This is a question and answers thread geared for newer readers. Since not all readers will be at the same place in the manga, all questions and answers should be treated as spoilers and placed in spoiler tags.
Bishokuya means something like Gourmet Hunter. It's basically the term used to describe people whose job is to acquire ingredients with capture levels. This applies to both good and evil people. Think of it as a job title.
The bad guys are also called Bishokukai, which is also the name of their group.