Marbled swamp eel in the Iberá Wetlands: where and when to see…

One of the most singular and evolutionarily surprising fish of the Iberá. Its elongated, cylindrical, scaleless body gives it the appearance of a snake, but it is a true fish. It can breathe atmospheric air by gulping mouthfuls at the surface. During severe droughts, it buries itself deep in the mud, weaving a mucous cocoon to keep its skin moist, surviving for months until the water returns. It exhibits a rare biological phenomenon: all individuals are born female and the largest ones transform into males as they age. Length: 60 to 100 cm. Weight: 1 to 2.5 kg.

Behaviour

Mainly nocturnal and fossorial: it spends the day buried or hidden in burrows that it digs in the mud. An opportunistic carnivore: small fish, crabs, frogs, snails and aquatic insects. At sundown it patrols the shores with undulating movements. It can crawl through the wet grass to move from pool to pool during rainy nights.

How and when to see it

Year-round. Very common, poking the tip of its head out at the surface among the water lettuce and water hyacinths to breathe air at dawn or during the night.

Where to see it in the Iberá

The gateways of the Great Iberá Park where marbled swamp eel has confirmed presence:

Laguna IberáSee the gateway → CarambolaSee the gateway → San NicolásSee the gateway → GalarzaSee the gateway →

Tours to see it

Verified providers operating at the gateways where marbled swamp eel lives. You contact them directly on WhatsApp from the app.

Species profile

Common nameMarbled swamp eel
Scientific nameSynbranchus marmoratus
GroupFish
StatusNo data

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