Dial eels (left), transmitters used in the research and release of specimens in the Mediterranean. (Photo: MNCN)
More light on the mysterious migration of eels
SPAIN
Friday, October 07, 2016, 23:40 (GMT + 9)
european Researchers have managed to follow in detail the long journey of 80 european eels (Anguilla Anguilla) and discover some of its mysteries, the findings are expected to help improve the conservation of this species, which is in critical danger of extinction.
With around 8,000 km long, the migration route of european eels is one of the longest and most unknown of the animal kingdom. A new study published in the journal Science Advances explains that this long journey and debunks some of the beliefs they had about the behavior of this species.
After more than ten years ago, a group of european researchers, including Javier Lobón-Cerviá of the National Museum of Natural Sciences (MNCN-CSIC), has revealed how the eels travel from the european mainland to the Sargasso Sea.
The distribution area of the eel extends from the Kola peninsula, north of Russia, for all basins of european rivers and the Mediterranean to the Black Sea and the Canary Islands.
When just measuring two centimeters. the young eels (called elvers) travel from the Sargasso Sea to european rivers where they live for between five and 20 years and have two metamorphosis before becoming adults. Before you die travel the thousands of miles that separate the place where they were born to spawn.
For this research project, which brings 12 european countries, the researchers placed transmitters to 707 adult eels (of at least 2 kg in order to avoid interfering with the animals), released in various places in the european continent. Once the fish were released into the sea began to receive data from 206 transmitters and were able to follow in detail the journey of 80 copies.
“Thanks to the signals of the transmitters, we discovered that they follow a routine when you move. By the day they move in the depths of the ocean and, at night, they continue their travel in shallower waters,” explains Lobón-Cerviá. “We have also found that the average speed was between 3 and 47 km per day, which makes it impossible for all to reach their destination in the spring,” continues the researcher of the MNCN.
Opposite to what was believed until now, not all eels are doing this trip in four months to lay their eggs simultaneously, but many take up to a year to arrive. In particular, the average duration of the journey of the eels marked has been eleven months.
Also, thanks to the data relating to the survival of the larvae in the Sargasso Sea, have shown that the spawning is prolonged from December to February.
“The data obtained in the study have helped us to clarify many details of this complex migration, significantly improving our knowledge on the dynamics of their population. This work will help us to improve substantially the management and conservation strategies of the species to be able to protect it”, concludes Javier Lobón-Cerviá.
The eel caught the attention of Aristotle, who claimed that “came from the bowels of the Earth”. But it was not until the early TWENTIETH century, when the biologist Danish Johannes Schmidt discovered that they were reproducing in the Sargasso Sea. Since that discovery, no one has captured no specimen in the open ocean, eels migrate towards the sea in the fall and does not re-know them until their offspring are returning to the rivers that one day they left their parents.
Thanks to data obtained have been able to clarify how it is produced the mysterious journey of the eels, have documented the attacks that they suffer on the part of whales, sharks and tuna and have discovered that, instead of a direct route, follow different migratory strategies.
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