Kaipara is a giant snapper nursery: Experts

Northlanders know the Kaipara Harbour is a great place to fish for snapper, but scientists have now confirmed why.
Ninety eight per cent of all snapper off the west coast of the North Island come from nurseries in the harbour. Scientists say their research shows how important it is to protect the Kaipara Harbour to preserve the $32 million snapper export industry.
In 2003, National Institute of Water and Atmospheric Research (Niwa) scientists collected juvenile snapper from seven estuaries along the west coast of the North Island. By testing their ear bones for eight different elements, the scientists were able to create a chemical signature to identify which estuary the fish came from, Niwa fisheries ecologist Mark Morrison said.
Four years on, scientists have collected a sample of 140 adult snapper from commercial catches, from Ninety Mile Beach to Mana Island in Wellington. They found that 98 per cent of the adult snapper were originally juveniles from Kaipara Harbour.
The discovery was a breakthrough for scientists working on ways to maintain fisheries stocks.
Snapper made up New Zealand's largest recreational fishery, and one of the country's largest coastal commercial fisheries with an annual export value of $32 million.
The findings showed the fragility of snapper and other coastal fish stocks, highlighting the importance of protecting natural habitats such as the Kaipara Harbour. "Any negative impacts on the production of juvenile fish in the harbour will cascade through into a much larger coastal ecosystem, ultimately having a huge effect on the abundance of fish over a 700km coastline."
Kaipara Harbour was under threat from human activities - particularly land uses which caused sedimentation and changes in water quality, Mr Morrison said.
It was likely other west coast harbours were also once important nurseries, he said. Niwa was now working on ways to restore and recover the habitats. This work included using artificial seagrass habitats to understand why the fish valued that environment, as well as the possible consequences on snapper numbers if the habitat was lost or destroyed.
"Now that we know more about where the important nurseries are, we need to know why snapper larvae settle there, and how we can stop degradation of their habitat," Mr Morrison said.
Niwa's aim was to advise coastal resource managers on the consequences of different habitat management of fish stocks to ensure that recreational, customary, and commercial fishing will continue.