Zono  (Bedotia geayi)

Classified as Vulnerable (VU) on the IUCN Red List (1).

Bedotia geayi is one of a number of small, attractively coloured fish species, commonly called zono or zona, which inhabit Madagascan waterways (1). This species has a yellowish body with a distinct dark line running along the flanks, ending at the base of the tail with a dark blotch. The sexes can be distinguished by the striking red spot that develops on the male’s chin during the breeding season, as well as by the colour of the fins. The male’s dorsal fin and anal fin are clear grey with red margins and the tail fin is grey with black margins; in contrast, the female’s fins are translucent, except for the tail fin which becomes yellow towards the base (2). As a point of interest, a relative of this species, Bedotia madagascariensis is commonly sold in the aquarium trade under the name Bedotia geayi, but differs significantly from this species in the colouration of its fins (2).

Bedotia geayi is currently known only from the Mananjary River in south-eastern Madagascar, where it occurs in the middle and upper reaches of the main river channel and its associated tributaries at altitudes of 300 to 600 metres above sea-level (1) (2).

A freshwater species, Bedotia geayi occupies fast-flowing mountain rivers flowing over sand or gravel bottoms (2).

Forming small groups of up to 12 individuals, Bedotia geayi can usually be found in the calmer regions of its fast-flowing habitat, where the water is shaded by overhanging trees. Its diet appears to consist predominantly of insects which have fallen from the trees into the water.

Bedotia geayi’s reproduction is believed to be similar to that of the closely related species, Bedotia madagascariensis (2), which attaches its eggs to vegetation, leaving them to develop unguarded (3) (4). Once hatched, the juveniles usually occupy the shallows near to the riverbanks, while the adults inhabit deeper water (2).

The detrimental influence of human development and invasive species in the lower reaches of the Mananjary River has restricted Bedotia geayi to higher altitudes, where these threats are less serious (2). Although, at present, this species is reasonably abundant within its limited range, these threats are continuing to cause its population to decline (1). The major problem in the future is likely to be competition from invasive species such as Gambusia holbrooki, which have completely replaced this species in the lower parts of the Mananjary River where the water is less shaded. As deforestation spreads to higher regions, these invasive species may eventually replace Bedotia geayi entirely (2).

There are currently no conservation measures in place for Bedotia geayi. As long as it remains relatively abundant, the main conservation priorities will be to monitor its population and habitat, thereby identifying any further declines and degradation, and ensuring that it is not being adversely affected by introduced species (2).

View information on this species at the UNEP World Conservation Monitoring Centre.