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It’s a deep dive into the stream at Papawai-Mangarara

Papawai-Mangarara Stream Care Group volunteers and organisation Mountains to Sea joined forces to measure the health of Papawai-Mangarara Stream. PHOTOS/MARY ARGUE

Mountains to Sea’s Liz Gibson investigates the set-nets.

Wairarapa residents are curious about what’s really going on in the freshwater streams.

That’s why the volunteer-led Stream Care Group and Liz Gibson from Mountains to Sea Wellington joined forces to explore beneath the surface of Papawai-Mangarara Stream.

Gibson said the group’s aim was to get some baseline information around the biodiversity and ecology of the stream.

“The intention is that as [Papawai-Mangarara Stream Care Group] do more restoration actions and we continue to monitor over time, we’ll start to see a shift,” Gibson said.

“We’ll start to see a return of more biodiversity. We’ll start to see improvement in water quality. We’ll start to see more shade.

“It helps us to get a good understanding of: Is our restoration action working?”

Papawai-Mangarara stream flows alongside Papawai Rd in Greytown to join the Ruamahanga River.

The Papawai Marae-based group expects restorative plantings to reach target numbers in the next three years.

Gibson said it was mainly humans impacting the health of our water and the biodiversity of our freshwater species, with sediment and a “significant” lack of trees held largely to blame.

“So this would have originally been part of what was a wetland complex that surrounded Wairarapa Moana, and those wetlands were drained for farmland, and a lot of the trees were cut down,” she said.

“The release of those trees means that a lot of sediment was ending up into the waterways, and it also reduces a lot of that habitat for biodiversity.

“So that would have been a big problem as sediment fills up all the gaps in the bottom of those streams, it can take away all those spaces for the food to grow, but also the places for things to live and hide.

“That’s had a really big negative impact.

“Also, the stream flows through quite an urban environment … because of that, it can have impacts from stormwater, from roads, from farm runoff as well can be an issue.”

Gibson said effluent from farm runoff could also make its way into the stream.

The group set freshwater traps looking for eels and fish species and collected water samples to look at the different bug species that may be floating around.

“If we found all of the different kinds of whitebait species, that would be incredible,” Gibson said.

“So the banded, the giant, the short jaw kokopu, koaro are another fish that likes really clean, healthy, quite bouldery rivers and streams, and then inanga as well.

“This is a place where I would expect to probably find inanga. It’s low-lying, if there is access to the ocean for these fish to get back up here, then that would be really amazing.

“Kakahi or freshwater mussels are another species that you see in some of the streams around the area, so the presence of those tells us that some fish would be present too, and they’re really good at helping to clean up the water themselves as well.”

Inspecting the catch. The group found one small longfin eel, but plenty of invertebrates.

Over a few hours, the team found one injured kokoputuna [longfin eel] and a broad mix of medium to low-sensitivity species like water boatmen, sandfly and midge larvae, amphipods, worms and damselfly larvae, and a very small number of the more sensitive mayflies.

Gibson said what was found when there was a search for invertebrates could tell us a lot about water quality and habitats.

Aquatic invertebrates vary among species in their sensitivity to poor water quality and impacted habitats; some species can only live in clean, cool, stone-bottomed streams with lots of oxygen.

While others are more tolerant of pollution, sediment, low oxygen and a lack of shade.

More sensitive species are often a crucial food source for our native freshwater fish.

“Our findings on this day tell us there are some water quality and habitat issues which we then investigated with further tests,” Gibson said.

In order to restore biodiversity, volunteers will need to continue with riparian plantings, increase shade cover over the stream and stabilise areas around the riverbed to reduce erosion.

  • For more information on how you can get involved, visit https://waip2k.org.nz/

Ellie Franco
Ellie Franco
Ellie Franco is Wairarapa’s Local Focus video journalist. She regularly covers in-depth stories on arts, culture, people, health, and the occasional pup.

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