Fishy business at Taitua Arboretum

15 MARCH 2007

An increasingly scarce breed of fish has been found at Taitua Arboretum and Council is working in partnership with DOC to ensure its preservation.

A population of giant kokopu, numbering between 15 and 20 adult fish, has been located in a lowland stream area of the arboretum. A connecting spring appears to have enabled the species to prosper by maintaining its favoured lowland stream habitat.

The finding of this population of the fish is significant for two primary reasons.

Firstly, giant kokopu is a chronically threatened species across New Zealand and the rarest of the six whitebait species. Waikato was traditionally a stronghold for the species due to its high availability of lowland stream habitats. Extensive clearing of land and agricultural development have gradually eroded the giant kokopu’s habitat so the species is now found to exist in pocket populations throughout New Zealand, of which the Taitua population is one.

DOC spokesperson Michael Lake says the Taitua Arboretum population of giant kokopu is also significant because it may be landlocked from the sea.

“Normally the start of the giant kokopu’s life cycle includes a short time spent out at sea before the young fish return to fresh water and migrate upstream in search of a suitable habitat. To get to Taitua Arboretum, the giant kokopu would not only have had to swim up the Waikato River, Waipa River and Ohote Stream but have also negotiated around 3km of farm drains and several small dams which is a big ask for a young giant kokopu.”

Council’s Parks and Gardens manager Bill Featherstone says that Council will work in close consultation with DOC to ensure that the giant kokopu population continues to thrive at Taitua Arboretum.

“The giant kokopu population is an exciting find for several reasons and Council is working closely with DOC to ensure that these fish are well protected.

“Taitua Arboretum has retained a degree of original swamp land water through the creation of ponds and retention of a high water table. It’s the preservation of this eco-system, which has become increasingly rare in Hamilton and the surrounding region due to growth and development, that has enabled the giant kokopu population to flourish at the arboretum.

“While the species’ nocturnal habits make it difficult for the public to see them by day, we encourage all Hamilton residents to take their presence as a reminder to keep drains and water infrastructure as clean as possible. Declining species such as the giant kokopu rely on clean bodies of water to boost their populations and find habitats in which they can thrive.”

Mr Lake says the protected Taitua environment has been the key factor in the giant kokopu population’s ability to thrive.

“The protected and well maintained environment provided by Taitua Arboretum and good land management practices that are implemented there have protected this giant kokopu population and allowed it to persist. Factors such as good fencing and planting around streams are all contributing factors to maintaining the species’ habitat at Taitua.

“DOC is in the process of implementing a national recovery plan to protect giant kokopu and other whitebait species. Important objectives of the plan include identifying, managing and advocating for the protection of habitat and migratory pathways, trialling habitat restoration and recruitment enhancement, and identifying and protecting unique land-locked populations.

“The giant kokopu at Taitua Arboretum are either land-locked or using extraordinarily strong migratory behaviour to find their preferred habitat. Either way this population is of great scientific interest to DOC and could help us learn how to better protect this threatened species throughout New Zealand. We look forward to working in close partnership with Hamilton City Council to safeguard and study these fish.”

The giant kokopu is perhaps best known in Hamilton for being the aluminium fish on all catchpits throughout the city as part of Council’s Fish on Drains campaign that addresses water quality in fresh water urban streams.

ENDS

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