Taxonomy & naming
The species was described in 1982 by the American ichthyologist Tyson R. Roberts, in a paper titled "Gobiocichla ethelwynnae, a new species of goby-like cichlid fish from the rapids in the Cross River, Cameroon," published in the Proceedings of the Koninklijke Nederlandse Akademie van Wetenschappen (Series C, Zoology, vol. 85, no. 4, pp. 575-587). Roberts collected the type series himself in March 1980 from the rapids in the mainstream of the Cross River about eight kilometres downstream of Mamfé. The holotype is held at the California Academy of Sciences (CAS 48901), and a large paratype series — some 288 specimens — is distributed among the major fish collections, including the Natural History Museum in London, the Field Museum, the Muséum national d'Histoire naturelle in Paris, the Royal Museum for Central Africa at Tervuren, and others. No synonyms exist; the name has been treated as valid by every subsequent reviewer (Teugels 1991; Stiassny et al. 2007; Dunz & Schliewer 2013). The genus Gobiocichla had been erected three decades earlier by Kanazawa (1951) for Gobiocichla wonderi of the Niger rapids; ethelwynnae is the second and only other member, and the two are sister rheophiles separated by hundreds of kilometres and two distinct drainages. Within the African cichlid radiation (subfamily Pseudocrenilabrinae), Gobiocichla belongs to a small assemblage of West-African current-adapted cichlids that also includes Steatocranus and the recently recognised Paragobiocichla (the Volta-drainage 'Gobiochromis' irvinei) — a convergence of goby-like, rock-dwelling forms rather than necessarily a single close-knit lineage.
Morphology
Gobiocichla ethelwynnae is a small fish, reaching about 3 in in standard length. Everything about its shape reflects a life spent clinging to rock in fast water. The body is elongate and nearly cylindrical — horizontally oval in cross-section — recalling a goby or a loach more than a typical cichlid, and the scales are reduced. The dorsal fin is long and low, carrying 18-19 spines followed by 11-12 soft rays, running almost the length of the back; the anal fin has 3 spines and 10-11 branched rays, and there are 34-36 vertebrae. Roberts distinguished it from its only congener, Gobiocichla wonderi, by being more elongate, more slender and somewhat more depressed, with a shallower caudal peduncle and smaller eyes. The mouth is slightly narrower and more subterminal than in wonderi, the upper jaw relatively non-protrusible, and the groove between the upper jaw and the snout greatly reduced or absent near the snout tip, so that the tip of the snout is visible from below — a set of features tied to scraping food from a hard surface against a current. Unlike many African cichlids, the dorsal fin never carries a 'tilapiine' ocellus. Coloration in life is muted and cryptic, dark and mottled to match the wet rock; bright nuptial colours have not been documented. Sexual dimorphism appears slight and is not well described in the literature.
Habitat
This is a narrow-range endemic of the upper Cross River (the Manyu, in its Cameroonian reach), a Lower Guinea river that rises in the Cameroonian highlands and flows west into Nigeria and the Gulf of Guinea. All known records come from the rapids around Mamfé in western Cameroon, from the main channel below the town downstream to the junction with the southern Munaya River; the type locality lies roughly 2–12 mi downstream of Mamfé. The species is strictly rheophilic. It lives near the river banks in flowing water of high turbulence and velocity, sheltering in small caves and cracks between stones, and is found only in rocky habitats with little or no sand or gravel — exactly the white-water micro-habitat that excludes most cichlids. FishBase classes it as benthopelagic and lists an in-situ measurement of around 82 °F and a pH on the alkaline side (8.2 at the recorded lower bound); the broader Cross drainage runs warm and generally circumneutral to slightly alkaline, though in-situ chemistry for this fish is sparsely documented. The estimated extent of occurrence is under 20,0 mi² and the area of occupancy under 2,0 mi², a genuinely small range confined to a single river's rapids.
Feeding
Gobiocichla ethelwynnae is an aufwuchs grazer — it feeds on the carpet of algae, diatoms and associated micro-organisms that grows attached to the rocks. FishBase places it at the bottom of the food web with a trophic level of about 2.0, consistent with a near-strict herbivore/detritivore. Roberts inferred from its anatomy and habitat that it presumably feeds on plants and other organisms growing on the rocky substrate, and field observation describes it foraging on algae using specialised, abrupt movements of the head: short, sharp jabs that scrape the film from the rock without surrendering position to the current. The reduced, subterminal mouth and the near-rigid upper jaw are the working tools of that behaviour. In the rapids community it occupies the same grazing niche that mbuna and Tropheus fill on rocky shores of the Rift lakes, but does so in flowing rather than standing water.
