Taxonomy & naming
Tachysurus heterofasciatus was described in 2026 by Weihan Shao and E Zhang, with co-authors Xingwei Cai and Tan Duc Nguyen, in a paper published in the journal Animals that used combined mitochondrial DNA and morphometric evidence to resolve the wide-ranging nominal species Tachysurus virgatus (Oshima, 1926) into ten separately evolving lineages across coastal south China and central-northern Vietnam. Populations nearly indistinguishable by eye turned out to be genetically and ecologically distinct, isolated from one another across the region's many independent coastal river systems.
T. heterofasciatus belongs to Bagridae, genus Tachysurus, within the T. virgatus species group. Morphologically it forms its own distinct morph-group (Morph-Group C) together with its sister species T. platystomus — the two are united by a moderately (rather than deeply) forked caudal fin and an unusually high vertebral count of 35–36, versus 30–34 in the rest of the species group. The pair shows 2.1% mitochondrial (cytochrome b) divergence, accompanied, per the authors, by clear differences in body proportions and coloration.
The holotype (YANGC47901, 4.04 in standard length) was collected by Ke Zheng in July 2024 from the Moyangjiang River within the E'Huangzhang Natural Reserve, Yangchun City, Guangdong Province — a coastal river draining into the South China Sea. Paratypes came from the same locality. The Catalog of Fishes (Eschmeyer, California Academy of Sciences) lists Tachysurus heterofasciatus Shao & Zhang, 2026 as the valid name, with no synonyms.
Morphology
Tachysurus heterofasciatus is a striped Tachysurus, easily told apart from the group's non-striped members (T. kyphus) by two continuous black longitudinal stripes running the length of the body from head to caudal peduncle. Unlike most of its striped relatives, its caudal fin is only moderately forked rather than deeply forked — a trait shared solely with its sister species T. platystomus among the group's striped members, and correlated, per the describing authors, with the pair's unusually high vertebral count of 35–36 (versus 30–34 elsewhere in the group).
From T. platystomus specifically, T. heterofasciatus differs by a longer dorsal spine (19.1–24.4% of standard length, versus 15.7–20.3%), a narrower mouth (8.9–11.7% of standard length, versus 12.3–14.7%), and — the character behind its name — a mid-lateral stripe distinctly rather than only slightly constricted at two points, at the posterior ends of the dorsal and adipose fins. Its dorso-lateral stripe also extends down to approach or touch the mid-lateral stripe, where in T. platystomus the two remain well separated.
Across the type series, standard length ranges from about 2.28 in to 6.18 in, giving a described maximum size of roughly 6.2 in SL — making it one of the larger-bodied species in the T. virgatus group. As in all Tachysurus, the skin is entirely scaleless, and the dorsal and pectoral fins carry a locking, serrated spine.
Habitat
Tachysurus heterofasciatus is known only from the E'Huangzhang Natural Reserve on the Moyangjiang River in Yangchun City, Guangdong Province, a coastal river draining into the South China Sea. The describing authors classify it as an obligate stream specialist, recorded exclusively in flowing montane stream habitat rather than the slower river mainstems used by some relatives — one of the paper's photographed habitat examples shows a montane reach of the Moyang River as the species' typical environment.
Stream-specialist habitat in this group is characterized as high-flow-velocity water over coarse gravel or boulder substrate with high dissolved oxygen, in contrast to the finer sand-and-silt, lower-oxygen mainstem channels used by some congeners — including T. qiongzhouensis, which the authors note occupies lowland mainstem habitat in the same Moyang River system, apparently partitioning the river with T. heterofasciatus by habitat rather than by geography. No temperature or pH data have been published specifically for T. heterofasciatus.
Feeding
No diet information has been published for Tachysurus heterofasciatus; the 2026 description is a taxonomic and phylogenetic study and does not record gut contents or foraging behavior. At the genus level, other Tachysurus are nocturnal benthic feeders that use their barbels to find invertebrate prey on the substrate after dark — a reasonable presumption, though not documented for this species.
Mating
No courtship or spawning behavior has been recorded for Tachysurus heterofasciatus. Genus-level, Tachysurus species tend to be seasonal spawners with paired courtship, but nothing specific to this species has been reported.
Breeding
Breeding biology is entirely undescribed for Tachysurus heterofasciatus. Presumed genus-level, Tachysurus are cavity or sheltered-substrate spawners with male egg-guarding, but this has not been confirmed for T. heterofasciatus, which has never been kept or bred in captivity.
In the aquarium
Tachysurus heterofasciatus is not in the aquarium trade. Described only in 2026 from a single montane-stream reserve in Guangdong, it has no husbandry record. Any care notes offered here are genus-level speculation for reference only: other small Tachysurus generally do well as peaceful, nocturnal bottom-dwellers, and this species' documented fast-water, gravel-substrate habitat suggests it would need strong water movement and high dissolved oxygen if it were ever kept, rather than the calmer water many bottom-dwelling catfish tolerate. Because Tachysurus skin is naked and scaleless, the genus is generally more sensitive to copper-based medications than scaled fish, and the locking dorsal and pectoral spines call for moving fish in a container rather than a net. None of this is confirmed for T. heterofasciatus specifically.
Conservation
Tachysurus heterofasciatus has not been formally assessed by the IUCN Red List and carries no official listing. In their conservation discussion, the describing authors specifically recommend Vulnerable status under IUCN Criterion D2 for T. heterofasciatus, alongside T. trimaculatus — both known from a single location with a substantial population but an extremely restricted range, and neither showing documented continuous decline or extreme fluctuation that would push the recommendation to a higher threat category. This is the authors' own preliminary assessment made in the description paper, not an official IUCN Red List listing.
The authors' broader point is that this kind of taxonomic resolution has direct conservation consequences: a population that was effectively invisible while lumped into a single wide-ranging "T. virgatus" can now be recognized as range-restricted and, in their view, warranting protective attention — something that would not have been apparent under the old, broader species concept.