Passive acoustic monitoring on the seasonal species composition of cetaceans from a marine observatory

Information on the species diversity of cetaceans can help us to understand the community ecology of marine top predators. Passive acoustic monitoring has been widely applied in the cetacean research, however, species identification based on tonal sounds remains challenging. In order to examine the seasonal changing pattern of species diversity, we applied an automatic detection and classification algorithm on acoustic recordings collected from the marine cable hosted observatory off the northeastern Taiwan. Representative frequencies of cetacean tonal sounds were detected. Statistical features were extracted based on the distribution of representative frequency and were used to classify four cetacean groups. The correct classification rate was 72.2% based on the field recordings collected from onboard surveys. Analysis on one-year recordings revealed that the species diversity was highest in winter and spring. Short finned pilot whales and Risso’s dolphins were the most common species, they mainly occurred in winter and summer. False killer whales were mostly detected in winter and spring. Spinner dolphins, spotted dolphins, and Fraser’s dolphins were mainly detected in summer. Bottlenose dolphins represent the least common species. In the future, the biodiversity, species-specific habitat use, and inter-specific interaction of cetaceans can be investigated through an underwater acoustic monitoring network.