What the Atlantic Mudskipper Is and Where It Lives
The Atlantic mudskipper (Fundulus heteroclitus) is a small fish that spends as much time out of water as in it, moving across mud and salt marsh with a distinctive hopping motion. It reaches about 4 to 5 inches long and has a stocky body, rounded head, and large eyes positioned high on its head—adaptations that let it see above the waterline while partially submerged. The fish is olive-brown to gray on top, often with darker bands or spots, and lighter underneath.
Atlantic mudskippers live along the Atlantic coast from Nova Scotia to Florida, in salt marshes, tidal creeks, and brackish estuaries where mud flats are exposed at low tide. They are most abundant in the mid-Atlantic region, particularly around the coasts of New Jersey, Delaware, Maryland, and Virginia. Unlike most fish, they are equally at home in shallow water and on exposed mud, where they hunt small invertebrates and rest between tidal cycles.
Key Takeaways
- Atlantic mudskippers are found along the Atlantic coast from Nova Scotia to Florida, primarily in salt marshes and tidal creeks where mud is exposed at low tide.
- They breathe air through their skin and the lining of their mouth, allowing them to survive out of water for extended periods as long as they stay moist.
- The best time to observe them is during low tide in warm months, when they are most active on exposed mud flats hunting for small crustaceans and worms.
- They are not a target species for recreational fishing but are important forage for larger fish and birds, and they indicate healthy salt marsh habitat.
How Atlantic Mudskippers Breathe and Move
Atlantic mudskippers do not have the specialized air-breathing organs of true mudskippers found in Africa and Asia, but they have evolved a remarkable alternative. They absorb oxygen directly through their skin and the mucous membranes lining their mouth and throat, a process called cutaneous respiration. This works only when their skin stays wet, so they must remain in damp mud or shallow water and cannot survive in dry conditions for long.
On land, they move by flexing their tail and front fins in a rapid hopping or skipping motion—the behavior that gives them their common name. This allows them to cover short distances across exposed mud to find food or escape predators. In water, they swim normally but spend much of their time in the shallows or partially out of water, where they can hunt more effectively in the thin layer between mud and water.
Habitat and Seasonal Patterns
Atlantic mudskippers are most abundant in salt marshes dominated by cordgrass and in the shallow tidal creeks that drain them. They prefer areas with soft mud, plenty of organic matter, and regular tidal flushing. They tolerate a wide range of salinity, from full seawater to nearly fresh water, which is why they thrive in estuaries where rivers meet the ocean.
They are most active from late spring through early fall, when water temperatures are above 50°F. During winter, they move to deeper water or burrow into mud to enter a dormant state. In summer, they are most visible during low tide, when they emerge onto exposed mud flats to hunt. Their activity peaks in the early morning and late afternoon, when water temperatures are moderate and light levels are lower.
Diet and Feeding Behavior
Atlantic mudskippers are carnivorous and feed on small invertebrates found in mud and shallow water. Their diet includes amphipods, small shrimp, copepods, insect larvae, and marine worms. They hunt by sight, using their large forward-facing eyes to spot movement in the mud or water. When feeding on exposed mud, they probe the surface and crevices with their mouth, sucking in prey along with mud and water, then expelling the sediment.
They are opportunistic feeders and will eat whatever small prey is available in their habitat. Their feeding efficiency is highest during low tide, when prey is concentrated in shallow pools and exposed mud. They also feed in water, where they dart quickly to capture small organisms drifting in the current or resting on the bottom.
Reproduction and Life Cycle
Atlantic mudskippers spawn in spring and early summer, typically from April through July depending on water temperature and latitude. Males establish small territories in shallow water or at the water's edge and court females with displays and vocalizations—they produce audible sounds by grinding their teeth and moving their gill covers. Females lay eggs in small clusters in shallow depressions or under vegetation, often in areas that are exposed at low tide.
The eggs hatch in about two weeks, and the larvae drift in the water column before settling into shallow nursery habitat. Young mudskippers grow quickly and reach sexual maturity in their first or second year. Most individuals live three to four years in the wild, though some may live longer. They are preyed upon by larger fish such as striped bass and bluefish, as well as by herons, egrets, and other wading birds.
Observing Atlantic Mudskippers in the Field
The best way to observe Atlantic mudskippers is to visit a salt marsh or tidal creek during low tide on a warm day, ideally in summer. Walk slowly along the edge of exposed mud flats and watch for movement—the fish often remain still until you are close, then dart away with their characteristic hopping motion. Early morning or late afternoon offers the best visibility and the most active fish.
Bring binoculars or a hand lens to see details of their behavior and coloration. Move slowly and avoid casting shadows on the mud, as mudskippers are sensitive to sudden changes in light. If you wade into shallow water, move carefully to avoid disturbing the bottom and clouding the water. Photograph or sketch what you see to build a record of their presence and behavior in your local marsh.
Ecological Role and Conservation Status
Atlantic mudskippers are not hunted or fished for sport, but they play an important role in salt marsh food webs. They are a significant food source for larger predatory fish, wading birds, and other wildlife. Their presence indicates a healthy, productive salt marsh with good water quality and stable tidal cycles. Mudskippers are also sensitive to pollution and habitat loss, so their abundance or absence can signal changes in marsh health.
The species is not listed as threatened or endangered, and populations remain stable across most of their range. However, salt marsh habitat continues to be lost to development, sea-level rise, and coastal erosion. Protecting and restoring salt marshes benefits mudskippers and hundreds of other species that depend on these ecosystems. Many coastal areas now have salt marsh restoration programs that create or expand habitat for mudskippers and other marsh residents.
Frequently Asked Questions
Can Atlantic mudskippers survive out of water permanently?
No. They can survive on damp mud for a few hours as long as their skin stays wet, but they will die if they dry out completely. They must return to water regularly to feed and to maintain the moisture their skin needs for respiration. They are not true mudskippers and cannot survive in dry conditions the way African mudskippers can.
Are Atlantic mudskippers found in freshwater?
They are primarily a saltwater and brackish-water species, but they can tolerate low-salinity water in estuaries and tidal rivers. They are rarely found in purely freshwater systems and are not a common sight in inland lakes or streams. If you encounter them in freshwater, you are likely near the tidal influence of a coastal river.
What is the difference between Atlantic mudskippers and killifish?
Atlantic mudskippers and killifish are related—both belong to the family Fundulidae—but mudskippers are specialized for life on exposed mud and can survive out of water, while killifish are primarily water-dwelling. Killifish are more colorful and are popular in the aquarium hobby, while mudskippers are rarely kept in captivity and are less well known to most people.
Why do Atlantic mudskippers have eyes on top of their head?
Their high-set eyes allow them to see above the waterline while most of their body remains submerged or on the mud. This gives them a clear view of predators and prey while minimizing their own visibility to predators. It is an adaptation to their unique lifestyle of spending time both in water and on exposed mud.
Can I keep Atlantic mudskippers in an aquarium?
They are difficult to keep in captivity because they require specialized conditions: brackish water, soft mud substrate, areas to rest out of water, and a diet of live small invertebrates. Most aquarists do not have the setup to meet these needs. It is better to observe them in their natural salt marsh habitat, where they thrive and contribute to the ecosystem.