Lion's mane jellyfish invade Whangarei Heads beach

This gorgeous, mound of jelly was one of many found washed up on the Whangarei coast after rough seas and high tides.

But while they look more like a discarded party dress than a toxic bomb, beachgoers are being warned not to go poking around underneath these jellyfish in case any poisonous tentacles still pack a punch.

Andrea Robinson, who supplied this photo, said there were many of them at the high tide mark at McKenzie Bay, Whangarei Heads, on Saturday but they were washed away again by the next day.

They varied in size from a large dinner plate to a 10-speed bicycle wheel.

Several people have reported a high number of jellyfish in the waters around the coast but it's "the beautiful, big, pink ones" that have caused the biggest stir.

The Advocate contacted Auckland Museum's curator marine invertebrates, Wilma Blom, who said, "Wow, that is some jellyfish!"

They were the lion's mane (Cyanea) species which were known to inhabit Arctic and cold north Pacific waters, Dr Blom said. Scientists were still arguing about exactly which species occur in southern Pacific, Australian and sub-Antarctic waters, she said.

The lion's mane is the largest known species of jellyfish. The name lion's mane is applied to a number of closely related species, some of which (such as Cyanea rosea and Cyanea annaskala) appear in our region.

Photo / Andrea Robinson

"One thing, though, is that you should treat all of them as capable of stinging, even after stranding," Dr Blom warned.

"However, your specimen appears to have lost all of its trailing tentacles, which is where most of the stinging cells are concentrated. But probably to be on the safe side, don't touch, or wash hands after touching."

Photo / Andrea Robinson

It was unusual to see large numbers washed ashore. They were not rare but people didn't see them often because they were oceanic, Dr Blom said.