Sergeant Majors at John Pennekamp

An underwater view of the sergeant major.

Many ocean visitors worry about being attacked by large, aggressive fish. However, while you’re exploring the reef, a fish more likely to start trouble is the size of an index card. The sergeant major is a combative little fish that can be quite nippy, particularly toward anything that comes between them and their food source.

Their name comes from their coloration rather than their attitude: They have prominent, vertical black bars on their sides, reminiscent of the insignia of a military sergeant major. The scales between the black bars can be white, silvery or blue-colored, sometimes with yellow highlights.

These bold members of the damselfish family are one of the most commonly seen fish in the Florida Keys, where they inhabit inshore rocky reefs, pier pilings and mangroves. Sergeant majors are omnivores and their wide-ranging diet consists of ocean bottom weeds, algae, crustaceans, fish, invertebrate larvae and fish eggs. Adult sergeant majors occur alone, in pairs or in loose groups, but they form large foraging schools when feeding from the water column. Juveniles are often found in shallow tide pools or under floating debris in small groups. Sergeant majors are fast swimmers and can negotiate areas with strong current.

These feisty fish also have a tender side. They take time out of their schedules to hold cleaning stations in the company of doctorfish and blue tangs, and together pick parasites and molting skin from green turtles.

Take a boat tour from our park to see sergeant majors in their natural habitat.