Recent reports have highlighted a concerning surge in the population of European green crabs within the Salish Sea, particularly within the Lummi Nation’s sea pond. The Lummi Nation reported capturing over 70,000 of these invasive crustaceans this year alone, raising alarms about the escalating threat they pose to the delicate ecosystem. This dramatic increase underscores the urgent need to understand and address the growing presence of European green crabs in this vital Pacific Northwest region. The situation prompts a crucial question for many following these developments: What Does Wsg Mean in the context of these conservation efforts?
Map showing the distribution of European green crab captures along inland Washington shorelines in 2021, highlighting areas with varying levels of crab presence and trapping efforts.
To clarify, WSG stands for Washington Sea Grant. This organization plays a pivotal role in marine research, education, and outreach throughout Washington State. As part of a national network of Sea Grant programs, Washington Sea Grant is dedicated to the sustainable use and conservation of coastal and marine resources. In the context of the European green crab invasion, WSG is actively involved in research, monitoring, and collaborative management efforts aimed at controlling this invasive species and mitigating its impacts on the Salish Sea ecosystem.
The alarming number of green crabs captured by the Lummi Nation signifies an exponential population increase within their sea pond since their initial detection in 2019. This location now represents the largest concentration of European green crabs along inland Washington shorelines. The Lummi Indian Business Council’s disaster declaration underscores the severe threat to tribal resources and emphasizes the critical need for enhanced control measures. These actions are essential to protect both the Lummi Reservation and the broader region from the accelerating spread and detrimental effects of this invasion.
Context within the Salish Sea
The rapid population growth observed in the Lummi sea pond contrasts sharply with trends in the wider Salish Sea. Across other sites, collective trapping initiatives spearheaded by WSG, the Washington Department of Fish and Wildlife (WDFW), and various partners have not indicated major range expansions of green crabs this year. Captures have largely been confined to locations where green crabs were already known to exist, primarily along the Strait of Juan de Fuca and in Whatcom and Skagit counties.
Furthermore, capture rates, an indicator of population size, have remained relatively low at managed sites. Notably, Drayton Harbor, near Blaine, even witnessed a significant decrease. These findings offer a glimmer of hope, suggesting that trapping, potentially aided by natural environmental factors, can effectively manage small, localized populations in many areas.
The stark difference in the Lummi sea pond situation raises important questions. This 750-acre artificial lagoon, established 50 years ago, supports salmon and shellfish hatcheries. Unfortunately, it now also harbors a rapidly expanding green crab population. The lagoon’s expansive shallow waters have limited connection to the natural tidal flows of the adjacent flats. This restricted tidal exchange results in dampened water level fluctuations and more extreme water temperatures compared to open water environments.
These unique conditions make the sea pond less favorable for natural green crab predators, such as larger cancrid crabs and fish that typically prey on juvenile green crabs in open shorelines. Additionally, the reduced water flow within the sea pond effectively traps larvae produced by the dense crab population. This larval retention increases survival rates in these conducive conditions until they reach settlement size. Conversely, larvae released in open tidal flats or marshes are often flushed out of the habitat, facing higher mortality rates before settlement. Those that do settle in open environments are also more vulnerable to predation as juveniles compared to their counterparts within the protected sea pond. Collectively, these factors transform the sea pond into an ideal “incubator” for European green crabs.
Washington Sea Grant (WSG) staff member, Amy Linhart, and Washington Department of Fish and Wildlife (WDFW) technician, April Fleming, inspect the Lummi Sea Pond for juvenile European green crabs in 2020, assessing recruitment levels. Photo courtesy of Emily Grason/WSG.
Currently, the sea pond appears to be the only environment functioning in this way within inland Washington waters. While not entirely isolated, the reduced water exchange compared to surrounding tideflats is a key factor. A significant concern is the potential for larval leakage from the sea pond, which could seed green crab expansion into neighboring coastal areas. Understanding the extent to which the sea pond population influences other sites requires ongoing investigation. Researchers continue to gather and analyze observational data, genetic samples, and oceanographic modeling predictions to better interpret these complex patterns of dispersal and impact.
Scaling Up Response Efforts at Lummi
Recognizing the urgency and the potential for further spread, the Lummi Natural Resources (LNR) department has dramatically scaled up its response efforts over the past two years. Trapping in 2020, involving collaborative efforts with WDFW and WSG, removed over 2,000 crabs from the sea pond during late summer. However, this August, as young-of-the-year crabs grew large enough to enter traps, average catch rates surged to nearly 300 green crabs per 100 trap sets. LNR trappers, with WDFW support when available, captured almost 6,000 green crabs that month alone, exceeding their capacity to manage and dispose of the captured crabs effectively.
Crew members from WDFW and LNR collaborating on European green crab removal efforts in the Lummi Sea Pond during September 2021. Photo courtesy of Emily Grason/WSG.
