In October 2005 an invasive sea squirt, Styela clava or clubbed tunicate, was discovered in Auckland’s Viaduct Basin and in Lyttelton Harbour. It was found soon after on the hull of a vessel that had sailed from Auckland to Picton, and in the Hauraki Gulf and Northland.
This sea squirt is a native of the north-western Pacific, and its initial spread in the 1950s coincided with increased shipping links during the Korean War, when it was accidentally introduced to many northern hemisphere coasts. The sea squirt was found to have reached Australia in 1972 and New Zealand in 2005.
It multiplies rapidly in suitable sites, spawning every 24 hours in water temperatures above 15°C. It competes with other filter feeders for food and space and disrupts native ecosystems and aquaculture. There are plans to eradicate the pest before it spreads further.
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Photograph by Ashley Coutts
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