The Suquamish Tribe is researching development of a hatchery program for cockles.
“While they are not harvested commercially by the tribe, they have cultural value,” said Elizabeth Unsell, a shellfish biologist for the tribe.
Tribal members have seen populations decline significantly on beaches where they harvest regularly, she said.
“Tribal members love them so we thought, ‘How can we help?’” she said. “We do not have data on the local cockle populations, but observed declines on popular cockle beaches have prompted a desire to help those populations rebound.”
Working with Puget Sound Restoration Fund (PSRF), the tribe sampled cockles in June from Sandy Hook, near Agate Pass, for spawning at the Kenneth K. Chew Center for Shellfish Research and Restoration in Manchester.
At the Chew Center, spawning is induced by heating the water temperature, said Ryan Crim, PSRF hatchery manager.
Like many other marine invertebrates, cockles are broadcast spawners. Individuals release their gametes (sperm and eggs) directly into the water column where fertilization and embryo development take place.
“Interestingly, cockles also are simultaneous hermaphrodites, meaning each individual is capable of spawning both as male and female,” Crim said. “Spawning individuals typically first release sperm and after some time, they switch and begin releasing eggs.”
In the hatchery, Crim collects eggs and sperm in small buckets and cross-fertilizes the gametes to maximize the number of parental crosses.
The resulting embryos develop into larvae that feed on algae and grow for a few weeks before transforming into juveniles, which will begin to look like tiny adult cockles, Crim said.
If all goes well in the hatchery, the juveniles, once big enough, will be transferred to the tribe’s shellfish nursery in Brownsville before being used in shellfish seeding projects.
Tribal staff would like to explore different out-planting methods and locations on beaches surrounding the reservation.
“Monitoring out-planting success may be challenging with this bivalve because of its capacity to move around easily,” said Viviane Barry, the tribe’s shellfish program manager. “Once released on beaches, a tagging experiment may be an interesting avenue to better understand the extent of cockle movement.”
Traditionally, tribal members harvested cockles by walking barefoot on the beach. When their feet struck a hard object, it was likely a cockle, Unsell said. In sandy substrate, cockles only burrow about two inches below the surface of the tideland, compared to littlenecks and Manila clams, which bury themselves deeper in their preferred habitat of gravel and sand.
Cockles also are much more mobile than other clams, Crim said. Manilas, littlenecks and butter clams tend to stay in place on the tideland, while the cockle, with its strong foot, often will move to other areas of a beach. The foot gives them mobility to escape from predators such as birds and sea stars and find refuge, such as under a dock to shade themselves from the sun.
The foot also is what the tribe traditionally prefers to consume, Unsell said.
Scientists from British Columbia have conducted studies about cockle spawning and their life cycle, which the tribe and Crim is using as a guide to develop the hatchery program.
“They found that the cockle is a great candidate for aquaculture, particularly due to its fast growth rate but its shelf life is not great, especially for commercial market,” Crim said. “For subsistence though, it’s great for tribes.”
Ryan Crim, hatchery manager for Puget Sound Restoration Fund, inspects a selection of cockles to spawn at the hatchery in Manchester. Photo: Tiffany Royal