Biogeography of Whitebait spawning grounds at non-tidal rivermouths

We recently published a study of īnanga (Galaxias maculatus) spawning grounds at non-tidal rivermouths in Pacific Conservation Biology. 

Article freely available here

Non-tidal rivermouths are common on the east coast of the South island and south-east of the North Island where they are commonly associated with high energy mixed sand-gravel beaches that form perched lagoons or hāpua at the rivermouth. 

At the outset of the study the spatial pattern of spawning in these environments grounds was unknown. Some of the interesting findings were that the location of spawning was close to the rivermouth despite the lack of salt water intrusion or tidal influence, both of which are associated with spawning grounds in tidal situations. 

A downstream fish migration evidently still occurs prior to spawning events and fish movements were surprisingly rapid in response to spawning cues in many instances. Spawning events are triggered by water level changes as occurs in tidal rivermouths, but appear to be more haphazard due to their origins being rain events rather than regular tidal cycles.Geographical aspects of the spawning locations were remarkably consistent across all seven study sites in key aspects such as the position in the catchment, relationship with water changes and presence of riparian vegetation. 

This provides a solid basis for identifying and managing spawning habitat in other non-tidal rivers. Effects we recorded included spawning on flood events that resulted in spawning grounds being located some distance from the active channel. As with tidal situations this places the eggs at risk from human activities in those same zones, but potentially presents a more difficult management proposition due to these events being less predictable. Their irregular nature suggests they are less likely to be accommodated in riparian zone planning and management. Importantly, the spawning grounds are located close to the peak water levels experienced on these events, which coincides with areas that are only briefly inundated. 

Recognising and protecting these emphemeral flood-zone areas is the key to effective conservation.

Read the full article here

Inanga ora ki te awa o Waitara

It's been great working on this project with Waitara Alive and the Ōtaraua Hapū along with Waitara High School students to better understand the health of whitebait spawning sites along the Waitara River. 

The project is comparing present day spawning site health and abundance to historical evidence collected from local kaumatua. By contrasting past with present, the Inanga Ora project team hope to identify how spawning habitat is changing, and what can be done to better protect it.

The project was funded by the 'Curious Minds' He Hihiri I Te Mahara. Participatory Science Platform.
Check out a recent update from the Venture Taranaki here

Earthquakes cause the relocation of spawning habitat on a catchment scale

The story of how whitebait spawning sites shifted to new areas after the Canterbury earthquakes - and became exposed to new vulnerabilities.
This spatial ecology study reveals how and where we can take action to protect them.

Read more here

New methods paper - Census survey approach for īnanga spawning habitat

Waterways and MERG have recently published details of a survey methodology for locating and mapping īnanga spawning sites near coastal rivermouths. 

Read more here.

Evaluation of Christchurch City Council's riparian management trial

Christchurch City Council (CCC) recently changed its riparian vegetation clearance practices for a trial period in the summer of 2016/17. While the trial has wider objectives around improved environmental outcomes, īnanga spawning habitat is directly affected by bank cutting and other forms of vegetation clearance. A survey of īnanga (Galaxias maculatus) spawning habitat was completed in April 2017 to evaluate effects of the trial.

Benefits of the trial included increasing the availability of high quality spawning habitat and the discovery of new spawning sites. The Avon/Ōtākaro supported a relatively high area of occupation (AOO) of spawning sites for a single month in comparison to other years. In the Heathcote/Ōpāwaho spawning was found at new sites including upstream of Opawa Road. However, egg production was relatively low in the Heathcote/Ōpāwaho versus the same month in previous years. This suggests a shift in the month of peak spawning activity or a possible adult population decline and requires consecutive month surveys to confirm the actual trend.

The full report is available on the CCC website here:
Response of īnanga spawning habitat to riparian vegetation management

NZ's largest known area of inanga spawning found in Christchurch waterways!

An unexpected result of our earthquake studies was the discovery that  īnanga spawning habitat had expanded, and was more extensive than ever previously recorded in Christchurch's waterways.

