January 6, 2025

It’s a season of new beginnings, and as we transition into the New Year, we continue to wrap up what 2024 meant in terms of the European green crab invasion in Washington. And as WSG Crab Team wraps up the 10th year of green crab monitoring, we also find ourselves reflecting on the last decade. In the next few blog posts, we aim to share some of these summaries and reflections. We will provide some updates about what monitors, trappers, and researchers have seen in the status and trends of the European green crab invasion in Washington state during 2024. And we’ll discuss what 10 years means to the program and what comes next for us as we enter the second decade of Crab Team.

2024 in Crabs

More than 1 million green crabs were removed from the shorelines of our state last year – by far a record year, though not one we are excited to have set as a state. That number also reflects a record high trapping effort, literally hundreds of thousands of trap sets. A host of partners contribute to this combined total, and share their observations with other trappers working around the state so that we each gain a fuller picture of the invasion dynamics. Some groups, like the WSG Crab Team monitoring network, trap explicitly for the purpose of tracking the invasion, some folks trap as part of projects to answer focused research questions, and many trap to try to reduce the population growth and spread of green crab. But when we can pull our observations together, we can learn much more than any of us could do alone! (If you are interested in more data explorations, check out the WDFW Green Crab Hub).

Because there is so much to cover, we will break this into multiple posts, the first of which will focus on the Salish Sea portion of Washington shorelines. 

Big Picture

Across the Washington portion of the Salish Sea, green crabs continued to slowly, but noticeably, expand their foothold in 2024. The 2023-2024 winter was a moderate El Niño year, with relatively warmer water temperatures that allowed for greater survival of green crab larvae. This was most evident in green crab concentrations in Whatcom and Skagit Counties. From Drayton Harbor through Padilla Bay, 2024 was a year of very strong “recruitment,” meaning a lot of juvenile green crabs started appearing in traps in late summer, continuing through fall. This influx of juveniles meant that overall at these sites, 2024 capture rates were much higher than 2023 rates, generally. 

This pattern didn’t hold everywhere, however. Sites along the north portion of the Olympic Peninsula had catch rates similar to previous years (but see Discovery Bay below), but fewer young of the year that were more consistently spread across the entire trapping season. Within Hood Canal, Seabeck and Dabob Bays continued to yield crabs at similar rates to last year, but without evidence of decline either. 

One concerning observation this year was the capture of a large green crab at Cultus Bay, on the very southern tip of Whidbey Island. This is the furthest into Puget Sound green crabs have thus far been confirmed, and this crab was large enough to have been present at the site for a few years. 

Thankfully, in spite of increased search efforts, no green crab have been detected in central and south Puget Sound. Additionally, no detections were made this year in the San Juan Islands or in the Whidbey Basin. We explore these patterns with some regional details below:

Strait of Juan de Fuca:

• Across this stretch of shoreline in 2024, sites where green crabs were found remained consistent with previous years, including sites where green crabs were found for the first time in 2023 along the western portion of the Strait: Neah Bay, Salt Creek, and the Tse-whit-zen Lagoon (in Port Angeles). 
• Populations did not appear to significantly decline at any of the sites. In fact, catch rates substantially increased in Discovery Bay, and a green crab was captured in Sequim Bay for the first time
  

  Crab Team volunteers at Kala Spit captured a green crab during monthly monitoring in April – the first at that site since 2018. Photo Courtesy of Kala Crab Team.

  in two years.

• The presence of crabs at each of these locations still remains largely concentrated to specific habitats, particularly those associated with a small amount of freshwater input. While green crabs don’t do well in large river channels, they seem to also do best where there is a small stream with regular flow, sort of a goldilocks situation.
• At most sites in this region, some young of the year were captured, and this occurred at a relatively consistent, if low, rate across the season.

Hood Canal:

• The only detection sites within Hood Canal were in the northern portion, Seabeck and Dabob, but catch rates did not reflect a decrease in numbers at either site relative to last year. 
• An oyster grower in the head of Dabob Bay has trapped a number of green crabs near their shellfish operations, which is not shown on the map above. 
• Most of the crabs captured in this region this year were quite large, and greater than 2 years old, with only a few new arrivals (young of the year). 
  

  Annual average catch rate (number of crabs per 100 trap sets) at four sites along the Strait of Juan de Fuca and Hood Canal. Click to enlarge.

Northern Water Bodies:

• Catch rates were quite a bit higher in 2024 than 2023 at sites with long term control trapping efforts (Drayton, Lummi, Samish and Padilla Bays), largely due to a very strong recruitment pulse of young of the year crabs arriving late in the season.
• One exception is that the catch rate within the boundaries of the Lummi Sea Pond remains low and in fact was lower than the catch rate on the tidelands outside of the sea pond. This underscores the separation of the sea pond from the oceanography surrounding it. 
  

  NERR biologist Angelica Lucchetto sets a minnow trap with Crab Team student assistant Zach Bengtsson at Padilla Bay, one of several sites in Whatcom and Skagit to see large increases in catch at the end of the 2024 season. Photo: WSG/Lisa Watkins

• Many of the young of the year were captured in specific locations within these water bodies, often accumulating near the northeastern portion of the water body, and/or associated with protective structures, like pilings.
• A similar pattern occurred in 2022, similar both geographically and seasonally. The following year, catch rates dropped as some of the young of the year didn’t survive the subsequent winter and many more could be removed when waters warmed up again the following spring.

Puget Sound:

• The Admiralty Inlet region was more active than in previous years: one crab was captured at Kala Point near Port Townsend and four crabs (0-1 years) at Lagoon Point, the first captures there since 2018. One green crab was captured in Cultus Bay, the furthest south in the main stem of Puget Sound green crabs have so far been confirmed (none were found during additional follow up trapping). This remains the leading edge of the invasion. These more consistent observations could indicate green crabs are building steam and pose a risk to regions further into Puget Sound
• Trapping in Central and South Sound was broader than in previous years,  including new sites and additional partners. Thankfully, efforts to date have yielded no evidence of green crab.
  

  Average annual catch rates (crabs per 100 trap sets) at four sites in Whatcom and Skagit counties with extensive trapping. Click to enlarge.

These observations combine to suggest that European green crabs continue to require dedicated management, and we could also use a little help from nature. In places like Drayton Harbor, there is good evidence that, without the particularly successful recruitment year, catch rates would have been much lower than previous years (around 2.5 crabs per 100 trap sets). This does hint that an intense level of trapping can result in reduced populations in the short term, at least on the scale of a single water body. In order for these gains to be sustained, even through warm winters, trappers are working regionally to reduce the potential sources of larvae. 

One comfort to many green crab trappers is that this winter is predicted to be a cold La Niña, which we hope will result in poor survival of any green crab larvae in Washington waters. Groups are already planning for 2025 trapping and discussing how soon they will be able return to the mud and clean up the crabs that eluded us in 2024.

–Emily Grason

Partner data contributed by: Washington Department of Fish & Wildlife, Northwest Straits Commission, Washington Department of Natural Resources, Padilla Bay NERR, Suquamish, Squaxin, Lower Elwha, Jamestown, Port Gamble, Lummi, Swinomish, Taylor Shellfish, Tulalip Tribes, and more than 300 monitors with WSG Crab Team!

Header photo: Statewide trapping partners from the 2024 WSG Trappers’ Summit hosted by Crab Team at the Clearwater Casino in Suquamish. Staff from partners working with tribes, agencies, and shellfish growers convened in December, sharing observations and questions to help advance green crab management in Washington State.