Publié le August 31, 2020

Whale Shark Mission 2020

Nausicaá sponsors the initiatives of the Megaptera association, which studies whale sharks. Ludwig Coulier, a carer at Nausicaa, is joining the association for a third Whale shark mission. From the 4th to the 10th of January, he will dive with mask and snorkel to try to identify whale sharks and fit tags that will follow the sharks’ movements for 300 days.

Let’s follow the Whale shark mission with Ludwig’s logbook!

 

Friday 3rd January 2020

Departure from Paris, to meet up in Djibouti airport!

 

 

Saturday 4th January 2020

We met up with Nicolas, our expedition leader, at the airport and we have now arrived in Djibouti!

From the beginning, we asked about the presence of sharks in Djibouti during the previous days.

It would seem that the lack of sightings over the last few days may be due to the heavy rainfalls.

 

 

 

 

 

So we’re off on a new whale shark expedition with Megaptera and its partner TERIA. Why Djibouti? Simply because whale sharks can be found in the Gulf of Tadjourah as early as November to feed on the abundance of plankton there.

The state of the world’s sharks is of great concern. Some 100 million sharks die each year mainly because of humans. The Megaptera association is dedicated to studying whale sharks to learn all about their reproduction, diet and movements. Therefore, the primary objective of the expedition is to locate sharks, count and identify them from one area to another and measure them – the absence of sharks is also important information as it may indicate a change in behaviour, migration or a decline in food. Tagging is an additional task to these missions and it represents the opportunity to gain additional data and increase our knowledge of these animals.

Let’s keep our fingers crossed and hope we quickly find some whale sharks!

 

This afternoon, we reached Ras Eiro. We got the tags ready for tomorrow. We placed them on the ship deck to test the connection with the satellites.

Sunday 5th January 2020

The end of the first day at sea. We went out this morning and again this afternoon to try and spot whale sharks. So far, we have not seen any sharks.

This evening, we logged on to the Argos site: the tags are working correctly.

I joined the members of the association on the boat who, like me, are taking part in this expedition. What is the purpose of this yearly expedition? To collect data to study the behaviour, habits and movements of whale sharks. The tag transmits data on the shark’s location via satellite when the shark comes up to about one metre from the surface.

The tag works for 300 days; when it becomes detached from the shark, water temperature data is retrieved.

Did you know? Water temperature is a good indicator of the depth of water the shark may have descended to. If the recorded temperatures are between 29 and 25°C, it means that the shark is at a depth of between 0 and 40 m.

Monday 6th January 2020

Swimming next to a whale shark is an extraordinary experience. It is really impressive!

Its size varies between 5 and 12 metres. It is the largest of the bony and cartilaginous fishes. Despite its large size, it is actually a fish and not a cetacean. The term whale in its name is simply in reference to the size of the animal.

The whale shark is impressive, but harmless, as it feeds on plankton. It can filter up to 6,000 litres of water per hour and swallow more than a tonne of food a day. It is easy to understand why whale sharks are found in Djibouti at this time of year: plankton is abundant.

 

 

Tuesday 7th January 2020

After two days spent searching in the Gulf of Goubet where, based on our information, the sharks were last sighted, we were lucky enough to encounter whale sharks 11 times.

It was a success because I was able to fit two tags! We will wait until tomorrow to see the first movements being tracked on the computer. The tag financed by Delanchy was placed on a 4-metre long male (which remains small for a whale shark).

To be able to fit a tag on the whale shark, we dive with mask and snorkel into the first few meters below the surface to approach them without disturbing them. The tag is fitted precisely above the dorsal fin, which is also a good place to protect it from external elements such as algae or waste. All this is carried out with the utmost respect for the individual.

 

Wednesday 8th January 2020

Photo-identification mission: during this expedition week, we also took advantage of the dives to photograph the whale sharks so that they can be identified. How? Simply by photographing a specific area just above the left pectoral muscle behind the gills. This uniquely patterned area with dots spread across its skin is the shark’s fingerprint.

We left the Gulf of Goubet this afternoon. However, we planned a final morning searching, hoping to find a few more whale sharks.

Result of the morning’s work: 6 encounters with 4 different sharks and the last two tags fitted!

 

Thursday 9th January 2020

The whale shark really is a fascinating animal. It can dive to a depth of 1,000 m. Males migrate over long distances, whereas females migrate short distances and return to their birthplace. The data collected by the tags will enable us to learn more about the sharks’ movements.

Today, we crossed the Gulf of Tadjoura to the north to continue photo-identification, but no whale sharks were sighted.

