Eugene Mopsik lays the smoked Alaska king salmon on his wooden cutting board — scales down, orange flesh up — and slowly draws his knife from side to side, creating a slice thin enough to see through.

But not too thin.

Each fish has its characteristics, and Gene Mopsik knows that king salmon will put up a fight.

Prized for its oily, buttery-soft flesh and briny aroma, smoked king salmon has a tendency to tear as it is sliced and placed gently, one by one, on a piece of waxed paper before it is folded into a package. A slightly torn slice of king salmon, even at $14 a quarter-pound, might go unnoticed by the end user, who likely will drape it inside of a bagel shmeared with cream cheese and layered in rings of raw onion for a classic brunch sandwich.

But clean cuts of salmon are a point of pride for the man in the apron and beret known as the Loxsmith.

Mopsik is the courtly counterman/cook/flower-tender/kibitzer at Biederman’s Specialty Foods, the fish-forward deli on Christian Street just off the Italian Market. He goes by @phillyloxsmith on Instagram, and even has a personalized “Loxsmith” director’s chair in the shop.

Biederman’s is deceptive. It’s an old-fashioned deli concept known as an appetizing shop, selling smoked fish, bagels, salads, and other nonmeat staples of the Eastern European Jewish American experience. Yet it opened only in January.

Biederman’s is not a legacy business, either. Its owner, Lauren Biederman, is a 25-year-old former Zahav waitress from Vermont with a palate for the good stuff, such as Osetra caviar.

Mopsik himself, at 72, is not a seasoned lox-slicer. He first cooked Jewish food as a young man in a summer camp in Connecticut. But for 32 years, he was a commercial photographer with a Wharton degree and a list of cool gigs all over: He was house photographer at the old Spectrum arena and a regular food photog for Philadelphia Magazine before building a less sexy but more lucrative career shooting forklifts, trucks, and other heavy equipment. From 2003, he spent 12 years as executive director of the American Society of Media Photographers.

Mopsik, who lives in Queen Village, was looking for something to do in late December 2020 when he stumbled upon his new line of work. “My daughter [Jennie] and I would frequently go for walks on weekends,” he said.

“We walked by Biederman’s and Lauren is in there [before its public opening], working. I’d never seen the place before and I knocked on the door and she let me in. We ended up having a half-hour conversation about smoking [food]. I’ve always been a foodie. I’d cook a full meal, just for myself, if my wife [Helen] was down the Shore.”

“At the end of the conversation, I said to her, ‘You know, if you need an old Jewish guy to be around the shop who’s good with knives and good with people and has a very big interest in food. ...’ She ended up calling me back about two weeks later, and said, ‘Come on in and try things out,’” Mopsik said. “At that point, we weren’t preparing anything. We were just selling the fish and the prepared items and packaged foods. I kind of encouraged her to add one of my mom’s recipes for farmer cheese and dill, and we made that, and then we made tapioca pudding, and we started making soups. We had a different soup every week and then we started moving into salads.”

Biederman said Mopsik arrived “right at the right time. I think Gene changed the foundation of what [the store] would have been. I’m not sure what it would have been, obviously, but since he got here right before we started, everything changed around.”

Mopsik, who bikes to work usually by 7:30 a.m., has overseen a dramatic boost in the inventory in the refrigerator cases. Latest additions: pickled green tomatoes (to complement the kosher dill pickles) and gigante bean salad.

“I’m always looking for new things. I have some old Jewish cookbooks from the ’50s that I look through. I felt it was something that fulfilled a kind of lifelong interest and gave me an opportunity to explore a passion at someone else’s expense,” he said, “which is always a good thing, and provide value to a young entrepreneur.” He said he had a lot of respect for Biederman for taking that leap.

Mopsik is not unaccustomed to shop work. For a spell, he worked for a florist, processing flowers. He said he considers his second passion, after food and family, to be gardening.

But at 72, “it took me a little bit to get used to standing all day again. After a few weeks, it wasn’t a problem. Now thankfully, I’m relatively fit. This is not beating me up. It’s making me feel better. I think my blood pressure is down and my sense of overall calmness is improved.”

Slicing fish — various salmons, sable, sturgeon, smoked tuna — is Zen. “When I’m slicing, I find myself in different places,” Mopsik said. “I’ve traveled the world extensively for work, and in my mind, sometimes, I find myself back in those places. I’m always looking for new patterns when it’s time to lay down the salmon. I try not to just throw it down on the paper. I try to think of the user experience. I try to lay it out in a manner that’s both attractive and utilitarian at the same time.”

And he has his race sailing. In fact, he built early dismissal on Wednesday afternoons into his agreement with Biederman so he can go out on the Delaware at Riverton Yacht Club. He sails out of Stone Harbor, N.J., on weekends.

His workweek has been “a lot of fun,” he said. “I like the personal contact, people coming in.”

Mopsik paused.

If I could have sat down and designed the perfect job for me at this point in my life, this is it,” he said. ”I mean, it’s perfect. The fact that I get paid is like a bonus. And she’s worried that I’m working too much. Do I look like I’m suffering?”