Distribution and threats of cetaceans near the East China Sea: an analysis based on local ecological knowledge (LEK)

Effective conservation and management of cetaceans require detailed information on species composition and spatial distribution. Local ecological knowledge (LEK) has increasingly been recognized as a valuable tool for assessing key species and biological resources, particularly in marine mammal studies. From November to December 2023, a large-scale LEK survey was conducted in coastal areas adjacent to the East China Sea. The study aimed to investigate the diversity, distribution patterns, population trends, and potential threats faced by cetacean species in the region. A total of 534 fishermen were interviewed across 59 ports and docks. During the survey, 11 cetacean species were recorded based on local reports, including the East Asian finless porpoise (Neophocaena sunameri), common bottlenose dolphin (Tursiops truncatus), Indo-Pacific bottlenose dolphin (Tursiops aduncus), Chinese white dolphin (Sousa chinensis), rough-toothed dolphin (Steno bredanensis), Fraser’s dolphin (Lagenodelphis hosei), pantropical spotted dolphin (Stenella attenuata), false killer whale (Pseudorca crassidens), pygmy killer whale (Feresa attenuata), short-finned pilot whale (Globicephala macrorhynchus), and killer whale (Orcinus orca). No sightings of large baleen whales were reported. Most respondents indicated that cetacean sightings were most frequent during August and September, with key hotspots located in Haizhou Bay, the East China Sea Bridge area, the mid-lower section of the Yangtze Estuary fishing ground, Dongtou, and the northern waters of the Nanji Islands. About half (50.19%) of respondents believed that cetacean populations are declining. Additionally, 20.22% reported incidental bycatch of cetaceans, primarily associated with trawl and gillnet fisheries. These findings provide a foundational understanding of cetacean distribution and threats in the East China Sea and offer valuable insights for future conservation strategies.