Magnetic orientation & navigation system of European eels

Translated from : Bulletin Electronique

A dark and rainy, eels leave fresh water to begin a long and last trip of 6000 km to its breeding ground, the Sargasso Sea. How are the eels they can find their way into the Atlantic Ocean? Researchers may have found the answer: the eels would use the Earth’s magnetic field.

Place of reproduction

European and American eels breed both in the deep water and salt. The spawning area and the zone of growth have not always been so remote, but the drift of continents has forced the eels to dramatically increase their travel time (5-6 months) to reach the Sargasso Sea. To date, no adult eel has been caught or even seen in the Sargasso Sea.

This area is extremely broad and deep, making it expensive and difficult expeditions. Several attempts at tagging were held but no individuals have been followed long enough to determine the exact location of reproduction. However, these markings have shown impressive swimming depths of up to 600-700 meters, “says Caroline Durif, a researcher at the Institute of Marine Research in Norway Austevoll (Havforskningsinstituttet).

Mythical

Today, the eel has kept all its mysteries. For 2,000 years, scientists are asking questions about its reproduction. Heeding neither larvae nor eggs, Aristotle thought that the eel had no gender (neither male nor female), it was an example of spontaneous generation, caused by the putrefaction of algae. In the late 1800s, the first larva of eel has been identified in the Mediterranean. From other eel larvae (leptocephali) were harvested in Atlantic. It was not until the early 20th century a Danish oceanographer (Johannes Schmidt) found, after years of sampling, that smaller (younger) larvae were located in the Sargasso Sea and that s’ therefore acting in the place of reproduction. But how eels are they then able to find these clear waters? Starting from the Norwegian coast, this is a journey of about 6000 km.

Using Earth’s magnetic field

Animals have many ways of moving in space. Some sail through the stars, others through their nose, or by following the ocean currents. But for a fish swimming at great depths, the earth’s magnetic field provides a reliable and this day and night.

The eels, which come from localities far apart from each other (northern Norway, Morocco, not from Mediterranean countries) require a navigation system for effective and accurate return to the same place and same time for reproduction . The perceived intensity of Earth’s magnetic field is theoretically possible to sail to the Sargasso Sea. It is likely that eel integrates a sort of map for the journey, she will use to return, “said Caroline Durif, is the assumption that it has tested with his colleagues at the Institute of Marine Research .

From North to South

This lab is almost unique in the world (this study and the experimental setup have been funded by the Council for Scientific Research Norwegian: Norges forskningsråd), magnetic north is changed each night to test the effect of orientation of the eel. Eels are isolated in a basin in the dark during their migration period in autumn. The coil giant to change the direction and intensity of the magnetic field, then by an infrared camera to observe the behavior of the eel. Caroline Durif was initially surprised when eels oriented themselves preferentially towards the east and north, which was simply not the direction of the Sargasso Sea (southwest). However, these directions correspond perfectly to those that have been taken out of the fjord or the eels were caught. It seems that the young eels learn the way to go back to the opposite when they leave the rivers and inland waters, “she says.

It is a discovery that has important implications for the management of this endangered species. The current management measures advocated moving the young eels which are located in areas at risk to less polluted areas, where fishing is less important and dams absent. But if these individuals are suddenly moved to unknown areas they would not find no way back and are therefore unable to reproduce.

A GPS

The study showed that the eel was sailing through the magnetic field. This intensity varies with latitude and allows the eel and other animals to determine their position on the earth. It’s a bit like a GPS, “says Caroline Durif. For now, researchers do not know the precise physiological mechanisms behind this system or any component of the magnetic field is perceived by the eels.

Eels are not sexually mature when they leave the inland waters. The factors that trigger this maturation are not known and is one reason why the European eel farming is far from being controlled. Experiments have shown that the magnetic field can affect the physiology of migratory species. Durif intends to examine the effect of the magnetic field present in the Sargasso Sea on the onset of sexual maturation.

European eel

• catadromous (breeds in salt water, grows in fresh or salt water)
• the European eel is highly endangered: recruitment is currently between 1 and 5% of pre-1980 levels
• on the red list of threatened fish species
• the sharp decline is due to overfishing, pollution, disease, construction of dams in the context of hydropower development and climate

Links :

• Caroline Durif, PhD Thesis (in French) : the downstream migration of the European eel
  
• Magnetoreception and magnetic compass orientation in European eel
• BBC News : Eel reveals its migration secrets
• ICES : Eel stocks dangerously close to collapse
• Eels french cooking video with Maïte
  

A regatta in Portofino on Wally yachts : what else ?

Next month will see the launch of the Nespresso Cup , a new international regatta gathering for the very first time exclusively the Wally Class.

This first edition of this sailing competition will be held from 7 to 9 May 2010 off the coast of Portofino in Italy. In all, 15 competitors will compete for three days (two races per day) with the participation of famous racers such as Loïck Peyron, Francesco de Angelis and Paul Cayard...

Peyron commented: "I've always found Wally Yachts very seductive, and am looking forward to finally experiencing them first hand on the race course during the Event. The spectacular venue of Portofino will be the perfect location for such an event."

I can figure out.

