Eels Migrate a Staggering 1,500 Miles
A long, dangerous eel migration from Canada to waters off of Bermuda has just been tracked for the first time.
An adult American eel was just tracked traveling nearly 1500 miles from the east coast of Canada, over the rocky continental shelf, into the deep ocean and, finally, at his destination: the Sargasso Sea near Bermuda.
The lengthy and perilous migration, documented in the journal Nature Communications, provides the first direct evidence that eels are capable of making such a journey. The migration was previously only theorized, based on sightings of adult American eels in North American inland rivers and surprising discoveries of their larvae far away in the Sargasso Sea.
The study "sheds light on an often under-appreciated species, which performs one of the longest and most amazing migrations in the animal kingdom," co-author Martin Castonguay of Fisheries and Oceans Canada told Discovery News.
Lead author Mélanie Béguer-Pon of Dalhousie University, Castonguay and their colleagues fitted satellite-transmitting tags to 38 adult eels collected from rivers and estuaries in Nova Scotia, Canada. The researchers then tracked the eels' movements upon release from the coast.
Predators swallowed some of the tags, but eight were tracked moving over the continental shelf and into the open ocean at a depth of 1.2 miles. A single eel, nicknamed "Star" by the researchers, was tracked to the northern limit of the Sargasso Sea.
Castonguay said that the eels may use temperature and salinity cues for orientation as they migrate on the continental shelf. It is not an easy trip.
"As eels leave freshwater, they sometimes have to pass hydropower dams and will often be killed going through turbines," he explained. "Moreover, evidence from a previous study of ours indicates that eels can be preyed upon by sharks and tunas as they try to exit the Gulf of St. Lawrence."
The eels do not eat during the journey, but instead rely upon fat accumulated during their time in rivers.
Each day, the eels also move up and down the water column, staying at deeper levels during the day, likely for predator avoidance. They also save energy by remaining in cooler waters throughout the day.
As for why they migrate so far in the first place, Castonguay said, "You can think of the Sargasso Sea as the Eel Mecca. There are over 30 species of eels spawning in the Sargasso Sea, but only two species invade continental waters during their growth phase: the American eel and the European eel."
He added that all other eel species spawning in the Sargasso complete their entire life cycle in the ocean.
Once at the Sargasso, the eels gather by species into select areas. The American eel spawning area extends more to the west, for example, while the European eels head to the east.
Defining the migration route to and from this site indicates areas that warrant protection to help ensure that the epic eel migration is not impeded. American eels are already classified as endangered and are on the IUCN Red List of Threatened Species.
John Casselman, a professor of biology at Queen's University, told Discovery News that any direct evidence on eel migrations is "sadly wanting, and is a pleasure to see." He said that the findings "help to unravel the mysteries of this iconic species. The more we learn, the more we will respect and appreciate this mysterious and ancient species."
Since the study's completion, the researchers have begun yet another investigation. They are using "an improved tag attachment method," according to Castonguay, and are hopeful that they "will have more spectacular results to report on in a few months, when the tags from this new experiment will float up to the surface and start sending their archived temperature and depth data to satellites."
A silver American eel equipped with pop-up satellite archival tag and released off Nova Scotia, Canada.
The month of June honors both National Ocean Month and World Ocean Day (June 8). What better time, then, to check out photos of undersea life and be reminded that things "down there" are just as important as things up here on land. Here, a manatee goes about its day. The manatee, also known as a "seacow," is an air-breathing herbivore listed as a federally endangered species. Manatees are slow moving and can't swim quickly away from boats. This often results in collisions that can kill or injure them.
Life's a beach. Mom and her baby elephant seal roll around in the sand in Ano Nuevo Island, Calif.
A humpback whale breaches in the Gulf of the Farallones National Marine Sanctuary, off the coast of California.
A blue rockfish fans for the camera in Monterey Bay National Marine Sanctuary, in California.
A Southern sea otter, aka,
Enhydra lutris nereis
, wonders what all the fuss is about, at South Harbor, Moss Landing, Calif. The World Ocean Day Photo Contest entrant was Submitted by Dr. Steve Lonhart.
A white-lobed sponge brightens up the scenery. It's one of several images of rarely seen deep-sea animals that were captured on camera in Olympic Coast National Marine Sanctuary during a NOAA expedition. Researchers used a NOAA remotely operated vehicle in waters 328 to 656 feet deep off the Olympic Peninsula in Washington State. The research was funded by NOAA's Coral Reef Conservation Program.
This image brimming with colorful marine life is from the Pearl and Hermes Atoll. It's a huge oval coral reef within several internal reefs and is the second largest among the six atolls in the Northwestern Hawaiian Islands.
Having no backbone isn't always a bad thing! Just ask any octopus. These boneless invertebrates know how to squeeze into (and out of) many a tight spot. They have three hearts, nine brains and blue blood. (Two hearts send blood to the gills, while the third pumper sends it to the rest of the body.)
Rapture Reef sits within the Northwestern Hawaiian Islands Marine National Monument. The monument encompasses more than 140,000 square miles of ocean and coral reef habitat.
A sea turtle swims off of the Hawaiian islands.
This seal is eager to wriggle its way back to freedom, as divers release it from fishing nets. Marine debris -- such as these nets -- makes a serious impact on its surroundings. From being an eyesore on a beach to injuring marine life or stopping a 400-ton vessel at sea, it causes problems that are difficult to ignore.
Grey matter artwork? Nope! It's a sharknose goby (
) propped up on brain coral in the U.S. Virgin Islands.