Crimson-spotted Rainbowfish

The Crimson-spotted Rainbowfish (Melanotaenia duboulayi) is a small freshwater fish in the family Melanotaeniidae, the rainbowfishes, native to coastal drainages of New South Wales and southern Queensland, Australia. It is one of the most widely recognized members of the genus Melanotaenia due to its bright coloration and hardiness across a range of water conditions. The species was described by William Macleay in 1884 and is closely related to the Eastern Rainbowfish (M. splendida), with which it can hybridize where ranges overlap. It remains common and is not considered threatened, occurring in slow-flowing creeks, rivers, lagoons, and swamps throughout its native range. Populations have also become established outside their native range through aquarium releases.

Crimson-spotted Rainbowfish are compact, deep-bodied fish reaching 6-10 cm.

• Body: laterally compressed, arched dorsal profile, especially in mature males
• Coloration: iridescent blue-green back and upper sides, silvery lower flanks
• Markings: rows of small crimson-red to orange spots running along the scale rows
• Fins: two separate dorsal fins; anal, dorsal, and caudal fins often edged in red-orange
• Tail: forked and mostly translucent Males are more vividly colored and deeper-bodied than females, which appear duller and more streamlined. It is distinguished from the similar Eastern Rainbowfish by its smaller size, deeper body, and more intense spotting pattern along the flanks.

This species inhabits slow to moderately flowing freshwater streams, rivers, lagoons, swamps, and backwaters along the eastern coastal drainages of Australia, from the Clarence River system in New South Wales north into southeastern Queensland. It favors well-vegetated margins with overhanging cover, submerged logs, and aquatic plants, typically in clear to slightly turbid water. Crimson-spotted Rainbowfish tolerate a wide range of temperatures, from cool upland streams to warmer lowland waterways, and can survive in still ponds as well as flowing creeks. They are most abundant in shallow, sheltered sections near vegetation rather than open, fast-flowing channels.

Crimson-spotted Rainbowfish are active, mid-water schooling fish that move in loose aggregations, particularly as juveniles, with schooling becoming less rigid in adults. They feed opportunistically during daylight hours on small aquatic invertebrates, insect larvae, algae, and plant material picked from the water column and surface. Breeding occurs in warmer months, when males display intensified coloration and court females among fine-leaved aquatic vegetation; eggs are scattered and adhere to plants via fine threads, with no parental care afterward. Adults may consume their own eggs. Within their ecosystem, they serve as both predators of small invertebrates and prey for larger fish and birds.