New species of freshwater fish found on Chathams

Forest and Bird, Issue 274, 1 November 1994, Page 6

New species of freshwater fish found on Chathams

IN THE FIRST ADDITION to New Zealand’s freshwater fish fauna for 27 years, a new species has been discovered in the Chatham Islands. Fisheries biologist Charles Mitchell discovered the new species in a landlocked peat lake at the headwaters of the Te Awainanga River in the remote south-west corner of Chatham Island in April. The small fish, which has not yet been formally named, grows up to 75 mm in length and is a galaxiid related to the kokopu, inanga and other whitebait species. However it is quite distinct from any other New Zealand fish.

The fish spends its entire life cycle in lakes, a relatively rare occurrence on New Zealand’s smaller islands where nearly all freshwater fish are diadromous species — that is they migrate between the sea and river systems for different stages of their life cycles. The fish are eaten by longfinned eels, the only other fish to be found in the same lakes. Mitchell made the discovery as part of a study of the potential impacts of the proposed Chathams hydroelectricity project. The project is an attempt to replace the island’s expensive and wasteful diesel-generated electricity system with a small low-impact hydro scheme. Mitchell says that the scheme will have no effect on the newly discovered fish. The Chathams remain relatively rich in native freshwater fish as there is no competition from introduced trout as on the mainland, while land use is not yet intensive enough in most areas to seriously degrade water quality. Ten of New Zealand’s 27 freshwater fish species are found on the islands. Mitchell has prepared a formal description of the new species with the help of the authority on New Zealand’s freshwater fish, Dr Bob McDowall.