ABSTRACT

The broadnose sevengill shark (Notorynchus cepedianus) is a large marine predator found in temperate coastal marine habitats. Despite being commonly encountered, details of its ecology are limited. To partially address this, we quantified the size and sex structure of N. cepedianus in Paterson Inlet, Stewart Island, New Zealand. A stereo-camera baited underwater video system (BRUV) was deployed in a shallow coastal embayment to capture underwater video of N. cepedianus for stereo photogrammetric measurement between June 2016 and November 2017. Individual sharks were sexed via observation of claspers. Three-dimensional underwater calibration of the photogrammetric system, using a precisely measured cube, indicated a mean error of <1%. Estimated total lengths ranged from 149.0 to 276.5 cm (n = 78 individuals, mean = 211.4, S.E. = 2.97). The observed sex ratio was heavily biased, with females making up 95% of the population in winter 2016 and 73% in summer 2017. This study provides new data on N. cepedianus in southern New Zealand as well a non-invasive, low-cost methodology that can be applied to other study areas.

摘要

宽鼻七鳃鲨 ( Notorynchus cepedianus ) 是一种在温带沿海海洋栖息地发现的大型海洋捕食者。尽管经常遇到，但其生态学的细节是有限的。为了部分解决这个问题，我们量化了新西兰斯图尔特岛帕特森湾N. cepedianus的大小和性别结构。一个带饵的立体摄像机水下视频系统 (BRUV) 被部署在一个浅海海湾中，以捕捉N. cepedianus的水下视频用于 2016 年 6 月至 2017 年 11 月期间的立体摄影测量。通过观察扣钩对个体鲨鱼进行性别区分。使用精确测量的立方体对摄影测量系统进行三维水下校准，表明平均误差 <1%。估计总长度在 149.0 到 276.5 厘米之间（n  = 78 个人，平均值 = 211.4，SE = 2.97）。观察到的性别比例存在严重偏差，女性在 2016 年冬季占人口的 95%，在 2017 年夏季占人口的 73%。这项研究提供了新西兰南部的N. cepedianus的新数据以及非侵入性、低成本可应用于其他研究领域的方法。