Brown Bag Seafood Co. fills a hole in the market, but building an independent-feeling brand based on sustainable seafood has not been easy to scale.

Amid closures, consolidations, mergers, and acquisitions, the once-surging fast-casual category is no longer the surest bet in town. Has it lost its mojo?

With fast casuals diving into the fray, seafood options in the limited-service restaurant industry are going upscale.