New sea squirt arrival in Northland

New sea squirt arrival in Northland

By Geomarine Research, Friday 4 September 2009

“A recent survey of the northern tip of Northland has shown that the Australian sea squirt cunjevoi is spreading only slowly around the coast”, marine scientist Dr Bruce Hayward told the New Zealand Marine Sciences Society Conference in Auckland on Friday. “Where it is growing it has taken over the low tidal rocks forming extensive, 10-20 cm deep mats overgrowing the mussel beds and other native intertidal life.”

The arrival of this sea squirt near Cape Maria van Dieman was first reported by Dr Hayward from Geomarine Research, Auckland, in 2007. “It has now spread along 9 km of rocky coast. It has the potential to spread right around the North Island and possibly the northern South Island.” 

Cunjevoi, or Pyura praeputialis to scientists, is native to exposed Australian rocky shores. It lives at low tide and at depths down to 12 m on exposed shorelines from West Australia around South Australia to southern Queensland. Cunjevoi was introduced to Chile many years ago and is now the dominant low tidal zoning organism along 70 km of its coast.

“Unlike the club sea squirt which arrived in New Zealand 7 years ago, cunjevoi may not be such a major threat to aquaculture, because it is mostly restricted to wave-exposed coasts. It is dramatically changing the shoreline however and appears to be out-competing natural green- lipped mussel beds, which may concern recreational harvesters,” says Dr Hayward. “It is too early to tell whether it will have any impact on the mussel spat that is collected on Ninety Mile Beach and is distributed from there to mussel farms around the country.” 

“Cunjevoi's pelagic egg and larval stages live for just 1 day, so it is unlikely to have crossed the Tasman Sea by natural means. Most likely it was transported to NZ by a boat coming from Australia. In Australia it is widely used by recreational fishers as bait. Perhaps a bucket of this bait was dumped overboard as a trading vessel was rounding the cape.”
 

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