Flavobacterial diseases in fish are caused by both well-known and recently described species within the famil ies Flavobacteriaceae and Weeksellaceae. G lobally, these Gram-Negative bacteria cause substantial losses in farmed and wild fish populations, where outbreaks can be relatively difficult to effectively prevent and control d espite over a century of scientific research . Herein, an introduction to the fish-pathogenic flavobacteria will be provided, which will then be followed by a discussion of some practical , science-informed guidance that can be used to reduce the risk of flavobacterial disease outbreaks in farmed and hatchery-reared fishes.