Présentation

Sea turtles - Ecovolonteer - Mayotte

Studies on sea turtles and their habitat for their conservation

  

Scientific framework :

 

Mission proposed by KELONIA which is the observatory of sea turtles in the island of La Réunion. This mission was part of differents studies about sea turtles and their habitats in the south-west of the Indian Ocean.

 

Study area :

Lagoon and beach of N'gouja, in the south-west of Grande Terre, Mayotte island 
carte mayotte

 

N'gouja is an ecologically rich area. Indeed, this is :

imagesCAXQ5FLS a feeding site ( sea grasses)
 P1000719 a egg-laying site (beaches of sand)

 

Two species of sea turtles are especially found in this place:    

PC060029

the green turtle 

Chelonia mydas

 yt11230-yt11231-dessus
 51A-Auc-dessus

and the hawksbill turtle

Eretmochelys imbricata

 PC060012-copie-1

 

A hotel was discreetly built behind the beach 20 years ago. 

P1000733 Little by little, turtles get used to see humans in water. Indeed, as long as some rules are respected, it's possible to observe these big but timorous reptiles very closely. 

That's why this site is exceptionnal and makes some scientific studies possible.

 

 

As a volunteer during six months (from september 2009 to february 2010), I collected data for this study (i didn't take part in the set up of the protocol or in the analysis of the data).

My mission also consisted in the welcoming of tourists and in making them aware of the preservation of sea turtles and their habitats (in the framework of a  collaboration between KELONIA and the hotel).

 P1000722

 

Observation of the populations during their feeding :

P1280014 The turtles were snorkellingly observed once or more per day in the lagoon and on the reef crest. Each observation lasted arround one hour and a half.

For each turtle carrying a tag I met, I recorded the code(s) of their tag(s), the species, the gender, the place where it was observed, and also some possible marks of injuries or some scales' abnormalities which would be useful for the individual recognition if the tag were lost.
 

The animals were also photographed under the water(photo-identification) because the scales' shape of the head and the carapace are a better way to recognize them than the actual tags. 

They were geographically located by calculating the GPS position and by mesuring the depth and the temperature of the water.

 

 

 PC080006
  C.m. tagged on the left flipper

Finally, some exhaustive counts were also done (by the line transect method) in order to know the proportion of tagged animals and the proportion of individuals in each class of sexual maturity.  

 

Observation of the population during the reproduction :

SANY0037 re-copie-1  

An inventory of the nesting females was daily made during the night patrols. They were individually identified by their tags' codes and their carapace were measured.

With coming and laying on these beaches, females face up to some risks like being poached or attacked by some wild dogs. These patrols were then a good way to keep an eye on the safety on the beaches against these risks.

 an exceptionnal laying during the day  
 SANY0045  

Despite the patrols, some layings could be missed. Every morning, the tracks left on the sand by the females were counted and I estimated the number of succesful layings. 

 track going down to the sea   
 

After that, the nests were cartographied and marked out to avoid people walking on them. A calendar of the emergences was set up and the success of hachings was estimated after the studies on the nest.

 

 

 P1000946
   marking-out of a nest with a coconut palm leaf


My mission  consisted, on the other hand, in supervising and informing the tourists when they wanted to see a laying. That was in order to make sure that people can see this beautiful phenomenon while preserving the quietness of the turtles
  

 

 

Study of the sea grasses :
Some samples of the sea grass beds were taken (by the quadrat method) to study their biotic (fresh biomass, density, height) and abiotic characteristics (substratum).

P1020308 re  P1020296
 sorting out of quadrats by species   weigh-in of the aerials parts

 


The temperature of the laggon was measured with a sonde. 

 

At low tide, by walking on it, people could destroy the sea grasses. A walking channel was installed in the middle of the lagoon to minimize this threat. The maintenance of this channel was also assumed.

 

Inventory of the resting areas :

 

tortue-marine-verte[1]

When they are resting, the turtles descend to the sea floor or on a solid substratum such as a rocky ledge and stay there for a certain time in an inactive state before ascending to breathe. These areas were located by a GPS.  

 

Tourists: counting and sensibilization :
This part of  my job consisted in making the public aware of the protection of the sea-turtles and making sure that the lagoon and the beach were not damaged and that the quietness of the turtles were respected. 

P1020379 re-copie-1  

For that,  I welcomed the clients of the hotel on their first day to speak with them about the rules on the site, especially about the way to approach the turtles under the water.  I was then available during the day to inform tourists and to answer their question, to go with them in the water to show them these huge animals (scholars groups for instance). They could also go with me during the night patrols to see a female laying its eggs.  


On the other hand, I also proposed  a lecture once a week :

- presentation of the sea-turtles (biology, life cycle, different threats)

- presentation of the present study and my mission

- presentation of the problem of poaching

-and collection of money by a sponsorship system for a local association named Oulanga na Nyamba (Environment and Turtles)

Finally, I counted the number of tourists twice a day (in the morning and in the afternoon) in order to study the possible impact of their presence on the turtle populations.

 

 

 

PROFESSIONNALS ACQUIRED

Knowledges about Sea Turtles

(espacially the Green and the Hawksbill turtles)

biology, behavior, predators, anthropic threats

differents ways to approach them

how to study and protect these species


Materials and Techniques

 

GPS

temperature sonde

quadrat method : taking and analysing

line transect method

underwater photgraphies

(in apnea, with a waterproof bag)

maintenance of a channel

(with buying new buoys and ropes, marines knots)

 

Working with public

 

welcoming, informing

making lectures

 

 

 

 

Working with

other professionnals

discussions, elaborations of plans

 

Dealing with ups and downs

alone and as quickly as possible

 

Organizing myself

 

during days and nights

depending on the work to do,

the materials available, the weather, the ocean tide times...

 

Working under the water

whatever the weather

 

Working in a tropical country

 

 

Diving

PADI Open Water Diver
 
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