Taxonomy & naming
Astyanax macal was described by Juan J. Schmitter-Soto in 2017 as part of a large-scale revision of the genus Astyanax in Middle America, published in the Journal of Natural History (vol. 51, nos. 21–24, pp. 1331–1424). The holotype is UMMZ 250291, a specimen of 2.5 in standard length, with paratypes from UMMZ 178599 comprising thirteen additional individuals, all from the upper Macal River, Cayo District, Belize. Eschmeyer's Catalog of Fishes is the authority for the valid name Astyanax macal Schmitter-Soto, 2017.
Astyanax is the largest genus of characins in the Neotropics and arguably one of the most taxonomically complex, with more than 150 described species ranging from the southwestern United States to the Rio de la Plata basin. Central American representatives form a biogeographically distinct assemblage, and Schmitter-Soto's 2017 revision disentangled several previously lumped forms. Within this context, A. macal occupies a narrow range in Belize's Caribbean drainage and appears most closely allied to other small Astyanax inhabiting Maya-area rivers.
Meristic characters that help define the species include a dorsal fin ray count of 10, an anal fin ray count of 21–24 (mean 22.5), and 34 vertebrae. Body depth runs 32–39% of standard length and head length 24–28% SL, placing it within the typical proportions for the genus. The humeral spot — a dark mark behind the pectoral girdle common in many Astyanax — is present but described as vertically oblong and inconspicuous in this species.
Morphology
Astyanax macal is a small, laterally compressed characin reaching a maximum recorded size of 2.5 in standard length in the holotype; FishBase reports a maximum of 2.5 in SL for the species. Like most of its congeners it presents the classic Astyanax silhouette: a moderately deep, streamlined body with a bluntly pointed snout, large eyes with an orbital diameter of 31–34% of head length, and a forked caudal fin. The body depth, at 32–39% SL, gives adults a slightly robust appearance without departing markedly from the genus norm.
Colouration is not described in lavish detail in available accounts, consistent with the understated appearance typical of many middle-American Astyanax. The humeral spot, a dark blotch often present just posterior to the pectoral girdle in this genus, is reportedly vertically oblong but inconspicuous in A. macal. A caudal peduncle spot or lateral stripe may be present, as in related species, but specific colouration data in preserved versus live fish are not detailed in the accessible literature. The smallest depth ratio of 12% SL or less is noted in the original description as a distinguishing character.
Habitat
The Macal River originates in the Maya Mountains of western Belize and flows generally northeastward to join the Belize River near San Ignacio, eventually draining to the Caribbean Sea. Astyanax macal is known from the upper reaches of this drainage, with the type locality recorded as between the communities of San Luis and Millonarios in Cayo District. The river here runs through karst and montane terrain, typically with clear to lightly turbid water, rocky or mixed substrates, and riparian forest cover.
As a benthopelagic freshwater species in a tropical Central American river, A. macal inhabits the water column above the riverbed and along the margins in areas with moderate to low current. No quantitative habitat data — temperature ranges, pH measurements, conductivity — have been published specifically for this species' localities, but the upper Macal is a highland Caribbean-drainage river typical of those in the Maya Mountains region, generally cooler and well-oxygenated compared with lowland Belizean rivers. The species is not known from any other drainage.
Feeding
No dietary studies specific to Astyanax macal have been published, but feeding ecology can be inferred from the broader genus. Astyanax species are generalised opportunistic omnivores, consuming a shifting mixture of aquatic and terrestrial invertebrates, small crustaceans, plant fragments, algae, and organic detritus depending on season, habitat, and availability. Several Middle American Astyanax populations shift toward fruit and seeds where riparian forest input is high, and toward aquatic insects and larvae in fast-flowing, well-lit reaches.
In the aquarium, members of the genus typically accept most standard foods readily: quality flake and small pellets form a workable base diet, and frozen or live foods such as Daphnia, bloodworm, and brine shrimp are taken eagerly. Given the Upper Macal's forested catchment, some plant-derived material is likely part of the wild diet.
Mating
No mating observations specific to Astyanax macal have been published. Reproductive biology is inferred from the well-documented patterns seen across the genus, which are essentially uniform: Astyanax are egg-scattering, free-spawning characins with no pair bond and no parental involvement beyond the act of spawning itself. Males pursue ripe females through open water or among vegetation, and spawning involves the near-simultaneous release of eggs and milt, with fertilised eggs sinking or adhering briefly to fine-leaved plants and substrate before the adults lose interest.
In river-dwelling populations, spawning likely coincides with seasonal cues — rising water levels, shifting temperature, or increased food availability — associated with the Central American rainy season. Dominant males may display mildly heightened coloration during courtship, but Astyanax are not known for elaborate visual displays compared with cichlids or livebearers.
Breeding
Breeding data specific to Astyanax macal in captivity are not available in the published literature or accessible hobbyist records. Based on typical genus behaviour, spawning in an aquarium setting would follow the pattern common to most small Astyanax: conditioned adults placed in a well-planted or mop-equipped breeding tank will scatter small, semi-adhesive eggs among fine-leaved plants or over a mesh bottom, hatching after roughly 24–48 hours at tropical temperatures.
Brood sizes in genus Astyanax vary widely but are typically in the range of several dozen to several hundred eggs per spawning event. No parental care is provided, and adults will consume eggs and fry if left in the spawning vessel; eggs and fry should be separated promptly. First foods for the free-swimming larvae are infusoria or commercial liquid fry food, progressing to freshly hatched brine shrimp as the fry grow. Whether A. macal has entered any formal captive-breeding programme is not documented; it is not an established aquarium fish.
In the aquarium
Astyanax macal is not a fish encountered in the ornamental trade under normal circumstances. As a narrowly endemic species described only in 2017 from a restricted Belizean river, it has not found its way into commercial collection pipelines, and aquarists are unlikely to encounter it. Any specimens kept would most likely be in a scientific or zoological collection context.
Were it to be maintained, care would follow the template of other small Central American Astyanax: a modestly sized aquarium of 23.5–31.5 in or more, soft to moderately hard water in the tropical range consistent with highland Central American rivers, good filtration, and a peaceful community of similarly sized fish. Astyanax are active schooling fish that do best in groups of six or more. A planted tank with open swimming space, moderate flow, and dim to moderate lighting would reflect natural conditions. Standard omnivore feeding applies. Given the species' conservation-unknown status and restricted wild range, responsible husbandry would prioritise captive breeding over wild collection.
Conservation
Astyanax macal has not been formally assessed by the IUCN Red List; its status is listed as Not Evaluated (NE) on FishBase. This reflects the recency of its description — the species was formally named only in 2017 — and the general lag between taxonomic recognition and conservation evaluation for narrowly distributed freshwater fishes.
Its biological profile gives reason for concern even in the absence of an official assessment. Endemism to a single river drainage in the Maya Mountains of Belize means the entire wild population occupies a geographically restricted catchment with no known outlier populations to buffer localised disturbances. The upper Macal River and its watershed face pressures including agricultural runoff, hydropower development (a dam on the Macal system has been a subject of environmental controversy in Belize), and changes in forest cover that can affect water quality and habitat structure in highland tributary systems. Formal evaluation of A. macal's population size, trends, and threat status would be a valuable contribution to Belizean freshwater conservation.