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

ABSTRACT
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.

TUHINGA-WHAKARĀPOPOTO
Whēuaua ana te kohi tohu nō te kōura i roto i ngā manga, inarā he wāhi tē taea te kautū, he wāhi tāpokopoko rānei.  Ko te whakaweku he wāhi kua waihangaia ki ngā tētē rarauwhe (Pteridium esculentum) e taea ana te whakamahi ki ngā hōhonutanga me ngā wāhi rerekē. I whakatauritea e matou ngā whakaweku, ngā rore minnow, ngā kupenga fyke me te whakahiko-hī-kōura ki rō wai Māori (Paranephrops planifrons) me te toitoi (Gobiomorphus spp.) i roto i nga manga e rua i te rerekē ngā kano āhuatanga me ngā kohinga ika o roto. I hopukina te rahi o ngā kōura pakari o ngā ira e rua, tae atu ki te maha o ngā kōura pakupaku (OCL 7–12 mm) kīhai i mau i ngā rore minnow, i ngā kupenga fyke rānei. Ko te kapinga i eke ki te 90 ōrau o tōna nui whai muri i te rua wiki, ā, ka ū tonu ngā hopukanga tohu CPUE i te 2 ki te 9 wiki.  I muri i te 9 wiki, ka heke te CPUE nā te pirau o ngā tētē rarauwhe. Ko te whakaweku he tino taputapu kohi tohu, nō te mea he iti rawa te utu mō te hanga, ka ngāwari te whakatakoto, ā, kāore hoki he take o ngā taputapu utu nui, o te whakangungu motuhake rānei.