Further surveys in 2016 found that even larger areas were being used. The total area of spawning was around 2x
the next largest area recorded anywhere in New Zealand !

Read more >>

New spawning sites found in Aromahana Lagoon in Greymouth

Dr. Mike Hickford and I recently visited an community restoration project on Cobden Island in the Grey River and nearby Aromahana Lagoon. Our main goal was to scope out a survey strategy for monitoring īnanga spawning in this area. Time was short but we did manage to find two new spawning sites. 

This is an innovative floodplain restoration project on an impressive scale. Thanks to Henk Stengs at DOC for showing us around!

Read more >>

Spawning habitat maps for Ōtautahi waterways

These maps show results from two years of spawning site surveys plus two years of straw bale experiments in the waterways of Ōtautahi Christchurch. Compare them with the Whaka Inaka maps where we took all of the known sites at the end of 2015 and tested if there might be others both in the gaps and further upstream/downstream. And yes there were.

These maps are available as free downloads. There's some other maps available too ..
check them out here www.resilientshorelines.nz/p/resources.html

Resilience research on whitebait featured in UC Chronicle

The September 2016 issue of the Chronicle He Kupu Whakamahara ran a story on our research into the resilience of whitebait spawning sites in Ōtautahi Christchurch following the earthquakes.

Follow the link here to the article online

Some recent publications relating to this work:

• Earthquake effects on spawning sites - download the original report here
• Identifying īnanga spawning sites in plans - short report available here
• Census survey approach to quantifying īnanga spawning habitat New Zealand Journal of Marine and Freshwater Research, 52(2), 284-294.
• Earthquake-induced habitat migration Aquatic Conservation: Marine and Freshwater Ecosystems, 2018; 1-11.

Ngāi Tahu Research Centre seminar: earthquake recovery in Ōtautahi Christchurch watwerways

Results from our research into the effects of the Canterbury earthquakes on īnanga spawning sites in the Avon Heathcote Estuary / Ihutai catchment in Ōtautahi Christchurch. It's a story of the resilience and recovery of an iconic New Zealand species following a major disturbance. Thanks to the Ngāi Tahu Research Centre and UC Audio Visual unit the recent seminar was videoed. View the clip on U-tube here.

New report on earthquake effects

The Waterways Centre for Freshwater Research and the Marine Ecology Research Group are pleased to provide a new report on the distribution of īnanga spawning sites in Ōtautahi Christchurch. Thanks to the Engineering New Zealand / Water NZ Rivers Group for supporting this work.

Highlights include comprehensive information on changes in relation to the Canterbury earthquakes, and a summary of the key implications for waterways management.

Read more here

Te Karere Interview: Ngāi Tahu team up with scientists for whitebait restoration project

Following the announcement of funding from the DOC Community Fund Te Karere TVNZ reporters interviewed the Whaka Inaka project team (including Shelley McMurtrie (project lead), Te Marino Lenihan (project partner) and Shane Orchard (project partner) to find out more about the collaboration between Ngai Tahu and Christchurch scientists.

Watch the news video here

Whaka Inaka project gaining media attention

Whaka Inaka: Causing Whitebait is a joint collaboration between EOS Ecology, Ngāi Tahu, and the University of Canterbury (UC). We recently receiving funding from the Department of Conservation Community Fund, and together with support from Brian Mason Trust, and businesses such as Ravensdown the project is getting underway!

Earthquakes cause a shift in the location of īnanga spawning sites

One of the main objectives for our whitebait conservation study was to determine if the earthquakes had altered the location of spawning sites for īnanga (Galaxias maculatus) for spawning. They are typically found in specific locations near the freshwater-saltwater interface at rivermouths. As such, īnanga spawning sites are potentially a very good indicator of change. Conversely, they may be especially vulnerable to changes that affect the availability or condition of suitable habitat.

And the answer is - yes, there has been a major shift in the location of spawning compared to all previous records!

Read more here

TVNZ coverage