Taxonomy & naming
Hoplias mbigua was described in 2015 by Azpelicueta, Benítez, Aichino and Mendez from specimens collected in the lower Paraná River near Nemesio Parma, Misiones Province, Argentina (holotype CI-FML 6763). It belongs to the family Erythrinidae — the trahiras and wolf fishes — within the order Characiformes, a small family that also includes the genera Erythrinus and Hoplerythrinus.
The species epithet mbigua comes from the Guaraní word for a riverine or aquatic bird and was chosen partly as a nod to the ichthyologist Isabelino Rodríguez, known by the nickname "Mbigua." As with several Hoplias described in the last two decades, H. mbigua was split out of what had long been treated as a single wide-ranging "Hoplias malabaricus" species complex; the genus has proven to contain far more diversity than its classical taxonomy recognized, and the Catalog of Fishes (Eschmeyer, California Academy of Sciences) is the authority for tracking these splits. H. mbigua remains a recently described, poorly studied species, and this article follows the original description and the limited literature available since.
Morphology
Hoplias mbigua has the classic trahira build shared across the genus: a robust, cylindrical, only moderately compressed body, a broad flattened head, and a large mouth armed with heavy, conical, unequal teeth built for gripping and crushing prey rather than slicing it. FishBase records a maximum length of 11.5 in standard length for adults (males and unsexed specimens), which is on the smaller end for the genus — some Hoplias, notably H. aimara, exceed a metre, while H. mbigua stays a comparatively compact predator.
Colouration and fine-scale morphological detail are not well documented in the available literature; the original description separates H. mbigua from other lower Paraná Hoplias primarily on meristic and morphometric characters rather than a distinctive external pattern. As in other trahiras, expect a heavy-bodied, somewhat mottled fish built for camouflage against submerged wood and vegetation rather than showy colour.
Habitat
Hoplias mbigua is known only from the lower Paraná River drainage in Misiones and Corrientes provinces, Argentina, with documented localities including arroyo Yabebiry, Nemesio Parma, Corpus, Garupá and Puerto Maní in Misiones, and Ituzaingó in Corrientes. This is a narrow, subtropical range compared to many of its congeners, and the species appears to be a lower Paraná endemic.
Like other Erythrinidae, Hoplias are benthopelagic fish of slow, structured freshwater habitats — river margins, backwaters and vegetated or woody cover where an ambush predator can sit motionless and unseen. As an air-breathing fish (a trait shared across the genus), Hoplias can tolerate low-oxygen water that would stress many other fish, including stagnant backwaters and dry-season pools. Specific water chemistry data for H. mbigua itself has not been published; given its subtropical Misiones range, water temperatures likely run cooler on average than the classic Amazonian Hoplias, tracking the more temperate climate of the lower Paraná.
Feeding
Hoplias mbigua is a piscivore, consistent with the genus as a whole: an ambush or pursuit predator that takes fish, and ecological work on Paraná floodplain Hoplias documents that congeneric trahiras — other Hoplias species — form a significant part of the diet for fish in this genus, alongside other prey fish encountered in the floodplain. Trahiras achieve dietary segregation from one another through morphological differences and niche partitioning rather than avoiding overlap outright.
No aquarium feeding record specific to H. mbigua has been published, but the genus is uniformly reported to take smelt, sprats, mussels, worms and cut meat in captivity, and does not require live food. Any tankmate offered to a Hoplias must be too large to be swallowed whole — this is a fish that will eat anything that fits in its mouth, congeners included.
Mating
No courtship behaviour has been documented specifically for Hoplias mbigua. Across the genus, breeding accounts describe a male preparing and defending a nest site — typically a cleared hollow in the substrate or among plant roots — ahead of spawning, but detailed information on pairing, triggers or seasonal timing for this species has not been published. Given how recently H. mbigua was described (2015) and how little subsequent study it has received, its reproductive behaviour should be considered essentially undocumented rather than inferred.
Breeding
FishBase lists maturity and breeding data for Hoplias mbigua as unknown, and no aquarium or field breeding record for this species has been found in the sources reviewed. What is documented for the genus is that several Hoplias and related trahiras are substrate nest-spawners: the male digs and guards a nest, and parental care of the eggs and fry falls to the male. It would be reasonable to expect H. mbigua to follow this pattern given its close relatives, but this is an inference from the genus, not a confirmed observation for the species itself — captive breeding of H. mbigua is not established, and this should be stated plainly rather than assumed.
In the aquarium
Hoplias mbigua is not an established aquarium fish — it is a recently described, narrowly distributed species with essentially no aquarium trade history, and this account should be read as extrapolation from the genus rather than species-specific care advice. At a documented maximum of 11.5 in, it would need a large, solitary setup: Hoplias are calm but genuinely predatory sit-and-wait hunters, and even a modestly sized trahira has powerful jaws and a serious bite. As with all Hoplias, it should be kept alone, never with tankmates small enough to be considered prey, and handled with a container rather than a net.
Because the species is air-breathing, it tolerates lower dissolved oxygen than many aquarium fish, but should still be given clean, well-filtered water. Suitable water conditions have not been published for H. mbigua specifically; genus-wide accounts cite roughly 79 °F and pH 6–7.5 as workable for related Hoplias, and the lower Paraná's subtropical climate suggests this species may tolerate, or even prefer, somewhat cooler water than tropical Amazonian trahiras. Given the total absence of trade or husbandry history, this is not a species to seek out casually — it is of interest chiefly to specialists and to those documenting an under-studied predator.
Conservation
Hoplias mbigua has not been evaluated by the IUCN Red List (Not Evaluated). Its recent description in 2015 and narrow known distribution — confined to the lower Paraná River in Misiones and neighbouring Corrientes Province, Argentina — likely explain the lack of a formal assessment rather than any evidence of security or risk one way or the other.
No population trend, threat assessment or targeted conservation data for this species is available in the literature reviewed. As a narrow-range endemic of a single river system, it would be a reasonable candidate for future assessment as more is learned about its distribution and abundance, but at present there is simply not enough published data to characterise its conservation status beyond Not Evaluated.