Taxonomy & naming
Pseudomugil connieae was described by Gerald R. Allen in 1981 and belongs to the family Pseudomugilidae, the blue-eyes, within the order Atheriniformes. Eschmeyer's Catalog of Fishes treats the valid name with a parenthetical authority, (Allen, 1981), indicating that the species has been combined with a genus other than the one in which it was originally placed. The genus name Pseudomugil derives from the Greek pseudes, meaning false, and the Latin mugil, a grey mullet — literally a 'false mullet,' a reference to a superficial resemblance in body form.
The specific epithet connieae is a patronym honouring Connie Lagos Allen, wife of the describing author. In English the fish is most often called the Popondetta blue-eye, after the town near which it occurs, though hobbyists also know it as Connie's blue-eye in tribute to its namesake. As with other members of the family, the common name 'blue-eye' refers to the iridescent blue ring around the eye that is characteristic of the group.
The blue-eyes are a New Guinea and Australian radiation closely allied to the true rainbowfishes (Melanotaeniidae), and they share the rainbowfish habit of a divided dorsal fin and mid-water schooling. Within Pseudomugil, P. connieae is set apart by its meristics — typically five to eight dorsal spines, ten to twelve dorsal soft rays, and sixteen to nineteen anal soft rays — and by the elongate, finnage-driven display of breeding males.
Morphology
Pseudomugil connieae is a small, slender blue-eye. FishBase records a maximum length of about 2 in SL in males and unsexed fish and around 1.5 in SL in females, so this is a fish of a few centimetres rather than the larger size of its melanotaeniid cousins. The body is elongated and laterally compressed, carrying the family's two separate dorsal fins — a short anterior dorsal followed by a longer posterior dorsal — together with the bright blue iris ring that gives the blue-eyes their name.
The species is sexually dimorphic, and the males are the decorated sex. They develop a yellowish cast to the breast and a thin yellow stripe along the flank, and their unpaired fins — particularly the second dorsal and the anal — grow longer and more pointed, often edged in yellow and dark margins that are flashed during display. Females are plainer and shorter-finned, a more uniform translucent fish.
Meristically the species shows roughly five to eight dorsal spines, ten to twelve dorsal soft rays, a single anal spine, and sixteen to nineteen anal soft rays — counts that, as in most blue-eyes, overlap with congeners, so live colour and finnage are the more reliable field characters. The reported trophic level of about 3.3 reflects its standing as a small invertebrate-leaning omnivore.
Habitat
Pseudomugil connieae is endemic to eastern Papua New Guinea, occurring within roughly a fifty-kilometre radius of Popondetta, between about 8 and 9 degrees south. It is found nowhere else. It inhabits clear, moderately to fairly rapidly flowing streams — both shaded rainforest reaches and more open, sunlit sections — across an altitudinal range of about 30 to 300 metres.
The water is warm and well oxygenated. FishBase gives a tropical temperature range of about 25 to 28 degrees Celsius, a pH range of roughly 7.7 to 7.9, and a hardness of around 10 dH or more — figures that describe clear, slightly alkaline, mineral-bearing forest streams rather than the soft blackwaters of many tropical fishes. The fish is pelagic in habit, schooling in the open water column of these flowing streams.
The entire known range is a small cluster of streams in one part of one province, which makes the habitat the central fact of the species' conservation. There is little geographic buffer against local disturbance, and pressure on the Popondetta-area streams translates directly into pressure on the global population.
Feeding
Pseudomugil connieae is an omnivore that feeds in open, flowing water, taking small invertebrates from the current and surface together with some plant and algal material — a diet consistent with its reported trophic level of about 3.3. In its clear forest streams it would encounter a steady drift of small aquatic insect larvae, micro-crustaceans, and terrestrial insects falling onto the surface.
In the aquarium it's undemanding within the limits set by its small mouth. A good flake makes the staple, supplemented with small live and frozen foods — newly hatched or adult brine shrimp, Daphnia, bloodworm — plus the algae and biofilm a mature, planted tank lets it graze. A varied diet with a real live or frozen component improves colour and breeding readiness.
