Mangrove Rivulus
Kryptolebias marmoratus
The Mangrove Rivulus is a tiny amphibious fish of South Florida mangroves that survives in crab burrows, damp logs, and shallow brackish pools.
Mangrove Rivulus live where water conditions change quickly. They use mangrove pools, crab burrows, leaf litter, and rotting logs, and they survive periods out of water by breathing through moist skin.
Most individuals are self-fertilizing hermaphrodites. This unusual reproductive system allows one fish to establish a population when it reaches suitable habitat.
Habitat:
Mangroves and Salt Marshes, Estuaries and Bays, Canals and Ditches
Area / Range:
South Florida, Florida Keys, Atlantic Coast, Gulf Coast
Diet:
It eats mosquito larvae, small crustaceans, worms, insects, and other tiny invertebrates found in mangrove pools and leaf litter.
Behavior:
It shelters in crab burrows and damp wood, leaves water when conditions become stressful, and moves across moist surfaces with body flexing.
Day, Night
Active Times:
Best time to see:
During warm wet periods in shaded mangrove pools and crab burrows. The fish is small and easily overlooked.
Florida Native Status:
Native
Conservation Status:
Removed from Florida's Endangered and Threatened Species List in 2017, but still managed through FWC's Imperiled Species Management Plan.
Safety Level:
Low Risk
Safety Information:
This fish is harmless. Avoid handling or disturbing crab burrows and decaying mangrove wood used as shelter.
Benefits to Property:
It consumes mosquito larvae and other small invertebrates and serves as an indicator of functioning mangrove habitat.
Property Concerns:
It causes no property damage. Mangrove trimming, shoreline filling, pollution, and altered tidal flow threaten its habitat.
Fun Fact:
It is one of the few vertebrates known to reproduce mainly through self-fertilization and can remain out of water for extended periods when kept moist.
Wildlife Laws:
Mangrove Rivulus remains covered by Florida conservation management. Mangrove alteration, collection on protected lands, and take without required authorization are restricted.
Identification:
The body is slender and usually olive, brown, or gray with irregular dark marbling. The dorsal and anal fins sit far back, and the rounded tail often shows faint bars or spots.
Credits:
Facts: Florida Fish and Wildlife Conservation Commission and Florida Museum. Images: primary and secondary.