The Danish Eel Expedition headed by DTU Aqua is in the Sargasso Sea between Bermuda and the West Indies to investigate the relationship between climate related changes in eel spawning grounds and the sharp decline of eel in Europe.
Leading experts from a range of Danish and international universities are taking part in the expedition, covering more than 20 research projects intended to fill the gaps in our knowledge about the breeding habits and early life of the valuable and critically endangered eel.
The expedition sets out to investigate the relationship between climate-related changes in the eel´s spawning grounds and the sharp decline of feel in Europe. In addition the researchers will attempt to;
1. shed light on issues such as why the eel spawns in the Sargasso Sea,
2. which route the eel larvae take back to Europe and
3. what they feed on during their long journey
Lack of knowledge about the needs and diet of the eel larvae is currently responsible for a significant bottleneck in the work to breed eel larvae at farms.
In the past 30 years there has been a dramatic decline in the European eel population, leading to that IUCN in 2008 added the eel to its list of critically endangered species. Today, the number of eel larvae returning to the coasts of Europe is merely 2–10 per cent of the levels seen in the 1970s. The dramatic decline seen means there is an acute need to understand how the eel’s life cycle is impacted by humans, environmental conditions and climate changes.
First phase of the Danish Eel Expedition 2014 successfully completed.
The researchers investigated conditions in the eels’ central spawning areas in the Sargasso Sea at 41 carefully chosen locations where cold and warm waters meet, believed to be ideal conditions for eel larvae.
Among many measurements taken, a comprehensive ‘24-hour vertical study‘ of a hotspot with a particularly high concentration of eel larvae was performed where the researcher found the largest quantities of larvae in a small band at a depth of 150 meters, just below where the water has the highest salt level. Additional measurements on the environment and organisms found in the area was taken to determine what makes that specific location so attractive to the larvae.
As part of the first phase, over 400 eel larvae were retained for further on-shore DNA analysis with the aim to see potential genetic differences in the populations as well as to determine if the two species which spawn in the Sargasso Sea—the American and European eel—interbreed.
Additionally, as no one has yet succeeded in catching a mature European eel in the Sargasso Sea, the expedition trawled for a number of night when the eels are assumed to spawn with the hope to catch an adult eel, but did not have any luck this time either.
The expedition will continue on leg two of the expedition where the key objective is to map the eastern frontier of the eel spawning area. On the third and final leg, the aim is to map the route of the eel larvae’s return to Europe, taking samples along the way.