Fresh water Fauna (Eel)

Fresh water Fauna (Eel)

by | Sep 19, 2015

Eels can often be spotted from the Jetty at Lake Mapourika, and are abundant in most freshwater eco-systems around New Zealand.  The size of the Eels found in Lake Mapourika can be a little unnerving, although when you get to know a bit more about them, fascination overcomes the fear!  They are truly a unique fish.

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Being one of the main food sources for the local Maori people, and also an important part of the ecosystem, the fresh water Eel is one of the most predominant fish in New Zealand fresh water systems.

 

Here are some interesting facts about the freshwater Eel:

 

 

  • Eels can climb waterfalls up to 20 metres high!

 

  • Fresh water Eels rely on the water salinity (salt) levels in order to determine their gender. When the salinity level is high in the water the eels will become male, this is a common occurrence in streams near the ocean as well as lagoons.

 

  • In order for the Eels to become female they must reach water with low levels of salt in the water, e.g fresh water lakes and rivers in the high lands. This is a major reason why the fresh water eel is endangered, as many fresh water rivers and lakes are now dammed to produce electricity.

 

  • There are two species of freshwater eel, the longfin and the shortfin. They are both super slow growing, the longfin especially may only grow approximately 15-25mm per year, that’s roughly the length of a paper clip per year!

 

  • Some of the biggest longfin eels recorded were 40kg in weight, and have been estimated to live to around 60 years.

 

  • When they are small eels eat live food such as insect larvae found in the rocks underwater, as well as worms and snails. When eels get bigger they start to eat other fish, fresh water crayfish and have even been known to snatch tiny ducklings from the waters surface

 

  • Eels breed only once, at the end of their life. When they are ready to do this they leave the fresh water and swim over 5000 km through the ocean from New Zealand to the deep trenches near Tonga, where they then spawn and die.

 

  • It takes decades for eels to mature to the age to mate, the average age for males is 23 years old, and 34 years old for a female.

Here’s a big one spotted from the Kayaks last summer:

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So come on out to the lake with us where you can spot this incredible species for yourself!

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Thanks for reading, and catch you all next week!