Lake Eacham - A Closed Ecosystem and A Near-extinction

A Closed Ecosystem and A Near-extinction

Lake Eacham (Yidyam) 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 native 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.