The following is an English translation, prepared (with permission) by the IOSEA Secretariat, of a 2011 Activity Report published in French and available online in the original language at: http://wwz.ifremer.fr/lareunion
Draft "Plan for the Conservation of Marine Turtles"
Review of objectives
The Delegation has been working since its inception on marine turtles, emblematic species in La Réunion. Several projects or actions are currently underway, all collaborative and all contributing to the elaboration, by 2013, of a catalogue of recommendations for the development of a turtle conservation plan for the islands and French waters of the Indian Ocean. To do this, the Delegation team (1) currently conducts the DYMITILE (Dynamic migration of marine turtles in the French islands of the Indian Ocean) project, (2) contributes to SWIOFP (South West Indian Ocean Fisheries Project), a major regional initiative (across SWIO) funded by the GEF through the World Bank and France via FFEM funds and (3) is providing technical assistance and scientific cooperation in the framework of several projects undertaken by Kélonia (the observatory of marine turtles in La Réunion).
Project Team 2011: J. Bourjea (DOI Ifremer, coordinator), Mayeul Dalleau (PhD, University of Réunion, Ifremer, Kélonia, CEFE-CNRS), national and international technical collaboration: Kélonia, CEFE-CNRS Montpellier, CLS, SIF (Seychelles), University of Exeter (UK), Marine Turtle Specialist Group (IUCN) and IOSEA MoU.
Achievements in 2011
DYMITILE Project (2010-2013)
The DYMITILE project aims to fill gaps in knowledge on post-reproductive migration of green turtles (Chelonia mydas) and those of immature loggerhead turtles (Caretta caretta) incidentally caught in longline fisheries of La Réunion. To do this, satellite telemetry (Argos) is used.
The ultimate goal of this project is to determine:
- feeding sites for green turtles laying eggs in the French islands of the Indian Ocean.
- migration corridors for this species and to evaluate potential interactions with offshore and coastal industrial fisheries
- the destination of loggerhead turtles caught accidentally by the longline fisheries of La Réunion.
Figure 1: Green turtle (left) fitted with an Argos transmitter on its nesting site, and loggerhead turtle (right) caught accidentally by a longliner and released after being fitted with an Argos transmitter (© J. Bourjea).
During this project, over 110 Argos transmitters are being deployed on green turtles laying eggs during and outside of peak nesting on the main breeding sites in the region: Europa, Juan de Nova, Glorieuses, Mayotte, Moheli (Comoros) and Tromelin (Figure 2). The first analyses show that these turtles have traversed up to nine different EEZs before reaching their feeding areas spread along the coast of six countries. The East African coast, from northern Mozambique to southern Kenya, as well as northern Madagascar, appear to be the main feeding sites for this species.
Figure 2: Argos recordings of migratory routes of post-nesting turtles.
In parallel, and through an active partnership with fishermen from La Réunion, 17 Argos transmitters were deployed on sub-adult loggerhead turtles caught accidentally by Réunion longliners (Figure 3). Tracking of their movements has shown that while some of these turtles present in the waters of La Réunion and Madagascar undertook migration to southern Madagascar and the southern tip of Africa, the vast majority travelled to the northwest of the Indian Ocean. During this journey, over the course of which some travelled over 13,000 km in seven months, the turtles traversed up to nine EEZs and some even changed hemisphere to situate themselves in the northern Indian Ocean off of Yemen and Oman.
Figure 3: Migratory routes of sub-adult loggerhead turtles caught accidentally by Réunion longliners and released after being fitted with an Argos transmitter.
SWIOFP - Component 5 (2005-2013)
The first results of the DYMITILE project helped convince other countries bordering the region to engage in this process. Thanks to the South West Indian Ocean Fisheries Project (www.swiofp.net), in which DOI provides the French coordination of component 5 on biodiversity, all countries in the region have engaged in these activities to study the spatial and temporal dynamics of marine turtles. In 2012, new Argos transmitters will be deployed from Mozambique, Tanzania, Kenya, Seychelles and Mauritius. It is expected, in early 2013, to merge the results acquired as part of the DYMITILE and SWIOFP projects to achieve a comprehensive regional analysis, which will be used directly in connection with the development of scientific recommendations for the NAP (National Action Programme, i.e. Conservation Plan) for marine turtles.
Other projects in collaboration with Kélonia
TORSOOI Project (2009-2011)
This project was completed in late 2011. It was mainly intended to develop tools to centralise, process, analyse and exchange information for the implementation of a regional strategy for the management and conservation of marine turtles and their habitats. To do this, a database was developed in PHP format (script code) MySQL (query language) in French and English (Figure 4). It contains data acquired over many years in various French territories in the Indian Ocean (Réunion, Glorieuses, Europa, Tromelin, Juan de Nova), as well as in project partner countries: Moheli (Comoros) and Nosy Iranja (Madagascar).
