Taxonomy & naming
Prochilodus harttii was described by the Austrian ichthyologist Franz Steindachner in 1875, based on specimens collected during the Thayer Expedition to Brazil of 1865–1866. The species epithet honours Charles Frederick Hartt (1840–1878), the Canadian-American geologist and paleontologist who collected the holotype during that expedition and went on to found Brazil's national geological survey. It belongs to the family Prochilodontidae — the "flannelmouth" characins — within the order Characiformes, a family the Catalog of Fishes (Eschmeyer, California Academy of Sciences) recognises as distinct from the closely related curimatas and headstanders on the basis of its thick, fringed, highly protrusible lips.
The genus Prochilodus contains a number of large-bodied riverine grazers distributed across South American drainages, several of which are important regional food and aquaculture fish. Prochilodus harttii is restricted to eastern Brazilian coastal and interior basins rather than the Amazon or Orinoco systems that carry the genus's better-known species, and its taxonomy has remained stable since Steindachner's description.
This fish was long listed as Prochilodus hartii; Eschmeyer's Catalog of Fishes now treats that name as a synonym of Prochilodus harttii, the valid name followed here.
Morphology
Prochilodus harttii shows the typical prochilodontid body plan: a moderately elongate, laterally compressed, silvery fish with a small, downturned mouth carrying thick, fleshy, protrusible lips adapted for rasping biofilm, algae and organic detritus from submerged surfaces. FishBase records a maximum length of 16.3 in standard length, a substantial size that places this species well outside what most home aquariums can accommodate as an adult.
Like other Prochilodus, it is built as an efficient, sustained-swimming grazer rather than a sprinting predator — a moderately forked tail, unremarkable fins, and a body form suited to holding position in current while feeding, and to long-distance migration along the river channel during the breeding season.
Habitat
Prochilodus harttii is native to eastern Brazil, documented from the Pardo and Jequitinhonha river basins and reported in the São Francisco River basin (Bahia State), all coastal and interior drainage systems distinct from the Amazon. Within these rivers it inhabits flowing channel habitat where it grazes rock and wood surfaces for periphyton and detritus, and it undertakes upstream spawning migrations tied to seasonal rises in water level and dissolved oxygen.
Research on the São Francisco basin population specifically documents how dam-altered flow regimes affect the species' reproductive activity downstream of large reservoirs, underscoring how closely its life cycle is tied to natural seasonal hydrology — water temperature and dissolved oxygen levels are described as critical triggers for its reproduction. Specific pH and temperature figures for this species were not found in the cited sources; note that eastern Brazilian rivers in this region are generally warm, though exact values are not documented here.
Feeding
Prochilodus, as a genus, are detritivores and herbivorous grazers, using their fringed, protrusible lips to rasp algae, biofilm and organic detritus from rocks, wood and sediment rather than pursuing live prey. This diet pattern is well documented across the genus, including close relatives such as P. nigricans, and is consistent with P. harttii's mouth morphology.
In any setting where this species were maintained, a diet built around spirulina-based flake or wafer, algae wafers and blanched vegetables such as zucchini, spinach or lettuce — with only occasional protein — would reflect its natural grazing biology; this is standard husbandry guidance for the genus rather than a species-specific study of P. harttii.
Mating
Prochilodus harttii is a long-distance migratory spawner. Research on the São Francisco basin population documents that its reproductive activity is closely tied to seasonal rises in water level, temperature and dissolved oxygen, consistent with the flood-pulse spawning migrations typical of the genus, in which adults move upstream in aggregations ahead of spawning rather than pairing off in fixed territories. No aquarium-scale courtship behaviour is documented for this species, and none should be expected — natural courtship and spawning in this species take place during river migrations, not in confined water.
Breeding
Prochilodus harttii is a migratory food-fish that is not bred in the home aquarium. Published research on induced reproduction in this species documents that spawning is achieved commercially through hypophysation — hormone injection to trigger ovulation and spermiation — rather than through natural spawning in captivity; controlled trials reported a 100% female response, an 80% male response and a 77% fertilisation rate at 73 °F. This reflects the species' biology as a flood-pulse migrant: in the wild it requires the cues of a long upstream migration and rising, oxygen-rich water to spawn, conditions that cannot be replicated in a tank, so commercial hatcheries rely on hormone induction to breed it at scale for stocking and food-fish production.
Given this, and given its adult size of over 15.7 in, P. harttii should not be regarded as an aquarium breeding project. It is a farmed and hormone-bred food and stocking fish, not a fish that spawns for hobbyists.
In the aquarium
Prochilodus harttii is not a realistic long-term aquarium fish. FishBase's maximum recorded length of 16.3 in standard length means an adult needs river-tank or large-pond dimensions well beyond a typical home setup, and like other Prochilodus it is described as an expert jumper that requires tight-fitting, secure cover if kept at all. Most species in this genus are farmed food fish first and aquarium fish only incidentally, and P. harttii's documented biology — large adult size, migratory spawning triggered by natural river flow, peaceful grazing temperament — fits that pattern rather than that of a manageable community fish.
Any keeper considering this species (most likely encountered as an unlabelled juvenile "silver characin" in the trade) should plan for eventual rehoming to a very large system, never release it into open water, and offer a herbivore-leaning diet of spirulina, algae wafers and blanched vegetables rather than a predator diet. It is a peaceful grazer, not an aggressive fish, and poses no special handling hazard beyond its jumping ability and eventual size.
Conservation
Prochilodus harttii has not been evaluated by the IUCN Red List; no assessment for the species was found in IUCN search results, so its conservation status is Not Evaluated rather than a documented category such as Least Concern or threatened. This is a common gap for regionally distributed South American river fish that are not tracked at the same intensity as widely traded or flagship species.
The species does carry documented human pressure: research on the São Francisco basin population shows that large-reservoir dam operations alter downstream flow and affect its reproductive activity, and, as with other Prochilodus, it is subject to commercial and subsistence fishing pressure across its native range in the Pardo, Jequitinhonha and São Francisco basins. Formal assessment of its population trend was not found in the cited sources.