SEA WEEK 2021 – Our amazing eels

SEA WEEK 2021 – Our amazing eels

Posted on March 7, 2021


Breaking the NZ travel bubble (all the way to Tonga).

What’s the first thing that comes to mind when you think of an eel? Slimy? Scary? River monsters? World traveller is unlikely to be high on your list, but it should be. Our wonderful eels don’t spend their entire lives lurking in our rivers, streams, and lakes. At the end of their lives, they make their way out of their freshwater homes, head out to sea, and manage to swim about 2500 km to the tropical Pacific Ocean.

So why do they do this? It’s to breed, a thing that they do only once in their lives. When the time is right, an eel’s instinct makes it swim down river, into the sea and across the ocean to deep waters near Tonga. Once there, female eels lay millions of eggs that are fertilised by males. After this, the eels die.

Eel eggs turn into crazy looking see-through baby eels, like the picture below. These babies make it to our shores by drifting on ocean currents for 9-12 months. Once they find the stream or river they want to call home, they change into a more eel-like shape and head upriver.  Once in their new homes, they spend their lives eating fish, grubs and even the odd duckling and when the time is right, the ocean calls them, and they head downriver again. And so, the circle of life continues.

So next time you see one of our eels, perhaps at the lakes in Pukekura Park, or the bridge at the Huatoki Plaza, remember these amazing creatures aren’t just slimy, they’re world travellers. They made their way from the pacific as wee babies, and will go all the way back again when they’re ready to breed and die. That’s one hell of a life story.

A few facts on our eels:

  1. The Maori name of eel is tuna.
  2. We have two main species of eels that live in NZ:
    1. Longfin eels. Only live in New Zealand, nowhere else in the world.
    1. Shortfin eels. They live in New Zealand, Australia, and the Pacific.
  3.  Our Longfin eels are one of the biggest and longest-lived in the world. They can live for 100 years, can grow 2m long, and can weigh more than 20kg.
  4. The number of eels in New Zealand is much less than it used to be, mostly due to fishing, the dirtying of fresh water, and loss of safe places for them to live. Longfin eels are classified as ‘at risk- declining’ which means their numbers are going down, and if this keeps on happening, they may face extinction.
  5. To help protect our eels try and keep our waterways clean, and make sure there are easy pathways for eels to head up and down rivers, streams, and lakes.

For more information please visit:

https://niwa.co.nz/te-k%C5%ABwaha/tuna-information-resource/biology-and-ecology/migrant-tuna-tuna-heke
https://www.doc.govt.nz/nature/native-animals/freshwater-fish/eels/freshwater-eels-in-new-zealand/
https://niwa.co.nz/te-k%C5%ABwaha/tuna-information-resource/biology-and-ecology/life-cycle-and-leptocephalii

An eel larva. Credit: Miller, 2009.

Reference:

Miller, M.J., 2009. Ecology of Anguilliform Leptocephali: Remarkable Transparent Fish Larvae of the Ocean Surface Layer. Aqua-BioScience Monographs 2(4). DOI: 10.5047/absm.2009.00204.0001