Sustainable management of freshwater crayfish (koura, Paranephrops planifrons) in Te Arawa (Rotorua) lakes, North Island, New Zealand

摘要

Freshwater crayfish or koura (Paranephrops planifrons White, 1842) support important customary fisheries for Te Arawa iwi (tribal members) in the Te Arawa lakes, North Island, New Zealand. Until recently, however, there was limited published information on which to base fisheries regulations. We sampled over 9000 koura in eight lakes using a traditional Maori harvesting method known as the tau koura which comprised bundles of bracken fern fronds (Pteridium esculentum) laid on the lake bed. We examined the catch rates and biological traits of koura in the Te Arawa lakes and the implications for the current fishing regulations and koura management. koura were present in all of the study lakes except Okaro, but harvestable quantities were only found in Rotorua, Rotoma and Rotoiti. The overall ratio of females to males was about 1:1. Egg-bearing koura were found throughout the year, but only occasionally during the summer months. Koura fecundity increased as a power function of orbit-carapace length (OCL). Size at onset of breeding for 50% of females, in lakes where koura were present, ranged from 22.1 mm OCL to 27.5 mm OCL. In addition to existing regulations, the following management measures are recommended: (1) implementing a slot limit with a minimum size of 28 mm and a maximum size of 39 mm OCL, (2) banning the taking of egg-bearing koura, (3) limiting deep-water harvest methods to the use of the tau koura, and (4) implementing a tau koura harvest season beginning on 1 December and ending on 31 March. (C) 2015 Elsevier B.V. All rights reserved.