In 1989, I met Mr Luca Bassani Antivari, founder of Wally Yachts onboard of a custom Baltic yacht which he christened 'Wallygator' for the cartoon character his children loved, just before he decides to build (with Luca Brenta yacht designer) a brand-new Wallygator, an innovative 83-foot carbon fast sailing composite sloop in a 'Wally style' (now named Mr Gecko).

This first Wally yacht proved to be fast and easy to sail, the 'flush deck' was as cleared as the one of an aircraft carrier, and Luca Bassani got a yacht on which he could cruise shorthanded with his family, but also allows him to compete around the buoys in maxi races or in transatlantic events.

Sailing aircraft or flying yacht ?

Some aircraft called S4-sail-6P, convertible in sailboat has been designed by Octuri (aka Yelken Octuri), who usually works in aeronautic industry in Toulouse (France) and wanted a four-seat aircraft that can be transformed into sailing at will.

The wings of the aircraft become the sails of the boat, they are indeed able to stand up and bow at different angles to follow the wind direction.

The aircraft has two propellers, which are arranged on the tail of the plane, one behind the other. The cockpit can be opened during the boat trips through a sliding glass canopy and finally, both located under the glass roof panels can be arranged in a horizontal position for the amphibious boat mode, in order to enlarge the living space cockpit.

Futurist concepts for the pleasure to dream.

Links :

• Octuri design agency / Trimaran sailing yacht convertible to seaplane
• N.Z. Inventor creates Flying Hovercraft
• Transaquatis Wing In Ground-effect (WIG) ship
• Ekranoplan WIG flying ship
• Talspace Seagull trimaran-type WIG craft
• SeaPhantom, speed boat based on NASA's Lifting-Body Airfoil design

French National Library online exhibition : the Unknown Sea

The French National library (BnF) presents a major online exhibition issued from a real exhibition which occurs from October 2004 to January 2005 at the BnF on the subject of the sea, entitled "La Mer, terreur et fascination" together with a pool of documentation and research centers on oceanology from Brest (Brittany, France).

The online exhibition presents the sea element through a scientific, artistic and imaginary approach.

Exhibition materials include manuscripts, illuminations, engraving, maps, literary and scientific texts, paintings, musical works, audiovisual workstations and films.

The time span ranges from the 13th century to present-day materials.

The Maps section contains pictures and short historical and cartographical descriptions of European and Arabic mappamundi, T-O maps, portolans, Ptolemy's Cosmographia and the Catalan Atlas.

The Island section shows and describes the depiction of islands in several historical documents like Medieval manuscripts, Ortelius' Parergon and the sea atlas of Bellin.

Links :

• Magnificent maps (The Guardian article)

Ocean acidification : the other CO2 issue

ACID TEST, a film produced by NRDC, was made to raise awareness about the largely unknown problem of ocean acidification, which poses a fundamental challenge to life in the seas and the health of the entire planet. Like global warming, ocean acidification stems from the increase of carbon dioxide in the earth’s atmosphere since the start of the Industrial Revolution.

Leading scientific experts on the problem, many of whom appear in the film and the outtakes below, believe that it's possible to cut back on global warming pollution, improve the overall health and durability of our oceans, and prevent serious harm to our world, but only if action is taken quickly and decisively.

Our oceans feed the world, provide jobs, and generate most of the planet's oxygen. Oceans cover 71 percent of the earth and contain more than 97 percent of the world's water. Our survival literally depends on their health. And yet few people realize that the oceans are suffering from a grave affliction caused by increased carbon pollution.

More than one quarter of the carbon dioxide from burning fossil fuels enters our oceans, where it makes the water more acidic. Scientists have just recently discovered that this rising acidity is threatening ocean life as we know it.

This documentary give our lawmakers - those with the power to limit carbon dioxide pollution - the opportunity to better understand what is happening to our seas due to our dependence on fossil fuels. It vividly illustrates what is happening to our oceans, and offers solutions to revitalize them.

Excess carbon dioxide is making marine waters more acidic, which causes a drop in carbonate, the key component in shells. When carbonate levels fall, it is more difficult for organisms to make their shells, which become thinner and more brittle.

Ocean acidity has increased an average of 30 percent since the industrial revolution. If we continue to dump carbon dioxide into our seas, ocean acidification could result in a "global osteoporosis", harming not only commercially important shellfish, such as lobster, crabs, and mussels, but also key species in marine food webs such as corals and plankton. That could send shock-waves up the food chain, threatening fish, birds, and mammals.

Rising ocean acidity will also hit our economy hard. In the United States alone, ocean-related tourism, recreation and fishing are responsible for over 2 million jobs. Indeed, the U.S. ocean economy creates two and a half times the economic output as the agricultural sector, contributing more than $230 billion to the nation's GDP annually.

We don't have to watch these economic opportunities evaporate in the face of acidification.

We can take steps to turn back the tide.

Links :

• Jean-Pierre Gattuso blog about European Project on Ocean acidification (EPOCA)
• NOAA PMEL Ocean acidification homepage
• BBC news
• An ominous warning on the effects of Ocean Acidification (Carl Zimmer)
• What's the worst that could happen? (Greg Craven)