After nearly three months out due to ill-health, I was finally back on the road and heading up to see my good friends at the Kirkcaldy Aquarist Society. The purpose of this visit was to do a presentation on Rainbowfish Identification and it seemed to go down well with a very healthy attendance. Identifying Rainbowfish can often be very difficult even to the most experienced aquarist; just pop into your local fish store and have a look at the often drab colourless young fish you will encounter.
During my lecture I concentrated on the southern lineage fish, Goldiei, Maccullochi, Australis and Nigrans. This group of fish have a closer relationship than you may think. They may inhabit the rivers of Australia, the Aru Islands and New Guinea and be separated by the sea, but 10,000 years ago during the last glacial lowering of our sea levels the Islands were all connected by what we call the Sahul shelf and formed the great continent of Sahul.
Found in Australia, the Aru Islands and the Island of New Guinea, the Goldiei group is large with species such as Melanotaenia trifasciata having many different colour forms based on geographical location. More study is needed and we may see these being split and new species being created. All the group show the same identifiable characteristics such as a dark mid lateral band and high arched back though this may vary in intensity with differing species. Species can vary in size from 7cm to 20cm.Goldiei group species can be recognised with its 2nd dorsal and anal fin hugging the body of the fish and both are more or less symmetrical in shape.
The Australis Group
Found mainly on Australia apart from two New Guinea species, M. rubrostriata and M. parkinsoni, The Australis group much like the Goldiei group, contains species with many different forms based on geographical location. Most fish in this group are riverine species and attain lengths of between 6.5cm and 16cm. The Distribution of the Australian species in this group is by far the largest of any of the groups with species being found in the central and northern coast of eastern Australia, along the northern coastline, down into central Australia and out to the north western coast. Of the two New Guinea species M. Rubrostriata is the most widespread and can be found in most creeks from the Mighty Fly River catchment area in Papua New Guinea and westwards to Etna Bay in West Papua.
The Maccullochi Group
A dwarf group of fish from the island of New Guinea with the exception of Melanotaenia maccullochi which can also be found in Northern Australia, highlighting the Sahul land bridge connection. This group seems to be becoming more available to the hobby with such fish as Melanotaenia ogilbyi being rediscovered and the stunning find that was Melanotaenia garylangei. One fish, Melanotaenia papua still regularly appears on import lists but sadly the fish always turns out to be M australis; Fish of this group grow between 6-8cm in length.
The Nigrans Group
Fish of this group can only be found in Australia. M. nigrans, M. gracilis and M. exquisita originate from the far north while M. pygmea can only be found in two small tributaries of the Prince Regent River in North Western Australia. These fish have a stream lined elongated body typical of a stream dwelling fish.
Hybrid Rainbowfish can also become very large and aggressive and a term is applied to such fish called “Hybrid vigour”. The aggressiveness is down to the increased vigour and health and resistance to disease these fish display and bullying can become out of control within the community set up. Hybrids in my opinion have no place in the hobby.
Written by: Alex Carslaw | Editor: Chris Englezou
Picture credits: Alex Carslaw | Wallace Tao |George Funkner | Mark Shaw | Leo O’Reilly | Matt Chilton |Dave Crossett