JBL Expedition Indian Ocean: part 1 - to the whale sharks near Madagascar

Whale sharks are not really suitable aquarium inhabitants and yet they are our first port of call on the Expeditie Indische Oceaan . Since the plankton bloom had attracted them to the region at the time of our trip, we included them in our program to have “a whale of a time”. I don't think there can be anyone not interested in experiencing one of the peaceful giants in the sea. The region around Nosy Be in the northwest of Madagascar is known for its whale sharks from October to November. During their migration they follow the plankton and thus come to be in the quite calm waters at the northwest tip of Madagascar.

In the morning we’re out on the open sea with a maximum of eight people per boat. We’ll be looking for any conspicuous flocks of seabirds above the water surface and as soon as we see a gathering of them, we’ll head for that spot. The closer we get, the better you can make out the swirling of the sea. Birds swoop down and attack small fish and plankton. Mackerel and tuna shoot up from below into the ever smaller fish swarm. And finally the whale shark arrives to put an end to the hunt. The whale shark is so close to the surface that you can easily see its tail fin outside the water. We estimate its swimming direction and slip into the water as calmly and quickly as possible. We catch a glimpse of the last fish disappearing into the mackerel’s mouths and then we discover the whale shark: Even though it measures about seven metres it is still difficult to locate at a slight distance. The dot pattern on its aqua-blue body blurs its contour with the deep blue of the open water. Only when it swims directly towards us can we make out this peaceful giant’s size. Wow - we have to be careful not to swallow water as our jaws gape open. What a beautiful and impressive sight! The whale shark is not really disturbed by us and comfortably continues on its course. Some of us try to follow it with powerful strokes of their flippers - but it’s no use. A slow whale shark is still faster than a snorkeler. The encounter only lasts a few short minutes, but we’re overwhelmed. The endless blue of the sea makes us feels so tiny as we admire this giant feeding on its small food. Slowly - though to us it feels quick - it disappears from our eyes and dives down. Despite very clear water we can now hardly see it at a depth of only 20 to 30 meters. We swim back to the boat and search for the next flock of birds above the water surface.

The observations of the whale sharks taught us several things: Even in the seemingly endless open water of the sea, whale sharks can find schools of fish – albeit often with the help of other fish and seabirds. Plankton is not always small: The largest plankton organism in the ocean is the Venus girdle, a comb jelly species which can be up to one and a half metres long. Plankton is not defined by size, but by its movement. Plankton organisms are animals that cannot actively move against ocean currents. On this occasion we also learned that many plankton organisms can use their nettles to sting badly. Some of our participants were only wearing swimming trunks and were heavily stung on their arms and legs. They looked like they had a severe case of scarlet fever. And we also learned that the "plankton-eating" whale sharks undoubtedly eat fish. And fish are definitely not plankton. They just don't hunt single fish like their toothed relatives. They slurp up the small fish in their huge mouth like fish soup.

Im zweiten Teil geht es um die Korallenriffe bei Madagaskar: JBL Expedition Indian Ocean: part 2 - the coral reefs near Madagascar

© 16.11.2018
Heiko Blessin
Heiko Blessin
Dipl.-Biologe

Tauchen, Fotografie, Aquaristik, Haie, Motorrad

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