ABSTRACT

Kākahi (Echyridella spp.) are freshwater cultural keystone species in New Zealand; they represent a valuable mahinga kai (species used as a food) resource and have high cultural significance to Māori, particularly to the Te Arawa and Ngāti Tūwharetoa iwi (tribal groups). Population densities of kākahi are thought to have declined in many locations in New Zealand, and accurate assessment methods are thus required to monitor changes in populations. A bathyscope method is currently used by iwi to monitor kākahi populations in lakes Rotorua and Rotoiti. It is unclear, however, how accurate this method is for determining kākahi abundance changes compared to underwater methods such as snorkelling. Comparisons at seven sites in Lake Rotorua and three sites in Lake Rotoiti show that significantly fewer kākahi are observed using a bathyscope relative to snorkelling (p < 0.0001). On average, snorkelling estimated 2.1 times more kākahi than the bathyscope method in Lake Rotorua, and 2.5 times more in Lake Rotoiti. We conclude that under suitable conditions, snorkelling is generally more effective than surface visual assessments using a bathyscope. Nevertheless, the bathyscope method is inexpensive, safe and simple, ideal for use by iwi and community groups for long-term monitoring of kākahi populations.

摘要

卡卡希 ( Echyridellaspp.) 是新西兰的淡水文化重点物种；它们代表了一种宝贵的 mahinga kai（用作食物的物种）资源，对毛利人具有很高的文化意义，特别是对 Te Arawa 和 Ngāti Tūwharetoa iwi（部落群体）。据认为，新西兰许多地方的卡卡希族人口密度已经下降，因此需要准确的评估方法来监测人口的变化。iwi 目前使用深海镜方法来监测 Rotorua 和 Rotoiti 湖中的卡卡希族种群。然而，与浮潜等水下方法相比，这种方法在确定卡卡希丰度变化方面的准确度尚不清楚。罗托鲁瓦湖七个地点和罗托伊蒂湖三个地点的比较表明，与浮潜相比，使用深海镜观察到的卡卡希鱼明显更少（p  < 0.0001)。平均而言，在罗托鲁瓦湖，浮潜估计比深海镜方法多 2.1 倍的 kākahi，在罗托伊蒂湖则多 2.5 倍。我们得出的结论是，在合适的条件下，浮潜通常比使用深海镜进行表面视觉评估更有效。尽管如此，深海镜方法便宜、安全且简单，非常适合 iwi 和社区团体用于长期监测 kākahi 种群。