Fisher’s memories help estimate coastal dolphin abundance

Estimating the abundance of marine megafauna like dolphins is essential for conservation, but traditional field-based methods are expensive and time-consuming. A new study led by Dr. Mingli Lin and colleagues presents an innovative and cost-effective alternative—using interview-based sighting histories to estimate dolphin abundance through local ecological knowledge (LEK).

The research, published in Water Biology and Security, analyzed interview data from fishers and coastal residents across mainland China to reconstruct sighting histories of the Indo-Pacific humpback dolphin (Sousa chinensis). By developing four indirect abundance indices—encounter rate, encounter rate in the past decade, sighting frequency, and mean annual sightings—the team found that all indices were strongly and significantly correlated with known abundance rankings of dolphin populations.

“Fisher's collective memory of dolphin sightings provides surprisingly useful information about population patterns,” say Dr. Lin, the study's lead author. “This is the first evidence that interview data can produce reliable quantitative insights into marine megafauna abundance.”

Previous attempts to use LEK for abundance estimation have been mostly limited to terrestrial species, such as tortoises, where locations and group sizes are easier to identify. “In marine environments, the difficulty of pinpointing sightings or estimating group size at sea have long limited this approach,” adds Lin. “Nonetheless, we managed to overcome these obstacles by using specific questions and multiple indices to capture long-term sighting trends.”

“This approach opens new possibilities for monitoring marine mammals, especially in developing regions where resources for field surveys are limited,” says  corresponding author Prof. Songhai Li. “It also empowers local communities to contribute directly to marine conservation through their own experiences”.

The researchers conclude that interview-based data can effectively complement conventional scientific monitoring, helping identify potential habitats, population trends, and conservation priorities for marine megafauna. With 85 of the world's 90 cetacean species occurring in the broader region, this approach could become a vital tool for evidence-based marine biodiversity management.

Contact author: Songhai Li; Institute of Deep-sea Science and Engineering, Chinese Academy of Sciences, Sanya, 572000, China; lish@idsse.ac.cn

Funder: This research was financially supported by the National Natural Science Foundation of China (42225604, and 42494883), Science and Technology Talent Innovation Project of Hainan (Grant No. KJRC 2023B03). Field survey was approved by the Research Ethics Committee of the Institute of Deep- sea Science and Engineering, Chinese Academy of Sciences (IDSSE- SYLL-MMMBL-01).

Conflict of interest: The authors declare that they have no competing interests or personal relationships that could have appeared to influence the work reported in this paper.

See the article: Exploring the potential of interview-based sighting history to estimate the abundance of a coastal dolphin, Water Biology and Security,  https://doi.org/10.1016/j.watbs.2025.100456