Strolling along one of Juneau’s sandy beaches, you might see footprints, remnants of bonfires, or a variety of birds. But what about what’s underneath the sand?
To answer that question, retired fisheries biologist Bob Armstrong frequently makes the trek down a rocky hillside toward Eagle Beach. He left the Alaska Department of Fish and Game in 1984, but at 80 years old, Armstrong still spends a lot of mornings observing local marine life.
“One of my favorite things to do is just sit down here with a chair and a cup of coffee,” he said.
Stepping over layers of blue mussels, Armstrong makes his way toward the shore at low tide. He has a tripod over one shoulder, a shovel in the opposite hand, and a camera bag slung across his chest.
Two years ago, on a day much like this one, Armstrong saw something that surprised him.
“A raven would dig up quite a large [Pacific] Staghorn Sculpin, maybe up to a foot and a half long,” he said.
Often found in shallow seawater, sculpins are scaleless, bottom-dwelling fish with heads much larger than their tapered tails. Pacific Staghorn Sculpins live all along the Pacific Coast from Alaska to Mexico.
Armstrong said this one was buried in about a foot of sand when the raven got to it.
“The sculpin would flip about on top of the sand,” he said. “It was very much alive, which also surprised me because they were living out of water.”
But, the fish, now plucked from its shrouded bed of wet sand, wasn’t what the raven was after. Instead, the bird picked up a nearby clamshell, which was concealing two clusters of sculpin eggs.
“[The raven] would grab the eggs and then fly off probably to its nest to feed its young the sculpin eggs,” Armstrong said. “This happened on three different occasions and I didn’t realize exactly what was going on until I looked at the videos.”
That prompted him to do some research, looking through scientific literature on sculpins, only to find that what he’d seen wasn’t well known or documented.
“With sculpins, it’s usually the male that guards the eggs until they hatch,” he said. “What I suspected happening, was that the female would lay her eggs near or on the head of the male sculpin and then put a horse clamshell on top of it to protect it and this seems extremely bizarre. It just really excited me.”
As Armstrong continued to observe the critters, he ran into his former coworker and fellow retired biologist, John Palmes.
“We’re both naturalists,” Palmes said. “We just really love nature. That’s our joy to go out there and look at that stuff and to understand it and try to figure it out.”
During their conversation, Palmes realized they’d both observed the same spectacle at different times on Eagle Beach: a disturbed area in the sand with a large horse clam shell sitting on top.
“Underneath the edge of the clamshell, I could see eyes,” Palmes said.
“So I just flipped the shell over and underneath there was a sculpin with a big mass of eggs on its head,” Palmes said. “They were molded to the shape of the shell.”
Palmes knows a lot about fish, but he’s never seen anything like this.
“This sculpin thing is so cool because it is so weird,” he said.
After seeing it again at another beach, Palmes started to wonder if the event had something to do with the tides.
“I think they lay their eggs and they dig themselves in, so that they’re pretty much free of predation for the time when the beach is nearly exposed,” he said. “The other thing that happens is they’re in warmer water. The sun provides higher temperatures and warmth to incubate the eggs. So I think that’s all part of the plan.”
Palmes said he can’t know for sure yet, but it would make a lot of sense. By sharing his observations, he hopes other beach-goers will keep an eye out for the phenomenon.
“It’s just a wonderful thing to do and it feeds you,” Palmes said. “The Lingít people say ‘when the tide is out, the table is set’ and it’s true.”
Armstrong and Palmes don’t have any plans to formally research this sculpin behavior, but with the help of some citizen science, Palmes said they might be able to solve this sea creature mystery just for fun.