Use of a traditional Māori harvesting method, the tau kōura, for monitoring kōura (freshwater crayfish, Paranephrops planifrons) in Lake Rotoiti, North Island, New Zealand

Abstract

Sampling of koura (freshwater crayfish Paranephrops planifrons) to assess population abundance and structure in lakes is often difficult or impractical because of the absence of representative methods. The tau koura is a traditional Maori method used to catch koura in central North Island lakes by placing whakaweku (bundles of bracken fern Pteridium esculentum) on the lake bed that koura then colonise. It has advantages as a monitoring tool over conventional methods, such as baited traps and dive surveys, as it samples all koura size classes, can be used in turbid waters and at a wide range of depths, and does not require expensive equipment or specialised expertise (e.g., SCUBA). We demonstrate its use to monitor koura populations in Lake Rotoiti (mean depth 32 m), North Island, New Zealand. Application of the method allowed differences in population size structure to be distinguished between a shallow and a moderate depth site within Lake Rotoiti and to discern seasonal breeding patterns. © The Royal Society of New Zealand 2009.