Skip to main content Skip to navigation

Molt Search

People standing on the beach

Photo by Jess Newley, Friends of the San Juans

Molt Search helps protect Washington’s shorelines from an invasive crab

The European green crab is a hardy and voracious predator native to Western Europe and Northwestern Africa.  This species has invaded intertidal zones around the globe and, according to the Washington Department of Fish and Wildlife, it is considered one of the world’s worst invasive species. 

This invasive crab threatens shellfish and juvenile Dungeness crab, eelgrass beds which provide critical habitat for juvenile salmon, the food supply for shorebirds, and the overall health of Washington’s marine waters.   

How you can help

Washington State University Extension and Washington Sea Grant have teamed up to launch a new volunteer-based early detection program called Molt Search.  If you enjoy walking on the beach, or have shoreline property, you can make a meaningful contribution to help prevent this voracious predator from establishing large populations in the Salish Sea.   

How does Molt Search work?

  1. You conduct a 20-minute search for crab molts on the beach (10-minutes if working with a friend, 5-minutes if working as a team of 4).   
  2. You take a photo of your molt collection,  
  3. You identify the molts you found,  
  4. If you’ve found European green crab molts or wish to collect data on Dungeness crab molts (an optional component of Molt Search), you take some measurements of some of the molts, and  
  5. You report your findings via the free MyCoast app.   

Molt Search Training & Events

Attend a Molt Search Training!  You’ll learn how to conduct a systematic survey for crab molts, how to properly identify the European green crab and distinguish it from our commonly found native crabs, how to take measurements of the crab molts and how to report your findings using the MyCoast mobile app. 

Training and event dates for 2024 have not been scheduled, yet.  Check back here or sign up for the Molt-o-Meter Newsletter to get information on upcoming events (and other crab news) delivered to your inbox. 

Read past Molt-o-meter newsletters

Molt Search Resources

Download the Molt ID guide and Molt Search protocol.  

Crab identification guide
Molt Search ID Guide

Molt Search Survey Protocol
Molt Search Survey Protocol

You can view the most recent Molt Search reports on the MyCoast website on the MyCoast Molt Search Reports page here or you can visit the MyCoast homepage here  The MyCoast app is free and available for download for Apple or Android.

Frequently Asked Questions

Frequently Asked Questions

How do I start Molt Search? 

  1. Joining Molt Search takes just a few steps: 
  2. Attend a training workshop. Held virtually and in-person across the region in summer months (see calendar).  Molt Search trainings cover European green crab invasion background, crab identification, and Molt Search protocols. 
  3. Create a MyCoast Account. This is where you’ll log your report, either via the app or the website. 
  4. Do Molt Searches on any of Washington’s Salish Sea shorelines, as often as you’d like. 

Where should I do a survey? 

This program is designed to get more eyes on more shorelines to help managers detect new populations of green crab. For this reason, your surveys are most valuable on shorelines of Washington’s Salish Sea. Molt Searches can be done on any shoreline where you have safe, legal access. Be aware of local collection and access regulations. Take a look at the map of where previous Molt Searches have been submitted. The more coverage, the better! 

Note: Molt Searches are welcome on Washington State Park shorelines, too! Scientific Research Permit #230603 covers these activities. 

When should I do surveys? 

Surveys are welcomed from any time of day or day of the year. Because molts are a result of crabs outgrowing their shell, you’ll likely find more during warmer months (May-October) when crabs are growing more quickly. You are welcome to conduct Molt Searches as frequently or seldom as you’d like. A monthly survey from a shoreline near you would be a great contribution to the dataset! 

Can my friends join me on a Molt Search? 

Yes! Molt Searches can be done in teams of up to 4 people, and only one of those must be trained. To help us maintain our data integrity, anyone who hasn’t yet attended a volunteer monitoring workshop should rely on a trained volunteer to direct the search and submit the group’s report via their MyCoast account. Have fun working together to gather and identify all the molts you can find!  

