"He's been here for 40 years full-time, 60-hour weeks and I've been with him for the last 25 years," his wife, Rosemary Johnston, told CBC News.
But they'll both soon be retiring from the restaurant business.
The old-school restaurant is closing its doors after Wednesday. Dave Johnston's parents first opened it in 1950.
"It's both happy and sad at the same time," he told CBC News. "Mentally, I’m a little sad, physically I’m very happy about the whole thing."
His parents started the restaurant and his mother worked at Penrose all the way into her 90th year.
The news that Penrose would be shutting down has prompted many customers to make sure they enjoy one last meal in the restaurant's final days.
"The last few days..it's been hectic, our staff has been, sort of run off their feet," said Rosemary Johnston, noting that Penrose has sold out of fish by 1 p.m. in some cases.
"We haven't been able to stay open for our supper hour," she added.
Dave Johnston said the future for the Penrose building is unknown.
"I've sold the property and they may have a restaurant here, that's entirely up to them," he said.
For anyone wanting to eat at Penrose one last time, the restaurant will open its doors at 11 a.m. on Wednesday. But the fish may go fast.
"Arrive early and avoid disappointment," he said.