canbolat, A. F., Candan, O., Fuller, W. J., Glen, F., Levy, Y., Rees, A. F.,
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Viada, S. T., Hammer, R. M., Racca, R., Hannay, D., Thompson, M. J., Balcom, B. J., & Phillips, N. W. (2008).
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APPENDIX I
Subject: Terms of Reference (TOR) for investigative expert panel on the increase in the number of
injured sea turtles in January 2019.
Further to the meeting held on February 17, 2019, it was agreed that a professional team of experts
would be established to examine the sea turtle mass stranding event of January 2019. The team will
examine the possible causes of turtle injuries, including the circumstantial connection between the
seismic surveys and the impact to the turtles and other reasons. The team will be comprised of
representatives of the Ministries of Energy and Environmental Protection, INPA, IOLR, Haifa University
and other professionals as needed.
Topics for examination by the professional team:
1. Preparation of a review of the relevant literature:
1.1 Sources of energy and their intensity in seismic surveys. Spread of energy waves of seismic
surveys in water (sound waves and shock waves), intensities, and affected space.
1.2 Shockwave and hearing injuries in turtles and their possible causes.
1.3 The habitat and migration routes of sea turtles in the eastern Mediterranean Sea.
2. Detailed analysis of the January 2019 sea turtle stranding event (analysis for December 2018 -
February 2019):
2.1 Presentation of the strandings along the coastline through time, cross-section of ages and sex.
2.2 Analysis of turtle strandings along the Israeli coastline versus weather conditions, waves,
currents, survey timing.
2.3 Presentation of the pathological findings of the injured sea turtles.
3. Macro-analysis of sea turtle strandings during seismic surveys carried out in Israel's maritime area
during the last decade and in its vicinity (Egypt, Lebanon, Cyprus), weather conditions, naval
announcements to the mariners (closed areas) and other possible causes.
4. OCEANOGRAPHIC MODELS
4.1. Reverse calculation of individual turtle stranding points (location and time) and correlation to
different source areas (seismic surveys or other areas such as closed military zones or fishing
activities in southern Israel).
4.2. Forward calculations from the survey points, according to the relevant dates and sea conditions
and the assessment of drifting of immobilized injured sea turtles without the ability to swim (if
there were turtles in the area where the survey was conducted where they could reach To be
decided according to the findings of section 1.1).
5. To examine existing means and R&D for early detection of turtles during seismic surveys.
6. Formulation of recommendations on new R&D aimed at reducing the existing information gaps on
Israel's maritime space.
7. Mapping in time and space of naval firing ranges or other activity in which explosives are used in
the maritime area to examine their possibility of being an additional source of damage to the
turtles.
8. In accordance with the findings of the investigation, submitting appropriate recommendations to
reduce the harm to sea turtles.
... Recommendations for regulators to improve the safety of turtles, re the introduction of potentially harmful energy include: The real numbers of blast-injured individuals as inferred from the above table are most probably grossly underestimated since dead turtles, even recently dead, as a practice are not brought in for scanning, but must have contained many similarly injured animals. As detailed below, these are very high numbers compared to mean turtle stranding rates for these months during the last decade (range 8-16), making this event highly unusual (Levy et al., 2019 Figure 3). Three turtles had fishing hooks and one had fishing lines in their digestive system. ...
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2 This report was prepared subsequent to a major sea turtle stranding event along the coast of Israel during the 2018-19 winter. The Ministry of Energy, together with the Israel Nature and Parks Authority and the Ministry of Environmental Protection established a multidisciplinary expert team to investigate the possible causes of this event. Acknowledgements: We would like to thank the following colleagues for productive discussions of this report:
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The IUCN Red List of Threatened Species
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IUCN (2019). The IUCN Red List of Threatened Species. Version 2019-1. http://www.iucnredlist.org.
Unusual Dolphin standings during an offshore seismic survey in Ceará Coast, northeastern Brazil. Proceedings XI Congress of the Latin American Society of Specialists in Aquatic Mammals
  • Aco Meirelles
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  • A C Amancio
  • Mra Motta
  • V L Carvalho
Meirelles ACO, Silva CPN,, Amancio AC, Motta MRA, Carvalho VL. (2016). Unusual Dolphin standings during an offshore seismic survey in Ceará Coast, northeastern Brazil. Proceedings XI Congress of the Latin American Society of Specialists in Aquatic Mammals. Valparaíso, Chile.
A review of the effects of seismic surveys on marine mammals
  • J Gordon
  • D Gillespie
  • J Potter
  • A Frantzis
  • M Simmons
  • R Swift
  • D Thompson
Gordon, J., Gillespie, D., Potter, J., Frantzis, A., Simmons, M., Swift, R. and Thompson, D. (2004). A review of the effects of seismic surveys on marine mammals. Marine Technology Society Journal 37, 16-34.