It may look like a load of old rope, but it’s hoped that a length of mussel spat rope will be the key to repopulating Lake Tūtira with eels.
Hawke’s Bay Regional Council (HBRC) freshwater scientist Dr Andy Hicks and Matthew Brady from Department of Conservation (DOC) arranged for the rope to be installed at the falls on Mahiaruhe Stream which is part of the northern outlet of Lake Tūtira. The rope was put over the falls on 27 November 2014.
HBRC and DOC science surveys have found plenty of elvers (young eels) downstream of the waterfall in Waikoau Stream. However in the waterways around Lake Tūtira there are only large, mature eels and no small eels.
The sheer waterfall on Mahiaruhe Stream is identified as a significant barrier to eel migration into the lakes. Elvers need to swim up Mahiaruhe Stream to reach the lakes, but the steep ravine and 30 metre waterfall make this journey difficult.
Avalon rope solution experts managed the installation of the rope as abseiling work was needed and Hoani Taurima from the local hapū Ngati Kurumōkihi and Tangoio marae, assisted with rope handling. The cost of the work has been shared by HBRC and DOC.
Historically the area was valued by Ngati Kurumōkihi for its eel population, which provided essential food supplies. Over time, the water and elements have smoothed the walls of the ravine in Mahiaruhe Stream and the waterfall has eroded to a steep and undercut face with fewer easy steps or cracks for the elvers to climb up.
“Elvers are remarkably good climbers and had been managing to make their way up the falls until 15 or 20 years ago, when either a single weather event or gradual erosion changed the shape of the waterfall enough to prevent even elvers from scaling the ravine and accessing the lake,” says Matthew Brady, DOC Biodiversity Ranger.
Hoani Taurima remembers his grandfather teaching him how to catch eels from an early age. “It was just what you did, it was important to help feed the whānau and guests at Tangoio marae, it’s something I want our mokopuna to learn to do and for them to teach their mokopuna."
The mussel spat rope is anchored down the side of the waterfall where it’s damp but not in the full force of water, and elvers should be able to use the fibre to climb up to the lake.
“The falls are sheer and the soft rock is difficult to anchor rope into so we hope that the rope will work, but there are other techniques we can try if this fails to enable eels to get into the lake,” says Andy Hicks.
In other parts of the country, local communities transport eels across the barriers in tanks. This kind of trap and transfer programme is another option to get eels into Lake Tutira, but it’s preferable that they make their own way there.
As the elver run is over the next few months, the HBRC, DOC and hapū team will return later this summer to see if there are any small eels upstream.
Other fish barriers sought
HBRC wants to know of other barriers around the region, primarily man-made ones such as culverts perched above the level of water. Farmers, fisherman, scouts, trampers or other people using waterways can tell HBRC about any barriers to fish passage they see. “We want to assemble a comprehensive database of fish barriers around the region so we make sure we fix the high priority ones”, says Dr Hicks. People can find out more and report any fish barriers at www.fishbarrier.co.nz.