Concern for wai kōura

Channell Thoms (Ngāti Kurī) hopes her  tau kōura will catch some freshwater crayfish.

Channell Thoms (Ngāti Kurī) hopes her tau kōura will catch some freshwater crayfish.

Most of us are familiar with the marine species of kōura (crayfish), but have you ever seen a wai kōura (freshwater crayfish)? Wai kōura were recognized as taonga species for Ngāi Tahu whānui in the Ngāi Tahu Claims Settlement Act (1998). They are still popular eating today, with a few aquaculture facilities even growing them as a delicacy. There are growing concerns though that wai kōura need some help.

Whakaora Te Waihora (WTW) staff have been out hunting during recent months, trying to find out where wai kōura are hiding in streams around Te Waihora (Lake Ellesmere). The aim is to find out how widespread wai kōura are, and to see if there is any way to protect existing populations by habitat restoration.

Wai kōura were once very commonplace but due to the removal of riparian vegetation and the introduction of the predatory trout, Paranephrops zealandicus, the wai kōura species found around Te Waihora, is now classed as ‘At risk – declining’ by the New Zealand Threat Classification System. As they are found nowhere else in the world, there is even more reason to protect them.

Whakaora Te Waihora staff have tried two methods of finding these cryptic critters – spotlighting and tau kōura. Spotlighting is great nighttime fun where you shine a strong spotlight into a stream- particularly along the sides and on the weed-beds where wai kōura like to hang out when hunting at night. If a wai kōura is looking towards you, their beady eyes reflect back in the spotlight like red stars.

Freshwater crayfish - wai koura.

Freshwater crayfish – wai koura.

Tau kōura are bundles of bracken fronds tied together then sunk to the river or lake bottom. The bundles make good homes for the wai kōura, who use them as hidey-holes during the daytime. They have been used traditionally to catch wai kōura, for example by Te Atiawa in the Rotorua lakes. The bracken bundle is left in a stream or lake for a few weeks, then brought up carefully with a net underneath to harvest the catch.

The tau kōura were not so successful in catching koura when used around Te Waihora. In fact not a single one was caught. Although this is partly due to a few technical problems – such as members of the public pulling them out of the water – they may also have been absent from those sites. Spotlighting did identify some sites where wai kōura are present but there were far more sites where they were absent.

Wai kōura seem to be found at sites where there are weed beds. Food for thought for those who regularly clear out the weeds in their drains or stream – they may be harming the chances of survival of any wai kōura present. Other studies have shown that native vegetation along a stream also helps wai kōura – one more reason for us get out a spade and start planting.