Taxonomy & naming
Scriptaphyosemion geryi was described by Lambert in 1958, with the type locality placed in the Conakry-Dubreska district of Lower Guinea. The authority is given in parentheses — (Lambert, 1958) — indicating that the species has since been moved from whatever genus Lambert originally placed it in to the current combination under Scriptaphyosemion, a genus erected to accommodate a cluster of small, predominantly West African killifish separated from the older, broader genus Aphyosemion on the basis of morphological and molecular characters. Eschmeyer's Catalog of Fishes (Fricke, Eschmeyer & Fong) recognises the valid name as Scriptaphyosemion geryi (Lambert, 1958).
The genus Scriptaphyosemion is sometimes called the 'script killies' in reference to the fine, often stripe-like patterning on the flanks of several members. It contains a small number of species distributed in coastal West Africa — Guinea, Sierra Leone, Gambia, and neighbouring Senegal — and shares broad similarities with related genera in the Aplocheilidae. Hobbyists following American Killifish Association (AKA) convention and the WAK (West African Killifish) reference system track S. geryi populations through locality codes such as GCLR 06 (Guinea coastal locality) and GM 97 (Gambia, 1997 collection), with at least 91 documented collection localities recorded across the species' range.
Morphology
Scriptaphyosemion geryi is a small, slender killifish reaching approximately 2 in total length in typical adults, with occasional large males reported to approach 3 in TL (FishBase; WAK reference library). The body is fusiform and slightly laterally compressed. Meristic counts from the WAK reference library give dorsal fin rays 13–15 and anal fin rays 16–17, counts consistent with others in the genus.
Males are considerably more colourful than females — the hallmark of sexual dimorphism in most Scriptaphyosemion. Body ground colour in males tends toward olive or brown with a pattern of red to reddish-brown spots or flecks on the flanks, and the unpaired fins typically show coloured margins or patterns of dots and streaks in red, blue, or yellow depending on the population. Females are cryptically coloured in warm brown or beige with little pattern, a common condition in substrate-associated killifish that rely on camouflage during incubation duty. Fin shape is broadly symmetrical and rounded in both sexes, without the extended caudal rays seen in some related genera.
Habitat
In the wild, Scriptaphyosemion geryi inhabits small, well-shaded brooks, streams, pools, and swamps set within the coastal savanna and forest-fringe zone of West Africa. FishBase records the distribution as running from the Gambia mouth southward to Port Loko in Sierra Leone, encompassing portions of Gambia, Senegal, Guinea, and Sierra Leone. The AKA species page documents the native countries as Gambia, Guinea, Senegal, and Sierra Leone, consistent with this range.
The water in these coastal habitats tends to be soft and acidic, stained with tannins from leaf litter and overhanging vegetation. FishBase gives a typical pH of around 5.5 and a temperature of approximately 73 °F. The WAK reference library notes that the species is non-seasonal — it is not an annual killifish and does not depend on pools that dry completely between seasons. Streams are small, shaded, often slow-moving or still, and typically shallow enough for the fish to access both the upper water column and the bottom within a short distance.
Feeding
Like most killifish of equivalent size, Scriptaphyosemion geryi is an opportunistic carnivore feeding primarily on small aquatic invertebrates. FishBase describes the wild diet as aquatic invertebrates, consistent with the generalist insectivore strategy typical of the genus: surface-dwelling and water-column insects, their larvae, small crustaceans, and worms form the bulk of natural prey in the soft, shaded streams it inhabits.
In the aquarium the species is straightforward to feed. It accepts live and frozen invertebrate foods — Daphnia, Artemia nauplii and adults, bloodworm, Tubifex, and mosquito larvae — as well as small dried or micro-pellet foods if the fish are conditioned to accept them. Feeding a varied diet of live or frozen invertebrates improves colour and breeding condition. As with most small killifish, twice-daily small meals are preferable to single large feedings.
Mating
Scriptaphyosemion geryi is a non-annual killifish and a plant spawner — the pair deposit adhesive eggs on fine-leaved aquatic plants, submerged roots, or floating spawning mops rather than burying eggs in substrate. This is a fundamental distinction from the annual killifish that bury diapausing eggs in peat for a dry-season dormancy; S. geryi lives in permanent or near-permanent water and its eggs incubate continuously in water without diapause.
