Marine Mammals Exploring the Oceans Pole to Pole

When diving animals help us to observe the oceans

Over 800,000 vertical profiles of Temperature and Salinity have been collected since 2004 in the World Ocean by attaching tags on marine mammals, such as Southern elephant seals.

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A trip to the Kerguelen Islands

Monday, 15 February 2016

Between December 18 2015 and January 18 2016, Fabien Roquet from the Stockholm University stayed on the Kerguelen Islands to put instruments on elephant seals. He is giving a short description of his amazing trip here.

For more than a decade now, I have been working with seal-derived oceanographic data, first as a data engineer, then as a PhD student and now as a researcher. Most of the time, this involves to stay seated in front of my computer screen. So much that it is sometimes easy to forget where these amazing data actually come from.

When Christophe Guinet proposed me to join the small team that would go to the Kerguelen Island this year to work on elephant seals, I joyfully accepted. Such opportunities are rare and priceless, plus it had been exactly ten years since I had visited the Kerguelen Islands and the best way to celebrate this anniversary was clearly to go there again.

On December 8, I embarked on board the R/V Marion Dufresne, the French ship that supplies the French Austral Islands several times a year. After a peaceful 10 days long trip, only interrupted by two gorgious days at the Crozet Islands, we arrived at Port-aux-Francais, the scientific and logistic base situated on the eastern part of the main island in the Gulf of Morbihan.

The “pop-eleph” team in Pointe Suzanne kitchen: (from left to right) Fabien Roquet, Thomas Jaud, Mary-Anne Lea and Baptiste Picard. Credit: F. Roquet (MISU, Stockholm)

This time, the “pop-eleph” team is composed of four people: Mary-Anne Lea, Baptiste Picard, Thomas Jaud and myself. Together, we had to 1) put GLS tags on 24 female fur seals, 2) install 14 CTD-SRDL tags on elephant seals, and 3) recover 10 tags from recently instrumented seals if possible. Most of the fieldwork had to be done at Pointe Suzanne where a hut has been installed by the French Polar Institute for scientists.

Suzanne Point (Pointe Suzanne in French) lies slightly less than 20 kilometers southeast of Port-aux-Francais. It is an incredible place. It consists of three kilometers of subantarctic seashore full of fur seals, elephant seals, gentoo penguins coexisting with great albatros, giant petrels, skuas and other Kerguelen shags. The Point is well protected from the wind and is covered with Cotula plumosa, a very soft herb perfectly suited for the long naps that are so appreciated in those regions.

Pointe Suzanne in the Kerguelen Islands, 18 km southeast of Port-aux-Francais. Credit: F. Roquet (MISU, Stockholm)

The hut is made of four wooden blocks, linked by a terrasse. Two rooms, a kitchen and a workshop. A solar panel produces the electricity, a water tank collects the rain and food is stocked in waterproof plastic barrels (named Touques). The kitchen has a gas stove and a oven. Life is definitely not too hard in Suzanne Point.

From December 22 until December 30, we installed GLS tags on the female fur seals. Global Location Sensing tags record the light level and temperature during two years, allowing to infer the trajectory of the animal during this period. Light measurements are indeed used to determine the timing of sunrise and sunset, which is then used to estimate the longitude (time of zenith) and latitude (length of day). Temperature can then be used to refine the location estimate.

Thomas Jaud and Joris Laborie are catching an instrumented elephant seal with the hood to recover an oceanographic tag. Credit: F. Roquet (MISU, Stockholm)

After new year’s eve spent in Port-aux-Francais (and a good shower), we returned to Suzanne Point to begin instrumenting elephant seals. Oceanographic CTD-SRDL tags were attached on female elephant seals weighing between 300 and 600 kg. Two persons hold the hood that will be used to catch the seal. Once the seal is stuck in the hood, an intravenous injection is administered to anesthetized the seal for a 30 minutes period, during which the seal will be tag. The manipulation, especially the catching phase, can be quite spectacular (and quite intimidating the first time), and yet it is not really difficult or dangerous. You just have to wait for the seal to get its head in the hood!

A female elephant seal a few hours after the instrumentation, hanging out with a few other seals in the comfortable Cotula plumosa fields. A few days later, she left the Island to look for food. She will return in several months when spring comes.
Credit: F. Roquet (MISU, Stockholm)

On December 18, after a month of fieldwork in the Kerguelen Islands, it is time to return on the Marion Dufresne. Two weeks later, we arrive in the island of La Réunion, a volcanic island in the subtropical Indian Ocean. Past the subtropical front, we have no choice but to accept that we have definitely left the realm of Kerguelen, as the temperature is now reaching 30degC and the sun is so high in the sky.

Back in Sweden, Kerguelen seems far away and yet so close. I just have to switch on my computer and connect to the data server and I can see them, living their marine life on the other side of the Earth, deep in the ocean.

YouTube video with a presentation of the trip HERE. And a Swedish summary on the website of the Department of Meterology at Stockholm University.