Moonsnail Shell Citizen Science

Moonsnail Shell Citizen Science

The Discovery Passage Aquarium is starting a brand new citizen science project, involving 2 iconic marine invertebrates found in Discovery Passage: moon snails and black eyed hermit crabs.


The Lewis' Moonsnail is the largest marine snail found along the coast of BC, and it also happens to be carnivorous! Their diet consists of clams,and sometimes other snails. To eat, the moonsnail uses its radula, a sharp tongue-like structure, to essentially drill a hole through the shell of its prey. You may have also come across a Lewis' Moonsnail's egg case during walks on a sandy beach. They look like the image below, and are often mistaken for garbage or other debris, and unfortunately, are removed from their habitat, or destroyed and crumbled.

Moonsnail shells are a staple piece of decor in every beachcomber's house, and while they are beautiful to look at on a bookshelf or window sill, they look even better as a home for a hermit crab. This was the idea behind our Shell Drive in July 2021 - to collect moonsnail shells and return them to the ocean, to be used by other animals.The event was very popular, and we ended up with a lot of  shells in great condition. 

Moonsnails' collar-shaped egg casings intrigue Vancouver Island  beachcombers - Victoria News

Black eyed hermit crabs are one of the largest species of hermit crab that reside around Vancouver Island. As they grow larger, moon snail shells become their only option for a home, as they cannot fit into any other species of snail's shell. Even though this is a common species found in the Pacific Northwest, not much is known about their ecology, if they migrate, or even their life span!

The black eyed hermit crab we have at the aquarium has quickly won over our hearts, and we would like to know more about them! Thus, the creation of this project.

The Citizen Science

This past week, we joined forces with a Grade 8 class at Southgate Middle School, to uniquely mark the moon snail shells we received from the Shell Drive. The students spent a good part of an hour carefully crafting each shell to be identifiable underwater. 

With these shells now marked, we will be distributing them around Discovery Passage. With the help of local divers and photographers, we should be able to track where the shells end up. Our main questions that we hope to answer are: 

  • Are there more Black Eyed Hermit Crabs in areas with higher availability of empty shells?
  • Do Black Eyed Hermit Crabs display site fidelity? (Do they leave and return to the same location over time?) 
  • How far does one individual Black Eyed Hermit Crab travel from the original site of the shell? 

An additional goal to this project is demonstrating that moon snail shells do an extraordinarily greater amount of good IN the ocean, as opposed to out of it. We are not saying you have to get rid of every single shell you have at home, but if you have boxes full of them tucked away, consider returning some to the beach.