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Kawhia Harbour News


The Kawhia Forum is now open for registration and participation.

Mauis dolphin sanctuary proposal

Dolphins prove they are priceless assets to New Zealand....(Stuff)

Foreign mussels in the Kawhia Harbour:

A member of the Kawhia Harbour Protection Society noticed birds feeding in specific areas on the mud flats. Curiosity about what caused them to be feeding in the same place each tide led him the edge of a massive mussel bed. Later two of us went out in a boat to determine the extent (hectares) and collect samples. Judging by the bed size they must have been there for more than a season.

The mussels are (not officially identified but reasonably certain to be) an exotic organism, Musculista senhousia , or Asian Date Mussel, or Carpet mussel. The 2cm shell is a pale green with amber zig zag lines across, anchored by a mass of attachment ‘hairs' that form a dense carpet, creating an oxygen depleted foundation, excluding most other marine life.

Sediments trapped amongst the mass of shell cover the greater part of the shells, leaving a small dark streak in the mud. The dark streak is the top of the shell where it opens to feed and circulate water. In places the dark marks make a mudbank look like a woven mat.

Biosecurity NZ told me they tend to make big beds that finally die, (probably by suffocation in sediments. In the meantime they will have established elsewhere to make yet another big bed.

The full impacts will not be known for a while. Control or removal is not practical with current technology or chemicals.

Carpet mussels were first seen near Auckland in the 1970's and have since spread to Whangarei, Waitemata, and Kaipara Harbours , Mahurangi, and Tamaki estuary. The Kawhia beds are the furthermost south. As the discussion continues we find they are in Aotea Harbour too.

We will keep you updated if we get any more information...John Dodgson - President KHPS

At the AGM:

In September our guest speaker drew attention to Spartina and Saltwater Paspalum, two salt tolerant, rapid growth, excluding plants that threaten the intertidal zone ecosystems within the harbour. Both are a much greater threat than the mangroves which are checked by colder temperatures.

A closer look at the Spartina growing in a wetland at Te Maika showed heavy stock browse and no chemical control as planned for in the DOC weed programme. The problem has been identified, money made available, consents applied for, yet the physical work did not happen. Over the summer it is intended to check the harbour edges and shallows to see how prevalent these two species are.

I am told that Canadian geese are building in numbers, breeding freely near Motutara peninsular.  The gut system of a Canada goose is very primitive producing large quantities of faecal matter. The novelty of the goose rapidly decreases when they alight in flocks on farmland and start to feed and foul ground. Around Raglan harbour they are starting to cause concern as their numbers are rapidly increasing. Is this a warning?

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