 

Friday 10th January 2020

Last day of the mission!

Time for the first assessment of the expedition. So we made 17 encounters with whale sharks during our dives. Photo-identification is not yet complete, but it looks like we found 8 different individuals during these encounters.

We managed to fit all four tags that we had taken with us. We now have to wait 300 days to be able to recover all the data.

 

Sunday 19th January 2020

Michel Vély, president of Megaptera posted a follow-up of the whale sharks on which the 4 tags were placed during the 2020 Whale shark mission on his Megaptera Facebook group Suivez les baleines.

His report is given below:

  • Three of the four tags deployed on whale sharks at the Goubet seabed have transmitted and sent data.
  • Teria 20 (196477 deployed on the 6th January 2020) and Nicolas 20 (196476 deployed on the 8th January) are still moving around on the Goubet seabed and communicate regularly.
  • However, Delanchy (196474 deployed on the 7th January) that had not transmitted since its deployment on the 8th January at the Goubet seabed has just communicated to us on the Somaliland coast

[Teria 20, Nicolas 20, Daniel 20 and Delanchy are the names given to each tag and indirectly to the shark to which it is fitted.]

  • This location most probably corresponds to a gathering and feeding site at the surface for these young whale sharks as identified in previous SHARKY DJ missions.
  • Delanchy travelled all this distance underwater, probably at an average depth of 40 m, as previous missions using MK10 tags have shown us, and recorded the pressures and therefore, the depths of whale shark movements.
  • Daniel 20 (196475) deployed on the 8th January has not communicated yet but, we are confident because whale sharks can travel long distances underwater.

 

Thursday 6th February 2020

Michel Vély continues to report updates on the satellite tracking of whale sharks.

It has now been a month since spot 6 tags were fitted to 4 whale sharks. Teria 20 and Nicolas 20 are located in Goubet (circle with number 2 on map 2), Delanchy (74) is wallowing around off the coast of Somaliland in the Berbera region. As we have identified in previous years, it seems that this area hosts a seasonal gathering of whale sharks associated with the one in Djibouti.

No doubt that in a similar way to what happens in Djibouti and in many other locations around the world (Seychelles, Mozambique, Madagascar, Belize, Nigaloo Reef, etc.) whale sharks come to the surface to feed for a period of time. Daniel 20 has transmitted north of the Eritrea/Djibouti border. It is south of the Red Sea, but has only given one position so far.

 

April 2020

The Megaptera-Teria association has been giving us updates of the tagged sharks since January.

Daniel 20, which is at the entrance of the Gulf of Tadjoura, has moved since the 14th April after 2 months of silence. It gave a new position on the 24th April. (photo 1: 15th February, photo 2: 20th April, photo 3: 24th April). Apparently, the tag is still on the whale shark and he seems to like this area.

 

The position of the other animals has not changed for a month. Photo: position of sharky-dj

 

 

 

 

Tuesday 26th May 2020

The Megaptera association gave an update on the location of the tagged whale sharks since the mission in January 2020. The maps show the position of the sharks on the 26th May:

  • The shark Daniel 20 (196475) transmitted on 26th May, whereas Teria 20 (196477) transmitted on 25th May. The other two transmitted on 23rd February 2020 for the Delanchy shark; the Nicolas 20 (196476) shark last transmitted on 25th March 2020. The tags only transmit when they are at the surface, so it is likely that these sharks are still underwater. For example, Teria 20 transmitted on 13th March and again on 25th May, after 77 days underwater.
  • Daniel 20 transmitted near the Arab Shoal located 35 nm from Djibouti in the Gulf of Aden. He has been at the surface regularly since the 14th April, which means that this area is identified as a potential gathering and feeding area.
  • Teria 20 has reached the Indian Ocean and is located in the shallow waters of Socotra, a Yemeni island off the Horn of Africa.
  • We are about halfway through the programmed tag transmission period, which is 300 days.

 

Wednesday 3rd June 2020

Update on the Delanchy whale shark (196474)!

He moved on the 3rd June and transmitted from the southern Red Sea region. This is excellent news.

Therefore, he has left the area of southern Yemen at the entrance to the Gulf of Aden where we last spotted him on 25th March. The tag can only transmit information when the shark swims close to the surface of the water. Between the 25th March and 3rd June, the Delanchy shark stayed underwater and therefore, the tag was unable to communicate any location information.

 

Crédit photos : Nausicaa, H-Al Qallaf-Megaptera, Megaptera-Teria

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