# Diversity and Distribution of Deep-Sea Cetaceans in the Northern South China Sea Based on Visual and Acoustic Surveys

## TL;DR

This study found high cetacean diversity in the northern South China Sea, but human activities threaten their survival.

## Contribution

The study combines visual and acoustic surveys to document deep-sea cetacean biodiversity in the northern South China Sea.

## Key findings

- 28 cetacean encounters involving 12 species and over 1000 individuals were recorded visually.
- Acoustic monitoring detected 53 cetacean occurrences, highlighting high biodiversity in the region.
- Human activities like fishing, shipping, and oil exploration pose major threats to cetaceans in the area.

## Abstract

Cetaceans serve a critical role in deep-sea ecosystems. However, the challenging environmental conditions and limited funding have led to a significant lack of data on the species diversity of deep-sea cetaceans. This study combined visual and acoustic survey methods to investigate whales and dolphins in the deep-water regions of the northern South China Sea. The findings reveal remarkably high cetacean biodiversity in these areas. Nonetheless, cetaceans in the South China Sea are facing severe anthropogenic pressures, including fishing activities, shipping traffic, and oil and gas exploration. Establishing and enforcing robust conservation policies is imperative to ensure the long-term survival of whales and dolphins in this region.

Cetaceans are essential for maintaining the balance and stability of deep-sea ecosystems. However, environmental challenges and limited funding have resulted in a marked lack of data on species diversity and the conservation status of deep-sea cetaceans. In this study, we undertook two research expeditions in the deep-water regions of the northern South China Sea, employing an integrated visual and acoustic survey approach. In total, 28 cetacean encounters, involving 12 species and more than 1000 individuals, were documented through visual observation, while acoustic monitoring recorded 53 detections. These findings demonstrate that the deep-sea waters of the northern South China Sea have relatively high cetacean biodiversity and constitute significant habitats for these marine mammals. Nevertheless, this area also experiences intensive human activities, with fisheries, maritime traffic, and oil and gas extraction posing primary threats to local cetacean populations. Improving the management of human activities in this marine zone is essential for ensuring the effective protection of cetacean species and their critical habitats.