Whangateau Harbour Important Nursery for Parore

Hundreds of young parore, mostly about a year old, were hovering under the Omaha Causeway Bridge this morning.  They were taking advantage of a calm spot in an eddy as the tide started racing out.

Hundreds of young parore shelter under the Omaha Causeway bridge as the tide begins to drop.  The western row of bridge support columns can be seen in the background.

Hundreds of young parore shelter under the Omaha Causeway Bridge as the tide begins to drop. The western row of bridge support columns can be seen in the background.

According to Mark Morrison from NIWA, who did his MSc thesis on parore, the Whangateau Harbour produces all the parore for the coast from Pakiri to Kawau Bay. There are two sandstone reefs in the Harbour which serve as nursery areas for parore. One is about 200 metres south of the Causeway bridge and can be seen from the bridge when the tide is low. The other is on the Point Wells side of Horseshoe Island and is a popular snorkeling area alongside the channel. Masses of necklace weed grow on the reefs providing a sheltered habitat for the young parore.

In late January hundreds of recently settled parore only 20mm long shelter amongst the branches of mangrove trees when the tide is in. Here they continue to pick plankton organisms from the water, at the same time as beginning their herbivorous life by nipping at micro-algae growing on the mangrove branches.

Juvenile parore only 20mm long sheltering among the branches of large mangrove trees in the southern part of Whangateau Harbour.  The barnacles on the branches at left give you an idea of the scale.

Juvenile parore only 20mm long sheltering among the branches of large mangrove trees in the southern part of Whangateau Harbour. The barnacles on the branches at left give you an idea of the scale.

The tiny parore settle from their planktonic larval stage at about 12mm long and can be found schooling in estuaries and the lower parts of creeks when they are hardly recognizable just developing their stripes.

This tiny parore only 12mm long is just beginning to show its stripes.

This tiny parore only 12mm long is just beginning to show its stripes.

Its Not Over Yet! The Cockle Die-Off Continues

The new cockle die-off event is still in progress, with rotting cockles beginning to create a stink on the Omaha side of the harbour.

A dead and gaping cockle still embedded in the sand is slowly spreading its shells apart as the muscles which hold the shells together gradually fail.

A dead and gaping cockle still embedded in the sand is slowly spreading its shells apart as the muscles which hold the shells together gradually fail.

Following the massive die-off of 80% of the Whangateau cockles in 2009, a new cockle die-off event was first noticed on 28th March 2014. Mahurangi College students were carrying out a regular monitoring of the Horseshoe Island shellfish transects when unusually large numbers of recently dead cockles were noticed by Karen Tricklebank and Roger Grace.

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Successful Shellfish Survey Day at Whangateau Harbour

 

Sieving the sand out of the samples to enable the shellfish to be counted and measured.  Eagleray feeding holes filled with water were handy on the upper shore.  Without them samples would have to be carried several hundred metres to water for sieving

Sieving the sand out of the samples to enable the shellfish to be counted and measured. Eagleray feeding holes filled with water were handy on the upper shore. Without them samples would have to be carried several hundred metres to water for sieving

The annual survey of shellfish, particularly cockles, on two transects east of Horseshoe Island in the Whangateau Harbour, was successfully completed on Friday 28th March by ten students and several adult helpers. Mahurangi College science teacher Wendy Dunn organized the students into pairs for the task. As the shellfish beds in the Whangateau Harbour are currently closed, a special permit is required to carry out the surveys.

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Serious bird predator on Horseshoe Island!!!

Footprints of a mustelid, probably a weasel or a stoat, were seen on Horseshoe Island on Saturday, barely five metres from the nest site of the endangered variable oystercatcher in recent years.

Oystercatcher eggs and chicks would have no hope against one of these aggressive predators of native birds, particularly ground-nesters.  Before the next nesting season we should set stoat traps on the island in the hope of removing the risk and improving the chances of successful nesting of the birds.

Predator trapping should be considered on a longer term basis for the island, as re-invasion would be easy for mustelids which could cross the sand flats at low tide from the mainland with ease particularly at night.

Kahawai school at Horseshoe Island channel

A school of several hundred young kahawai was seen in the channel behind Horseshoe Island on Saturday.  This was the largest number of kahawai I have seen in this area, and is a very encouraging sign.  There were also large numbers of adult parore, and the usual school of around 200 trevally which have grown since last summer.  There were no juvenile snapper, however, which were common in the summer but have departed for winter.

With 8 to 10 metres visibility, this is the clearest I have seen the harbour waters since the big cockle die-off in 2009.  There had been no rain or wind for several days, however, and the water on the coast is very clear at the moment too, which all helps the harbour’s water clarity.

Part of a school of hundreds of young kahawai in the channel behind Horseshoe Island on Saturday.

Horseshoe Island Weed Blitz – Again

Horseshoe Island Weed Blitz - Roger Grace

Horseshoe Island Weed Blitz - Roger Grace

On Sunday 3rd July the Whangateau HarbourCare Group and several helpers from the local community, Forest and Bird, and DOC cleared wattles and a few small gorse plants from Horseshoe Island in the Whangateau Harbour. “Last year we missed our regular weeding and the wattles had got away again”, said Roger Grace of the Harbour Care group. “If we keep on to it annually we can simply pull the new wattle seedlings out of the sandy soil, but this time they had grown to three or four metres high and needed cutting off at the base and painting with Vigilant gel.”

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