Lake Eacham

Lake Eacham (originally Yidyam or Wiinggina) is a popular lake of volcanic origin on the Atherton Tableland of Queensland, Australia, within the World Heritage listed Wet Tropics of Queensland. It is within the locality of Lake Eacham in the Tablelands Region local government area. Lake Eacham (Yidyam) was formed over 9,130 years ago when molten magma from the Earths mantle rose to the surface and heated the water table. The steam that resulted from the boiling water was trapped underground, until massive explosions signalled its release. Huge cracks appeared in the ground and the trees that once lathed the mountainside were levelled and burnt. Eventually, after the eruptions, groundwater filled the crater and the trees grew back, creating the tranquil lake used today by families and tourists for recreation. There are no streams that flow into or out the lake, and since water is only lost through soakage and evaporation and only replenished through rainfall, the level can fluctuate up to 4 metres between wet and dry seasons. Lake Eacham is isolated from any other watercourse (making it an enclosed catchment). How any fish arrived there to begin with is a mystery, but somehow, the Lake Eacham rainbowfish (Melanotaenia eachamensis) found its way into the volcanic lake. Unfortunately for the small species, other larger fish were introduced into this closed system and eventually, these larger fish ate the Lake Eacham rainbowfish into extinction - at least as far as the lake was concerned. Aquarists had been collecting the fish from the Lake Eacham National Park (illegally) and were very successful at breeding them. These private collections became the source stock to reintroduce the fish to the lake. However, the cause of the species initial demise was still living in the lake and proceeded to deplete the entire population of reintroduced stock. Ichthyologists working in the rivers and streams of the Atherton Tableland have found the Lake Eacham rainbowfish in the Tully, Herbert and Johnstone Rivers and Dirran Creek. In addition to the rainbowfish, Lake Eacham has two native fish species: The gudgeon Mogurnda adspersa and the hardyhead Craterocephalus stercusmuscarum. Other fish in the lake are non-native human introductions.