On a small island in Indonesia, a black-throated creature swam through the “acid water” of a stream. The scaly animal was seemingly unbothered by its surroundings — until it was captured.

Heok Hui Tan looked at the captured animal and recognized it as a black water fighting fish, according to a study published Aug. 28 in the Raffles Bulletin of Zoology. At least, he thought he recognized it.

The roughly 2-inch-long fish was too “stressed” to be properly identified at first, Tan wrote in the study.

Only after preserving the specimen did the researcher notice that its throat pattern didn’t match any known black water fighting fish. He had discovered a new species: Betta andrei, or Andre’s betta fish.

Andre’s betta fish has a “black lower jaw” with a “large black pitcher-shaped mark” on its throat, the study said. The rest of its body is “yellowish-brown” with spots of iridescent scales.

Photos shared by @FishInTheNews on X, formerly Twitter, show Andre’s betta fish and the stream where it was found. One photo shows the throat patterns of black water fighting fish. Figure j shows the throat pattern of the new species.

Andre’s betta fish has only been found in “acid water habitats in Singkep Island,” the study said. The fish was captured from a “tannin-stained” stream that runs through a “swamp forest.” Singkep Island is a small island about 430 miles northwest of Jakarta, the capital city of Indonesia, and along the northern coast of the much-larger island of Sumatra.

Tan named the new species after Andre Chandra, “an intrepid fish collector and enthusiast.” Chandra helped Tan “in procuring specimens and information; fishy discussions and good meals.”

The new species was identified from the color and scale pattern of one specimen, the study said. Researchers did not provide a DNA analysis of the new species.

The discovery of Andre’s betta fish suggests that there might be more species of black water fighting fish to be discovered on Indonesian islands, Tan wrote.

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