Category: Planting and management

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Pakiri horse mussel beds

For the last eight years I have been working on restoring green-lipped mussel (perna canaliculus) beds in the Hauraki Gulf. The main reason we started with that species was that there is a commercial supply. However there is a bigger native mussel that has even more potential than green-lipped mussels, both as a habitat and water cleaner. 

Horse mussels / Hururoa (atrina zelandica) are huge pumps, they are more than twice as big as green-lipped mussels (up to 400 mm in length) but have fragile shells which are vulnerable to fishing gear. They also  don’t move (unliked green-lipped mussels) and are sensitive to changes in substrate.

Last century horse mussel beds were some of the best fishing spots in the Hauraki Gulf. I regularly ask divers about horse mussels; Where did you see them? How dense was the bed? etc. There are spots with horse mussel in the Gulf but I don’t know of any significant beds left, if you do, please let me know about them.

I was recently sent these images of a stunning horse mussel bed in Pakiri.  They are from a report titled “Mangawhai – Pakiri Sand Study, Module 2: Technical Report, Marine Sands” by NIWA 1996. They show a large and dense horse mussel bed that has since been destroyed by sand mining. The beds ran the whole length of the embayment in depths of 15 -20m. I am posting them here to show the kind of seafloor we could have, if we treated it better.

We don’t yet understand the horse mussel lifecycle or what species / substates might attract juveniles. It’s interesting to note: presence of finger sponge and branching red algae, the hard edge to the bed and the way some of the shells align.

Overseas there have been attempts at restoring similar species (photos below). Seachange called for the “Initiation of a horse mussel restoration programme, with an initial focus on the Mahurangi and Whangapoua harbours.” But we could look at restoring any of the sites with historic beds. Wouldn’t it be awesome if we stopped smashing the seafloor, and bought back these giant pumps to clean the water, and create homes for fish.

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Stream Health Monitoring guides

As communities get increasingly worried about the declining quality of their waterways there is more interest stream health assessments. I am a huge fan of the Waicare Invertebrate Monitoring Protocol (WIMP) which is simple enough that school students can use it. However the Waicare programme has been largely defunded by Auckland Council and there is no way for the public to share WIMP data. NIWA and Federated Farmers of New Zealand have put together https://nzwatercitizens.co.nz/ based on the New Zealand Stream Health Monitoring and Assessment Kit (SHMAK). It is great but incredibly hard to use, the manual is horrific. I believe this is being addressed but will take years. To help, the science learning hub has made this great guide for teachers and students. NIWA have put together some videos. They are not published together anywhere online so I have posted the list below:

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Fires at Point England

On the night of the 5th of April 2020 I noticed emergency services lights at Point England. Today I counted three areas of previously un-mowed grass on the south-eastern end that had been burnt and two partially forested areas on the northern end. The fires look like intentional arson to me, with drought conditions over hopefully we wont see any more burning. I’m very disappointed to loose some of the trees I planted. Damage to fences (including an area removed by emergency services) needs to be fixed before the dotterel breeding season begins (Auckland Council reference: 8110308091). I’m grateful to emergency services for managing the fire risk and to the mowers who have kept the tinder dry grass very short.

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Roost heights at Tahuna Torea

Today I took photos of the shorebird roosts at Tahuna Torea when the tide had just covered the main spit roost. The tide height was predicted to be very high today (3 August 2019) at 3.4M Westhaven 8:53am. Conditions were relatively calm and the tide had not (yet) hit the high tide line on the Little spit.

Names and locations of roosts
The tide was about 20cm (in height) from the high tide line.
Pathway
And the pathway which is sometimes flooded was about 20cm above the water.
The spit had just been compromised with just a few Black-back gulls and one Caspian tern remaining
Little spit was about 50cm above the tide
Little Godwit Island was about 60cm above the tide
South Godwit Island was about 75cm above the tide
North Godwit Island had about 40cm above the tide
The Southern end of Lockley Island had about 40cm above the tide
The Northern end of Lockley Island had about 40cm above the tide

I have seen tidal debris in the mangroves around Lockley Island that were above the height of the island (indicating that it sometimes gets swamped) but I think it would have made an ok roost today.

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Weeds on Motukorea

After the fire on Browns Island, lots of noxious weeds took hold. Although it looked like the crater was going to be dominated by bracken the weeds are winning. Black nightshade is dominant and there are thousands of woolly nightshades coming up, some as large as 1 meter wide already. Inkweed, apple of sodom and boneseed are also sitting up above the kikuyu.

Click for high res 360° image of the crater

Wooly Nightshade

I casually pulled up about 100 mullien but did not make a noticeable impact. Most disturbing was this animal dropping I found on a large mullien leaf.

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Forestry and water quality

When I first heard about erosion in the Hunua Ranges causing havoc for Auckland’s water supply I wondered if it was because of recent deforestation. Drone footage shot by Watercare confirmed that theory for me (see stills below from this video). It seems strange media are not talking about it. To me it looks like just another case of our water being compromised for private profit.

A little bird told me Watercare own the land and were in the midst of replanting it with natives – it would be good to know the full details. I will email them.

Response
http://www.watercare.co.nz/about-watercare/news/Pages/Watercare-to-regenerate-pine-forest-in-Hunua-Ranges-with-natives.aspx
(2,089-72 = 2017) So sometime in 2017 they decided to start harvesting. But the wood in the pictures looks at least months old. My guess is the harvesting that caused the contamination was done in 2016 for private profit. Hard to tell from the information received. Awaiting a report with interest.