Taxonomy & naming
Vieja fenestrata was described by the German-born British ichthyologist Albert Günther in 1860 as Chromis fenestrata, on Mexican material. As with the rest of the Middle American 'Cichlasoma' assemblage, it spent generations in that catch-all genus and was later shuttled through Paraneetroplus and Theraps before settling, in current usage, in Vieja; the Catalog of Fishes lists it as valid (Vieja fenestrata). Its synonymy is unusually tangled. Günther's own Heros parma (1862), described from the Río Papaloapan at Tlacotalpán — which is now treated as the effective type locality of the species — falls into synonymy here, as do Regan's Cichlasoma sexfasciatum (1905) and Cichlasoma gadovii (1905). Some twentieth-century authors also treated the Pacific-slope Vieja guttulata as a synonym of fenestrata, but the two are now recognised as separate species on opposite slopes. The species sits in the Neotropical subfamily Cichlinae among the heroine cichlids; the modern herichthyin revision (McMahan et al. 2015) and subsequent checklists retain it in Vieja.
Morphology
Vieja fenestrata is a stout, tall, laterally compressed cichlid; it reaches about 12 in standard length, and large aquarium fish develop the steep forehead and incipient nuchal hump characteristic of the genus, most pronounced in dominant males. The ground colour ranges from olive and silvery-grey to a pearly, faintly bluish or greenish sheen, often with pink or coppery tones on the head and breast in conditioned fish, and the flanks carry a row of dark mid-lateral blotches together with a dark spot at the base of the tail. As in most Vieja the colour deepens and the markings sharpen with maturity and spawning condition, while subadults are plainer and more uniformly silvery. Sexual dimorphism is modest: males grow larger and carry the heavier forehead and hump, ripe females are deeper-bodied; reliable separation of the sexes outside breeding condition is difficult.
Habitat
The species is native to the Atlantic (Caribbean) slope of southern Mexico, where it ranges across the Papaloapan drainage — its type-locality system — and adjacent basins including the Coatzacoalcos, with the IUCN assessment recording it from the Mexican states of Veracruz, Tabasco, Oaxaca and Chiapas. It is a fish of warm, slow, low-gradient water: lakes, lagoons, oxbows and the sluggish lower and middle reaches of rivers, over soft mud and sand among submerged wood. It tolerates brackish conditions — the IUCN account classes part of its habitat as marine neritic and notes occurrence in the Laguna de Términos coastal wetland complex — reflecting the euryhaline tendency seen across the genus. In-situ and aquarium-derived chemistry point to warm, near-neutral to alkaline, moderately hard water, consistent with the calcareous lowland country it occupies; the documented range of altitudes runs from the coastal plain up into foothill reaches of the Papaloapan system.
Feeding
Vieja fenestrata is a large omnivore with the strong herbivorous and detritivorous bias typical of its genus. It works the soft bottom and submerged wood of slow lowland water for plant material, algae, detritus, fallen seeds and fruit and the small invertebrates living among them, using robust jaws suited to tearing and grazing vegetation rather than pursuing prey. Studies of its early development and ecology place it firmly among the plant-and-detritus-feeding heroine cichlids rather than the piscivores, though, like all big cichlids, it will opportunistically take animal food. In the riverine and lagoon community it functions as a large-bodied grazer and processor of plant detritus in the lower-gradient reaches.
Mating
The species is a monogamous, biparental substrate spawner that becomes territorial as a pair forms. Outside breeding it is reasonably tolerant for so large a cichlid, but a settled pair claims and defends a territory around a chosen spawning surface, and — as throughout the genus — pairing can be combative, with a male liable to harass an unready female, so a well-matched pair in adequate space matters. Courtship follows the heroine pattern of lateral displays, jaw-locking 'wrestling', quivering and the joint cleaning and inspection of a flat hard surface, accompanied by the deepening of body colour and the female's increasing girth as she ripens.
Breeding
Vieja fenestrata is a biparental, open substrate spawner. The pair cleans a flat hard surface and the female lays her eggs on it in the open, after which both parents share guarding and fanning; the early development of the species has been studied in some detail and follows the standard heroine-cichlid course. After hatching the wrigglers are typically moved to pits excavated in the substrate and the free-swimming fry are led about and defended fiercely by both parents. Precise wild fecundity figures are not well documented, but the genus typically produces several hundred fry per spawning, and large females of this comparatively big species can be expected toward the upper end of that range. In aquaria it spawns in the usual biparental manner once a compatible pair, a flat spawning site and a digging substrate are provided; the limiting factor is the management of the pair's spawning aggression rather than any difficulty in obtaining eggs.
In the aquarium
Vieja fenestrata is a robust, attractive large Central American cichlid that is kept by enthusiasts of the group but is uncommon in the general trade. At an adult size around 12 in it needs a large tank: a footprint of roughly 180 × 23.5 in (about 120 US gal) is a sensible minimum for a single fish or a settled pair, with more space advisable if larger tankmates are kept. Water chemistry is undemanding within the species' natural envelope — a near-neutral to mildly alkaline pH (about 7.0–8.0), moderate hardness and a temperature of roughly 77–84 °F suit it well — and its brackish tolerance means it is forgiving of harder water. As a big, messy feeder it needs generous filtration and substantial regular water changes, but not strong current; aim returns to break the surface for gas exchange.
Use a sand or fine substrate, since the fish digs, and furnish the tank with sturdy rockwork, roots and driftwood that provide cover and break up sightlines; décor must be stable, as an adult rearranges it. Rooted plants are generally futile with Vieja — they uproot and eat vegetation — so greenery is best treated as food or kept to tough, potted or floating species. Diet should respect the species' plant bias: spirulina and other green foods, blanched vegetables and quality vegetable-based pellets as the base, with frozen or live invertebrates as supplements rather than the staple; overfeeding rich protein is a common cause of digestive trouble and head-and-lateral-line erosion in big Vieja.
Temperament is robust but workable. Outside breeding the species is relatively even-tempered for its size and combines well with other large, sturdy Central American cichlids and big catfish or characins able to hold their own; nothing small enough to be eaten is safe. Aggression rises sharply at spawning, when a guarding pair can dominate even a large aquarium, so ample space, broken sightlines and the readiness to separate fish are the standard safeguards. The usual keeper mistakes are underestimating the adult size, overstocking and feeding too richly rather than any fussiness in the fish.
Conservation
The IUCN Red List assesses Vieja fenestrata as Least Concern (assessed 5 September 2018 by O. Mejía Guerrero, published 2019), with the population trend recorded as decreasing. The Least Concern listing reflects the species' relatively wide distribution across several Atlantic-slope drainages of southern Mexico and its tolerance of a broad range of habitats including brackish coastal water, which together make it far less vulnerable than the genus's narrow-range endemics such as Vieja hartwegi. It carries no CITES listing and occurs within at least one protected wetland (the Laguna de Términos area). The broader pressures on its lowland habitat are the familiar ones — deforestation, pollution, water extraction, altered river flow and the spread of introduced tilapia — and the decreasing population trend signals that these are taking some toll, but none is currently judged severe enough to threaten the species at the population level. Of the Vieja treated here it is, with the lowland generalists, among the more secure.