By Emily Funnell, Technical Advisor – Aquatic and Reporting Unit

Earlier this year we carried out a survey in some of the ponds and bog tarns in Southland’s Waituna catchment.

This work was undertaken as part of DOC’s Arawai Kakariki wetland restoration programme in the Awarua-Waituna Wetlands.

Waituna Wetlands

We have always known that giant kōkopu, kōura/freshwater crayfish and other species can be found lurking in in the tarns and ponds, but we have never known how extensive their habitat was.

Freshwater crayfish/kōura

In April we had a peek in a number of ponds all around the catchment, many on public conservation land, but also a few on private land.

Surveying in the Munroe Dam

I would like to be able to say that we found these waterways teeming with fish, but unfortunately only a couple of sites fitted this description.

Giant kōkopu in the Waituna catchment

Giant kōkopu and other freshwater species were largely absent from most of the catchment ponds, except at the Munroe Dam and in the tarns on the southern side of the lagoon. These two sites had more giant kōkopu than we could shake a stick at, and with a good range of sizes.

Giant kōkopu

Unfortunately, the ponds and tarns around Carran Creek, and those to the west of Waituna Creek, were all devoid of freshwater fish. This indicates that we may have been overestimating the use of these habitats by fish—with fewer populations than we thought.

Network of bog tarns at Waituna Lagoon

So, what is the value of this information? We now know where the secure populations of giant kōkopu are in the catchment, so we can carry out more focussed investigations and management.

Cicada at Waituna

The beauty of these sites is that there are few threats to them in their isolated locations. With little habitat change, we anticipate that these populations will be around for a long time.