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 35 years ago I went scuba diving
in Lake Eacham and was able to see the beautiful Rainbowfish. I was
unaware that this was an experience that my children could never have.
My son now lives in Cairns where he is 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 would not 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 speciesaustralis.
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 defense.
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.
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 stock. 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. However, 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
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
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