Taxonomy & naming
The brown coscarob was described in 1831 by the English zoologist Edward Turner Bennett as Chromis taenia, from material attributed simply to Trinidad ('apud Trinidad'). It is the second-oldest described species now standing in Cichlasoma — only the type species, bimaculatum, is older — and it carried the species through more than a century of taxonomic reshuffling. The modern understanding of the name rests on Sven O. Kullander's 1983 monograph, A Revision of the South American Cichlid Genus Cichlasoma, where he redescribed taenia (page 90) with a full diagnosis, description, distribution and illustrations and retained it within the tightly restricted Cichlasoma. Kullander's revision is the work that cut the genus down from a sprawling assemblage of around a hundred nominal species — most of them Central American — to a small, monophyletic core of South American acaras built around bimaculatum; taenia is one of the dozen or so species that survived that pruning to remain in Cichlasoma sensu stricto, within the tribe Cichlasomatini of subfamily Cichlinae. The Catalog of Fishes lists Cichlasoma taenia (Bennett, 1831) as valid, the parentheses recording the move out of the original genus Chromis. The epithet taenia is Latin (from Greek tainia) for 'band' or 'stripe,' for the dark lateral band that runs along the fish's flank.
Morphology
Cichlasoma taenia is a small-to-medium acara reaching about 5 in in standard length (FishBase) — toward the larger end of the genus, comparable to its relative Cichlasoma orientale. In build it is a typical Cichlasoma: a moderately deep-bodied, laterally compressed cichlid of generalised shape, with a terminal mouth and the rounded-to-pointed unpaired fins of a substrate-spawning cichlasomatine. The colour pattern, as the name advertises, is dominated by a dark longitudinal band (taenia) running along the flank, set against a brownish to silvery ground — the source of the common name 'brown coscarob' — together with the genus-typical caudal-fin-base spot and vertical trunk bars that can flush in with mood and breeding condition. Kullander's redescription supplies the meristic and squamation characters that separate it from its congeners within this look-alike group of acaras. Detailed sexual dimorphism is not separately published for the species; on the genus pattern, males tend to grow somewhat larger with longer-pointed fins and ripe females are rounder-bodied, but for taenia this is best read as the expected acara pattern rather than a documented account.
Habitat
Cichlasoma taenia has an unusual distribution for the genus: it occurs on Trinidad and in the Golfo de Paria drainages of northeastern Venezuela — the freshwaters that drain into the gulf separating the island from the South American mainland. This places it at the very northern margin of Cichlasoma's range and makes it one of the few members of the genus to live on a Caribbean island, a distribution it shares with the wider Trinidad freshwater fauna, which is essentially a continental (Venezuelan) one stranded by the island's recent geological separation from the mainland. FishBase classes it as a benthopelagic tropical freshwater fish and records a temperature range of about 75–81 °F and a pH from around 7.0 upward — warm, broadly neutral lowland water. As a generalised acara it is a fish of the slower, structured parts of these lowland rivers and streams — margins, pools and backwaters with cover — rather than fast open channels. Its range falls within the freshwater province of the Orinoco's eastern fringe and the Trinidad–Paria region.
Feeding
No dedicated diet study is published for Cichlasoma taenia; FishBase estimates a trophic level of about 3.0 from its size and the diets of close relatives, placing it in the omnivore-to-carnivore band typical of the genus. On the pattern of Cichlasoma and the broader cichlasomatine acaras, it is best understood as a generalist benthic feeder, taking small aquatic invertebrates — insect larvae and small crustaceans — together with detritus and some plant material gleaned from the substrate and the structured margins of its rivers. Acaras of this kind work the bottom and the leaf litter, taking mouthfuls of sediment and sorting edible items, but they are flexible opportunists rather than dietary specialists. In its lowland river community taenia occupies the middle of the food web, a small invertebrate-leaning omnivore that is itself prey for larger predatory fishes.
Mating
Reproductive behaviour has not been documented in detail for Cichlasoma taenia, but the genus and the wider cichlasomatine acaras are highly uniform in their breeding biology, and the species can be expected to follow that template. These are pair-bonding, biparental substrate spawners. A male and female form a pair, select and clean a spawning surface — typically a flat stone or a cleared patch of firm substrate — and defend a territory around it together. Outside of breeding small Cichlasoma are relatively peaceable, loosely social fish, but a pair coming into condition becomes territorial around its chosen site. Courtship follows the familiar acara repertoire of mutual lateral displays, fin-spreading and quivering and trial passes over the cleaned surface before spawning. As in related acaras, pairs form most reliably when fish choose their own partners from a group rather than being forced together.
Breeding
On the genus-typical pattern, Cichlasoma taenia is an open, biparental substrate spawner. The female lays adhesive eggs in rows on a cleaned hard surface, and both parents tend the brood through the standard cichlasomatine division of labour — the female staying close to mouth and fan the eggs, the male patrolling the perimeter and repelling intruders. After hatching the wrigglers are moved to one or more pits dug in the substrate, and once free-swimming the fry are herded and guarded as a school by both parents. Specific clutch counts for taenia are not published; acaras of this size lay on the order of a couple of hundred eggs per spawn. This biparental open-substrate strategy — eggs on a surface, larvae in a pit, a guarded free-swimming shoal — is the reliable acara pattern, and there is no published account of any departure from it in this species, whose breeding has simply not been documented in detail.
In the aquarium
Cichlasoma taenia is little known in the aquarium hobby; it is rare in the trade, and the keeping notes that follow are extrapolated from the genus, several members of which (notably Cichlasoma portalegrense and Cichlasoma dimerus) are familiar, easygoing aquarium acaras. At under 5 in it is a medium-small cichlid — a pair would be comfortable in a tank of around 30–40 US gal or more, with a longer footprint helping a pair hold a territory at breeding time and letting a group sort out a pairing naturally.
Water should track its warm Trinidad-and-Paria lowland rivers: temperatures around the mid-twenties Celsius and broadly neutral, moderately hard water suit it, with FishBase's wild figures of roughly 75–81 °F and pH from about 7.0 upward as a guide; stable, clean water and regular partial changes matter more than precise chemistry for a generalised acara. Aquascaping should echo the structured river-margin habitat — a soft substrate the fish can dig in, driftwood and rockwork for cover and sightline breaks, and at least one flat stone as a potential spawning slate. Feeding is straightforward for an omnivore: a varied diet of small prepared foods alongside live and frozen invertebrates brings out the best condition. On the genus's temperament, expect a comparatively peaceable fish away from spawning that becomes territorial around a nest; robust, similarly sized community fish make sensible companions, and raising a group together to let a pair form is the surest route to breeding.
Conservation
The IUCN Red List assesses Cichlasoma taenia as Least Concern (assessed 28 October 2020). It is distributed across Trinidad and the Golfo de Paria drainages of northeastern Venezuela, and although that is not an enormous range, the species is reasonably represented within it and is not flagged as facing a population-level threat. It carries no CITES listing. FishBase notes a minor commercial fishery interest where it occurs — it is a food fish of small local importance — but this is not identified as a conservation concern. The general pressures on lowland Caribbean and northeastern-Venezuelan freshwaters form the backdrop against which its status should be read: habitat alteration, pollution and, on a densely populated island like Trinidad, urban and agricultural impacts on streams. None of these is documented as an active danger to this particular cichlid at present, but as a fish with a relatively confined range straddling an island and a mainland gulf coast, its outlook is tied to the condition of those lowland drainages.