Hunt on for giant kōkopu

Recent DNA sampling of water from Nukumea Stream in Ōrewa showed a lot of fish life, as well as birds and even rats passing through.

However, scientists were surprised that it did not pick up any DNA of giant kōkopu – a threatened species previously released in large numbers into the stream.

The sampling was undertaken by the environmental group Whitebait Connection, which is supported by the Hibiscus and Bays Local Board to work with schools in protecting and restoring freshwater environments.

Auckland programme coordinator, Sarah Dimitrijevic, says as it was a single sample, the results are only a guide.

She was happy to see that another threatened species, inanga, are present.

“We were concerned about inanga numbers as we had worked to restore their spawning habitat. In 2019 we had a number of sediment pollution events and last year surveying was very limited, so it was nice to see that our planting had developed to allow fish to lay eggs,” she says. “On the other hand there were plenty of pests found – including the mosquito fish, which is a significant problem in poor quality water. Improving water quality gives native fish a chance to out-compete these.”

Sediment continues to affect the stream and Sarah says water clarity has dropped this year due to sediment whenever there’s heavy rain. “Part of that is a natural process, but more development will increase the problem. It is imperative that any new development adheres to best practice sediment management.”

In late March 2019, 1000 giant kōkopu were released in the stream in a project led by NIWA. However, Sarah says about a week after the release there was a massive sediment deluge (HM April 17, 2019).

“We did find some after that, but not many,” Sarah says. “Certainly not all of them would be expected to survive, regardless, but heavy sediment is particularly detrimental to certain native fish including kōkopu.” 

The hunt is now on to find live giant kōkopu.

A full fish survey will be undertaken in mid-August, including placing two large nets and up to 10 smaller ones over 200m of the stream. Sarah says the traps are checked regularly and it is important that the public leaves them alone.

Local volunteers work with Whitebait Connection on things such as monitoring water quality – if you’d like to get involved, email sarah.d@whitebaitconnection.co.nz

More than just whitebait: Of the five fish species consumed as whitebait, four are threatened with extinction, including inanga and giant kōkopu. One, banded kōkopu, is not currently threatened. • Inanga and banded kōkopu are in Nukumea Stream, and the search is on for giant kōkopu, pictured, which were released there as a trial to increase their numbers. • Giant kōkopu can grow to more than 50cm. They live in streams with overhanging vegetation as they feed on fallen insects. Their threat status is listed as ‘declining’ – the same as North Island brown kiwi and little penguin/kororā. Source: Forest & Bird