Puka shell necklaces are super famous and they sell in most of the jewelry shops here in Hawai‘i, but most people do not know what a puka shell is. You can walk on the beaches here in Hawai‘i and pick up these small round white shells, which are quite common especially after large surf.
When I scuba dive, I often find cracks in the lava reef just packed full of puka shells. Not all puka shells are the same shell.
Puka shells are just the top part of a cone shell that has been ground down in the surf. The top part of the shell is the hardest part due to the round circular patterns that are growth lines in the shell. The more circular lines in the shell top means it is an older shell. Similar to the growth rings in a tree.
It may take years for one dead whole cone shell to be ground up in the surf to produce one puka shell on the beach. Hawai‘i has a lot of puka shells because we have big surf. Many other tropical islands have no puka shells because there is a barrier reef protecting the beach from the surf.
Sometimes you can find hundreds of puka shells up on the beach, but divers rarely see live cone shells out on the reef so where do all of these puka shells come from? There are about 10 different species of cone shells that make pupu‘ala the puka shell, but once they are ground down it is hard to tell one species from another.
I spent many hours out scuba diving looking for live cone shells, day and night, as I know there must be a lot of them out on the reef to make so many puka shells on the beach. For years, I was confused because I could only find one or two cone shells in an hourlong dive and that would not make up for the hundred puka shells I found on the beach the same day.
I finally was given a clue as to where the live cone shells live. It was a small trail in the sand that gave it away. I found a 3-foot long little trail through the sand next to the reef and wondered what made the trail. At the end of the trail was a small mound of sand.
I slowly put my gloved hand under the mound and brought up a beautiful 2-inch long live flea cone! For the rest of the dive, I found a dozen more little trails in the sand and dug up a dozen more flea cone shells. As soon as I put the live cone back on the sand, it buried itself within a few minutes and was gone.
Now that I know where the future puka shells are living, I find them all the time and now know what makes our puka shells. I also found out that pupu‘ala feeds on small worms that live in the sand and they slowly crawl through the sand looking for worms to eat.
So the beautiful puka shell necklace you wear is actually the top part of a worm predator. You can see pupu‘ala in action in my new movie coming out soon called “Amazing Hawaiian Sea Shells.” It will be posted up on my YouTube at Underwater2web. If you sign up on the YouTube channel, you will receive all of my new underwater movies as soon as they come out.
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Terry Lilley is a marine biologist living in Hanalei Kaua‘i and co-founder of Reef Guardians Hawai‘i, a nonprofit on a mission to provide education and resources to protect the coral reef. To donate to Reef Guardians Hawaii go to www.reefguardianshawaii.org.
