Featured Research

from universities, journals, and other organizations

Threatened eels disappear in the deep ocean on their way to the Sargasso Sea

Date:
February 10, 2014
Source:
University of Southern Denmark
Summary:
When the threatened European eels cross the Atlantic Ocean to get to the Sargasso Sea to spawn, they swim in deep water. But this does not protect them from predators, researchers report: Even in deep water the eels are hunted and eaten.

The European eel.
Credit: Anders Asp.

The European eel is in decline, and all over the world biologists are struggling to map its mysterious life cycle in order to bring its numbers back up. One of the great puzzles is why and how the eel each year travels thousands of kilometers to get to the Sargasso Sea to spawn.

A European monitoring project has provided a group of eels with data loggers before their big trip across the Atlantic, and now biologist and associate professor Magnus Wahlberg from Southern University and colleagues from DTU have got a surprising message from the data loggers:

"It turns out that eels are hunted and eaten by whales. It happens in surprisingly deep waters where we normally think that the eels would be safe," he says.

To date only a single case of a whale with an eel in its stomach has been described in the scientific literature. So these large marine mammals are usually not included in the discussion, when biologists talk about the eel's natural enemies.

"We do not know exactly which whale species are at play, but a good guess would be the pilot whale," says Magnus Wahlberg.

Stuck in the belly

The new knowledge that whales actually hunt and eat eels comes from three events in the North Atlantic in 2009 and 2010. 156 eels had been provided with data loggers and sent off on their journey across the Atlantic Ocean. Three of the tagged eels never made it, but ended their lives in the belly of a larger animal. In these bellies the data loggers continued to record data, and after a while they were excreted by their new host animal and washed up on a shore. Here they were found by passers-by and returned to the researchers.

The data loggers told a detailed story. Suddenly on 600 meters depth they got surrounded by a warmer environment than the cold North Atlantic waters that surrounded the eels. The temperature rose suddenly from 10 degrees to 36 degrees Celsius and indicated that the data loggers were no longer sitting on an eel, but had reached the inside of a larger, deep-diving marine mammal.

The temperature continued to go up and down: "We imagine that every time the host animal took in a new and cold prey in its stomach, the temperature dropped," says Magnus Wahlberg.

According to the recorded depth profiles it is unlikely that the hunters were seals.

"Seals do not dive this deep. The dive patterns better suit that of a pilot whale," he explains.

Magnus Wahlberg is not quite sure what the new data on eel hunting in deep water mean.

"It might be quite common for whales to hunt eel in deep water and that we just have never seen it before. This knowledge may be important for understanding how marine deep-water ecosystems functions," says Magnus Wahlberg.

The three tagged eels were launched from Ireland and France. Between 25 and 256 days later their data loggers washed up on the coasts off Bindal in Norway and Isle of Coll in Scotland.


Story Source:

The above story is based on materials provided by University of Southern Denmark. Note: Materials may be edited for content and length.


Journal Reference:

  1. Magnus Wahlberg, Hεkan Westerberg, Kim Aarestrup, Eric Feunteun, Paddy Gargan, David Righton. Evidence of marine mammal predation of the European eel (Anguilla anguilla L.) on its marine migration. Deep Sea Research Part I: Oceanographic Research Papers, 2014; 86: 32 DOI: 10.1016/j.dsr.2014.01.003

Cite This Page:

University of Southern Denmark. "Threatened eels disappear in the deep ocean on their way to the Sargasso Sea." ScienceDaily. ScienceDaily, 10 February 2014. <www.sciencedaily.com/releases/2014/02/140210101951.htm>.
University of Southern Denmark. (2014, February 10). Threatened eels disappear in the deep ocean on their way to the Sargasso Sea. ScienceDaily. Retrieved October 22, 2014 from www.sciencedaily.com/releases/2014/02/140210101951.htm
University of Southern Denmark. "Threatened eels disappear in the deep ocean on their way to the Sargasso Sea." ScienceDaily. www.sciencedaily.com/releases/2014/02/140210101951.htm (accessed October 22, 2014).

Share This



More Plants & Animals News

Wednesday, October 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Cadaver Dogs Aid Search for More Victims of Suspected Indiana Serial Killer

Cadaver Dogs Aid Search for More Victims of Suspected Indiana Serial Killer

Reuters - US Online Video (Oct. 21, 2014) — Police in Gary, Indiana are using cadaver dogs to search for more victims after a suspected serial killer confessed to killing at least seven women. Linda So reports. Video provided by Reuters
Powered by NewsLook.com
White Lion Cubs Unveiled to the Public

White Lion Cubs Unveiled to the Public

Reuters - Light News Video Online (Oct. 21, 2014) — Visitors to Belgrade zoo meet a pair of three-week-old lion cubs for the first time. Tara Cleary reports. Video provided by Reuters
Powered by NewsLook.com
'Cadaver Dog' Sniffs out Human Remains

'Cadaver Dog' Sniffs out Human Remains

AP (Oct. 21, 2014) — Where's a body buried? Buster's nose can often tell you. He's a cadaver dog, specially trained to find human remains and increasingly being used by law enforcement and accepted in courts. These dogs are helping solve even decades-old mysteries. (Oct. 21) Video provided by AP
Powered by NewsLook.com
White Lion Cubs Born in Belgrade Zoo

White Lion Cubs Born in Belgrade Zoo

AFP (Oct. 20, 2014) — Two white lion cubs, an extremely rare subspecies of the African lion, were recently born at Belgrade Zoo. They are being bottle fed by zoo keepers after they were rejected by their mother after birth. Duration: 00:42 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins