Preliminary exploration of Balaenoptera edeni edeni population distribution in surrounding waters of Weizhou Island based on environmental DNA

Cetaceans, as apex predators in marine ecosystems, play a key role in maintaining ecological balance and stability. The Eden's whale (Balaenoptera edeni edeni) in Weizhou Island is the only baleen whales population that consistently appears in the waters near China. However, their specific distribution around Weizhou Island remains unclear. Due to their extensive range and active behavior, conducting stable tracking surveys via visual means is challenging. Thus, combining environmental DNA (eDNA) technology, we assessed the distribution status of Eden's whale habitats around Weizhou Island during different periods (April 2022 and January 2023). The study reveals that in April, Eden's whales were visually observed and detected via eDNA in the hotspot distribution area (Between Weizhou Island and Xieyang Island) (n=3). They were also found in the southwest waters of Weizhou Island (n=2), with one site solely identified through eDNA. In January, Eden's whales were visually observed and detected through eDNA in the hotspot distribution area (n=1) and detected through eDNA in the eastern waters off Weizhou Island (n=1). The findings indicate that compared with visual observation, eDNA technology exhibited higher sensitivity and could be utilized to verify the distribution of Eden's whale. Furthermore, potential hotspot distribution areas for Eden's whales were identified in the eastern and southwestern waters off Weizhou Island. In conclusion, this research validates the feasibility of utilizing eDNA technology for monitoring the distribution of Eden's whales around Weizhou Island. Besides, it provides further clarification regarding the distribution status of Eden's whale habitats around Weizhou Island, which supplies essential baseline information for the effective monitoring and scientific conservation of this population.