The WAK reference library notes an interesting behavioural pattern: younger pairs tend to spawn higher in the water column, depositing eggs on floating mops near the surface, while older, more established pairs shift to spawning closer to the bottom, using substrate mops or lower-level vegetation. This 'switch spawning' behaviour — noted also by the British Killifish Association — means that providing both surface and bottom spawning sites improves egg collection across the life of a breeding pair. Spawning takes place over extended periods of days to weeks rather than in a single concentrated event.
Breeding
Eggs are deposited singly or in small numbers on plant leaves or mop fibres and incubate in water at around 75 °F. The WAK reference library gives an incubation period of 13–21 days under normal conditions, with some sources extending this range to 17–29 days depending on temperature. There is no diapause; the eggs develop continuously, and the keeper can either leave them in place (with careful management of predation risk from the adults) or pick them by hand from mops daily and incubate them separately in shallow containers of conditioned water.
Fry hatch very small and require infusoria or similarly fine first foods — commercial fry powder, vinegar eels, or paramecia — before graduating to newly hatched Artemia nauplii. The WAK library specifically notes the very small size of newly hatched fry as a care point. Breeding water in the reference library is given as 75 °F, approximately neutral pH, and soft at DH 2, though the British Killifish Association notes that the species tolerates a somewhat broader range of pH 6.8–7.4 and DH 7–10 in captivity. Aged, clean water is emphasised by both sources.
In the aquarium
Scriptaphyosemion geryi is considered one of the more accessible species in its genus — moderately demanding but not fragile — and is a rewarding choice for hobbyists with an interest in African killifish or West African biotope aquaria. A small tank of 15.5–31.5 in length (Aqualog) is adequate for a pair or small group. The species is timid by nature and does best with dimly lit conditions and heavy plant cover or dense mop arrangements that provide visual security; both killi.co.uk and the British Killifish Association emphasise the species' preference for a well-planted, shaded environment.
Water quality should be clean and well-oxygenated with gentle flow. The British Killifish Association recommends pH 6.8–7.4, hardness DH 7–10, and temperature 73–75 °F using aged water; Aqualog gives a somewhat broader range (pH 5.0–7.0, temperature 75–84 °F), and FishBase notes pH 5.5 and 73 °F in the wild. In practice, soft to moderately hard water around neutral pH and a temperature of 73–77 °F suits the species well. Regular partial water changes with conditioned, aged water are important — killifish generally react badly to build-up of dissolved waste products.
Male conspecifics may display and spar; in a small tank a single pair or a small group with one male to several females is the standard approach. Tankmates, if any, should be small, peaceful, and similarly undemanding — other West African dwarfs, small rasboras, or non-competitive bottom dwellers are appropriate; boisterous or nippy species will stress the fish. The charming patterning of males and the accessibility of breeding make S. geryi a good entry point into killifish keeping.
Conservation
The IUCN Red List assessed Scriptaphyosemion geryi as Least Concern (LC) in 2019, noting that the species has a sufficiently wide distribution across Gambia, Guinea, Senegal, and Sierra Leone that it does not currently meet the thresholds for a threatened category. The AKA species page records 91 documented collection localities, suggesting the species is reasonably widespread within its range of coastal West African streams and savanna waterways.
Nevertheless, the habitats it occupies — small, well-shaded coastal brooks and forest-fringe streams — are vulnerable to the land-use pressures operating across West Africa: deforestation, agricultural conversion, burning of savanna margins, and catchment degradation that increases sediment loads and water temperatures in what should be cool, shaded streams. Unlike annual killifish that can repopulate from dormant egg banks after habitat disturbance, non-annual species such as S. geryi have no such buffer; local population loss is immediately reflected in the standing population with no recovery from buried eggs. Continued monitoring of habitat condition across the range, particularly in Sierra Leone and Guinea where forest cover is declining, remains important to confirm that the current Least Concern status holds.