A pair of marine biologists were walking along Coast Guard Beach in Eastham when they spotted a shiny-scaled fish washed up on the rocks.
Tasia Blough and Owen Nichols at first couldn’t agree on what type of fish had caught their eyes.
“I picked it up and immediately recognized that the fish has little photophore organs on its body,” Blough said, referring to the fish’s light producing organs. “He told me, ‘It’s just a herring.’ But I told him to look at the tiny photophores.”
The fish was dead when they stumbled upon it during a walk on Feb. 17. Nichols spent an hour looking around the beach for another example of the fish, but came up empty.
When the couple got home, Nichols pulled out a fisheries field guide from 1953. He quickly identified it as a Mueller’s pearlside fish, which is also known as a silvery lightfish, he said.
The species is so rare, the last recorded sightings In Massachusetts were in Nahant and Provincetown in the 1800s, Nichols said. But he suspects the fish is a more frequent visitor to localwaters.
“It’s one of those species that’s here more than people think,” said Nichols, the director of marine fisheries research at the Center for Coastal Studies in Provincetown. “But a lot of people probably walk past just a tiny little silver fish on the beach.”
They used a UV light to examine the fish’s organs. “It just gives you an idea of what they actually look like,” Blough said.
She was familiar with the fish since she spent a semester at sea, conducting research in a “rocking wet lab,” 1,000 meters underwater.
“It was really cool to find an animal that we usually have to go out in the middle of the ocean for, in a very, very deep area — to find it at your feet is pretty, pretty amazing,” Blough said in an interview Thursday.
The fish is known to feed close to the water’s surface. But what made it wash ashore on Cape Cod?
“It’s kind of a big mystery,” Nichols said.