Pacific blue eye

The Pacific blue-eye generally reaches a total length of around 3–3.5 cm (1 1⁄8–1 3⁄8 in) long; males can reach 8.8 cm (3 1⁄2 in) and females 6.3 cm (2 1⁄2 in). The size of Pacific blue-eyes found north of the Burdekin Gap increases directly with distance from the gap, males and females being the same size. South of the Burdekin Gap, the species exhibits marked size difference between sexes, which becomes more pronounced as the distance from the gap increases. The elongate body is partly transparent and pale yellow or olive with a silver operculum and belly. The scales are relatively large and longer vertically than horizontally. The eye is large and has a blue iris. There are two dorsal fins, the first arising in line with or just posterior to the longest pectoral fin ray. The forked tail fin has rounded tips. The bottom and top edges of the tail fin are edged with white. The male has extended filaments on its dorsal, anal and pelvic fins. There are black markings at the base of the anterior rays of the anal and rear dorsal fins, and the front (anterior edge) is sometimes white and the rear (posterior) edge greyish in colour. The male's fins may turn orange during breeding season. Preserved specimens generally discolour to yellow or tan. The Pacific blue-eye can be distinguished from the highly invasive and noxious introduced eastern mosquitofish (Gambusia holbrooki) by its forked tail fin.