Eels are ancient creatures that evolved over 50 million years ago.
There are 15 species of freshwater eels found around the world.
A female longfin can grow to almost two metres long, weigh more than 25 kilograms, and live to be over 100 years old.
The oldest longfin on record was 106 years old.
Longfins breed just once – at the end of their lives.
Males are generally ready to breed at 25 years old, but females until about 40 years old, and sometimes much older.
When ready to breed, eels travel an astonishing 5,000 kilometres to spawning areas in the tropic Pacific Ocean.
At the spawning area, females release up to 20 million eggs.