September 29, 2025

By Mel Lemke, WSG Science Communications Fellow

A basket cockle (Clinocardium nuttallii) half buried in sediment. Photo courtesy of Elizabeth Unsell.

Basket cockles (Clinocardium nuttallii) are saltwater clams native to the Pacific Northwest. With their charismatic ruffled shells and colorful banding, they are easily recognizable at low tide, peeking out from their fine-sediment habitats among eelgrass beds. These clams are more than just beautiful: as a preferred First Food (a food gathered and consumed since time immemorial), they hold significant cultural and nutritional value for the Suquamish Tribe.

“The smiles, joy, and connection that cockles bring to folks is worth its weight in gold,” says Suquamish Tribal Council member and elder Jay Mills, noting the importance of cockles in celebratory settings. Cockles are a favorite delicacy that, when possible, are featured in Suquamish clam bakes, an important feature of birthdays, weddings, funerals, and other gatherings and celebrations. Consuming cockles helps the Suquamish people to maintain their history, traditions and connection to the land, waters and one another.

Despite their importance to the Suquamish Tribe, cockles are not as available to Tribal members as they once were. Traditionally the Suquamish harvested wild cockles in abundance, waiting for low tides to find the clams on Puget Sound’s tidelands. But in recent years, increased ecological stressors from human-caused pollution, alongside the transmissible bivalve neoplasia (clam cancer), may have negatively impacted some of the Sound’s bivalve populations. Stresses to wild populations combined with limited knowledge on how to rear cockles using mainstream aquaculture practices have made basket cockle availability to Tribal members a significant area of concern. 

A Washington Sea Grant-funded research project aims to enhance subsistence access to cockles for the Suquamish People by investigating restorative aquaculture strategies that aim to minimize or eliminate any negative impact on wild cockle populations. “Native species aquaculture [is] a complicated topic,” notes Elizabeth Unsell, a shellfish biologist with the Suquamish Tribe and the lead on the project. While conventional aquaculture may focus on simply producing more cockles, native species restoration aquaculture needs to also ensure the health of wild cockle populations. This is done largely through understanding and maintaining wild genetic diversity.

Cockles protected from crabs by predator exclusion mesh during experiments. Photo courtesy of Elizabeth Unsell.

The first step towards increasing cockle abundance and access, then, was to document the genetic diversity of Washington cockles. This analysis provided critical background knowledge to the researchers, giving them a frame of reference to use while learning about cockle aquaculture and aiming to safeguard the health of wild populations. The results of this initial genetic testing demonstrated that while some populations of cockles show genetic variation, many cockle populations in Washington state have substantial genetic similarity. A high degree of relatedness between known cockle populations is a good thing for the project because it allows researchers to transfer cockles between strongly related populations without risk to wild cockle population genetics. 

With this knowledge, experiments could begin to determine the best methods for supplementing cockle populations. The two-part project included a transplantation experiment to investigate methods for successfully transporting batches of juvenile cockles from locations of high abundance to low abundance. The team harvested cockles from geoduck tubes in south Puget Sound, where they are a nuisance to geoduck farmers, and moved them to a beach in Central Sound for close monitoring. Cockles were out planted using several different treatments to test which treatment would result in the greatest success in terms of survival and retention. Some cockles were placed in a garden bed, some under predator exclusion mesh, and some on bare substrate with no protective garden bed or mesh. Researchers then repeatedly returned to these treatments to sample cockle survival and retention over time.

The results of the transfer experiment were clear. “We determined that if we want to transfer cockles on any sort of scale, we need to be protecting those animals with mesh if we want higher survival and retention rates,” Unsell says. 

Armed with information on how to successfully transplant adult animals, the researchers took another step in the process of restoring cockle access: learning more about hatchery production of cockles. Specifically, the team is investigating different hatchery strategies aimed at increasing the genetic diversity and survival of cockle offspring. 

Cockles on shore at low tide with Mt. Rainier in the background. Photo courtesy of Elizabeth Unsell.

Though the nature of cockle reproduction is fascinating, it can also make rearing the clams in hatchery conditions somewhat complicated. “Cockles are simultaneous hermaphrodites, which is super fun,” Unsell remarks. “Every animal is seasonally producing both sperm and eggs, alternating one after the other.” However, this also means cockles are susceptible to “selfing,” or fertilizing their own eggs–not ideal for maintaining a genetically diverse population. Luckily, cockles are successful batch spawners, meaning multiple reproductive individuals release their gametes into the water at the same time. Because this strategy can increase overall genetic diversity and reduce the probability of selfing, another goal of the research project is to examine the genetic diversity produced by different family sizes used for batch spawning. By assessing the genetic diversity of the offspring produced by different batch sizes and comparing these genetics to wild cockles, the team can find the best number of cockles to use when spawning in hatchery conditions in order to optimize the genetic diversity and create cockles with higher potential to thrive. 

The research project is still underway, and one future step is to fine tune the best out planting techniques for hatchery produced cockles. Unsell and the team are excited to care for the hatchery-bred cockles until they are old enough to use in the next round of out planting experiments, and to learn more about successful breeding and rearing strategies. While the science behind cockle restoration aquaculture is exciting, the project doesn’t just focus on cockles from a research perspective. To highlight the cultural significance of cockles and the importance of cockle restoration, in February 2025 the Suquamish Tribe hosted Celebrate the Cockle: Weaving Together Tradition & Science, a multi-day event that brought together Tribal and other folks from across the region and as far north as Alaska to talk about all things cockle. Despite a power outage, the event showcased a mix of culture, science, and restoration learnings, and further highlighted the importance of basket cockles to Tribal members, scientists and community members alike.

With the continued dedication and hard work of Tribal members, aquaculturists and research teams, the restoration of the basket cockle for subsistence access is one step closer. Though restorative aquaculture is a complicated and sometimes lengthy process, the hard work is well worth it, and the support for these efforts is extensive. The hope is that cockle restoration will ultimately protect access to a culturally significant, preferred First Food. By using ecologically restorative practices, the return of cockle abundance will not only benefit the people who love them, but will safeguard the health of wild cockle populations, ensuring they can be enjoyed by generations to come.