Changing Planet

Rapa Expedition: Fish Finding Their Footing

After days of foul weather, the clouds have parted and the Hanse Explorer has arrived at Rapa Iti, the site of the latest National Geographic Pristine Seas expedition. The science team has returned from their first dive to survey the biodiversity hidden under the waves surrounding this remote southern island and we’ve had another busy, great and productive day here on Rapa. It’s blowing a “hooley” offshore but life underwater is great! Dr. Alan Friedlander, Pristine Seas Chief Scientist, reflects on the trip so far.

Manu_San_Felix EELS GENETIC SAMPLING JPG
Collecting freshwater eels for genetic samples (the eel was released unharmed!). (Photo by Manu San Felix)

By Alan Friedlander

After a few days diving around Rapa, one of the most striking things that we’ve noticed is the large number of endemic species we see on the reef—those species found nowhere else on Earth. After fish eggs are fertilized, they are at the mercy of the wind, waves, and currents and can float around in the open ocean for weeks to months and can be carried thousands of miles away from their birth place.

How, then, is it possible that fish born on Rapa can find their way back to their tiny island in such a vast expanse of ocean? Recent research has shown that these baby fishes, no more than an inch in length, are far more competent than we once thought. They can swim against currents, they can hear and they can smell. By using all of these senses they can stay close to home and increase their chances of survival. This is how these small, remote islands maintain life so far from the nearest coral reef.

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A school of Rapa sweepers (Perpheris rapa) in what would have been the dark. This is the first underwater photo of the species. (Photo by Manu San Felix)

Another amazing find was our discovery of large freshwater eels in the streams that flow into the sea. These eels can live at sea for a year or more as young but need to find freshwater habitats as adults. How do they sniff out these trickles of fresh water in this huge ocean? It is not by chance, but by the tenacity of life that these animals continue to thrive in these tiny freshwater specks in the middle of the ocean.

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A Rapa toby (Canthigaster rapensis), which is found only in Rapa. (Photo by Manu San Felix)
Another angle on the Rapa toby, posing for the camera. (Photo by Manu San Felix)

All of these fish finding their way is very similar to how these islands were settled by the early Polynesians, who had little more than the sun and stars to guide them across thousands of miles of open sea. At a time when European sailors limited their travels to being within sight of land, Polynesian navigators were traversing the entire Pacific Ocean on a regular basis and colonizing distant islands. They brought with them a sophisticated understanding of the sea and how to live sustainably with limited resources. We can learn a great deal from these past practices in order to develop strategies that can alter the current trajectory of resource decline and improve the quality of our planet for future generations.

 

Read All Posts From the Rapa 2014 Expedition

Learn More About Pristine Seas

Worldwide Voyage Using Traditional Polynesian Navigation

 

The Pristine Seas expedition to Rapa is sponsored by Blancpain and Davidoff Cool Water.

Paul Rose is an ardent explorer, television presenter, journalist, author, and Vice President of the Royal Geographical Society, and an Expedition Leader on the Pristine Seas team.

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