Sea snails make waves

Whangarei resident Kathryn Blanchard took this photo of a tonna tankervillii she found on a Bay of Plenty beach but several have been washing up on Northland beaches.

The Northland coast continues to serve up surprises with some people who have lived locally for years recently finding large sea snails on beaches for the first time.

The inhabitants of tonna tankervillii shells, more commonly known as the cask shell, are not pretty - larger than average but, like all snails, are the usual inky, slimy, fleshy-footed creatures.

However, the distinctively ribbed, curled, honey and cream coloured shells are lovely, and bigger than most sea shells found in New Zealand.

One Waipu resident has lived at Waipu Cove for 51 years has only in the past week found tonna sea snails.

And last week Whangarei resident Kathryn Blanchard also found one washed up when she was at a beach near Mount Maunganui. Ms Blanchard said she was tempted to keep the shell, but as it had a live inhabitant returned it to the sea after taking photographs.

Usually the snails are found on Northland beaches after strong easterlies or storms at sea, but the scientific world isn't getting overly excited about the recent shore visits.

According to New Zealand's top malacologist (mollusc specialist) Bruce Marshall, science collection manager at Museum of New Zealand Te Papa Tongawera, the snails are not rare, even if they're also not often found alive on shore.

It would take toxicology tests and other examinations to determine if there were other environmental causes but there were no concerns at this stage, Dr Marshall said.

Ngunguru marine expert Wade Doak said the efficient predators live beyond the surf line on open sandy beaches where they dine on sea cucumbers, other slugs and molluscs, or any marine life they can get the better of.

In turn, the snails are a favourite tucker of eagle and sting rays.

Mr Doak has seen rays use their wings to scoop away a dish of sand to expose the snails which they crush in their hard mouths. There are many species in the tonna genus with tankervillii being the most common on the north east coast of New Zealand and in Australia from Torres Straight down the east coast.