Four large eels have been found dead in the Kākāriki Stream, under Waikanae's David St bridge, in mysterious circumstances.

Kāpiti Mana Forest & Bird chairman Russell Bell was saddened by the deaths.

"They hung out under the bridge in the shade during the day and I used to see them hunt up and down the stream during my evening walks.

"Eels can spend 20 to 60 years and longer in New Zealand rivers, lakes and wetlands depending on species.

Advertisement

"They eat insect larvae, worms and water snails, then as they get bigger, fish and fresh-water crayfish.

"They only breed once in their lives, at the end of it, in sub tropical waters.

"Consequently, their population is determined by those returning to the sub tropics to breed, having survived life in New Zealand.

"Humans, dams and perched culverts, habitat loss and water quality have caused their decline.

"I can't tell whether someone killed these four deliberately or accidentally by something like cement wash entering the waterways."

Mr Bell said long finned eels are classified as 'at risk — declining' and only live in New Zealand, while short finned eels are not threatened and also live in other Pacific countries.

"We are lucky in Kāpiti.

"We can still look from a bridge and see whitebait.

"We can hear morepork at night, see reasonably rare birds such as bellbirds and grey warblers, fern birds and even New Zealand dotterels.

"Our native birds, fish, wetlands, estuaries and forests are part of what attracts many of us to the Kāpiti Coast.

"Eels are also part of our heritage and our taonga.

"We need to be mindful of the effects our actions have on the natural world surrounding us."