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

Abstract

Sampling of kōura (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 kôura is a traditional Maori method used to catch kôura in central North Island lakes by placing whakaweku (bundles of bracken fern Pteridium esculentum) on the lake bed that kôura then colonise. It has advantages as a monitoring tool over conventional methods, such as baited traps and dive surveys, as it samples all kôura 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 kôura 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.