Tuna and Inanga Spawning
Summary: Students from Kuranui College have been involved in a term long investigation around Lake Onoke, Inanga spawning and Eel migration with the Whitebait Connection programme in Wairarapa Moana.
Lake Onoke forms the mouth of the Wairarapa Moana wetland complex. All water flowing out of the catchment must pass through it, and many of our native fish species must do the same to complete their life cycle.
Maori used this knowledge to catch migrating eels by setting hinaki (nets) during the hikurangi, providing a year round supply of food. The tuna could be caught with ease at the mouth of Lake Onoke when it naturally closed, and the eels backed up in the thousands, waiting for the mouth to burst open.
The wetlands that once dominated this area have now been converted to pastures, and considerable effort goes into controlling the once natural wetland flooding. These huge changes to the cycle have also caused changes to the landscape and biodiversity. Lake Onoke no longer closes naturally as it once did, and once the waters are backed-up beyond a certain point, the diggers arrive to open it. The Kohonui marae used to stand of the edge of the wetland whilst in was flood. Now you can’t even see the waters from it’s gates.
Students from Kuranui College have been exploring the past of the lake and Wairarapa Moana catchment to understand it’s future and discovering a lot about the people who call it home, and the animals that live here. We focused on inanga (whitebait species) and tuna, because of their local significance. As one student commented “I feel more passionate about the lake and the eels now, because they mean a lot to this community.”
Our investigations began at the Lake Onoke, where Inanga spawning was suspected, but not confirmed. A night visit the evening before showed clear evidence that they were in the middle of spawning activity which usually happens 2-3 days after the full moon and over the high tides. We left them to it and set our nets for the night.
The next morning, Kuranui College arrived with Cheryl Iro and her Enviroclass. The weather was wild, but armed with waders and spare gumboots we drove the 4WD around the lake edge until we reached out nets.
Ready for action with students from Kuranui College.
Over 1000 inanga were found in our fyke nets
along the canals on the eastern side of Lake Onoke.
There we found the biggest haul of inanga ever. Over 1000 fish had swum into our hinaki overnight, many with bellies filled with egg and milt. Eels had also followed the food and many were found having a feast as well. The tuna are known for sticking around during spawning time and sucking up the eggs of the inanga.
After checking the nets, students placed out haybales at the high-tide zone, which we hoped to come and check out on our second visit. Investigations were finished off with some hot chips at the Lake Ferry pub.
Students setting out haybales on the edge of Lake Onoke.
On the second field trip, our access to the haybales was thwarted by the rising levels of Lake Onoke. The mouth had closed and the waters had backed up so much that access was only possible a short way around, and we knew our haybaes would now be submerged. Showing once again that part of being an environmental scientist is often about getting things wrong, and then trying something else.
Reuben Tipoki joined students on the second field trip, and we went to the mouth of the lake to check hinaki that had been set the night before. The haul was amazing, over 120 eels had swum into the net. Many were young, but some were on their migration as evidenced by the change in their features. Reuben taked with the students about how the eels were caught and prepared, and then we began the rather slimy and squeally job of returning them to the lake.
Setting hinaki with Reuben
Returning eels to the lake
Habitat assessment of Inanga spawning grounds were also completed after some more adventurous 4WD. These assessments and resources for Inanga Spawning projects can be found here at WBC Inanga Spawning Resources.
Students from Kuranui College have now taken this knowledge back to school, and are working on a plan to involve and inspire more students from the College. They are also now planning their kaitiaki projects, and will be working with other local community groups to get these underway.
Kuranui College students on the edge of Lake Onoke.
“I’ve seen what lives there, and what needs to be improved to help, and that it’s possible for us to help”
A huge thanks to Greater Wellington Regional Council and the Department of Conservation
for their funding and support for these projects.