Unsolved mystery: the case of the weathervane scallop

August 23, 2019

Mariculture in Alaska centers mainly around oysters. Kelp, blue mussels and geoduck clams are also farmed, but in much smaller quantities. Many Alaskans, including members of the governor’s mariculture taskforce, want to boost this fledgling industry to diversify the state’s oil-dependent economy, and researchers are trying to help develop alternative species for ocean farmers.

One of the species being examined is the weathervane scallop, also known as the giant Pacific scallop or Patinopecten caurinus.

Weathervane scallops in a holding tank in Juneau. Photo by Paula Dobbyn/Alaska Sea Grant

Prized by five-star chefs and seafood connoisseurs, weathervanes are a bit of a mystery animal. Major gaps exist in our understanding of the tasty mollusks, which are native to Alaska. In scientific literature, weathervanes are described as one of the most “data-poor” fisheries in Alaska, despite more than four decades of commercial harvesting.

“We as a scientific community know very little about weathervane scallops” said Diana Perry, who recently completed her one-year Alaska Sea Grant State Fellowship, working at NOAA Fisheries in Juneau.

Kevin McNeel, a fishery biologist with the Alaska Department of Fish and Game, said scientists have basic unanswered questions including how to properly determine the age of a weathervane, how fast they grow, and how abundant they are in Alaska waters.

“We also have a lot of questions about when the scallops spawn. Do they spawn multiple times a year?”

Answers to such questions would help better inform ecosystem management of weathervanes, which fall under both federal and state oversight.

Diana Perry observes weathervane scallops she studied at the Alaska Fisheries Science Center in Juneau. Photo by Paula Dobbyn/Alaska Sea Grant

The commercial fleet that harvests weathervanes in Alaska is also small. A handful of vessels based in Kodiak dredge them from beds located between 50 and 100 meters below the ocean surface. Other than the area around Kodiak Island, weathervane beds are located southeast of Prince William Sound in Yakutat Bay, in areas along the Alaska Peninsula and Aleutian Islands, and in the Bering Sea, according to Gordon Kruse, a fisheries professor emeritus at the University of Alaska Fairbanks College of Fisheries and Ocean Sciences.

Despite the small size of the fleet, the scallops are a delicacy in high demand. Driven by strong state and federal interest in increasing U.S. mariculture, Perry’s assignment was to take a deep dive into the world of weathervane biology to advance the science.

Working at the NOAA Fisheries building at Lena Point in Juneau and under the supervision of fisheries biologist Kristin Cieciel, Perry piloted a research project on weathervane reproduction and population structure, attempting to spawn the large scallops in tanks and then grow them in fresh seawater. One of the goals was to create protocols for future weathervane and pink scallop hatcheries.

“I’ve been working with the Alaska Department of Fish and Game to do, among other things, a growth-rate study, because at this point we don’t even know at what rate they grow. We wanted to find out whether weathervanes, or scallops in general, have the potential to bring aquaculture diversity for people who have farms in Alaska,” said Perry. “It’s still a work in progress.”

Besides measuring their growth and getting the weathervanes to spawn, Perry also studied the development of their gonads using the science of microanatomy.

The project was intriguing but not easy. Weathervanes are “testy and notoriously hard to work with,” Perry said.

“We’re still trying to get them to spawn in the lab. We haven’t gotten to the growing-out phase but we hope to get there soon. We don’t have a nursery for them, but in theory once we get to that phase we will be able to spawn them and get them to grow,” she said.

Although Perry’s fellowship is over and she has left the state to pursue doctoral studies at the University of Florida, another researcher is continuing the work. And Cieciel, Perry’s former supervisor, says the genetics methods Perry developed are being applied to other shellfish.

Former Alaska Sea Grant State Fellow Diana Perry and Kristin Cieciel, fisheries research biologist, Alaska Fisheries Science Center. Photo by Paula Dobbyn/Alaska Sea Grant

“We’re dipping our toes into abalone and oysters,” Cieciel said.

Shoreline in Juneau, Alaska. Photo by Paula Dobbyn/Alaska Sea Grant

Margo Reveil, owner of Jakolof Bay Oyster Co. and president of the Alaska Shellfish Growers Association, would like to see weathervanes become a part of her mariculture business. But numerous obstacles must be overcome first, she said.

Unlike oysters, scallops are generally shucked and only the meat—the adductor muscle—is sold. That extra processing can mean higher labor and equipment costs. Scallops also have a much shorter shelf life than oysters.

“Once you harvest them, they have to go to market immediately,” Reveil said. “They don’t survive being out of the water long. You have three to five days to sell them fresh or you have to freeze.”

Despite the challenges, Reveil hopes weathervanes will eventually be farmed in Alaska waters. She’s experimented with growing kelp and mussels, and would love to have another bivalve among her products.

“We’re always trying to diversify our farm.”