Lake Eacham Rainbowfish - Melanotaenia eachamensis

The Lake Eacham Rainbowfish (Melanotaenia eachamensis) was scientifically described by Allen & Cross in 1982. It was collected in 1978, but wasn’t recognized as a species until four years later. It was believed to have been completely extinct from the wild by 1987, but in 1988 another population was found. This fish can no longer be found in Lake Eacham, but it lives on in nearby Dirran Creek and Lake Euramoo.

Description
The Lake Eacham Rainbowfish can reach a length of 6.5 cm (2 ½ inches). The body has silvery sides while the back is brownish or olive coloured. In some specimens, a narrow brownish stripe can be seen between each horizontal row of scales. The dorsal, anal and caudal fins are all reddish in colour. Males can develop pale dots close to the fin base. The Lake Eacham Rainbowfish is not very flamboyant compared to the more commonly kept rainbowfishes from Australia.

Geographical distribution, habitat and conservation
Lake Eacham Rainbowfish is found in the north-eastern corner of the Australian continent. Their natural habitat is crater lakes and a creek in the rainforest. Earlier, this species was believed to live in the crater lake Lake Eacham only. Crater lakes are often quite isolated and are known to easily give rise to endemic species that can be found nowhere else in the world, not even in nearby lakes and waterways. The Lake Eacham Rainbowfish has however been found in Lake Euramoo 14 km (almost 9 miles) north of Lake Eacham and in the Dirran Creek 22 km (almost 14 miles) south of Lake Eacham as well, which is very fortunate since the species was eradicated from Lake Eacham during the 20th century. As late as the 1970s, Lake Eacham Rainbowfish was still very common in Lake Eacham. It lived there together with only two other known species of fish: the Northern Trout Gudgeon (Mogurnda mogurnda) and the Fly-specked Hardyhead (Craterocephalus stercusmuscarum).

In 1987, a fish collecting survey carried out by the Queensland Fisheries Department failed to find any Lake Eacham Rainbowfish at all in the crater lake. They also failed to find any Northern Trout Gudgeon. Before Lake Eacham Rainbowfish was found in Lake Euramoo and the Dirran Creek, it was believed to be the only Australian fish species to have become extinct in the wild since the Europeans came to Australia. The reason behind its demise is most likely invasive species; more precisely the Banded Grunter (Amniataba percoides), Mouth Almighty (Glossamia aprion), Archerfish (Toxotes chatareus) and Bony Bream (Nematalosa erebi). These four species are all commonly occurring in a nearby reservoir named Tineroo, from which they were caught and deliberately introduced to Lake Eacham by fishermen.

When the results of the 1987 survey became known in Australia, 24 specimens of aquarium kept Lake Eacham Rainbowfish could be located thanks to the efforts of the Australia New Guinea Fishes Association (ANGFA). Coordinated breeding attempts took place among the aquarists and offspring was donated to both the Walkamin Research Station and the Taronga Park Zoo for use in their respective breeding programs. After a few years, roughly 1000 Lake Eacham Rainbows were reintroduced to Lake Eacham, but the attempt was not successful. If we want to see Lake Eacham Rainbows in Lake Eacham again, we will probably be forced to eradicate the introduced species from the crater.

Keeping Lake Eacham Rainbowfish in aquariums
Keeping Lake Eacham Rainbowfish is not very tricky. It is commonly combined with other rainbows and blue-eyes, but it can be kept with many other small and peaceful fish species as long as they appreciate the same conditions. You don’t need a very big aquarium; a 35 litre (10 gallon) aquarium can comfortably house 8-10 Lake Eacham Rainbowfishes. Keep the water temperature at 23-27 degrees C (73-81 degrees F) and the pH-value at 7.0-7.4 (neutral or slightly alkaline).

Breeding Lake Eacham Rainbowfish
The Lake Eacham Rainbowfish readily spawns in aquariums. You can either keep a pair or a group consisting of 2-3 females for each male. Lake Eacham Rainbowfish spawns among bushy plants in the wild and will therefore appreciate java moss and spawning mops in the aquarium.

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Other Australian Rainbowfishes

Cairns Rainbowfish
Threadfin Rainbowfish
Exquisite Rainbowfish
Murray River Rainbowfish
Slender Rainbowfish
MacCulloch’s  Rainbowfish
Black-banded Rainbowfish
Pygmy Rainbowfish
Western Rainbowfish
Chequered Rainbowfish
Eastern Rainbowfish
Desert Rainbowfish
Banded Rainbowfish
Ornate Rainbowfish