Taxonomy & naming
Rhinogobius cliffordpopei was described by the American ichthyologist John Treadwell Nichols in 1925 from material collected at Tungting — the Dongting Lake basin in Hunan Province, China — which stands as the type locality. The Catalog of Fishes (Eschmeyer, CAS), the authority for valid names, records the current combination as Rhinogobius cliffordpopei with the parenthetical authority (Nichols, 1925), indicating the species was originally placed in a different genus. Earlier combinations in the literature include Gobius cliffordpopei and Ctenogobius cliffordpopei; both names have since been superseded.
The species belongs to the family Oxudercidae as recognised under modern taxonomy (subfamily Gobionellinae), a placement confirmed by mitochondrial genome sequencing that resolves its position within the goby clade. Note that older sources may list the family as Gobiidae, which historically encompassed much of what is now split across Gobiidae, Gobionellidae and Oxudercidae; the core goby characters — including the fused pelvic sucker disc — are shared across all three. Rhinogobius is a large and taxonomically active genus of East and Southeast Asian freshwater gobies; new species are described periodically and the limits of some nominal species remain debated.
Morphology
Clifford Pope's goby is a moderately large Rhinogobius, with FishBase recording a maximum total length of 5.5 in — substantially bigger than many of the small, nano-tank Rhinogobius species in the hobby. The body is elongate and cylindrical toward the head, tapering to a compressed tail, with the blunt snout and large eyes characteristic of benthic predators that hunt by sight among rocks and gravel.
The defining anatomical character of this, as of all true gobies, is the pelvic sucker disc: the two pelvic fins are fused at their bases into a muscular cup that functions as an adhesion organ, allowing the fish to hold station on rock surfaces in fast current. This immediately separates Rhinogobius from the sleeper gobies and gudgeons (Eleotridae), whose pelvic fins remain separate. Rhinogobius cliffordpopei shows the typical goby two-dorsal-fin arrangement — a short, spiny first dorsal and a longer soft-rayed second — and the rounded caudal fin standard for the genus. Precise colour pattern data for this species are sparse in the accessible literature, but Rhinogobius species typically display brown, grey or buff ground colours with variable spotting and barring that provides camouflage on rocky or gravelly substrates.
Habitat
The species is recorded from temperate freshwater river systems in China — the Liao River in the north, the Yangtze River basin in central China (including the Dongting Lake system, its type locality), and the Qiantang River in Zhejiang Province — and from Vietnam. These are well-oxygenated, flowing freshwater habitats: the rivers, streams and lake inflows of the temperate East Asian lowlands and foothills. FishBase classifies it as benthopelagic, consistent with the benthic lifestyle of Rhinogobius generally.
The temperate distribution is an important ecological signal: unlike many tropical aquarium gobies, Rhinogobius cliffordpopei inhabits rivers that experience marked seasonal temperature change. Inferred temperature preferences fall in roughly the 64–75 °F range, based on the climate of its range. This makes it a cool-to-temperate-water species, more akin in thermal requirements to some of the European stream gobies than to the tropical Brachygobius or Stigmatogobius of Southeast Asia.
Feeding
FishBase records a trophic level of 3.4 for Rhinogobius cliffordpopei, placing it firmly as a secondary consumer — a small predator of invertebrates rather than a plant-feeder or detritivore. This is typical for Rhinogobius: the genus hunts small aquatic invertebrates, insect larvae, small crustaceans and similar benthic prey on and among rocky substrates.
In aquaria, Rhinogobius gobies generally behave as micro-predators and are often reluctant to accept dried or flake foods, at least initially. Live and frozen foods — bloodworm, brine shrimp, daphnia, cyclops, small aquatic insect larvae and similar meaty items — are the appropriate diet. Where aquarium experience with closely related Rhinogobius species is any guide, conditioning this fish for long-term health and any breeding attempt calls for a varied menu of live and frozen invertebrates rather than reliance on prepared foods.
Mating
Rhinogobius cliffordpopei is a resident freshwater species — unlike many stream gobies it does not have an amphidromous life cycle in which larvae are swept to sea — and it is therefore a cave or substrate spawner with male parental care, following the standard pattern of the genus. Males establish and defend territories around a spawning site: typically a rock crevice, undercut stone, or similar sheltered cavity in the streambed.
Courtship in Rhinogobius follows the pattern common to goby cave-spawners: the male intensifies his colours and fin displays and leads a receptive female to the spawning site. Females in breeding condition may show a more rounded abdomen and subtle colour changes, though specific descriptions for this species in the accessible literature are absent. The male is the territory holder and does not pair permanently; females spawn and then leave the site.
Breeding
Rhinogobius cliffordpopei is a cave or substrate spawner: the female deposits adhesive eggs on the roof or wall of a hard surface — a rock crevice, cave, shell or similar cavity — and the male guards and fans the clutch until hatching. This is genuine parental care on the male's part: he aerates the eggs with fin movements, removes dead or fungused eggs and actively defends the spawning site. Because the full cycle takes place in fresh water with no marine larval phase, the species is in principle captive-breedable given appropriate conditions.
However, published aquarium breeding accounts for Rhinogobius cliffordpopei specifically are sparse or absent from the accessible literature at this time. The species' temperate distribution means that — as with several Japanese and Chinese Rhinogobius — a cooler spawning temperature and possibly a seasonal cool period may be relevant triggers. Aquarists wishing to attempt breeding would be guided by the successful protocols documented for other temperate Rhinogobius species: well-oxygenated, flowing water, rocky décor with suitable crevices, live-food conditioning of adults, and water temperatures in the cooler part of the species' range during the spawning window.
In the aquarium
Rhinogobius cliffordpopei is an infrequently encountered species in the aquarium hobby; documented aquarium care data are sparse. The guidance that follows draws on what is known of its natural distribution and on experience with closely related Rhinogobius kept by temperate-goby enthusiasts. Given a maximum size of 5.5 in TL it is not a nano fish: a tank of at least 31.5–39.5 in in length is appropriate for adult specimens, with rocky décor that provides caves, crevices and line-of-sight breaks, since male Rhinogobius are territorial and will compete for refuge sites.
Water quality should be high, with good oxygenation and moderate to strong flow mimicking a river or stream environment. Temperature should be kept temperate — roughly 64–75 °F — not the 79–82 °F of a tropical community tank. This fish should not be kept in brackish water; it is a pure freshwater species from major inland river systems. A close-fitting cover is advisable: gobies in general are capable jumpers, and an uncovered tank invites losses. Diet should prioritise live and frozen invertebrates; dried foods may be refused or only reluctantly accepted. Males should not be kept together in confined space without ample cover. Mixing with peaceful, similarly-sized fish that prefer the mid-water or upper levels is feasible, leaving the substrate zone to the gobies.
Conservation
Rhinogobius cliffordpopei has not been formally assessed by the IUCN Red List and is recorded here as Not Evaluated (NE). FishBase notes high resilience and low vulnerability to fishing pressure, which is broadly consistent with a wide-ranging river-system species distributed across multiple major Chinese drainage basins, though these metrics are modelled estimates rather than field surveys.
The species inhabits some of China's most economically active and hydrologically modified river catchments — the Yangtze system in particular has experienced heavy development pressure, including dam construction, channel modification, pollution and water withdrawal. The long-term effect of these changes on Rhinogobius cliffordpopei populations is not documented in the accessible literature. As with many small-bodied Chinese freshwater fishes, a formal IUCN assessment using range, population trend and habitat-quality criteria would provide a clearer picture. Until that assessment exists, the conservation status of this species remains genuinely unknown.