Using unmanned aerial vehicle (UAV) surveys and image analysis in the study of large surface-associated marine species: a case study on reef sharks Carcharhinus melanopterus shoaling behaviour.
A novel image analysis-based technique applied to unmanned aerial vehicle (UAV) survey data is described to detect and locate individual free-ranging sharks within aggregations. The method allows rapid collection of data and quantification of fine-scale swimming and collective patterns of sharks. We demonstrate the usefulness of this technique in a small-scale case study exploring the shoaling tendencies of blacktip reef sharks Carcharhinus melanopterus in a large lagoon within Moorea, French Polynesia. Using our approach, we found that C. melanopterus displayed increased alignment with shoal companions when distributed over a sandflat where they are regularly fed for ecotourism purposes as compared with when they shoaled in a deeper adjacent channel. Our case study highlights the potential of a relatively low-cost method that combines UAV survey data and image analysis to detect differences in shoaling patterns of free-ranging sharks in shallow habitats. This approach offers an alternative to current techniques commonly used in controlled settings that require time-consuming post-processing effort.
['Rieucau|Guillaume|G|', 'Kiszka|Jeremy J|JJ|', 'Castillo|Jose Carlos|JC|', 'Mourier|Johann|J|', 'Boswell|Kevin M|KM|', 'Heithaus|Michael R|MR|']
D000818:Animals D001522:Behavior, Animal D017753:Ecosystem D007091:Image Processing, Computer-Assisted D011114:Polynesia D012754:Sharks
UAV image analysis Carcharhinus melanopterus shoaling behaviour blacktip reef shark