Taxonomy & naming
Leporinus piau was described by the American ichthyologist Henry Weed Fowler in 1941, with a type locality at Salgado, Ceará, in northeastern Brazil. It belongs to the family Anostomidae — the headstanders — within the order Characiformes, a family whose genus-level boundaries have been reworked repeatedly as the Catalog of Fishes (Eschmeyer, California Academy of Sciences) has absorbed new revisions; Leporinus itself remains a large genus of elongate, obliquely swimming characins distinguished from the true anostomines (Anostomus, Pseudanostomus) by dentition and body proportions.
The common name "piau" is not unique to this species — it is a generic Brazilian Portuguese name applied to a range of slender, silver-bodied Leporinus and related characins caught by subsistence and sport fishers throughout the northeast, so Leporinus piau is best identified by its binomial and its restricted native range rather than by the vernacular name alone.
Morphology
Leporinus piau has the classic headstander build: a fusiform, laterally compact, torpedo-like body built for steady cruising and for tilting into the head-down grazing posture the family is named for. FishBase records a maximum length of 13 in fork length, a solidly mid-sized characin — well beyond the scale of a typical community nano fish and large enough to need a genuinely spacious tank as an adult.
Detailed published colour-pattern data for this species is sparse; like many Leporinus it likely shows the genus's typical silvery flanks, though specific banding or spotting patterns are not documented in the available sources and should not be assumed from photographs of similar-looking congeners.
Habitat
The species is native to northeastern Brazil, documented from the Salgado river system and associated with the wider Parnaíba drainage, placing it within the Caatinga freshwater ecoregion — a seasonally dry, warm interior region very different from the classic Amazonian blackwater image most characins are associated with. FishBase classifies it as a pelagic, tropical freshwater fish.
Specific pH, hardness and temperature ranges are not given in the available sources; as a Caatinga-basin fish it likely experiences warm water with strong seasonal flow variation, but precise water-chemistry figures are data sparse and are not stated here to avoid guessing.
Feeding
FishBase describes Leporinus piau as omnivorous with a predominantly herbivorous diet, consistent with the genus's aufwuchs-grazing habit — rasping algae, biofilm and soft plant material from submerged wood, rock and leaf litter in its head-down posture, supplemented with some animal matter such as small invertebrates.
In the aquarium this translates to a plant-and-vegetable-forward diet: blanched vegetables, spirulina-based flakes or pellets and algae wafers should form the bulk of feeding, with occasional protein such as bloodworm or brine shrimp. Soft-leaved live plants are at real risk from a grazing fish this size and should not be relied on as furnishing.
Mating
Documented detail on courtship in Leporinus piau is limited. FishBase notes the species breeds in densely grown, weedy areas, which points to a substrate- and vegetation-associated spawning event rather than open-water broadcasting, consistent with the pair-forming behaviour reported more generally for the genus. No sexual dimorphism or specific pairing behaviour is documented in the available sources, so none is asserted here.
Breeding
Leporinus piau is an egg-scatterer that spawns among dense weed growth, and the available literature does not describe any parental care of the eggs or fry — consistent with the wider pattern in Leporinus and Anostomus, where a handful of species have been reported to spawn in aquaria (and some Leporinus are farmed commercially) but most, including this one, are rarely if ever bred at home. Prospective breeders should treat this as an unbred-in-the-hobby species pending further documentation rather than assume standard characin egg-scattering husbandry will reliably succeed.
In the aquarium
At a documented maximum of 13 in, Leporinus piau is a large, active characin that needs a long, spacious aquarium as an adult — this is not a fish to size a tank for at purchase length. As with its better-known relatives in Leporinus and Anostomus, keepers should expect a robust, food-and-algae grazer that may nip soft plants and can become territorial or fin-nippy toward slower tankmates as it matures; it is best combined with similarly robust, fast-moving fish rather than delicate or long-finned species.
The species has little documented presence in the mainstream aquarium hobby — it is primarily known as a regional food and game fish in northeastern Brazil — so care information beyond general Leporinus husbandry (open swimming space, strong filtration, vegetable-rich diet, secure driftwood and rockwork for grazing) is data sparse and should be treated cautiously.
Conservation
The IUCN Red List assessed Leporinus piau as Least Concern on November 7, 2018, citing its wide distribution across northeastern Brazilian basins including the Salgado and Parnaíba drainages, and its established economic and sporting fishing importance in the region. There is no indication in the available sources of significant population decline or habitat-specific threat requiring a higher conservation category at this time.