Days numbered for kai moana, says US expert

Better savour those oysters or green-lipped mussels while you can, because New Zealand shellfish could be obliterated by greenhouse gases.

An American expert told a University of Otago conference that a ‘‘massive shellfish extinction event’’ could be on the cards.

Todd Capson will speak with government officials and scientists today on what must be done to prevent the rapid disappearance of seafood lovers’ favourite fare. ‘‘It’s not always a gradual change. If you exceed a certain threshold, things die.’’

The issue arose because CO in the ocean transformed into an acid, Capson told the delegates at the Foreign Policy School seminar during the weekend. Rising levels of the gas from carbon fuels meant more of this acid – ‘‘the same thing that makes Coca-Cola fizzy’’ – dissolved the substance oysters and other shellfish needed to make their shells.

Without enough calcium carbonate in the seas to make a fully developed shell in their first days of life, the baby creatures died.

Capson said Americans have already experienced the devastation ‘‘ocean acidification’’ could bring. In 2007, seafood farmers off the coast of Oregon and Washington states lost nearly 80 per cent of their shellfish stock.

Once-thriving habitats suddenly became dead zones, leaving a NZ$340 million industry that employed 2000 workers on the brink of collapse, Capson said.

Last year, affected American aquaculture workers visited their Kiwi counterparts with a chilling warning. ‘‘This happened to me and it’s going to happen to you.’’

During his time in New Zealand, Capson, of the US Sustainable Fisheries Partnership, will also meet with the seafood industry to discuss how ocean acidification can be monitored and farmed shellfish protected.

Green-lipped mussels and other shellfish were also put at risk by run-off from the land that led to algal blooms on the coastlines, Capson said. Radical change was needed to ensure such seafood species did not vanish, he said.