Information from Wikipedia.
Longfin Eels are a type of eel residing in New Zeland.
Like other members of the Anguillidae family, Longfin Eels have a rather unusual migration system where they grow and mature into fertile adults in freshwater water systems then migrate to the sea to breed; a catadromous breeding system.
This breeding system also ensures that their mating system is randomised.
The New Zealand Longfin eel is a very long lived fish with records of females reaching 106 years old and weighing up to 24 kg. Longfin Eels have the slowest growth rate of any eel species studied, growing between 1 - 2 centimetres a year.
Male and female Longfin Eels differ in length and in the age at which they migrate with males averaging 666 mm but reaching up to 735 mm in length with an average age of 23 years (12 – 35 years). Female Longfin Eels are considerably larger with an average length of 1156 mm, but can range from 737 to 1560 mm. These females range in age from 20 to 60 years before migrating. The average age of migration varies between the North and South Islands of New Zealand with the North Island eels having younger migration ages and thus faster generation times.
Longfin eel blood contains neurotoxin. Making it highly deadly if it gets in a wound or in the eye. It takes four teaspoons of longfin blood too kill a human being.