Editorial: Riddle of the giant sea snails

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

It is continually surprising what lies beneath our seas.

This week, large sea snails have washed up on Northland beaches. On east coast beaches as far south as Mount Maunganui, for that matter.

The large sea snails - tonna tankervillii - are more commonly known as the cask shell.

Unlike scallops, which wash up on our beaches after a big blow, cask shells aren't too tasty.

Unless you are a sting ray, which are fond of crushing the shells and eating the contents.

Why they have appeared on Northland beaches is a mystery that would only be unravelled by scientific testing, and it seems no one is concerned enough to go that far.

Also, tonna tankervillii is as common as sea snail muck, and only items on the endangered list warrant concern when they start washing up miles from their natural environment en masse.

Which is interesting. There have been no storms recently that have washed the snails on to beaches, and these things are the size of a cannonball - probably a bit lighter though - so they'd take some pushing ashore.

It makes me curious. If birds - something that we encounter almost daily - started dropping out of trees, we would want to know why. Particularly if it was happening across the North Island.

In the absence of a storm, has recent seismic activity affected these sea creatures? Have they been poisoned by pollution?

Has a giant school of stingray swum the length of the North Island on some form of migratory feast, discarding tonna tankervillii in a left, right and centre frenzy?

Or have tonna tankervillii decided to evolve and come ashore?

The ocean is a mystery, and it seems that the presence of these common sea snails on our beaches will also remain a mystery. Which I find odd.

I thought humans were more curious than that.