Atlantic Mudskipper

The Atlantic mudskipper is a fish that has made a home on land. It walks across mudflats on its front fins, breathes air, digs burrows, chases rivals, and spends far more of its life out of the water than in it — a living illustration of the kind of animal that first came ashore hundreds of millions of years ago.

Overview

Atlantic mudskippers live in the intertidal zone of tropical West Africa — mangrove forests, estuarine mudflats, and brackish lagoons — where the tide exposes vast areas of soft mud twice a day. When the tide is out, the mudflats are covered in mudskippers hopping, feeding, and squabbling; when it comes in, they retreat into burrows or climb clear of the water. They tolerate a wide range of salinity, from nearly fresh to fully marine.

An amphibious fish

The mudskipper is a goby with a suite of adaptations for air and land:

• Air breathing. It exchanges gas through its skin and the wet lining of its mouth and throat, and stores air in enlarged gill chambers, allowing it to stay out of water for hours as long as it stays moist.
• Walking fins. The stout pectoral fins are set on muscular bases and used like limbs; the fused pelvic fins can act as a suction disc.
• Periscope eyes. The eyes sit on top of the head, can be raised and lowered, and give almost all-round vision above the mud surface; the fish dips them into a pool to keep them wet.
• Burrowing jaws. A mudskipper excavates its burrow by taking mouthfuls of mud and spitting them out at the entrance.

Behaviour

Mudskippers are territorial and social at once — living in dense colonies but each defending a burrow and feeding area. Disputes are settled with fin displays, gaping mouth-to-mouth stand-offs, and leaps. The burrow is central to survival: it holds moisture and an air pocket, provides refuge from herons and other predators, offers cool shelter from the tropical sun, and serves as the nest.

Reproduction

In the breeding season a male renovates his burrow and performs energetic jumping displays at its mouth to attract a female. She lays her eggs in a chamber inside, attaching them to the walls above the waterline, and the male tends them — repeatedly gulping air at the surface and releasing it into the egg chamber to keep the developing embryos oxygenated until the larvae hatch and are washed out on a high tide.

Conservation

The Atlantic mudskipper is common and listed as Least Concern. It is locally harvested for food and bait and collected for the aquarium trade, but the main long-term threat is the destruction and pollution of West African mangrove and estuarine wetlands through coastal development, aquaculture, and oil extraction, which would remove the specific muddy, tidal habitat the species depends on.