As an active, constant feeder it does best on small portions offered several times a day rather than a single large meal, and food that stays in the water column or near the surface suits its open-water feeding style better than food that sinks quickly out of reach.
Mating
Like other blue-eyes, Pseudomugil connieae is an egg-laying, plant-spawning species with no parental care. Males are the displaying sex: a courting male intensifies the yellow of his breast and flank stripe and spreads his elongated dorsal and anal fins, flicking and flaring them at females and at rival males. This finnage display, rather than a dramatic colour change, is the species' principal courtship signal.
Display and spawning peak when several males are present, since the males show best when competing — so breeders keep the species in groups, not isolated pairs. A shoal of six or more both settles the fish and draws out the males' display.
Receptive females spawn among fine-leaved vegetation, the eggs attaching to the plant substrate. This is a continuous trickle-spawner rather than a clutch-layer: a female releases a few eggs each day over a long stretch — a pattern that shapes how it's bred in captivity.
Breeding
Breeding Pseudomugil connieae follows the standard blue-eye approach. The species is an egg scatterer that spawns into fine-leaved plants — Java moss is ideal — or onto synthetic spawning mops, with the small eggs attaching to the medium. There is no parental care, and adults will eat eggs given the chance, so the spawning substrate is generally moved to a separate rearing container.
Spawning is spread out rather than concentrated. A female typically lays only a few eggs a day, but continues over a period of weeks, so a steady trickle of eggs accumulates on the mops or moss. Hobbyist reports give an incubation of roughly two weeks before the eggs hatch, the exact time depending on temperature within the species' warm preferred range.
The fry are tiny at hatching and need correspondingly small first foods — infusoria and the like — before they graduate to newly hatched brine shrimp and finely crushed flake. Expect to be patient. Growth is slow, and eggs and fry are easily lost to predation or poor water quality, so a dedicated, mature, gently filtered rearing tank gives the best results. Kept well, the species is reported to be long-lived for so small a fish — several years, and under good care occasionally much longer.
In the aquarium
Pseudomugil connieae is a peaceful, sociable, middle-level swimmer suited to a planted community of small, gentle fishes. Keep it in a group of at least six — for its own security, and so the males display against one another and stay at their most colourful. A modestly sized but well-planted tank with open swimming space and some water movement suits it, mirroring the clear, flowing streams of its native range.
Water should be clean, warm, and well oxygenated. Wild habitat data point to about 25 to 28 degrees Celsius and a pH near neutral to slightly alkaline, around 7.7 to 7.9, with moderate hardness. Hobbyist care guides sometimes recommend a higher and harder range — pH 7.5 to 8.0 and 12 to 18 dGH — but those figures skew above the wild-stream norms and should be treated as the upper end rather than a target; stable, well-filtered water with good flow matters more than chasing precise numbers. Bright lighting and a planted layout show the fish to best effect and encourage the morning display behaviour.
Tankmates should be similarly small and peaceful — other blue-eyes and small rainbowfishes, peaceful rasboras, small tetras — and nothing large or boisterous enough to beat this delicate fish to the food. Given clean water, good food, and its own kind, it's hardy and rewarding, valued more for its shoaling and finnage display than for bold colour.
Conservation
Pseudomugil connieae is assessed as Endangered (EN) on the IUCN Red List, under criterion B1ab(iii). The listing is driven by the species' extremely restricted geographic range — a single small area within about a fifty-kilometre radius of Popondetta in eastern Papua New Guinea — combined with a continuing decline in the quality of that habitat. A narrowly endemic stream fish of this kind has little resilience: there is no large outlying population to absorb local losses, so degradation of the Popondetta-area streams bears directly on the whole species.
The species is Not Evaluated under CITES and CMS; its protection rests on the IUCN assessment and on the condition of its wild streams rather than on trade regulation. It is collected and traded commercially as an aquarium fish, which makes captive breeding doubly valuable — both to relieve any collecting pressure on the small wild population and to maintain the species securely in the hobby.
Because P. connieae breeds readily in aquaria, aquarists are well placed to help — by keeping and propagating captive-bred stock rather than wild-caught fish, and by holding viable lines within hobbyist and association breeding networks. For a fish whose entire wild range could be undone by changes to one cluster of streams, that captive insurance counts.