To rapidly increase trapping capacity, LNR partnered with personnel from WDFW, WSG, and the Northwest Straits Commission (NWSC). This collaboration tripled trapping efforts throughout the remainder of the summer and fall. A logistical advantage of the sea pond is its minimal tidal fluctuation, allowing for tide-independent trapping, unlike open water tideflats. This enabled near-continuous weekly trapping and the deployment of shrimp traps, which are effective for green crabs in permanently submerged locations. At peak operation, trappers deployed 500 traps simultaneously, pulling 1,200 trap sets weekly and exploring previously untapped areas of the sea pond. This level of effort surpasses the trapping intensity seen at most sites annually. These intensified techniques, unfortunately, revealed a more severe infestation than initially anticipated. In September and October alone, field staff trapped over 60,000 green crabs, marking one of the largest collaborative trapping operations of its kind on the West Coast. Despite this massive effort, capture rates continued to climb, peaking at approximately 900 green crabs per 100 trap nights by October.
Lummi Nation tribal leadership is deeply concerned about the escalating green crab numbers on reservation tidelands and is committed to coordinating a comprehensive response with tribal, state, and federal partners. While exponentially increasing trapping and removal is crucial, addressing the severity of green crab population growth necessitates a more holistic strategy. This strategy must effectively reduce and contain crabs within the Lummi sea pond and prevent further spread into Lummi Bay and adjacent areas of the Salish Sea.
Concurrently, ongoing monitoring and removal trapping at other Salish Sea locations remain vital. These efforts are essential to prevent smaller populations from reaching a critical threshold that could trigger rapid, unmanageable growth. Promising early results from trapping efforts at sites like Dungeness Spit and Drayton Harbor suggest that intensive, early intervention can effectively protect shorelines. In essence, proactive and intensive trapping can prevent localized outbreaks from becoming widespread infestations. However, the unique characteristics of the Lummi sea pond demand not only intensified efforts but also tailored management approaches to address this specific environment effectively. Crab Team, a program led by Washington Sea Grant (WSG), will continue to provide ongoing support to the Lummi Nation’s efforts throughout the planning and implementation process.
–Emily Grason (WSG) & Bobbie Buzzell (LNR)
2021 Detailed Reports for Salish Sea Sites
The following summaries provide updates from various sites across the Salish Sea, excluding the Lummi sea pond. Generally, capture rates remained low, and none approached the scale of removals seen on the Lummi reservation.
Graph illustrating average annual European green crab catch rates at four intensively-trapped sites in the Salish Sea, showing trends over recent years and highlighting variations in population levels.
Strait of Juan de Fuca
Sites along the Strait of Juan de Fuca experienced a slight increase in capture rates compared to 2020. This may be linked to growing green crab populations in coastal estuaries of Oregon and Washington, potentially releasing more larvae that are carried along the strait’s southern shore.
- Dungeness Bay: 8 crabs captured in 875 traps. Due to the significant decrease in capture rates in 2020, the USFWS reduced removal trapping efforts this year. The absence of young-of-the-year crabs in this season offers hope for continued low numbers next year.
- Sequim Bay: 16 crabs captured in 963 traps. Trapping by the Jamestown S’Klallam Tribe consistently yielded crabs, even into early November. While the total remains smaller than other sites and the capture rate is relatively low, the increase compared to previous years is concerning.
- Port Townsend region: In May, WDFW captured two green crabs at Bishop’s Point on Indian Island Naval Base during assessment trapping. No other crabs were found at historical sites like Kala Point or Scow Bay.
Whatcom County
Beyond the Lummi sea pond, WDFW and NWSC continued removal trapping at Drayton Harbor and monitored other locations in Whatcom County.
- Drayton Harbor: 135 crabs captured in 4,349 trap sets. The second full year of collaborative removal trapping at Drayton Harbor showed significantly lower capture rates than the previous year, including very few young-of-the-year crabs, indicating a positive trend.
- Sparse captures in other Whatcom County sites: Besides Birch Bay (one crab captured), Squalicum Harbor remains a site of interest. Five crabs have been captured in Squalicum Harbor, including two in a demonstration pot set at the Marine Life Center.
Skagit County
With small numbers of green crabs detected in Padilla Bay since 2016 and in Samish Bay since early 2019, trapping efforts have intensified at both sites.
- Padilla Bay: 12 crabs captured in 1,041 trap sets. In the fifth year since the first green crab capture, continuous trapping by Padilla Bay NERR staff has monitored the slow but consistent presence of green crabs. Crab Team volunteers at the Swinomish Casino marsh captured the first two green crabs at that location this year.
- Samish Bay: 118 crabs captured. Shellfish growers Bill and Andy Dewey (Taylor and Chuckanut Shellfish) conducted the majority of removal trapping from their boat throughout the season. Combined with WDFW and Padilla Bay National Estuarine Research Reserve trapping, capture rates are slightly higher than 2020 but within the range of other sites in Whatcom and Skagit counties outside the Lummi sea pond.
6 DEC 2021
