May Day is traditionally a celebration of workers' rights, marking the anniversary of an 1886 general strike that won the eight-hour workday.
But the restaurant industry is one remaining bastion where substandard working conditions are often the norm and efforts to organize are met with strong resistance.
"Any restaurant jobs are seen as disposable or transient," said Diana A., an employee of Fat Salmon sushi restaurant in Center City.
"Some people don't stay in these jobs very long and a lot of them are people who are disadvantaged in some way, they're not educated or younger or elderly or don't have the immigration status ... and so it's easy for them to be taken advantage of."
With that in mind, Diana and six of her coworkers have gone on strike from Fat Salmon, alleging wage theft, illegal tip pools and employer retaliation.
"When I started, I was told about how there are menu tests in which you earn what you get based on how you score," employee Claire T. said.
"So for about a year and a half, I've been missing out on 10 to 30 percent of what I should have been making, and I just don't think that's fair and I didn't realize it was a violation of the law until recently."
Workers also claim Fat Salmon's owner hosts nights out at bars, pressures female employees to return to the restaurant and comes onto them.
"He also pressures male coworkers to get other female coworkers to drink and become intoxicated so he can prey on them," Diana said.
Fabricio Rodriguez of the Restaurant Opportunities Center said the workers, who have filed an unfair labor practice charge with the National Labor Relations Board, are taking an "innovative action."
"A lot of folks, when their rights are being violated, just quit," he said.
"But they're not going to go back to work until these issues are resolved."