The European eel (Anguilla anguilla) has puzzled people for thousands of years. No one could find their eggs.
The Greek philosopher Aristotle thought that European eels might be sexless and regenerate spontaneously from mud. In central Europe, myths abounded about mysterious matings between snakes and fish.
It wasn’t until the 1920s that Johannes Schmidt was able to provide a realistic hypothesis. Through painstaking data-analysis of young eels collected in the Atlantic Ocean and the Mediterranean Sea, Schmidt narrowed down the potential spawning site to the Sargasso Sea. The Sargasso Sea is a region of the Atlantic Ocean, roughly northeast of central America, about 5,000 to 10,000km from the known habitats of the adults. The youngest European eel larvae have been found in this sea and nowhere else (by Schmidt and other scientists after him).
How the eels navigate this distance is still unknown
The idea grew that adult European eels migrate thousands of kilometres to spawn and hatch in the Sargasso Sea. It lacked direct evidence but remained the best one. In the last 10 to 15 years, satellite tags helped track adult European eels from several locations in Europe to the Azores islands.
Last October, new research showed that European eels migrate to the Sargasso Sea. Eels captured in the Azores islands were tagged and then observed to continue their journey to exactly where they were expected – the Sargasso Sea, over 5,000kms away – an incredible journey! But the story does not stop here, how the eels navigate this distance is still unknown.
Unfortunately, the European eel is a critically endangered species, with an estimated 95 per cent decline in juveniles since the 1980s. We can now answer Aristotle’s question of where the European eels come from. Let us hope that we don’t have to ask another question in the near future; where did they go?
For more, Scientific Reports study check here.
Sound Bites
• Only nine per cent of plastic produced is actually recycled. Experts agree that the way to tackle the problem of plastic pollution is at its source – by reducing the amount of virgin plastic used. It might seem heartening to hear Fortune 500 companies make pledges to reduce their plastic footprint. However, a new study found that these same companies have not made any efforts to change their operations to actually reduce plastic production.
• Annually, about 20 million sharks are caught accidentally on long lines trying to catch fish like tuna and swordfish. Now, one-third of sharks are threatened with extinction. A new invention called ‘SharkGuard’ has been designed to solve the problem. The device emits a short-range electric pulse that repels sharks. A trial in the Mediterranean Sea showed a lot of promise with 91 per cent fewer sharks caught.
DID YOU KNOW?
• There are polar bear ‘jails’ in some Arctic towns like in Churchill, Manitoba, Canada. The bears are released in winter so that they can hunt on the sea ice.
• Some Arctic and Antarctic fish have the same antifreeze protein in their blood that allows them to live in sub-zero temperatures. The same protein evolved twice.
• In the Antarctic, a breeding colony of icefish covering an area the size of Malta has been found. The nests are evenly spaced with one fish per nest keeping watch.
• Underground dens of Arctic foxes create heat and enrich soil, resulting in patches of denser vegetation that helps herbivores survive the winter.
• Antarctic blue whales (the largest whales) were almost wiped out by whalers. Following a ban in the 1960s, these animals are now making a comeback.