July 2, 2024

July Fish of The Month - Flagfish Jordanella floridae

July Fish of the Month – Flagfish Jordanella floridae

Dr. Geoffrey Smith

NWFSC Biology Instructor

With the upcoming 4^th of July holiday, it seems appropriate to highlight a fish named for its resemblance to the American flag. The Flagfish Jordanella floridae is endemic (naturally found in no other areas) to Florida. It is found in freshwater streams, creeks, ponds, lakes, and various types of wetlands from the Ocklocknee River near Tallahassee west through the big bend and peninsular Florida (Figure 1). The Flagfish is a member of the family Cyprinodontidae, which includes a number of species that have a wide range of salinity tolerances from fresh water to full strength seawater (and even hypersaline or saltier that typical ocean water). However, the Flagfish has a much narrower salinity tolerance and is found almost exclusively in freshwater, but there are some populations found in slightly brackish waters. Whatever waterbody the Flagfish are residing in, they are almost always found in very dense aquatic and emergent (growing out of the water’s surface) vegetation. They are omnivorous, feeding on small invertebrates and aquatic plant matter. This species displays sexual dimorphism, which means you can easily tell a male from a female based on external characteristics, coloration in this case. Both sexes have a relatively large, dark spot on their side. The males have alternating red and tan to white stripes with iridescent blue to white areas, hence the name Flagfish (Figure 2 top). Females are generally various shades of tan and brown and have a dark spot at the back of their dorsal fin (Figure 2 bottom). The small size of this species, about 2 inches maximum, precludes it from being sought after as a human food source. However, the bright coloration of the males has gained some attention in the aquarium industry, especially among native fish enthusiasts.