Archives For Waituna

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 sign. Photo: itravelNZ | CC BY 2.0.

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.

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 for freshwater fish at Munroe Dam.

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. Photo: Andy Hicks.

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. Photo: Andy Hicks.

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.

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. Photo: Andy Hicks.

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.

By Sarah Thorne, Awarua Wetlands Project Manager

It sounds like a bad joke. What is green, stringy and lurks at the bottom of Waituna Lagoon? The answer is Ruppia. Or it should be. But right now the future is not looking very green for this aquatic plant.

Ruppia on a shovel.

The life support system for Waituna Lagoon

So what is Ruppia?

Ruppia is a green, salt tolerant aquatic plant that grows on the floor of Waituna Lagoon like a meadow of long wavy seagrass. It’s essential for a healthy lagoon and is the life support system for the lagoon.

Just like grass, its roots hold the sediment together. Its leaves use up nutrients and create oxygen and they also provide a home for fish and aquatic invertebrates to live. It is even a meal for some fish and wildlife.

Without Ruppia the water quality declines, animal numbers decrease and the lagoon could become dominated by algae. Put simply: healthy Ruppia means a healthy lagoon and healthy fish.

A clump of Ruppia at Waituna Lagoon.

Ruppia is very sensitive to water levels

What’s up?

DOC has just received the latest annual monitoring report from NIWA, which describes the health of the ruppia beds in the Waituna lagoon. This year’s results recorded the lowest number of sites with Ruppia and a reduction of overall cover of Ruppia since annual monitoring began in 2009. One of the species—Ruppia megacarpa, was only found at one of the 48 monitoring sites. Nuisance algal species that cause algal blooms and could smother Ruppia plants were also recorded in the lagoon during the monitoring.

Ruppia growing in sediment at Waituna Lagoos.

A recent NIWA report describes the health of the ruppia beds

Why should we be worried?

We know that Ruppia is very sensitive to water levels, salty conditions during spring germination, nutrient loads (nitrogen and phosphorous) and water clarity. Even though some overseas species of Ruppia are marine species, ours are freshwater and estuarine species that are only tolerant of salty conditions as opposed to being salt lovers

Ruppia growing on the floor of Waituna Lagoon.

Ruppia grows on the floor of Waituna Lagoon

What’s next?

It is hoped that under ideal conditions (high water levels and low salinity) Ruppia will flourish in the lagoon again.

DOC is working with locals and the Waituna Partners and Working Groups to help create the best conditions possible for Ruppia in the Waituna Lagoon.

A piece of Ruppia being held from Waituna Lagoon.

It is hoped that under ideal conditions Ruppia will again flourish in the lagoon.

A full copy of the report is available on the DOC website.

This week’s photo shows Waituna Lagoon—the location of a recent community open day marking the first year of DOC’s partnership with Fonterra.

Waituna Lagoon, Southland, New Zealand.

The natural habitat at Awarua-Waituna, including the 1350 hectare Waituna Lagoon, is one of five key areas that DOC and Fonterra are working together to improve over the next ten years.

The open day was a chance for the local community to see the work being undertaken at Waituna by Fonterra and DOC, in conjunction with Ngai Tahu, the Southland District Council and Environment Southland.

“In the first year our focus has been on monitoring and science. We’ve got to get this right to ensure the whole project sets off in the right direction and can make a real difference,” said Fonterra Living Water Project Manager, Nicola Toki.