One fish, two fish, what the hell is this blue fish?

Each season, Southeast fishing guide and lodge owner Rick Hedding helps catch three or four blue lingcod.

It's a small portion of the thousands of fish he helps anglers reel in from his Naukati Bay Adventures lodge on Prince of Wales Island. Still, the first time he saw the glacier-blue, semi-transparent skin, he was perplexed.

"It looks like it's nuclear or something," he said in a phone interview Tuesday.

A Facebook post from the lodge in July caught attention last month, with pictures of the blue-tinted lingcod going viral.

Despite its looks, the fish is not nuclear. Biologists aren't exactly sure why some lingcods turn bright blue; however the cause appears to be a bile pigment that gets into the tissues of the fish, causing them to change hue from their normal reddish-brown.

It also happens to "cousins" of the lingcod, a smaller fish called a rock greenling, according to NOAA Fisheries spokeswoman Maggie Mooney-Seus. The two fish often share similar habitats.

Mooney-Seus said in an email that sightings of the blue lingcod in Alaska are rare.

But photographer Daryl Pederson spotted another blue lingcod Friday in Prince William Sound. The fish was caught by his brother, Brian Pederson, near Knight Island.

"I'd never seen one before. They're a cousin of a greenling and I've heard of a greenling being blue but I've never heard of lingcod being blue," he said in a phone interview Tuesday.

Pederson didn't get a chance to taste the fish. It was small, only 20 inches long, and his brother ended up throwing it back after snapping a few photos.

But Hedding has eaten the cooked fish. He said the blue color disappears once the fish is cooked, so it looks and tastes like regular lingcod.

The fish in his Facebook post was caught by Hedding's great-niece, Wisper Reynolds. That fish, caught in Sea Otter Sound, was about 24 inches long. Hedding released it too.

But just catching it made the 10-year-old's day.

"She loves pinks and purples," he said. "For the rest of the day, that was 'teal fish.'"