To validate data, a quality control approach has been developed in the framework of this project: 100 000 data were verified from field survey sheets and individually validated before inclusion in the database. A quality criterion (1: validated data; 2: doubtful data; 3: invalid data) was assigned to them. 70% of the data could thus be qualified as "1" and only 4% as "3".
Note that this approach was carried out in close collaboration with the “Q² cell” of Ifremer, the development of TORSOOI having been made so that all data is ultimately stored onto disks for the long-term by Q ² via Sismer (Scientific Information System for the sea: a national central marine database managed by Ifremer).
MODIOT (2011-2012): Modelling the oceanic dispersal of juvenile green turtles in the southwest Indian Ocean
An important phase of the life cycle of green turtles remains largely unknown to date. This is the pelagic juvenile stage, following emergence until the recruitment phase (arrival) at feeding areas along the coast. This phase, known as "the lost years" due to the almost total lack of knowledge about them, is nonetheless crucial for understanding the spatial distribution of this species at the regional level. The most widely accepted hypothesis today is that during their pelagic phase, juveniles drift with ocean currents, in a manner that is essentially passive. Many experts believe that during this drifting phase, the juveniles gradually develop a "map" of the areas visited, then make use of that map in their adult lives to navigate effectively on their return journey between their feeding and breeding areas,
Managing to learn about ocean areas covered by juveniles during their first phase of pelagic life is a challenge. With the current state of technology at our disposal, this knowledge cannot be acquired with by Argos transmitters, as they are much too heavy and bulky for a hatchling just after its emergence. One way to begin to understand potential migration pathways is through the realisation of simulations using hydrodynamic models: it is indeed now possible to perform simulations of ocean currents, their temporal evolution, and residual trajectories of water bodies. MODIOT aims, with a hydrodynamic modeling tool, to simulate potential trajectories of juvenile green turtles from the main nesting beaches of the SWIO, proposing as the main hypothesis that the drift of young emerging turtles is essentially passive.
As part of this project, we used the "ARIANE" Lagrange drift simulation software developed by CLS. After a phase of adapting the tool to our needs, the first simulations reveal significant differences in the drift forecast (potential), whether the starting point is from Europa (south of the Mozambique Channel; Figure 5, at left) or from an island north of the Mozambique Channel (Glorieuses; Figure 5, at right).
Figure 5: Simulation of potential drift of particles for 1 year (intended to represent juvenile turtles drifting passively), from Europa in the south of the Mozambique Channel (left) vs. Glorieuses in the north of the channel (right). The simulations are based on realistic hydrometeorological conditions, with 10 particles being "released" per day on both sites throughout the period 2002-2007.
We find that the vast majority of hatchlings from Europa are caught by the eddies of the southern Mozambique Channel and rejoin the Agulhas current before ending up in “cold” water south of the 30th southern parallel (or even the 40th), which means certain death. Only a tiny minority can potentially move north, but without ever potentially passing north of Madagascar. For Glorieuses, although a number of particles also descend to the south, a significant proportion of them remains in the intertropical zone corresponding to the thermal optima of juvenile green turtles, with some reaching the equator or even the northern hemisphere.
The next step will involve simulations of drift with the actual trajectories (Argos transmitters) of post-homing obtained through DYMITILE, to see if there is a relationship between feeding sites of adults and areas traversed by juveniles in the course of their passive drift, during their "lost years".
Spatial dynamics of immature green turtles on their feeding areas (2011-2013)
Also as part of the establishment of the NAP / Conservation Plan in the Indian Ocean, Kélonia is conducting a project whose goal is to understand the behaviour of juvenile green turtles once they arrive on their feeding grounds (or "developmental habitat"), at areas of high human habitation (La Réunion) vs. sites free from human pressure (Europa).
In 2011, a first mission saw the deployment of Argos transmitters equipped with GPS technology ("Fast Loc GPS") on immature green turtles feeding in the mangroves of Europa. This technology can track turtle movements with an accuracy of ten meters, and thus relate spatial behaviour with habitat. The earliest recordings are shown in Figure 6.
Figure 6: first recordings (in Europa, mainly in mangroves) of GPS positions of immature green turtles captured and released after being fitted with an Argos GPS transmitter.
This study will be completed in La Réunion with the deployment of 10 Argos GPS transmitters (funded via the CHARK project).
The objectives for 2012 are to finalise the field study and analysis of data from the DYMITILE project, to coordinate the deployment of tags in the framework of the SWIOFP, to finalise the MODIOT project (rendering the final report), to deploy Fast Loc GPS tags in La Réunion, to begin drafting recommendations for the national Turtle Action Plan (Conservation Plan) for submission to DEAL Réunion, and to highlight (through scientific publications) all of these results. Additionally, it is worth mentioning that Mayeul Dalleau is conducting a doctoral thesis on this subject at the University of La Réunion, under the co-supervision of Kélonia and Ifremer, supported through mid-2012.