Persistence of a significant population of rare Canterbury mudfish (Neochanna burrowsius) in a hydrologically isolated catchment

Abstract

Canterbury mudfish (Neochanna burrowsius) are endemic to a small region of Canterbury, South Island, New Zealand and classified as nationally endangered. We reviewed data from the New Zealand Freshwater Fish Database and trapped fish in July 2006, and January and February 2007 in the Waianiwaniwa Valley, Canterbury to determine the importance of this catchment for mudfish conservation. Mudfish were found in 19 of the 28 sites sampled. Waianiwaniwa Valley sites accounted for 47% of all Canterbury mudfish database records of mean catch per unit effort (CPUE) ≥6 fish. The population comprised young recruits (<60mm total length (TL)) through to mature adult fish (>120mm TL) indicating a healthy population. Drying of the lower mainstem, and low dissolved oxygen levels in summer create a unique catchment free of larger predatory fish and with reduced competition from other fish species. We estimated that mudfish occur in at least 24.3 km of the Waianiwaniwa River, making this catchment the most important refuge known for the conservation of this species.

Keywords:

• endemic species
• conservation status
• mudfish distribution
• predatory fish