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Eels found living in Auckland stream that doesn't flow to sea - How did they get there?

It’s a discovery that’s boggled the minds of two expert ecologists - two eels living in a stream below Auckland's Grafton Bridge – a stream which runs into nothing.

It poses the question: How did they get there?

The Waiparuru stream runs along the gully 50 metres below the bridge.

Auckland Council freshwater ecologist Matt Bloxham and ecologist Nick Goldwater told 1 NEWS they were surveying the area one evening for bats.

“We wandered down to the stream, we put on our spotlights and about half way up under the little wooden bridge we saw some movement. On closer expectation there was this lovely 70cm shortfin eel,” Nick says.

Matt says it’s a big deal because there is absolutely no connectivity to the sea.

He says the only feasible explanation is the city's drain pipes.

“They must have slithered their way from the sea, up through the pipes and somehow wriggled the rest of the way on land to the stream – which is remarkable as it’s about a 35m incline and about 2.5 kilometres of pipes.”

But this adventure story has a sad side.

“I guess the tragedy is they're never going to be able to get back to the sea to complete their life cycles. Their story sort of begins and finishes here,”  Nick says.

The eels aren’t the only pair to slither their way into the stream.

A banded kōkopu was spotted during 1 NEWS’ visit to the stream.

The fish is one of five species in the whitebait family and the ecologists say for a coastal fish, it’s again a head scratcher as to how it’s made the journey.

With the Waiparuru Stream teeming with life again, Auckland council saying it’s planning to invest $20,000 to keep the ecosystem ticking along.

There’s even a proposal to introduce kōura, otherwise known as freshwater crayfish.

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One scientist says the only feasible explanation is the city's drain pipes. Source: 1 NEWS