From Wildlife Extra:
95% population decline in European eels spurs tracking research
Eels tagged to help scientists understand migration
January 2013. Nobody knows the underlying biological mechanisms of the European eel’s migration. Thanks to an EU-funded research project called eeliad, now about to reach completion, biologists have revealed some of its secrets, including a better understanding of its biology and migration route.
All European eels living from Northern Africa to Iceland are believed to migrate thousands of kilometres to the Sargasso Sea (The Sargasso Sea lies in the middle of the North Atlantic) to spawn. Findings of newly-hatched eel larvae in the Sargasso Sea strongly support this theory. But no eggs or adult eels have ever been caught in the area.
600 eels tagged
By attaching satellite and data storage tags to about 600 eels from different places in Europe the project scientists were hoping to map the route of the spawning eels. “We could track the satellite tags as far away as the Azores. This suggests that the eels take a different route to the Sargasso Sea than previously thought. It seems as if they’re saving energy by hitching a ride on the Azores Current,” Kim Aarestrup tells youris.com. He is a senior scientist at the Technical University of Denmark (DTU), in Silkeborg and one of the leading researchers behind the satellite tagging.
“Very little is known of the oceanic part of the eel’s life history,” says Martin Castonguay, an eel expert and research scientist at The Maurice Lamontagne Institute in Mont-Joli, Canada, adding: “The most important thing the eeliad project provided is that it gave us the first observations of adult eel migrations in the open Atlantic Ocean for distances up to 1,300 km from the release point.” Although he has not been a part of the project, Castonguay believes it has been “very successful”.
Among other things the project scientists also tested the spawning ecology of the eels by using genetic research, combined with a fisheries biology technique for tracking fish movement called otolith microchemistryand modelling methods. The analyses were undertaken both on eel larvae collected in the Sargasso Sea and on glass eels collected from the coastline of Europe and North Africa. “Our genetic research showed that the eels living all across Europe mate randomly. This is very unusual for animals that are so widely distributed. It strongly indicates that the European eels are spawning in the Sargasso Sea and nowhere else,” says Thomas Dammals, a research scientist at DTU who was involved with the genetic research in the project.
95% decline in eel populations
Even though the European eels is still surrounded by mystery, “the eeliad project has successfully addressed some issues,” notes Reinhold Hanel, director of the Thünen Institute of Fisheries Ecology in Hamburg, Germany, “these include questions about the diving behaviour of eels in the open ocean and a provisional clarification of the migration routes of eels leaving the Baltic Sea. And I certainly expect some more [results] after complete data analyses.” Today, the population of the European eels is now less than 5% of what it was 40 years ago. According to Reinhold Hanel, there is an “urgent need” to do more research on this elusive species.
European eels use the Earth’s magnetic field to navigate the 6000 mile journey to the Sargasso Sea: here.
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