Pacific Blue-eye - Pseudomugil signifer
Pacific Blue-eye - Pseudomugil signifer

Pacific Blue-eye - Pseudomugil signifer

The Pacific Blue-eye was scientifically described by Kner in 1865. Its scientific name is Pseudomugil signifer.

The Pacific Blue-eye can become 7 cm (2 ¾ inches) long. Most specimens will however stay much smaller than this.  

The Pacific Blue-eye comes in at least 15 different known geographical variants and it can sometimes be hard to fathom that they actually belong to the same species since they look so dissimilar to each other. The populations vary dramatically when it comes to colouration, markings and fin proportions. The body colour can be anything from silvery blue to a yellowish tan. The upper back is decorated with dark scale outlines and many specimens – but not all – are also adorned with white dots that form a mid-lateral row along the body. Dorsal, anal and caudal fins are clear or yellowish and have white margins.

Geographical distribution, habitat and conservation
The Pacific Blue-eye lives in streams and estuarine environments along the eastern coast of Australia. It can be found from the Cooktown area on the Cape York Peninsula to Ulladulla in New South Wales.

The environment along the Australian east coast varies a lot and the Pacific Blue-eye is a really adaptable fish. The species is present along the mainland shore as well as on offshore islands such as the Low Islets. The Pacific Blue-eye is not only found in various geographical locations; it is also frequently subjected to seasonal and tidal changes. It can be found in pure fresh water as well as in sea water salinity, and the typical Pacific Blue-eye habitat consists of mangrove environments highly affected by tidal changes. The streams where you can find Pacific Blue-eye are normally clear and surrounded by forest.

Pacific Blue-eyes have been found in pH 5.5 as well as in 7.8. Most Pacific Blue-eyes are used to water temperatures around 22-28 degrees C (72-82 degrees F), but for the populations living in the southernmost part of the range the winter can cause the water temperature to drop down to 15 degrees C (59 degrees F).

The Pacific Blue-eye is listed as “Not Evaluated” on the IUCN Red List of Threatened Species.

Keeping Pacific Blue-eye in aquariums

Pacific Blue-eye
Pacific Blue-eye - Copyright
The Pacific Blue-eye can be kept in a species aquarium or be combined with other peaceful species of roughly the same size in a community aquarium. Even a small 30 litre (8 gallon) is large enough for a small group of Pacific Blue-eyes. This species is commonly kept both in Australia and other parts of the world. It has been available in Europe since the 1970’s.

As mentioned above, the Pacific Blue-eye is used to significant changes in water temperature in its natural habitat, but such changes are not required in the aquarium. You can keep the water temperature in the 22-27 degrees C (72-81 degrees F) range year round. The recommended pH-value is 6.5-7.5 (slightly acidic to slightly alkaline).

Pacific Blue-eyes that hail from estuarine environments are known to appreciate some salt in the aquarium; roughly 0.5 grams per litre is a good rule of thumb.  

It is important to provide your Pacific Blue-eye with a varied and nutritious diet in the aquarium. You can for instance combine dry prepared foods with live foods such as brine shrimp and daphnia.

Breeding Pacific Blue-eye
The Pacific Blue-eye is normally bred in groups and becomes sexually mature when it’s about six months old. The group should always consist of at least 2-3 females for each male, since the males can be aggressive towards the females. It is also important to include plenty of suitable hiding spots. Be prepared to evacuate disinterested females if the males become overly aggressive. If you want to increase the chances of spawning in the aquarium, feed your Pacific Blue-eye ample amounts of live food.

During the breeding period both sexes will develop stronger colours than normal, but this is especially noticeable in the male. He will for instance display a black band on the upper edge of his pectoral fin. In some specimens, the black band is accompanied by a white band.

The fishes will need a suitable spawning medium in the aquarium, e.g. java moss or spawning mops. This species prefers to deposit the eggs no more than 10 cm (4 inches) from the bottom.
The females will release up to a dozen eggs per day and you should therefore inspect the spawning medium regularly. The safest course of action is to move the spawning medium with the eggs to a separate aquarium.

Pacific Blue-eye eggs are surprisingly large considering the size of the females and need a long incubation time. If you keep the water temperature in the higher end of the recommended range, the eggs will normally hatch within 16 days. If the water temperature is lower, the incubation can last for up to three weeks. Since the fry are so big when they hatch, they can normally be fed brine shrimp as a first food. It is a good idea to combine the brine shrimp with infusoria and finely ground flake food, especially if you suspect that the fry need to grow a bit before they can devour brine shrimp with ease.

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