Every Seashell Has a Story: Hawaiian Stromb, a Very Rare Find

by B. N. Sullivan

Over the years we have become quite adept at finding shells underwater, but some species that we wanted for our collection were elusive for a long time. There were some we had seen in books or displays that we just never came across in the ocean. In other cases we had found the shell, sometimes on numerous occasions, but only ones that still had the critter living inside.

As I mentioned in an earlier post about shell collecting and diving, we do not take live shells that we find in the ocean, so we are especially delighted when we come across an uncommon or particularly beautiful shell that also happens to be empty.  In the previous post, we told the story of finding an Arabian Cowrie in the Red Sea.  In this post and the next, we'll tell the stories of a few more very special seashell finds.

The shell on this page is a Hawaiian Stromb (Strombus vomer hawaiensis),  a very rare Stromb subspecies endemic to Hawaii.   [Click on the photos for a larger view.]  Not only does it exist only in Hawaiian waters, the Hawaiian Stromb only dwells at depths below 25 meters (more than 80 ft), so the likelihood of finding it on a beach is nil, and snorkelers will never get to see it in the water, either.

The find was quite accidental: we weren't even looking for shells at the time.  We were doing a deep dive -- on a mission to photograph some cerianthid tube anemones that lived on a sand flat at Puako at a depth of about 40 meters (around 130 ft) and below.  Not wanting to rack up any more decompression time than we had planned and prepared for, we had descended quickly to the sand flat, and we were hustling to the spot where we knew the anemones lived.

The surface of that particular sand flat is relatively barren terrain, with very few rocks or other features -- just hard-packed sand and mud, gently sloping into the deep for as far as the eye can see.  For that reason, things that stick up out of the sand -- even small things like the cerianthids we were there to photograph -- are relatively easy to spot.  In this instance, what Jerry spotted as he swam along was the pointy tip of the Hawaiian Stromb shell protruding from  the sand.

As Jerry tells it, he recognized immediately that it was a piece of shell, but he figured it probably was a broken shell.  He dug it up, curious to see what kind of shell it might be, way out there in the middle of nowhere.  I watched him uncover what turned out to be a whole shell, not a fragment.  

When Jerry picked it up and brushed the sand away with his glove, I heard him shriek and saw his eyes widen behind the faceplate of his dive mask.  He held out the shell to me, and it was my turn to shriek when I realized what species it was.  The aperature of the shell was packed with sand, indicating that there was no animal inside.  What an exciting find!

This Hawaiian Stromb was a bit crusty from having been buried in the sand for who knows how long, but it cleaned up very nicely.  Our specimen is 7 cm (2.8 in) long.  It has become one of the greatest treasures in our seashell collection.

More seashell stories to come, after Wordless/Watery Wednesday...