Barton Springs Eel Sighting, From the Sargasso to the Springs

A remarkable biological encounter occurred at Barton Springs Pool on April 22, 2025. While diving near the spring vent just west of the diving board, EMS educator, Search and Rescue Operations Specialist, and longtime regular swimmer, Bill Hanson, caught a glimpse of the elusive American eel (Anguilla rostrata). Although 2 resident eels thrived in the springs for over a decade, they have not been observed in the Springs in several years, and populations are in steep decline across much of their habitat range. 
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“As I was descending toward the cave, I saw the head of a large fish emerge from the opening,” Hanson recalled. “The body following behind this fish’s head kept coming, relentlessly. I finally accepted that what I was seeing was a 3–4 foot, beautiful blue eel.” 

Hanson, who has been swimming at Barton Springs for nearly 17 years, had never seen anything like it there. “It swam northeast, undaunted and calm… kind of a battleship-blue, without a blemish on its skin.” By the time he surfaced and alerted others, the eel had disappeared. Two additional sightings were reported later that week by Barton Springs "regulars", and these sightings have sparked wonder and excitement. 

“Eels remind us that nature is still full of mystery,” says Dr. Melanie Stiassny, a leading ichthyologist at the American Museum of Natural History. “Their story is one of the most extraordinary in the animal kingdom.” The American eel spends most of its life in freshwater before migrating to spawn thousands of miles to the Sargasso Sea, a warm, gyre-bound region of the Atlantic Ocean east of the Bahamas. After hatching, the leaf-like larvae drift in the ocean currents for up to a year before transforming into transparent “glass eels” and making their way inland via rivers and streams. Once in freshwater, they develop into yellowish pigmented “elvers,” eventually maturing into adults and living in lakes, estuaries, or springs for 30 years (or more) before returning to the Sargasso Sea to breed and then presumably die.

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Student views a live American eel at Barton Springs University

The complex life cycle of this fish faces dangers around every bend. Dams and levees block upstream migration routes, urban development degrades freshwater habitats, and pollution affects water quality. Commercial overfishing, particularly of juvenile eels in the glass eel stage, has also dramatically reduced populations. Moreover, the species has never successfully reproduced in captivity, which limits recovery efforts. ​According to the U.S. Fish and Wildlife Service, American eel populations have declined by over 80% in some regions since the 1970s and in 2014, they were officially listed as endangered by the IUCN. Since American eels are mostly nocturnal and avoid light, they are rarely observed in the wild, making any sighting significant.

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So, how did the eel end up in the Springs? American eels possess the ability to breathe through their skin, a trait known as cutaneous respiration. This allows them to leave the water for several hours and travel short distances across wet land, which may explain how the recent rains enabled this individual to access the Springs.

The reappearance of the American eel at Barton Springs is a signal of hope. As an indicator species, the eel reflects the health of these waters and offers proof that the pathways between the sea and the Springs have endured despite the age of concrete and control. Hanson, known for his love for all things wild at Barton Springs (he even attempted a Heimlich maneuver on a fish choking on a crawdad), sees the eel’s presence as a reminder that even in urbanized landscapes, nature still has the capacity to surprise us, “It reminded me how little we really know about what shares this water with us.” 

The eel has returned to Barton Springs, one more reason Barton Springs remains a place of awe. Who will be among the few lucky enough to see it? 

Eel paintings by Kate Csillagi, SOS Communications Director.