Evaluation of a traditional Māori harvesting method for sampling kōura (freshwater crayfish, Paranephrops planifrons) and toi toi (bully, Gobiomorphus spp.) populations in two New Zealand streams

• Published in: New Zealand journal of marine and freshwater research Vol. 52; no. 4; pp. 603 - 625
• Main Authors: Kusabs, Ian A., Hicks, Brendan J., Quinn, John M., Perry, William L., Whaanga, Hēmi
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis 02-10-2018; Taylor & Francis Ltd
• Subjects: Bracken fern bundles; Bullying; Catch per unit effort; Colonization; Crayfish; Electric fishing; Evaluation; Ferns; Fish; Fishing nets; Freshwater; freshwater crayfish trap; Freshwater crustaceans; Freshwater fishes; Fronds; Gobiomorphus; Habitats; Harvesting; Inland water environment; Mātauranga Māori; Nets; optimum soak time; representative catch data; Rivers; Sampling; Streams; Substrates; Training; Traps; Underwater habitats; Whakaweku
• ISSN: 0028-8330; 1175-8805
• DOI: 10.1080/00288330.2018.1481437

Representative sampling of crayfish in streams is often impractical, especially in non-wadable habitats, or in areas with soft substrates. Whakaweku are artificial habitats made from bracken fern (Pteridium esculentum) that can be used successfully in a range of habitats. We compared whakaweku, minnow traps, fyke nets and electrofishing for sampling freshwater crayfish (kōura; Paranephrops planifrons) and bullies (toi toi; Gobiomorphus spp.) in two streams with differing stream characteristics and fish assemblages. Whakaweku captured a full-size range of kōura of both sexes, including small kōura (OCL 7-12 mm) that were not caught by minnow traps or fyke nets. Colonisation by kōura reached 90% of maximum after 2 weeks and CPUE was constant from 2 to 9 weeks. After 9 weeks, CPUE decreased due to decay of the fern fronds. Whakaweku are an effective sampling tool that are inexpensive, simple to set, and do not require expensive equipment or specialised training.