September 10, 2023

Decline of Tuna

Decline Of Tuna

The long decline of the Long Fin Eel
in Taylors Stream, Merivale

by Peter Bishop, 11 years
Heaton Normal Intermediate School

Aotearoa has, for an extraordinarily long time, been host to a beautiful array of animals that have been living safely and happily in our lands. However, much to the dismay of many New Zealanders, many of the aforementioned creatures are going the way of the Dodo. This Think Piece specifically discusses the longfin eel/tuna of the Ōtākaro/Avon River, located in Christchurch/Ōtautahi and around.

The Ōtākaro/Avon River and Ōpāwaho/Heathcote River run through all of Christchurch/Ōtautahi, and is home to the largest freshwater eel in the world. They swim to the area from a mysterious place near Tonga to live the lion’s share of their life here in one of Aotearoa’s rivers, lakes and wetlands, whose lives have already been shortened from 80 years to around 40 years on average.

With the increase of Ōtautahi’s population, the city which had once been swampland has been drained a long time ago and the homes that inhabit it have grown closer and closer to the lands around the rivers. As a result of this the developing city has almost “swallowed the wetlands whole” so to speak leaving only the main awa and their feeder streams. Me and the other students of my class are extremely worried that the humans of the area are not adequately taking care of the rivers of the Banks Peninsula, and especially Christchurch/Ōtautahi. If you live in river areas containing eels, or if you can sacrifice some of the time in your day to save the tuna, what can you do to help them survive and thrive into 2070? If you know anybody around these areas could you encourage them to do certain things that would help all the eels in the area?

These are all valid questions and we wish to answer them all before the end of this Think piece.

If you want to help you could gain permission to plant native plants in areas around the Ōtākaro/Avon River and Ōpāwaho/Heathcote River to protect the stream banks to make them strong and provide shade and food source for the tuna. These plants can also filter dirty water that might flow from the river banks in rain. Firstly you have to make sure that there is a plethora of native plants in the area around the bank to prevent the spillage of dirt to the stream and so when it rains into the stream and to help filter the dirt/sediment. This strategy works well although there is always the risk of the plants falling into the streams which are horrible for the eels as well as it means more mud in the awa which takes oxygen out of the river. This also suffocates plants that grow in the stream, so it is quintessential that you are placing the plants in a way where they both cover the surrounding dirt so it doesn’t get wet and then collapse into the river.

Decline of Tuna

Me with the cap next to Arapata Reuben

Another tip you can use is also to be sure that you never drop any lawn trimming or leaves and rubbish into the river where it could cause the eels of the river to starve as the grass will rot into mud and cover the bottom of the awa in sediment where bugs live, one of the main food sources that keeping them from dying. Tuna should always be treated with much respect and until they are thriving in the city awa and they should never be fished in the city while the population is declining, and especially not if they have a larger size than average due to the factit most likely means that they are female tuna and thus if hunted they can not reproduce, lowering the world population.

All these actions will help the habitat of the tuna. The best strategy is to just spread information to cause awareness of this issue, as I never even thought of it until Jenny from the Te Tuna Tāone project came. She showed us around Taylors Stream, and got us to explore the awa and we found this problem, where we worryingly only found a grand total of two eels.

The other thing we all need to do is to make sure you don’t drop anything into the gutters and drains around our streets. As in most of Ōtautahi the muck/litter/dirt you see in our gutters and drains is not picked up very often or filtered. Instead, it is ejected via underground pipes straight into the rivers, not a filter system, this is called the stormwater system.

It will take the positive actions of everyone, over many decades to have a single tuna/eel survive as long as they used too. Before the tuna’s habitat was changed by humans, eels used to often live for longer than one hundred years each, now we are lucky if they live to 60 years. If we want them to return to their long natural life, in a modern world, they will need every bit of help they can get from all of us from you and you.

Can you do your bit?