Taxonomy & naming
Rasbora marinae was formally described by Heok Hui Tan and Maurice Kottelat in 2020 in the Raffles Bulletin of Zoology (volume 68, pages 750–758). The description is based on material from type localities in northwestern Borneo, and the species is placed in the large genus Rasbora within the family Danionidae (formerly treated as a subfamily of Cyprinidae).
The species is most closely allied to Rasbora cephalotaenia, sharing its bold mid-lateral stripe and spotting pattern, and the authors' analysis separates it from that species on the basis of meristic and morphometric differences. The genus Rasbora has been the subject of extensive revision since Kottelat and Witte (1999) carved out several satellite genera — including Boraras, Trigonostigma, Trigonopoma, Brevibora, and others — but R. marinae is placed squarely within the residual Rasbora clade, and no subsequent transfer has been published. The Catalog of Fishes (Eschmeyer, CAS) is the authority for valid nomenclature; no synonyms are recorded for this species.
The species epithet honours Marina Wong, a prominent naturalist affiliated with the Brunei Museum, in recognition of her contributions to knowledge of Brunei's biodiversity.
Morphology
Rasbora marinae reaches approximately 2.5 in in standard length, placing it at the larger end of the small-stream Rasbora guild in Sundaland. The defining mark is a well-defined mid-lateral dark stripe that runs continuously from the tip of the snout to the caudal fin, much as in the related R. cephalotaenia. This horizontal band is accompanied by rows of black spots along the flank, giving the fish a spotted-and-striped appearance that makes it recognisable in hand specimens and in freshly caught material.
Beyond these diagnostic features, the general body plan is the typical Rasbora form: a moderately elongate, laterally compressed cyprinid with a terminal to slightly upturned mouth suited to feeding in mid-water and near the surface. The freshly caught specimen illustrated from the Tatau, Sarawak type locality shows the pattern to good effect. Detailed counts of fin rays, lateral-line scales and other meristics are provided in the original description and distinguish it from the sympatric R. cephalotaenia.
Habitat
The type series was collected from streams in northwestern Borneo, specifically in Brunei Darussalam's Belait and Tutong Districts and in Sarawak north of the Tatau basin — including the Lambir Hills area — extending into the Baram basin. These are lowland to foothill forested stream systems characteristic of Sundaland, draining peat-swamp and mixed dipterocarp forest.
Like most Bornean stream rasboras, R. marinae almost certainly inhabits clear to lightly tannin-stained water flowing over sand and leaf litter beneath closed forest canopy. Such streams tend to be warm (roughly 75–82 °F), soft, and acidic (pH typically 5.5–7.0), with low conductivity. Deforestation and peat-swamp drainage across this portion of Borneo place such habitats under ongoing pressure, and the relatively restricted range of the species makes habitat quality particularly relevant to its long-term security.
Feeding
No specific dietary studies have been published for Rasbora marinae. Like other members of the genus from comparable Bornean habitats, it is presumed to be an omnivore and opportunistic micropredator, taking small aquatic and terrestrial invertebrates — insect larvae, microcrustaceans, small worms — along with algal films and organic detritus from the water surface and mid-column.
In the aquarium, rasboras of this size and type readily accept a varied diet of quality dried foods supplemented with live or frozen items such as daphnia, cyclops, small bloodworm and brine shrimp. Offering a range of foods is advisable both for condition and for encouraging natural foraging behaviour in a species that may be unfamiliar with commercial prepared foods.
Mating
Rasbora marinae has not been bred in captivity in any documented account, and no field observations of its reproductive behaviour have been published. Based on the biology of the genus and family, it is expected to be an egg-scattering, non-guarding spawner — the reproductive mode universal in danionid rasboras.
Courtship likely follows the danionid pattern: a ready male pursues a gravid female through vegetation or over fine substrate, driving her repeatedly until eggs and milt are released together. No nest is built, no territory is defended, and neither parent shows any guarding behaviour after spawning. The adhesive or weakly adhesive eggs fall among plants, moss, or bottom debris, where adults will consume them given the opportunity.
Breeding
Rasbora marinae has not been bred in captivity in any published record. As a newly described, rarely imported species, no established aquarium breeding protocol exists. Based on the biology of the genus, breeding would be attempted following the standard approach for Sundaland forest-stream rasboras: soft, warm, acidic water (pH 5.5–6.5, temperature around 77–81 °F), a heavily planted or moss-covered tank, and well-conditioned adults fed on a varied diet.
Eggs are scattered adhesively among fine-leaved vegetation or moss; adults should be removed promptly after spawning to prevent predation on the eggs. Fry would be expected to hatch in two to three days and become free-swimming shortly after, initially requiring infusoria or commercial fry foods before graduating to freshly hatched brine shrimp. These details remain speculative until the species is successfully kept and bred in captivity.
In the aquarium
Rasbora marinae is not currently available in the mainstream aquarium trade and has not been established in hobbyist collections to any documented extent. As a recently described species from a geographically restricted range in Brunei Darussalam and Sarawak, it has not entered commercial fish channels.
Should it become available, husbandry would follow the template for medium-sized Bornean forest-stream rasboras: a spacious, well-filtered tank with soft, acidic, warm water (approximately 75–82 °F, pH 5.5–7.0, low conductivity), peat or botanical filtration, subdued lighting with floating plants, and a quiet community of similarly sized, non-aggressive fishes. Like all rasboras it is a shoaling species and should be kept in groups of at least six individuals. Given the pressures on its wild habitat, any specimens entering the hobby should ideally come from captive-bred sources rather than wild collection.
Conservation
Rasbora marinae has not been assessed by the IUCN Red List; as a species described in 2020 it falls outside the current assessment cycle and carries a status of Not Evaluated (NE). Its known range is relatively restricted — Brunei Darussalam (Belait and Tutong Districts) and the adjacent portions of Sarawak — which makes it inherently more vulnerable than widespread congeners.
The lowland and foothill forested streams of northwestern Borneo that constitute its habitat have experienced severe deforestation and peat-swamp drainage over recent decades, driven by oil palm expansion, logging, and infrastructure development. Species with small, fragmented distributions in such habitats are disproportionately at risk from habitat loss, even when direct exploitation pressure is low. Given how recently the species was described, baseline population data are lacking; a formal IUCN assessment taking into account its range size and habitat trajectory would be a worthwhile step.