If your friends want to do more molt searches on their own, help them find an upcoming training to learn how to submit their own data. 

How do I know if I’ve found a molt or a dead crab? 

Because we’re interested in the presence or absence of green crabs and Dungeness crabs, don’t fret too much about this distinction. 

If you’re unsure, feel free to submit additional photos of the individual in question with your report and add any notes or observations in the Field Notes/Comments section on the last page of the MyCoast reporting form. Sometimes it can be tricky to tell if the shell in your hand is a molt or dead crab. To get to the bottom of it, we’ve outlined four questions you can ask yourself: 

  1. Is there any obvious trauma? Some predators will leave specific clues behind after munching on crab shells. Looking for these clues may help you distinguish between a molt or a dead crab that met an unfortunate demise. 
  1. How heavy is it? Molts are typically much lighter than dead crabs with tissue still in-tact. 
  1. Does it open? Because molting crabs essentially climb out the back of their shells, the shell of a molt should easily open on a hinge (much like a jewelry box). If it’s hard to open, it’s likely a dead crab. 
  1. What’s inside? Molted shells should be quite clean inside, while dead crabs may contain goo or crust of internal tissue. Remember that feathery gill tissue appears in molts too. 


A molt (left) will have a clean shell interior, and open like a jewelry box hinging at the eyes. A dead crab (right) may be filled with “goo” of various colors in the middle section of the shell and attached to the inside of the carapace. Note that both crabs appear to have gills, while the molt actually only has the molted coverings of the gills. Photos Jeff Adams and Emily Grason 

Curiosity piqued? Read even more in this WSG Crab Team blog post.

What if I find a species I can’t identify? 

The Molt Search ID guide has many of the species that we think you are likely to see in your molt surveys, but it doesn’t include everything and every beach is different. It also can take some practice to feel confident in your species identifications!  

If you find anything you can’t identify, make sure the molt is in your collection photo and leave us a note in the Field Notes/Comments section on the last page of the MyCoast reporting app. You can also include an additional, close-up photo

of your mystery molt. 

Can I edit a report after I submit it? 

You can edit or delete reports from your computer via the MyCoast website. From there, log in to your MyCoast account and then use the top menu bar to navigate to “My Account” > “My Reports” to view, edit, and delete your submitted reports. If you have trouble, feel free to send the Washington Sea Grant Crab Team an email ( with any notes or amendments. 

What happens to my data after I submit the survey? 

Each and every report you submit gets monitored by Washington Sea Grant staff for reports for European green crab findings. Visit to view all the new reports coming in. 

Whether or not a report includes green crab, the locations of Molt Searches will be included in annual planning conversations where Washington Sea Grant works with WDFW and local partners to best distribute limited monitoring resources across the region. It’s important to know where searches have yielded no evidence of green crab presence, so that search efforts can instead be focused on locations that have yet to be explored. 

All confirmed detections of European green crabs in a new water body will be directly communicated to WDFW and relevant local partners. From there, managers may initiate a follow-up trapping effort to determine the extent of the location population. Based on the outcome of that assessment, managers and scientists discuss what ongoing efforts may be appropriate for the site—ranging from continued monitoring, repeated assessments, or intensive control trapping. Learn more about how European green crabs are managed in Washington at WDFW’s European Green Crab Hub. 

How can my group host a Molt Search training?  

We are currently developing our plans to further expand our workshop offerings. There are currently two ways your group can hold a local Molt Search training.  

  1. Send a representative to our annual train-the-trainers workshop, where they’ll learn how to organize a public-facing Molt Search workshop and teach these protocols in your local community. Workshops given by facilitators who attend a “train-the-trainers” are supported by Molt Search advertising and materials. 
  1. On a limited basis and with some date coordination, Molt Search staff can send a trainer to your group’s meeting. 

Start a planning conversation by sending us an email:   

WSU logo

Molt Search program logo

Washington Sea Grant logo