Lake Eacham Rainbowfish

Keeping and Breeding This Extinct Fish

People sometimes talk about "The Australian Rainbowfish", but this is misleading.  There are many types of Australian Rainbowfish.  In some areas of Queensland, it seems that almost every little watercourse or lake has at least a colour variety. In some cases, they are subspecies or even distinct species.

Lake Eacham in the Atherton tablelands in the hills above the tropical city of Cairns is a volcanic lake, about 215 feet deep. About 50 years ago I went scuba diving in Lake Eacham and saw the beautiful Rainbowfish. I was unaware that this was an experience that my children could never have. My son lived in Cairns where he was a vital crewman on that MIGHTY WARSHIP, Pride of the Royal Australian Navy, whose very name strikes terror into the evil hearts of our enemies, HMAS Mermaid.  If my son went diving in Lake Eacham he wouldn’t see any Rainbow Fish.

The Lake Eacham Rainbowfish is a distinct species, with the scientific name Melanotaenia eachamensis. It is related to the Eastern Rainbowfish, Melanotaenia splendida, subspecies splendida, although its mitochondrial DNA could suggest a closer relationship with a Western Australian Fish, Melanotaenia splendida sub species australis. It is not known how the ancestors of the Lake Eacham Rainbowfish got into the lake which was only formed about 13,000 years ago. They developed without large predatory fish, so when these were introduced to the lake the Lake Eacham Rainbowfish had little defence.

In the 1980's it was suddenly realized that there were no Rainbowfish in Lake Eacham. Instead there were several species of predatory Australian fish including the Mouth Almighty, Glossamia aprion. These had been put into the lake to improve the fishing, apparently with the approval of some parts of the local government.

The Lake Eacham Rainbowfish was extinct!

However, just as people can irresponsibly put fish into lakes, they can also illegally take them out.  The desperate search began to find people who had removed Lake Eacham Rainbowfish before they had all been eaten. This was not to punish these people, but to get breeding stock to establish a captive breeding population. Enough Lake Eacham Rainbowfish were found to breed from, and the species was saved for the time being. Its status in the wild was still listed as extinct.

Later several wild populations of the Lake Eacham Rainbowfish were found. And the present conservation status of the Lake Eacham Rainbowfish is "Endangered". It is not clear how these got into the places they were found. Some were pure Lake Eacham Rainbowfish, but some of the populations were hybrids between the Eastern Rainbowfish and the Lake Eacham Rainbowfish. I suspect that some of these populations were from recent human releases of the fish, rather than completely natural ones.

An attempted restocking of Lake Eacham with 3000 Lake Eacham Rainbowfish failed. There was no sign of them after four months. They were missing, presumed eaten. Until all the introduced predators can be removed, reintroductions are likely to fail. This leaves the question of how to rid a reasonable sized lake of all fish. Poisoning them could work, but the poison would also kill other things like crustaceans and frogs.

Another possibility that has been considered is to put a large number of Barramundi, Lates calcarifer, into the lake. This highly predatory fish starts off as male and later changes into a female. This sex change can only happen after the Barramundi migrates to the sea. This is not possible in Lake Eacham which is very fresh and totally enclosed, so they would all stay male, growing bigger and eating all the other fish. Eventually the male Barramundi would die of old age, leaving the lake free for the reintroduction of it rightful owners. You can see the things wrong with this idea.

Lake Eacham Rainbowfish for the Aquarium

Occasionally the Lake Eacham Rainbowfish has been offered for sale and it is a good aquarium fish. It reaches about two and a half inches (seven cm) long and is peaceful  It is a good community fish kept with similar sized or smaller peaceful fish. The normal conditions for a mixed community, pH of seven with a temperature of 24̊ C (75̊ F) are suitable.

Food

The Lake Eacham Rainbowfish is an omnivore and benefits both from some small live food and from algae or other plant type food.

Companions

The Lake Eacham Rainbowfish is a schooling fish and several should be kept together. Other small, peaceful fish can be kept with it, for example: other species of Rainbowfish, Flame Tetras, Rummy Nose Tetras, Harlequin Rasboras, Lemon Tetras, Emperor Tetras, Head and Tail Light Tetras, Glass Bloodfin Tetras, Glowlight Tetras, Peppered Catfish, and White Cloud Mountain Minnows. Avoid large or excessively boisterous fish as well as predators.

Breeding

The Lake Eacham Rainbowfish is easily bred in aquariums. More females than males are usually suggested. They will spawn among fine leaved plants like Java Moss.

Sources and Picture Credits

I am indebted to the following sources for information about the Lake Eacham Rainbowfish: The Aquatic Community, The Department of the Environment and the Arts of the Australian Government, and to Chambers Wildlife Lodges for information about Lake Eacham. 

Steve Challis