Published on 23 April 2018

Piha's Giant Shore Anemones

A while ago I had the pleasure to read the book Seashores, an ecological guide by Julian Cremona. I knew rocky shores were highly rich ecosystems but this book increased my curiosity so I decided to go exploring the rock pools down by the beach. I undusted my old compact Lumix and water case and spent a few days having a go at underwater photography as the water was quite warm (about two months ago). In the process I learned heaps, discovered species I never heard of and came across some really interesting websites.

You might not be aware on how much goes on in these rock pools. At first sight they might appear half-empty,  with just a few mussels and crabs, but if you take the time to look closer, what you discover might blow your mind. One of my favorite species out in these ecosystems are sea anemones, or kotore, in Te Reo Māori. 

Giant Shore Anemone, Oulactis Magna, is probably the most abundant sea anemone species here in Piha. It can be found in pretty much every rock pool from North Piha to the Gap. They look amazing and come in different colors and sizes, with a body diameter of about 100mm max. They're known to be able to live up to 70 years, which sounds like an awful lot to me! When they're not closed and all the tentacles are spread, they resemble a beautiful flower, with sometimes more than 150 tentacles gracily flowing around their cylindrical body.

Oulactis Magna

Oulactis Magna, Lion Rock - March 2018

The tentacles are equipped with a stinging mechanism that paralyses the prey and deposits it into the central cavity. You can usually spot rests of small crustaceans or shells outside of the cavity as a result of this process.

Giant Shore Anemone group

A busy rock pool, Lion Rock - March 2018. Note the remains of the predated shell in the cavity of the anemone in the center.

During low tide you can visit the rock pools and enjoy these magnificent animals. If they are submerged they're likely to be open, and that's when I like to photograph them. If they're not underwater, then they're closed and look like lollies. Depending on the type of sea anemone, you might find it in the bottom of the rock pools or hanging on the walls, well away from direct sun light.

If you're keen to learn more about sea anemones and other species inhabiting rocky shores, then I strongly recommend you the Collins field guide to the New Zealand seashore by Sally Carson and Rod Morris. It's a magnificent book with great images and descriptions to help you identify and understand any creature you might come across along New Zealand's shoreline.

I also got inspired by Dr. Matt Jones blog and his excellent inter-tidal sea anemones guide. His explanations are easy to get as he doesn't use much sci-ency jargon and his pictures are amazing. If you're into Instagram make sure you follow his account. Hopefully you'll find it as fascinating as I do! I'll be posting more material in future entries. Kia ora.