Mating
Reproductive behaviour in Gobiocichla ethelwynnae is poorly documented — the fish has been little kept and never studied in detail in the wild. FishBase, drawing on aquarium literature for the genus, characterises it as probably a cave-spawner that practises pair-bonding, albeit weakly. That fits both its habitat, which is full of the crevices and small caves a substrate-spawning cichlid would use as a nest, and the pattern seen in its better-known relatives among the West-African rheophiles. In rock-dwelling, current-adapted cichlids of this kind, pairs typically defend a small territory centred on a sheltered crack or cavity rather than forming the large open arenas of sand-dwellers. Beyond this, courtship, sexual signalling and the degree of territoriality have not been described for the species and should be treated as inferred rather than observed.
Breeding
No detailed account of spawning, clutch size or fry development exists for Gobiocichla ethelwynnae, in the wild or in captivity. The best-supported statement is that it is probably a biparental cave-spawner with weak pair-bonding — the reproductive mode typical of small rock-dwelling African river cichlids, which lay an adhesive clutch on the wall or ceiling of a crevice and guard it. Genus-typical and family-typical figures for comparably sized cave-spawning African cichlids run to roughly a few dozen up to a couple of hundred eggs per clutch, with the substrate and the brood tended by the parents until the fry are free-swimming, but no specific egg count has been published for this species and that range should be read as indicative only. Spawning triggers, incubation time and parental duration are undocumented. This is one of the genuine gaps in the species' biology: an honest profile can only note that breeding follows the cave-spawning pattern of its rheophilic relatives, without inventing numbers the literature does not supply.
In the aquarium
Gobiocichla ethelwynnae is essentially an aquarium rarity. It is not a regular import, has no established trade and no settled hobby common name, and its specialised requirements put it firmly in the domain of dedicated rheophile keepers rather than general community aquarists. Anyone attempting it must recreate a stretch of warm, fast, highly oxygenated river: a long tank with powerful flow from one or more circulation pumps or powerheads, a hardscape built almost entirely of smooth boulders and stacked rockwork riddled with caves and cracks, and little or no sand — mirroring the bare rocky rapids it is found in. Strong filtration and turbulence are not optional extras here but the core of the setup, because a torrent fish kept in still water tends to languish. Water should be warm (around 82 °F, in line with its in-situ temperature) and on the harder, circumneutral-to-slightly-alkaline side rather than soft and acidic. Diet should centre on algae and vegetable matter — a well-lit tank that grows a natural algal film on the rocks suits its grazing habit, supplemented with spirulina-based and other vegetable foods, with only modest amounts of meatier fare. As a small, rock-bound grazer it is not aggressive at community scale, but tankmates must share its demand for current and oxygen; soft-water blackwater fish or placid still-water species are a poor match. The honest summary is that this is a difficult-to-source specialist fish, kept by very few, and husbandry guidance for it is extrapolated from its habitat and from experience with the better-known rheophilic cichlids rather than from a deep body of aquarium literature.
Conservation
The IUCN Red List assesses Gobiocichla ethelwynnae as Endangered (EN, criteria B1ab(iii)+2ab(iii)), in an assessment by T. Moelants dated 16 February 2009; the population trend is recorded as unknown. The listing rests on the species' tightly restricted distribution — an extent of occurrence under 20,0 mi² and an area of occupancy under 2,0 mi², confined to the rapids of a single river around Mamfé — combined with a continuing decline in habitat quality. The threat the assessment singles out is deforestation in the upper Cross catchment, which degrades the river through increased sedimentation and altered runoff; a sediment-laden, silted river is directly hostile to a fish that depends on clean, current-swept rock and the algal film it carries. As a strictly rheophilic, rock-restricted endemic, it has no refuge in alternative habitat and is intrinsically vulnerable to anything that dams, silts or pollutes its short reach of rapids. It carries no CITES or CMS listing. The species shows how the narrow-range rheophiles of West-African rivers — far less celebrated than the Rift-lake cichlids — can be among the most exposed.