Keeping eyes on precious Whangateau Harbour
Photo: Pippa Brown. Photographer Dr Roger Grace stands next to Wavelets in mangrove seedlings taken in a few cm of water in the setting sun of Whangateau Harbour.
The death of 80 per cent of the cockle population at Whangateau Harbour early this year is threatening the harbour itself, says marine biologist Dr Roger Grace.
This week, Auckland Zoo is holding a photography exhibition, Eyes on Whangateau Harbour, to coincide with World Environment Day on June 5.
The Whangateau Harbour, known for its abundant marine life and inter-tidal environment, is recognised as the least spoiled mainland estuary in the Auckland region.
Its uniqueness extends both above and below the water. Dr Grace equates it to how other estuaries in the Auckland area must have been in pre-human times.
The clarity of the water is mainly due to the abundance of cockles.
“If the cockles die there won’t be as many to filter the water,” says Dr Grace, who is also a Whangateau HarbourCare Group member and Greenpeace photographer.
He attributes their sudden decline to “another of those climate change things”.
Photo: Pippa Brown. Photographer Dr Roger Grace with flounder.
The combination of low tides at midday and very hot conditions happened twice this year in January and February and “although the event is not unusual in itself, frequency is a factor”, he say.
High temperatures probably played a major part, but a toxin or parasite could also be involved, says Dr Grace.
“This would weaken the cockle beds and make them less likely to cope with high temperatures,” he says.
The quality of water is due to other factors too. The catchment area surrounding the harbour is small and residential areas of Omaha and Point Wells have been kept to sandy low-lying areas where runoff is filtered through the sand.
“It is important not to develop higher ground,” says Dr Grace. There is an increased danger the amount of silt going into the harbour will increase when surrounding forestry is harvested.
Despite losing 80 per cent of the cockle population this year, Dr Grace thinks the quality of the estuary water is better than the rest of Auckland.
The water leaving the harbour can be clearer than that coming in from the open sea, he says.
“Visibility can be up to 15m in the harbour. It is a snorkeller’s paradise in the right conditions,” he says.
The Whangateau HarbourCare Group hopes to either promote the area around Shoe Island for a marine reserve or extend the area west from the already protected Kahikatea forest into a scientific research area.
Both would achieve the same thing, he says.
They hope a shellfish ban will prevent further depletion of cockle stock.
The group wants a proper management plan in place to stop further degradation of the estuary and has put together a 10-point protection plan for the harbour.
By Pippa Brown ⋅ June 4, 2009 ⋅
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