鲻银汉鱼 · Pacific Blue-eye

Overview

The widespread Australian Pseudomugil signifer varies substantially in size, color, and fins between localities. Most forms are peaceful, but breeding males from some larger northern populations can fight severely. A single compatibility rule is therefore inappropriate for every stock.

Distribution & habitat

Its range follows much of Australia's east coast, from northern Cape York to southern New South Wales, with some offshore-island and western Cape York populations. Northern and southern forms, including populations on opposite sides of the Herbert River, show pronounced differences.

Habitats include fresh water, marine conditions, mangrove creeks, salt marshes, lowland swamps, clear forest streams, blackwater, and artificial canals. Cooler wild conditions chiefly concern southern populations in winter and should not be generalized to all origins.

Aquarium setup

Start with a footprint around 60 × 30 cm; larger northern forms need substantially more space. Dense planting, floating cover, and wood soften the light. Maintain a mature system with plentiful oxygen and moderate flow.

Avoid immature aquariums and rapid chemical changes. Despite broad salinity tolerance, marine salt is unnecessary: fish from brackish habitats can live and breed in fresh water. Stability remains important.

Diet & feeding

Food chiefly consists of floating or suspended plankton and small invertebrates. Water fleas, brine-shrimp nauplii, and microworms are useful live options, with fine floating dry food also accepted.

Behaviour & compatibility

Maintain at least eight to ten. Most forms can join carefully selected communities of similarly sized fishes with matching needs. Larger northern males, however, become highly intolerant of one another in breeding condition and may kill subordinate fish in restricted quarters.

These stocks need spacious accommodation, potentially with suitable open-water companions to distribute attention. Increasing conspecific numbers cannot compensate for inadequate space.

Sexual dimorphism

Males are generally larger and brighter, developing elongated unpaired fins. Some wild populations have filamentous dorsal and anal extensions that are often lost after capture. Their absence in captive fish is therefore not sufficient evidence of female sex.

Breeding

This egg scatterer provides no parental care and can consume its own offspring. Natural breeding follows the wet season. Warm conditions encourage daytime activity, and females deposit small batches over several days, attaching eggs by fine threads.

One method uses six to eight adults, or a male with two or three females, in a sponge-filtered container with mops or moss. Collect eggs daily. Alternatively, a larger established colony aquarium with elevated moss and trailing roots may allow fewer young to survive with less intervention.

Incubation takes about ten to twenty-one days. Fry can immediately eat brine-shrimp nauplii, microworms, or appropriate powdered diets. Offer small meals at least twice daily, remove leftovers, and make regular small water changes.

Notes

Fish from the northern and southern extremes failed to hybridize in captive experiments, and some analyses suggest multiple taxa may be involved. This is not a settled taxonomic split. Retaining locality labels and distinct breeding lines is preferable to treating all forms as identical ornamental stock.