Inanga Now seminar

A seminar held in October 2022, organised by Project Parore’s Science and Technical Advisory Group (STAG). Seeking an up-to-date picture of current research on the state of these fish, reasons for their decline and restoration issues to inform local enhancement initiatives.

This summary of events was provide by Keith Gregor, STAG member

DAY 1 – Cafe Scientifique evening session

The program began with a well-attended Cafe Sci where firstly Kelly Hughes (ATS Environmental) explained the work he is involved with creating fish passages. Locally this work has been driven by Project Parore and is making good progress. Creating fish passage is essential for completing the whitebait life cycle and dovetails well with current habitat restoration efforts. He stressed the importance of maintaining the health of all the whitebait species as they in turn support a huge range of higher predators in both the fresh and saltwater environment. Some interesting links, talks and essays on the ATS Environmental website.

Second up was a presentation by Kim Jones of the Whitebait Connection where she described the life cycle of the whitebait species and outlined some of the reasons for their decline, including damage to adult river habitat, barriers to entering these areas and loss of spawning habitat. She talked about restoration efforts around Whangarei and the latest research and discussed the importance of knowing the whereabouts of the salt wedge to determine the “Love Zone” for whitebait. There appear to be large regional differences in whitebait behaviour, for example in the Bay of Plenty region the juvenile whitebait don’t seem to spend as much time at sea as in other areas. At the Ruakaka River they found that spawning could occur up to 500m upriver from the normal extent of the saltwater wedge and that the April spawning extent was the best predictor of the full extent of spawning.

She stressed the importance of having suitable habitat for spawning activity and said vegetation with good interlocking structure and rootmass like sedges and grasses are ideal (kikuyu is OK, though not dense enough when its really long). The Whitebait Connection have recently developed a planting regime and included a range of suitable plants which may serve as a valuable template for local restoration. This planting plan is available on the Whitebait Connection website, along with other resources including powerpoints.

Kim also mentioned trials with straw bales (not hay) to create instant spawning habitat and these had been successful additions to their experiments. Low bank angle is an important component of creating larger areas of suitable habitat (7-20 degrees), although eggs were still found on steep banks. Some shade is useful, especially on north- and west-facing areas, and also appropriate overhanging plants.

DAY 2 – Field Trip

This commenced with a walk around areas beside the Uretara River in the centre of town. It was led by Rae (who conducted the recent whitebait research for Project Parore) and was a very valuable information sharing tool.

As the group walked from the Landing, across the SH2 bridge, along the Haiku Path and back to the Arts Junction, this year’s spawning sites were rechecked for eggs, historical spawning sites were visited, planned habitat improvement was discussed and discharges from culverts were examined.

Feedback was that the planned habitat changes around the banks of the Uretara were suitable and in some cases would require little earthworks and planting. Determining the location of the salt wedge was crucial and monthly measurement of this was encouraged to measure variation over time. Measuring how far up-river the tide affects water levels was also deemed to be important in decisions around creating habitat for spawning and rearing, and these measurements could be achieved with little effort or expense. The group found this type of informal information-sharing “walk and talk” very useful.

DAY 2 – Presentations

After lunch we returned to the Arts Junction for a number of short presentations. Firstly Rae He-Jung presented her report on the pilot investigations that we had undertaken in the Te Mania and Uretara streams.

Next, Peter Ellery from Maketū Ōngātoro Wetland Society presented an interesting talk on the borrow pits and associated whitebait habitat created beside the lower Kaituna River. He stressed the importance of getting the depth of the entrances to the ponds right, to enable the ponds to retain water which was refreshed on each incoming tide, and said keeping the ponds small (10 – 15m) was best as they can hold large numbers of fish while being easier to manage. They have done extensive plantings, mostly natives, but a few golden weeping willows which he believed provided great overhanging shade without the other issues related to willows. Ensuring good access tracks was important for maintenance, which includes predator and terrestrial and aquatic weed control (raking aquatic weeds from the bank twice a year) and they have also installed some floating wetlands to help with water quality.

He believed the ponds were a great success for spawning and also for rearing of whitebait as the Bay of Plenty has lost a huge proportion of it’s wetlands through drainage for farming. Peter was also championing introduction of aquacultured kōkopu, although he recognised DOC concerns over translocation of fish as outlined in “A Risk Analysis of Fish Translocations” by Cindy Baker. Peter also guided a field trip to the borrow pits the following week which was a very timely follow up for the Project Parore attendees and a useful way to extend our collaborative networks.

Then Kim Jones came back to the stage to present more information on otolith studies by Eimear Egan which reinforced that the BOP inanga were not spending much time at sea. She provided links to the Whitebait Connection planting guide and discussed the Whitebait Watch by Shane Orchard on iNaturalist – anyone can access this and input data and observations.  She showed a video on creating ‘benches’, gentle sloped areas approx 7m across next to a drain, as inanga habitat at Takahiwai Marae and further discussed their trials with straw bales. She provided lots of useful information and links and said she looked forward to hearing about Project Parore’s progress in this space.

The final presentation was by Assoc. Prof. Nick Ling of the University of Waikato who discussed Whitebait’s position on the IUCN Red List, genetic differences between the whitebait species and also using various methods to locate whitebait spawning locations. These have included using drones with LIDAR systems or photography to map habitat and his research in applied animal behavioural science. The latter was fascinating. A great deal of time had been spent searching for whitebait eggs and now a dog has been trained to sniff out these eggs. Clearly the Project Parore team was keen to have a visit from the dog and handler over the next spawning season to efficiently determine egg position across the various rivers in our area. Nick also pointed out that we need to factor in the impacts of climate change and sea level rise when planning our habitat enhancement program.

The day rounded off with a “where to from here” discussion session, which again was well-received.  Participants agreed on the importance of the Mountains to Sea approach. Engaging and educating the community was seen as important, with plantings are a good way to get people in. A scent dog could also be a crowd-puller. An emphasis on involving students at all levels, working collaboratively with local and regional councils, creating local questions which could be answered through student research and being mindful that there were potentially large regional differences so that we need to find out what is happening in our own rivers and streams.

Feedback was very positive for the whole program and attendees were keen to see a repeat of this format of information sharing in other areas of the country.

Recommendations to STAG

  • Monthly or regular monitoring of the position of the salt water wedge across all catchments
  • Determine the height of the tidal push in the 8 rivers that Project Parore is interested in
  • Develop a plan in association with the Regional and WBOP District Council to enhance habitat, particularly along the Uretara (taking into consideration the impacts of sea level rise)
  • Map suitable spawning and rearing habitat in the 8 rivers to sit alongside information on the salt water wedge locations
  • Attempt to get the egg-sniffing dog to visit over the next spawning season in 2023. Link this to school engagement studies. A sniffer dog will be a big hit with all and also include Kelly Hughes work with this, as it is interesting hands-on material. Provide teachers with links to all the Whitebait Connection information
  • Complete cover page of Rae’s report and send electronic versions to delegates
  • Keep in contact with Peter Ellery re fish translocation progress and discuss whether we should consider it here
  • Uretara river cleanup day to remove debris from the banks and in the Uretara
  • Examine the culvert plumes in the Uretara, what are their chemical makeups?
  • Source some straw bales to extend habitat experimentation on the Uretara
  • Set up a monitoring plan for spawning 2023 and discuss how widely this will be undertaken.

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