Habitat use by deep-sea chondrichthyans in the New Zealand region

Worldwide, half of all sharks, rays and holocephalans are found in the deep sea. Primarily due to low commercial interest in many of these animals, research has historically not been prioritized for these species. Of the 112+ species of chondrichthyans found in New Zealand waters, approximately 80% of species are found in the deep sea, and a high percentage of these have a high level of data deficiency. Habitat use has been identified as a knowledge gap for deep-sea chondrichthyans, and it is important to understand how habitat utilisation varies among the different life stages when assessing the risk of fishing activities and other anthropogenic impacts. In New Zealand, much of what is currently speculated about habitat use is based on research trawl survey data and has not been confirmed with in-situ observation. Here, a series of readily available deep-sea video collections, video surveys conducted by the National Institute of Water and Atmospheric Research (NIWA)’s Deep Towed Imaging System (DTIS) and the National Museum of New Zealand (Te Papa), have been analysed to characterise areas of importance for encountered deep-sea chondrichthyans. A Generalised Linear Model was used to analyse the observations. It was found that many chondrichthyans are associated with substrate that their prey items they prefer. The video footage has uncovered potential nursery areas, which for chondrichthyans were previously unknown in the New Zealand deep-sea region. This information is important for informing the management of species’ risk to fishing and other habitat disturbances, including future seabed mining in the deep sea.