Cockles Raised in Floating Nursery for Population Boost

Suquamish Tribe shellfish biologist Elizabeth Unsell was nervous about spreading several years’ worth of work on a beach recently, in the form of thousands of thumb-sized cockles.

“This is the first batch of these juveniles that we’re putting out in the real world,” she said. “So much work has gone into making sure they survived spawning and their time in our shellfish nursery in the past year.”

The tribe has been working with the Puget Sound Restoration Fund (PSRF) to establish a cockle broodstock program as part of the tribe’s effort to reestablish a population on its reservation.

This has been a controlled and monitored grow-out trial, to avoid interactions between wild and hatchery populations, said Ryan Crim, PSRF’s hatchery director.

Adult cockles were collected from the beaches at Kiana Lodge and George Lane in 2019 and taken to the federal Kenneth K. Chew Center for Shellfish Research and Restoration in Manchester for spawning and rearing.

After the adults were spawned and the offspring were reared to juvenile sizes, the cockles were transferred to the tribe’s floating shellfish nursery (a floating upwelling system called a FLUPSY) in Brownsville last summer. They stay in the FLUPSY feeding on plankton until they are big enough to be relocated to the tribe’s beaches.

On the beach, clams are divided up into plastic mesh bags that are clipped to an anchor line, protecting them from predators.

The first transfer was successful, Unsell said, with only a handful of mortalities out of the more than 3,000 that were placed in the bags in May. More than 80,000 were added to the bag system in early June.

“The shellfish feed on algae and plankton, and there is a lot of food in the water right now, which helped their growth in the FLUPSY,” Unsell said. “We hope the clams will continue to grow quickly in the bags on the beaches.”

The shellfish is a delicacy for tribal members, with older generations remembering harvesting them by the dozens. But tribal members have observed a significant decline the past few decades, Unsell said. 

The tribe and PSRF also are learning more about the cockle’s life cycle and genetics, testing them for diseases and determining best hatchery practices.