Bamboo and flood debris lead to eels stranding

An alert member of the WBRA spotted numerous dead eels at the mouth of the Waiorongomai Stream at the south end of Waikawa Beach. He alerted us, but also went directly to the Greater Wellington Council, as it’s in their district. Daan said on 16 March 2021:

Last weekend we walked as usual on the beach in the direction of Otaki. In the stream that flows from the lakes to the sea, we noticed a large number of dead eels. From the outside, there appeared no damage to the animals (other than being picked at by gulls) which makes one think of (agricultural) poisoning.

Eels not surviving is not a good sign, as typically these animals can deal with pretty poor water quality before dying.
I have informed the Greater Wellington Council, who have assigned their duty officer Nicola Fenn to the case.

Dead longfin eel.
Dead longfin eel. Photo by Daan.
Mouth of the Waiorongomai Stream on a map.
Mouth of the Waiorongomai Stream on a map.

Nicola Fenn soon replied:

Yesterday I attended the stream mouth and have found … that the cause of the eel death is because fish passage does not exist due to the invasive bamboo as well as flood debris within the river mouth. Eels essentially became stranded on the beach and perished.

Since, we have contacted Iwi, our Pest Plant Control, GWRC Land Management and Flood protection about getting the consents necessary to get the mouth cleared as well as control of the invasive plants including the black seeded grass within the channel.

Thanks for notifying us and hopefully we will be able to get the stream managed with the bamboo and beach debris cleared with a management plan for future maintenance to be carried out.

Thanks Daan, for notifying us, and for taking action to help protect the eels.

One thought on “Bamboo and flood debris lead to eels stranding”

  1. I have seen this in the past. It is more likely that the eels are migrating to the sea to spawn in the ocean as they do in Autumn every year when they reach a certian age.

    Shortfin males migrate in February–March, and longfin males in April. The females soon follow, and both males and females die after spawning. Studies show the species also migrate at different ages:

    Shortfin males at an average of 14 years (38–58 centimetres), females at 22 years (50–100 centimetres).
    Longfin males an average of 23 years (48–74 centimetres), females at 34 years (75–180 centimetres).

    The Waiorongomai Stream mouth has been very dry this year, even longer than previous years, not a lot of rain to fill the swamp behind and keep it flowing.

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